Transmission Running Hot

[Fubar]

Hi all; if it's not one problem it's another:( At least it seams that way for me lately.

Here's my current concern; while climbing long grades or steep mountain passes my trans gets hot to the point where "Transmission Hot" appears on the center console.

I know simply pulling over and leaving it in park and letting the motor run for 10-15 minutes brings everything back to normal. It's just a pain..

But considering I'm not towing anything and the trans is reaching this "Too Hot" condition, I'm wondering if getting a larger trans pan, one that will hold an additional 3 quarts if this would solve this problem?

I guess a larger trans cooler might also help but with my recent past engine running hot issue, which I can happily say has been solved, anyway with this past trouble in mind I don't really want to stack something else in front of the new radiator.

So would something like this work? It say it supports up to yr 02 and the list of trans that it says it will fit doesn't list the one in the Hummer (Hydra-Matic 4L65-E).

http://www.xtremediesel.com/index.asp?PageAction=VIEWPROD&ProdID=29

Thanks in advance for any suggestions:D

[H2 Ranger]

Check some of the racing parts suppliers, they have many configurations as it pertains to Transmission coolers. Some offer remote cooling fans and alternate mounting locations, additonal remote filters, larger oil supply lines, etc. Anything that give addition oil supply and cooling area mass will help. Hope you get it resolved.

[MarineHawk]

Is this normal? Or is something wrong with the tranny? Also, do you have the two/haul mode thingy? Would it help? Mine shifts higher and more sharply in the tow haul mode.

[Fubar]

Thanks guys.
Adding a larger radiator that holds 2-3 extra gallons along with adding a couple additional rows of cooling fins solved my run hot issue with the motor/supercharger. Even though the trans got hot the engine coolant remained at or below 210 which is normal for the H2.

So I was just hoping that by adding a larger pan to the trans that the same would hold true for that system.

I'll continue looking at options.

Just running around town there's never any problem with the trans getting hot but it seams that when its under any prolonged stress/load and the temp continues to climb. I would expect the temps to climb if I was towing anything but I wasn't.

The trans was just serviced in April. I'm guessing they pulled the pan changed the filter and re-filled it with oil. I'll check to make sure they actually filled it.

As for the tow/haul button, good question. I don't know I've never used it, it is there. The trans was not hunting or shifting as I was going up the grade. 2000rpm's 60-70-mph I wouldn't think that would be too much for the truck.

On the my trip to Big Bear 8200 feet up and doing 20-mph up windy roads I kind of expected to see the trans temp raise just not as high as they did.

What concerned me most was on the way home from Ca there are two 5000-ft passes spanning 25 miles 16 miles on one and 9 miles of climb on the second or may it's reversed either way near the top of the second pass the trans got to the point where I needed to pull over. Outside air temps were 80-85 not what I would consider a problem.

I'm rambling... Thanks again for the suggestions.

I see an F250-F350 in my future (possibly):D

[Fubar]

Phil,
wouldn't adding an additional tranny cooler possibly make the trans run too cool most of the time under normal day to day driving and possibly cause a problem of its own?

I've been told that if you make the front part or one part of the trans too cool the back end or other part has to work extra hard to make up the temp difference. I don't know anything about trans or how they work so this may be complete b/s..

Adding a trans cooler seams like it would be the lesser complicated or cheaper way to go.

Thanks

[Fubar]

Phil,
looking at your pictures of your install of the Hayden Ultra Cool I can't install the unit in the same place due to the fact that the innner cooler for the S/C is currently there. I have no doubts that installing a trans cooler where you have it would reslut in much cooler trans temps.

The other possibility might be to place the additional trans cooler in front of the radiator and put a fan on it to make up for the lack of air coming threw the front grill.

[H2 Ranger]

Has the overheating been since the vehicle was new? or has it started since service?

If its been that way since service:
1. Maybe the bands were adjusted too tight thus causing excessive friction.
2. Is the pick-up filter properly installed?
3. Is there any line restriction including bent or twisted lines?


Seems like you might have noticed it earlier if its been overheating. Additional cooling and or fluid capasity is always a good route to go.

[RIC-H0]

If it's still under warranty, I would definetly take it in. Mine actually started overheating the same way, and then it went out about a month later.
Got a newly rebuilt factory trans, and never had that problem again.
Have you checked your trans fluid lately? I'm sure it's black by now if it's overheat so many times. Either way, I would change out your trans fluid.

[Fubar]

Has the overheating been since the vehicle was new? or has it started since service?

If its been that way since service:
1. Maybe the bands were adjusted too tight thus causing excessive friction.
2. Is the pick-up filter properly installed?
3. Is there any line restriction including bent or twisted lines?


Seems like you might have noticed it earlier if its been overheating. Additional cooling and or fluid capasity is always a good route to go.

RE: 1, anything is possible but the trans remains at it's normal operating temp most of the time. It only climbs when going up long or steep grades.

RE: 2, I haven't a clue. With the other stuff the the tech from Cerriots Hummer f u c k e d up I wouldn't be surprised to find that he's messed up the filter install as well.

RE:3 No there are no bent or twisted lines. The only two lines I see are both 1/2-3/4 inch coper for the incoming and return of the ATF from the radiator back to the trans.

It's only 90 this morning at 7:30 I'll go out and crawl around and see if anything jumps out at me as being wrong..

Thanks for the list of stuff to check.

[Fubar]

Phil,
Thanks for all the advice.

I need to find a mechanic here in town I can trust and that is proving to be difficult.

[H2 Ranger]

Heres one for you and there are others..

[Fubar]

Ric,
Thanks, I'll check with the dealership and see if they would be willing to check the condition of the trans under warranty.

It will not come as a surprise to me if they tell me that because of the supercharger I had them install that my trans is no longer covered.

The trans fluid was changed in mid April along with having trans maintenance done. this was done when the truck broke down due to a valve guide that got sucked into one of the heads while on my to Ca for a visit to my folks. The heads and exhaust had to come off anyway so I told them to service the trans.

[Fubar]

H2Ranger, ya I was looking at those on-line last night. I'm just a little leary of anything made by flex-a-lite because of the troubles I've had in the past with there fans. In all fareness the fans were probably just fine it was just a crapy job of installing the control module that I believe caused my past problems with the fans.

Thanks though I will continue to look that option and others.

Heres one for you and there are others..

[Fubar]

question; does the truck need to be in drive when the trans fluid level is being checked? I mean do I need to tackel a neighbor and ask for help with checking the fluid level or will placing the truck in park and letting it get up to operating temp work?

[H2 Ranger]

If this condition has started since service, Have them reacheck the adjustments something is not right. Mine has a SC too and I dont have such conditions but mabee someday.... But in Heat regard such has Phil indicated it can be many things Slippage of clutches, lubrication restriction, fluid condition, etc. Do you have a good performance Transmission shop in the area? And a good aftermarket cooler would definitly help. I really dont think you will run into a condition (UNLESS YOU LIVE IN THE ARTIC) where you will need to worry about low transmission tempature. The higher the temp the more friction. Let us know the outcome.

[H2 Ranger]

question; does the truck need to be in drive when the trans fluid level is being checked? I mean do I need to tackel a neighbor and ask for help with checking the fluid level or will placing the truck in park and letting it get up to operating temp work?

dont ask me to help, but no just operating temp., and check in park.

[H2 Ranger]

H2Ranger, ya I was looking at those on-line last night. I'm just a little leary of anything made by flex-a-lite because of the troubles I've had in the past with there fans. In all fareness the fans were probably just fine it was just a crapy job of installing the control module that I believe caused my past problems with the fans.

Thanks though I will continue to look that option and others.

you can attach any fan to the cooler (pusher or Puller)depending on mounting and location conditions.

[PARAGON]

I would fashion a heat shield over the exhaust crossover first, before I did anything else. The radiant heat could simply be cooking the bottom of the tranny pan when working hard as your exhaust temps would be running higher than a stock rig would and that would show up on an extended grade climb. Cheap and easy that might just help.

[Fubar]

on the dipstick it says check level while parked and ideling. Ok done.

The level while not apparent in the pictures was between the two holes on the stick, the color seams ok. It's not supposed to be clear is it? It doesn't smell burnt.

[Fubar]

I'm pretty sure nothing else is going to fit infront of the radiator.

[Fubar]

dropping the trans pan will not be a problem as the exhaust is well out of the way. There is about 5 inches between the under body protection and the pan

[Fubar]

here are shots of the supply lines for the atf.

[Fubar]

there doesn't appear to be anything leaking and the trans fluid level seams to be ok.

I'm having a new AC unit installed in the house today so will not be able to take the truck to the dealership. I'll get to it and let you know what if anything they have to say or suggest.

The dealership that did the trans service is in Ca not practicle for me to get back to so I'll try my local dealership and see if they'll cover taking a look at the trans under warranty.

Thanks again to all of you for your suggestions.

[Fubar]

I would fashion a heat shield over the exhaust crossover first, before I did anything else. The radiant heat could simply be cooking the bottom of the tranny pan when working hard as your exhaust temps would be running higher than a stock rig would and that would show up on an extended grade climb. Cheap and easy that might just help.

Paragon, thanks. I can see in this pic exactly what you mean. The exhaust is pretty close to the pan.

http://www.elcovaforums.com/forums/attachment.php?attachmentid=21016&d=1147882275

[H2 Ranger]

The "blotter test" sounds interesting. Now thats a new one on me. Sounds like the sticky lifters and the quart of transmission fluid to unstick the lifters trick. Mabee a check with the amsol and 25 dollars will give more exact information. Not to say it dont work, its just new to me. I would like to know more about that suggestion though. But thanks Phil, I recieved everything! From the looks of the pics I dont see evidence of the pan being removed. Mabee a few pressure checks might reveal something, but again I think a trusted transmission performance shop might shed more light on the situation. FWIW My exhaust is in the same location and you stated the engine temp is normal right? If you cant trust the shop do the show me the money and ask to see it in some form of publication and verify what they are doing. If they dont want to do it then take it eslewhere.

[RIC-H0]

Do the blotter test;

A quick way to test for worn ATF (in the t-case and tranny) is to do a blotter test. Place a couple of drops of ATF on a paper towel and wait 30 seconds. If the spot spreads out widely and is red (or maybe brown), the ATF is likely OK. But if the spot does not spread out and is dark, the ATF is oxidized and should be changed.
That's a good one Phil, I need to keep that one in mind.:)

[H2 Ranger]

Phil, For the cost of transmission fluid I know what I would do! I totally agree with you. I think this problem needs more checks done. pressures and bands and new filter and oil changed. Mabee its worth it if it saves the transmission.

[Fubar]

Quote: H2 Ranger (FWIW My exhaust is in the same location and you stated the engine temp is normal right? )

Yes the engine temp stayed within it's normal range, while the trans displayed "Trans Hot" on the center console. By normal range I mean when the trans was at it's hottest the engine coolant never got more than the width of the needle above 210 however 185 is normal for my truck now with the 160 t-stat, so the engine coolant was affected by the hot trans.

However lets keep in mind my truck is far from "normal or stock" the S/C produces more heat, thats a given, a combination of a larger radiator, new high flow catalytic converters and 160-t-stat seam to have fixed the engine coolant run hot issue.

Depending on who you talk to about my previous run hot condition with the motor most are pointing to the catalytic converters being plugged and a continuing leaning condition being brought on by 1-3 clogged or partially plugged fuel injectors.

After having the passenger side head replaced because a valve guide got sucked into the head due to the motor running too lean and getting too hot on too many occasions, (although I argue the point too many) it was exactly 3 occasions and never driven for long under excessive heat but I guess that was enough to cause the problem. Having replaced the catalytic converts with higher or free flowing ones I probably could have gotten away with not going to the expense of changing the radiator or changing the t-stat, but it's done now and engine wise seams to be working correctly.

I don't think any one thing caused my truck to run hot. I think it's been a lot of things combined.

I'm just hoping the problem with the trans is easier to realize and solve.

Starting with a larger pan which will hold more fluid and a larger trans cooler if a place to locate it can be found I'm hopeful whatever is happening with the trans will be resolved.

The trans shifts fine, the trans operates at normal operating temps with city stop/go driving. There is no apparent slippage so I don't think anything internal is wrong, it's just getting too hot on steep or prolonged hill climbs.

Thanks again guys for all the suggestions:D

[PARAGON]

I'm not 100% that ATF blotter test is totally accurate, but it does seem to give a good indication. I always work on the basis, when in doubt change it. If ATF is very dark, smelly, or opaque, I change it.

The original dino ATF in my t-case went bad very quickly, and I change it every 10k now, worthy checking if you've never looked at it. same goes for the diffs, which don't ever require a fluid change according to the manual, just a top up. The fluid in them goes bad as well.

I've started using Royal Purple in the diffs and t-case and been very happy with it so far.Completely accurate. It's a test that's used when evaluating oils and fluids for oxidation and breakdown. The blotter test lets you know that the fluid still flows because it spreads through the paper. If it is oxidized and gunked up, it will sit and not spread very much. They test how long fluids can sit at certain temperatures (mainly engine oil, tranny fluid, gear oil) to make sure it can not break down under extended use at XXX temperature.

[H2 Ranger]

Learn more every day and even more researching. Little more to the story than whats said:

http://www.practicingoilanalysis.com/article_detail.asp?articleid=355&relatedbookgroup=OilAnalysis

[HUMTECH]

did'nt read the entire post but if your trans is getin hot enough to throw A warning(not just by the gauge) and your not towing you have an issue. New trucks should handle any environment without issue when left stock. Adding A supercharger will not affect trans temp unless you really work it up A steep grade with A lot of added weight as any H-2 will drop to 3rd and no tcc lock up while climbing A long grade. If you are towing and remove the trailer your trans shift adapts take A little while to adapt but should still not cause A heat concern. Have it checked out while under warranty even if it costs A few bucks, at least they have your concern on record if it fails 10k miles out of warranty.

[Fubar]

did'nt read the entire post but if your trans is getin hot enough to throw A warning(not just by the gauge) and your not towing you have an issue. New trucks should handle any environment without issue when left stock. Adding A supercharger will not affect trans temp unless you really work it up A steep grade with A lot of added weight as any H-2 will drop to 3rd and no tcc lock up while climbing A long grade. If you are towing and remove the trailer your trans shift adapts take A little while to adapt but should still not cause A heat concern. Have it checked out while under warranty even if it costs A few bucks, at least they have your concern on record if it fails 10k miles out of warranty.

Ya the issue is lack of air getting to the trans cooler caused mostly because of the inner-cooler for the S/C blocking 2/3rds of the front gril. So one of two things needs to happen; get more air to the trans cooler which isn't possible due to lack of space to mount a fan anywhere or locate a secondary cooler somewhere else under the truck with a fan and two thermal dynamics dictates that if you add more fluid you increase the ability to dissipate heat, add more fluid or increase the surface area said fluid transverses and both will reduce heat.

Enough to make a difference I don't know. But I have to start some place.

If there was actually something mechanically wrong with the trans the run hot condition would be present in day to day driving and not only when climbing steep or prolonged grades. However the truck never downshifts while going up the two passes between here and CA. I've always figured it was because there is now ample power being produced by the sc so that the trans doesn't need to hunt for a gear to help move the weight of the truck. The trans will downshift if I floor it (3000-3500rpms) going up the grade. But keep the rpms around 2000 and it never downshifts.

Here's some food for thought; from Vegas to Moab 400+ miles there is a 9000 foot pass that you go over and the truck has never over heated going up that pass. Between Vegas and Ca there are two 4000ft passes and on each and every trip I've made since having the SC installed two years ago April the trucks trans has gotten hot. I don't get it.. It has to have something to do with the grade % and the length and the reduded air flow to the cooler.

I'll check with my local dealership but I'm almost certain they are going to say the trans is not covered by warranty becasue of the supercharger.

[KenP]

Not sure how much difference a bigger tranny pan will make, but a fonned pan will help a little. You'll have to remove the exhaust to replace it, and some of the deeper ones will not fit because of the exhaust location, so make sure you measure first. That seems pretty expensive also.

I added an additional tranny cooler it made a quite a difference;

http://www.*******club.com/tech/tranny_cooler.html

If you are concerned about redicing flow to the main rad, you could mount one somewhere else and have a fan for it. I think someone else did that ?Great write-up Phil. I thought of your problem when I read Fubar's post.:)

[KenP]

Fubar, FWIW, our old truck NEVER got hot. Even during the VA Beach to Moab run. Heck, our new truck doesn't get hot either. Somethin's rong, brotha.

Find a place to mount a 4 pass trans cooler in front. Look hard, I know there's space. That'll solve your problem.

Keep us updated, buddy.

[Fubar]

Ken thanks.
mount a trans cooler up front, where?

there are 3 coolers stacked (4) if you count the inncooler for the s/c in front of the radiator.

The 3rd in line or 2nd largest I'm guessing is the current trans cooler, don't know what the other two are.

Perhaps if the front most one bracketed by the black braces can be relocated a new or additional trans cooler could go in it's place. ?

[H2 Ranger]

Check out this article talking about xsmn cooling;

http://www.carcraft.com/techarticles/116_0308_cool/


Also consider the following mods:

Shiftplus electronic Improver kit

Shift improver kit (for valve body)

both from B&M

Both of these kit reduce slippage and heat buildup

[drmiles]

Fubar, I have 05 with the SC, and a 10,000lb trailer. Not many hills here but we do have 100+ days. Transmission has never run hot!! I use Royal purple Synthetic. My 03 Tranny ran hot just before 2nd and 4th gears failed!!! :(

[Fubar]

Check out this article talking about xsmn cooling;

http://www.carcraft.com/techarticles/116_0308_cool/


Also consider the following mods:

Shiftplus electronic Improver kit

Shift improver kit (for valve body)

both from B&M

Both of these kit reduce slippage and heat buildup

Ranger thanks for the info and the suggestions. The article was informative and I'm seeing that there are options out there. I just need to find a quality repair shop here in town. Thanks again.

[Fubar]

Fubar, I have 05 with the SC, and a 10,000lb trailer. Not many hills here but we do have 100+ days. Transmission has never run hot!! I use Royal purple Synthetic. My 03 Tranny ran hot just before 2nd and 4th gears failed!!! :(

Well that sucks. Define or explain for me if you can exactly what was happening when your trans ran hot before you suffered gear failure. Were you towing your trailer, climbing mountain passes I mean really working the trans? Or was it getting hot during normal day to day use?

I'm thinking my simplest short term solution is reduce the number of trips I make in the H2 to Ca since it's on that route that the trans seams to be having its issues. Driving around town the trans has yet to get hot. I have something else to drive so not taking the H2 to CA isn't a big deal. It's an inconvience but not a big deal.

I'll continue looking for a qualified shop here in town. I agree with all of you that I have some kind of problem with my trans.

But it's kind of like going to the doctor, you get there and whatever was bothering you enough to go in the first place refuses to surface while you're there and you end up asking the doc to fix something he can't see is broke...

Vegas is flat there is a 9000ft pass going North on I-15 toward I-70 which has yet to cause a problem for the trans and then the two 4000ft passes on the way to Ca. Getting to any of these is a 2-4hr journey which is a bit much to ask a mechanic to commit to in an attempt to duplicate the problem. What I've heard from a couple places I've been to is drive it till something breaks..:confused: Ahhh NO I don't think so. Needless to say both those shops lost any potential bussiness I may have brought there way. I'm about frustrated enough to put the H2 on a flat bed and have it towed to HGW.

[kodiakz]

Damn!! I just started having the exact same issues with the same setup. I can run around town and not have any problems. The minute I go up a little pass, both motor and tranny heat way up very quickly. I do believe that it could have something to do with the intercooler's heat exchanger blocking the other coolers. I also might look into the idea of putting in a heat sheild since that left with the stock exhaust. I also noticed that the engine temp will immediatley jump to 220-230 range if I run the ac on a hot day. I have had many other s/c gm motors and they never ran hot like this one.

Fubar, what size radiator did you put in and has that completely solved your motor temp issues?

What do you guys think about putting in some sort of slotted insert in place of the black plastic one in the hood for more air intake? I think I saw one on an H2, but if I remember correctly, it looked like a retarded scoop:confused: Does the programming done to the pcm affect the temps at all? I know that the programming for the shift points/firmness could affect that side of things but what about motor temps?

[Fubar]

Kodiakz,
I'll have to check with the shop that did the install of the radiator for the size. I know it holds 3 extra gallons and I believe was 2 inches thicker then the stock unit. I know the radiator would not work with the H2's stock clutch fan in place it barley fits with the electric fans.

I would think that any quality radiator shop should be able to get one for you or have one made. It is made out of the same material as the stock unit it's just deeper/thicker. I can tell you although just my personal opinion backed with some research and personal observations, to stay away from aluminum radiators.

I'm still considering a deeper trans pan:
http://www.maghytec.com/index.asp?PageAction=VIEWCATS&Category=3

I still need to get a hold of them to verify if the pan they are offering will fit the model of trans in the H2. The "Hydra-Matic 4L65-E" is not listed as a trans that their pan will fit on.

I also looking at one or two additional trans coolers to be placed in the front grill next to the inner-cooler for the s/c but the available space is only 8x8.5 so I'm not certain I can find anything to fit that space, then there is the further reduced air flow to consider by adding anything to the front grill area.

Removing the existing trans cooler and replacing it with something larger seams like the most do-able option but I'm still researching.

[Fubar]

Oh and on my recent trip to ca (last weekend) the engine coolant never got above normal 210 even though the air outside was 100-110 in places.:D So I'm pretty sure the larger radiator has solved my engine cooling problems.:D Even while climbing the mountain passess with the a/c on the engine temp never got above normal. The trans on the other hand... well thats another story. I had to pull over twice and sit with the trans in park for 10-15 minutes till it came back down within its normal range. :mad: And yes going threw Death Valley at or around midnight it was still hot as h.e.l.l.

[kodiakz]

"I had to pull over twice and sit with the trans in park for 10-15 minutes till it came back down within its normal range"

How many times can you do that without damaging the tranny??

[Fubar]

"I had to pull over twice and sit with the trans in park for 10-15 minutes till it came back down within its normal range"

How many times can you do that without damaging the tranny??

don't know. keep an eye on the trans fluid I guess. Hopefully I'll get the issue fixed before it becomes a larger problem.

[kodiakz]

Did you try Magnusun tech line and see if they have any suggestions or have run into this issue? May give them a jingle tomorrow and hope they have a solution.

[Fubar]

good luck.
they will probably tell you to get a Ron Davis aluminum radiator. Don't do it.. find another option.

I'd have your trans checked by a qualified mech to make sure there is nothing actually wrong with it. If he says it's ok then get a trans cooler and a deeper trans pan.

I spoke the folks at Mag-hytec today (jerry) 818-786-8325
http://www.maghytec.com/index.asp?Pa...ATS&Category=3

The pan will fit our transmissions. just make sure you've got more then 4 1/2 inches between the exhaust cross over pipe and the flange where the pan bolts to the bottom of the trans.

If not then get a trans cooler at the very least.

Personally I'd have someone route the trans fluid lines out of the radiator and plug the holes. Leaving the stock trans cooler in line will probably be a good thing just add a secondary cooler.

[Fubar]

http://www.thermotec.com/products/full/11600/11600.html

It was also suggested to me today to look into this. especially if a deeper trans pan is used.

[H2 Ranger]

I have read a lot about transmissions lately and would like to make some Preventive Maintenance suggestions that might help concerning overheating:
Transmission temp: a Lead Builder says 175 degrees. Another says Transmission lasts longest 175 degrees.
Excessive heat can cause the oil to break down: Leads to varnishing of internal parts, from the burnt oil, provides more resistance to internal bearing and clutch surfaces, Clutch material becomes softer and more prone to wear.
If your engine is running at say 210 constantly then expect your transmission to run the same as they are joined at the radiator in a stock configuration (supercharging makes and generates more heat ).
Transmissions have filters: The filter collects particles of Clutches and Small metal shavings. The oil supply is drawn from the pan so the oil supply will slow when the filter is clogged.
If your bands are out of adjustment overheating can occur.
If your oil lines are clogged expect overheating
If your exhaust is too close to the transmission expect increased temperatures.
If your Engine Exhaust is too restrictive (clogged cat converters) the engine temp can increase.
If you have internal wear of parts overheating is not uncommon.
What are some things you can do to prevent overheating?
Do your scheduled maintenance and in some conditions do it more often. If you go off road or tow often, consider it not normal condition as the transmission works harder thus building more heat.
Do your filter changes: a clean filter will keep your fluid moving unrestricted
Have the mechanic check band adjustments: As the clutches wear they need adjusted and clutches that are not properly adjusted and lead to heat buildup.
Supercharging = More heat keep an eye on your gauges and temperatures.
More fluid capacity means better temp control: additional coolers, larger oil pans, in line thermostats, etc. can help you control heat.
Consider separating the cooling of the Transmission and Engine coolers: Often the temps vary from engine and transmission the engine often runs 20 or 30 degrees hotter and this decreases transmission life. A word of caution if you live in cold areas Canada, Alaska, etc. The Radiator provides preheat for the transmission and you need it when your oil is colder. I would not recommend rerouting the Oil Supply from the radiator in this circumstance.
Keep the Radiator surface clean: Allowing the surface area to be clogged with dirt and debris hampers good heat transfer. Keep those cooling fins washed and clean as much as possible.
Go to your dealer and ask: See what the latest warranty claims have been about or even talk to the mechanic he works on them all the time. These guys are a valuable source of information and can really give you ideas in what to look for.
Exhaust Maintenance is important: Often we ignore the exhaust accept when it is leaking. Cats and exhausts can become clogged and internal passageways loose and broken. Thermal wrapping exhaust can keep heat away from transmissions. Replace suspected exhaust components or consider larger diameter exhausts. Consider rerouting exhaust systems.
After market additives can help reduce heat: There are some synthetic base oils that reduce friction and that leads to reduced heat.
Consider higher volume Fans, thermostats, and aftermarket Fan systems: After market fans and thermostats can make the engine and transmission run cooler providing more surface area temperature control.

Waiting till the problem is present can lead to damage that may require you to have the transmission rebuilt. While the list is not everything it can provide a good basis to start and some ideas to assist you. All said and done overheating may be a sign of internal damage and not a lot you can do about it accept Inspection and possibly rebuilding of the Transmission. Happy Motoring!;)