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tyler1bo
01-31-2012, 01:09 AM
Alright guys I need to regear my '08 SUT from the stock 3.73's..what would my best option be? Keep in mind that mine is the new 6-speed. My 3.73's just aren't strong enough to push 38's with 20's. Help please!

EuroHummer
01-31-2012, 01:16 PM
I went with 4.56s. I have 37s. With the 38s, you might want to go to 4.88s. Depends on how much you travel on the highway, and how much time offroad.

tyler1bo
01-31-2012, 02:28 PM
Right now it's more highway than offroad..my truck is about 90% street 10% offroad

guruerror
01-31-2012, 05:28 PM
Check out this 'gear calculator': http://www.4lo.com/calc/geartire.php

My 05 had 4.10s stock, when I move to 37s it started to drag ass, so punched my info in the 'calculator' to find out what gears would give me an effective ratio closest to stock.

The tire size change had reduced my effective ratio to 3.88 and the calculator indicated that 4.33s would put my effective ratio back up to the stock level. Since they don't make 4.33s I went to the next 'lowest,' 4.56s, and have been a happy camper every since.

tyler1bo
01-31-2012, 07:03 PM
It's showing me at 4.05..do you think 4.10's would be enough?

charles06
01-31-2012, 07:03 PM
I did 4.88's with 38" Toyos and it made a HUGE difference. That gearing works well with my new 40's as well.

tyler1bo
01-31-2012, 07:08 PM
Does yours have the 4-speed tranny or 6? Mine has stock 3.73s with a 6-speed. I punched my numbers in the gear calculator and it's saying I should move to 4.10s

2010_5thgen
01-31-2012, 07:27 PM
those 6 speed tranny's are crazy. i drove my buddies 08 yukon denali and that thing was just stifting like crazy. seemed like at cruising speed, it didnt know if it wanted to be in 5th or 6th.

regearing should help with MPG and the pickup right? ive noticed mines a bit sluggish off the bat and it stays in 2nd gear longer than it used to. is this normal with a lift and larger tires?

tyler1bo
01-31-2012, 07:42 PM
Yes it should help both MPG and pickup..surprisingly though my I reset my CPU after the lift and I'm currently getting 11.5 hwy/city driving, which is brilliant for me. I would like to regear though because my shifting is getting sh*tty and slow, feels like my tranny is slipping. I took it in the shop to see if my tranny was okay and I think it's just my gears not being strong enough..I slip from 1st to 2nd kinda..

charles06
01-31-2012, 08:11 PM
I have the 4 speed.

I always wonder how accurate those MPG readings are after I've changed the gearing, tire size, and used a tuner.

tyler1bo
01-31-2012, 08:21 PM
I still think it's pretty close..course I'm not stompin on it either..just cruisin mostly besides hwy. I think at worst i'm getting 10

charles06
01-31-2012, 08:49 PM
Yeah, I try not to get too caught up in it. I just tell myself I'm getting more than what shows. Haha

guruerror
01-31-2012, 09:04 PM
Does yours have the 4-speed tranny or 6? Mine has stock 3.73s with a 6-speed. I punched my numbers in the gear calculator and it's saying I should move to 4.10s
I've got the 4-speed...

If the calculator says 4.05-4.10 then the 4.10s would put the performance closer to what you were used to before the tire size change. But to really get things back in order you should also use a programmer to let the 'computer' know that you've change the tire size and gear ratio; that should get your shifting and whatnot straightened out.

tyler1bo
01-31-2012, 09:56 PM
I have a programmer. I'm using a superchips flashpaq at the moment.

guruerror
01-31-2012, 10:23 PM
You should be good to go then...looks like the Flashpaq allows you to adjust tire size and gear ratio just like my Cortex.

With some 4.10s and a re-program you should get your pep back, your shift points and cruising speed will be closer to normal, your speed-o will read correctly, and you may even get a whole MPG out of it.

tyler1bo
02-01-2012, 02:05 AM
Not a WHOLE MPG!!!! ;) Yes it's either 4.10's or 4.56's..

Bimmer9938
02-01-2012, 09:47 AM
I did 4.88's with 38" Toyos and it made a HUGE difference. That gearing works well with my new 40's as well.


How much did it improve your MPG?

2010_5thgen
02-01-2012, 02:06 PM
so 4.10 or 4.56 are good for 38" tires? i think im going to start with a tune, but im gonna take mine to a shop that has a AWD dyno to do a custom tune.

tyler1bo
02-01-2012, 04:40 PM
A custom tune will probably be the best. You probably need to look at 4.56 to 4.88 gears. I believe you have stock 4.10s. I think I may go with 4.56 because I'm not sure 4.10s will be that much of a difference. Do any of y'all know a good place to find gears?

guruerror
02-01-2012, 05:30 PM
www.trailduty.com...more specificially: http://www.trailduty.com/index.php?cPath=112_118_436&osCsid=06204aafa0fce370230cd11dd8a5fc9b

MVR 155
02-01-2012, 05:35 PM
If you struggling with the idea of 4.10 vs. 4.56 then I would suggest using the calculator to see what your highway cruising RPM's will be, if you will be fine with the 4.56's then I would go that route as it will likely yield better mileage and pick up around town and have a minimal effect on highway mpg's.

Also keep in mind that while 4.10's will get you back to stock RPM's you are still moving a larger amount of unsprung weight with larger wheels tires so you likely will still be a bit short on performance vs. stock with the 4.10's.

tyler1bo
02-01-2012, 06:12 PM
I think that just convinced me! I will look at 4.56s on trailduty.com for a decent price. Thanks for the help guys! I would have known what to do if I had the 4-speed but I wasn't exactly sure with mine.

2010_5thgen
02-01-2012, 08:59 PM
what have we determined would be good on the 4 spd? and how will the gearing effect highway driving along with city driving? i dont wanna be cruising at 65mph and 2500RPM or anything.

guruerror
02-01-2012, 09:11 PM
I guess I don't see how 'how many speeds' your tranny has would effect a person's decision on what gears to purchase for the diffs.

It's all about the ratio of the drive shaft to the diffs...unless I'm missing something.

tyler1bo
02-01-2012, 11:09 PM
For your truck I've seen/heard 4.56s and 4.88s..charles06 runs the same setup as us and he has 4.88s, he loves them.

H2Much
02-02-2012, 02:49 AM
I too am running 4.88's and 40's on the tires; I love it and drives great on city streets and on highway. The only part where I am having a power struggle is when I get going over 70mph and there is any incline in the road. This will cause my ride to struggle a little bit on power and causes it to jump into 3rd gear. I am rocking the 4 speed too though, so I know that the power distribution will be different if you have a 5 or 6 speed, so keep this in mind.

I have been researching to see what is going to be the best option for me to fix this dilemma. I want to avoid the supercharger based on the ridiculous cost, so I am looking into the following: a turbo, a custom tranny, any little upgrades like a throttle body spacer, any other custom works to get the added muscle I need to roll at higher speeds. If it comes down to it and I end up having to go the supercharger route, than I will more than likely buy a new crate engine that is more powerful than my existing one and spend the $5 G's towards something that won't blow up.

Then again, I am always open to feedback from you pros out there who have been there, done that...

pwrhse2k
02-02-2012, 04:14 AM
I too am running 4.88's and 40's on the tires; I love it and drives great on city streets and on highway. The only part where I am having a power struggle is when I get going over 70mph and there is any incline in the road. This will cause my ride to struggle a little bit on power and causes it to jump into 3rd gear. I am rocking the 4 speed too though, so I know that the power distribution will be different if you have a 5 or 6 speed, so keep this in mind.

I have been researching to see what is going to be the best option for me to fix this dilemma. I want to avoid the supercharger based on the ridiculous cost, so I am looking into the following: a turbo, a custom tranny, any little upgrades like a throttle body spacer, any other custom works to get the added muscle I need to roll at higher speeds. If it comes down to it and I end up having to go the supercharger route, than I will more than likely buy a new crate engine that is more powerful than my existing one and spend the $5 G's towards something that won't blow up.

Then again, I am always open to feedback from you pros out there who have been there, done that...

Get a DMAX conversion!

Consider this....The GEICO commercial with the little piggy flying down a zip line of a snow capped mountain - Just before he passes the chump on the opposite zip line, he pauses and says "Pure Adrenalin...Weeeeee....Weeeeee?Weeeeee" That is the exact feeling you'll have after driving a DMAXed H2! GET A MF DMAX conversion!!! You will not be sorry. 'Nuff Said!

2010_5thgen
02-02-2012, 01:52 PM
Get a DMAX conversion!

Consider this....The GEICO commercial with the little piggy flying down a zip line of a snow capped mountain - Just before he passes the chump on the opposite zip line, he pauses and says "Pure Adrenalin...Weeeeee....Weeeeee?Weeeeee" That is the exact feeling you'll have after driving a DMAXed H2! GET A MF DMAX conversion!!! You will not be sorry. 'Nuff Said!
for what....around 25K.... there has to be a cheaper way to get good power without going boosted or swapping in a diesel.

charles06
02-02-2012, 02:33 PM
I'm still able to pull up slight inclines without the truck downshifting at speeds over 70mph. I think the long-tube headers made a big difference, too.

2010_5thgen
02-02-2012, 04:21 PM
i think im going to start with a tune before i jump into gears. that will be my last resort if i dont notice any improvement from the tune.

charles06
02-02-2012, 06:12 PM
i think im going to start with a tune before i jump into gears. that will be my last resort if i dont notice any improvement from the tune.

You won't. Same thing I did.

guruerror
02-02-2012, 06:19 PM
i think im going to start with a tune before i jump into gears. that will be my last resort if i dont notice any improvement from the tune.
I'd just do the gears...it's not terribly expensive or complicated...and it has DEFINITE gains that you will DEFINITELY notice.

...and, plus, you may be up for a diff fluid change anyway. Kill two birds with one stone.

Stellar
02-02-2012, 06:20 PM
I absolutely recommend 4.88's if you're going to spend the money for new ring and pinions. Throttle response will be dramatically better and if you choose to run 40's down the road or tow, you'll make it easier for your motor to get the power to the wheels.

tyler1bo
02-02-2012, 07:12 PM
This has become a good little thread..;) keep it up! And charles06 would you please post some pics of your rig!!

charles06
02-02-2012, 07:38 PM
I know. I know. Still being lazy.

I agree with the 4.88's. You won't notice the 4.56's enough.

2010_5thgen
02-02-2012, 08:13 PM
I'd just do the gears...it's not terribly expensive or complicated...and it has DEFINITE gains that you will DEFINITELY notice.

...and, plus, you may be up for a diff fluid change anyway. Kill two birds with one stone.
actually, before i bought my truck off the lease, i had all the fluid flushed and changed. now running royal purple in the diffs.
wont a tune be needed anyways if the gears are changed? not to mention i dont have my speedo matched up right.

2010_5thgen
02-02-2012, 08:14 PM
I know. I know. Still being lazy.

I agree with the 4.88's. You won't notice the 4.56's enough.
so 4.88's will be good with 38" tires? what will i notice after having them installed? and will anything be compromised?

guruerror
02-02-2012, 08:14 PM
Correct...you'll need to tune for the gears and tire size.

guruerror
02-02-2012, 08:16 PM
so 4.88's will be good with 38" tires? what will i notice after having them installed? and will anything be compromised?
Your highway cruising RPM will be higher but it should jump off the line...well, as much as a big metal box can 'jump.'

2010_5thgen
02-02-2012, 08:19 PM
will these work? http://www.amazon.com/Precision-GM9F488-Model-Pinion-Ratio/dp/B003EM73FQ

charles06
02-02-2012, 09:50 PM
Get 4.88's and a Superchips programmer. But set your speedo with a GPS unit as your reference for speed. I realized after some playing that I had to set my tire size smaller than the actual 38".

tyler1bo
02-03-2012, 02:51 AM
I was amazed at the performance tune on the
Superchips programmer, my truck came alive off the line. Seemed like it wanted to run instead of lugging around all the time.

H2Much
02-03-2012, 04:00 AM
Agreed. I run Superchips on my setup as well, really gets rid of the sluggish pull off of the line. I don't need a drag racer, but it sucks having a truck with the lift and tires that has no balls- definitely need the chip

tyler1bo
02-03-2012, 06:28 AM
Yes, the truck actually jumped better with the tune after all I had put on it vs. stock! I'm really interested to see how it runs with different gears..

2010_5thgen
02-03-2012, 03:10 PM
Your highway cruising RPM will be higher but it should jump off the line...well, as much as a big metal box can 'jump.'
i dont know if id like that though....running over 2K rpm at 70 or so.....doesnt sound good to me..not to mention about 6 mpg's. that'll drain my tank before i even get to Cleveland.

tyler1bo
02-03-2012, 05:22 PM
I'm wondering what that will do to mine too..my hwy miles are higher now than they used to be. City driving would be great..that's where it usually gigs me.

Hellz
02-03-2012, 06:51 PM
screw the Dmax ( sorry to those that did it)
waste of $25k for 5 mpg gain and lots of torqe and some HP on a used engine and unknown install and problems down the line.meanwhile, your paying more $ at the pump to fill the same 33 gallon tank.

same amount, you can buy another H2, do some decent mods to it, have cash to $$$ to actually fill the tank, and take the GF or wife out.

when i return from my deployment, my plan is to:

Regear to 4.88- $2000 ( rounding up and adding hidden costs)
new long tube headers and exhaust - $1500 ish
new tuner - $400

right now
2003 H2 @ 100K miles
8.9 mpg city (according to the DIC).. and i would guess about 10 mpg HW (maybe more, maybe less). i dont have a light foot. baby shifts alot, but i love cruising at 80 MPH. ( love the looks people give as i cruise by people ont he HW)
4.10 gears
K&N CAI
year old tune up ( plugs only)
Diablo Tuner
37 BFG M/T KM2 on 20 rims

thinking about possibly swapping the heads out and manifold to gain alot more HP.. but i think my tranny is under, but near its limits and not far from starting to feel abused. i would love to get a 6 spd tranny from a new H2 instead of the 4 spd i have now.

ill run this into the ground, and when the engine is dead, i will do a 600+ HP RWHP crate engine and a 6 spd tranny rated for 750 HP and do it all over again.

2010_5thgen
02-03-2012, 07:32 PM
has anyone ever put a 7.0 LS7 in a hummer? i know its pretty much made for racing, but a 427 would be pretty bad ass in these. 505hp....a good 150 more than stock and will bolt right in? sounds like a no brainer.....unless theres transmission issues. not to mention you can get them pretty cheap from junk yards or on line.....theres always some idiots that buy z06's and then wreck them right off the bat.

tyler1bo
02-03-2012, 08:45 PM
I've seen one with a Z06 cam. That's gotta be pretty sweet.

2010_5thgen
02-03-2012, 08:47 PM
Even doing a mild can would really wake these trucks up.

tyler1bo
02-03-2012, 08:53 PM
I would love to hear that. I think that truck also had dynatech headers, exhaust, 6 inch fabtech, 38x15.50 mud grapplers with 20x12 rockstars. It's nasty.