4.56 gears?

[Mike97ZJ]

Well I think the engineers have to compromise with the bean counters.

My theory is this:

The lowest gearing GM offers in any of it's trucks is 4.10. So going to 4.56 would be an added expense for them, as its not an off the shelf part.

The trucks with the 4.10's are 3/4 and 1 tons, and those come with 245/75R16's stock, which are only about 30" tall.

And I actually believe that in some cases, lower (numerically higher) gears can IMPROVE gas mileage, depending on tire size. With the lower gears, the engine has to work less to accelerate. Since it will accelerate faster, you don't have to be on the gas as much to get up to speed.

Now maybe higher gears CAN help increase gas mileage, but only on flat or downhill highway with the cruise set at 65-70mph. But who drives 100% of the time on perfectly flat highway?

Anyway, just a theory and something to think over.

I've already done the 4.56 gear swap on my imaginary Hummer.

1997 Grand Cherokee TSi
It's got some lift, skids, and rock rails, among other things.