I have put a 4" lift w/ 35 12.50 16 Nitto mud grapplers on 16x10 sim bead locks. I knew some power would be lost but didn't expect this much of a loss. I just installed a Airaid and feel a small difference. But my main question is is safe to run on the freeway @ 70mph out of Overdrive? Will anything be damaged, besides my M.P.G ?

 

I have heard its bad for the transmission, but don't know that from experience. I am about to change my wheels too, I have a cold air intake, new exhaust, and Jet Performance Chip, I'm hoping I don't need to change the gears.

 

Im thinking I could shave some weight off the pig by switching to an aluminum wheel of the same size when more applications are available- I should have weighed mine before I mounted them but never thought it would be this big of an issue. Does anyone know what the approx, weight of the Cragar 352 D in a 16"x10 is? I can't find a weight listed- then i'll compare vs. aluminum.

 

I think your fine. As long as you are running up in the 2000-3000 Rpm range your okay. The overdrive would overwork your transmission if you used it.

 

I was okay with the power difference at first when I moved to 35" tires, but I have changed my mind after driving on the freeway and with the air conditioner on.

Here is a good discussion of the problem and fix:

https://www.jk-forum.com/forums/modified-jk-tech-2/5-13-gears-automatic-35-tires-report-observations-8716/

For the cost of those "performance" accessories, you could have new gears with much better performance and MPG. You figure DC went to different gears as they changed maximum factory tire size, so that would be the sound way to increase your performance and MPG after the tire size boost. Your car's components will run closer to factory specs and may save your argument if you have any warranty issues with the engine or transmission.

 

It's not the weight so much as it is you've changed your final drive ratio, change your gears and life is good.

 

I was sitting here reading some posts about what happens to the 4 door JK rubicon when you put on 35" tires...then i found some numbers that said what the avg MPG is with the 4.10 and the 5.13 gears...

So here we are:

Cost Justification for regearing to 5.13 (with 35" tires)

4.10 Gears: 13 MPG * 21 Gallon Tank = 273 Miles / tank
5.13 Gears: 15.5 MPG * 21 Gallon Tank = 325.5 Miles / tank

Difference of 52.5 Miles / tank
- Which gives you an extra 3.39 Gallons of gas at 15.5 MPG for those 52.5 Miles
at a cost of $3.00 / Gallon that is $10.17 savings / Tank

For one year, the savings is:
(assumption: 1 fillup per week)
$528.84

I found the prices of the superior 5.13 front/rear on quadratec:
$229.99 for a total of $459.98.

So, in basically one year you have paid for the gears (excluding labor if you aren't doing the work).

 

ok to answer the original question running 70 mph w/o overdrive will not hurt your engine at all. Last car i had ran 3500 RPMs in 5th gear on the freeway and never once had a problem with it. If you think about it, running over drive causes your transmission to down shift everytime you get to a hill putting more stress on the trans having to shift all the time (if u live where there are hills everywhere)

 

BigJerm- thats exactly what happens when I do not turn off the OD @ 65 mph Im running about 2750 rpm and the transmission does down shift constantly a gear, and Im not even going up any hills. I figured constant down shifting was worse than just turning it off. As far as I&I's comment re: using the A/C -your right, here in Phoenix its about 109 and A/C is a must which also robs power futher complicating power struggle.

 

35s and stock gears will hurt your tranny though. It will shift/need shifting more and theat creates wear and most of all heat.

Regearing is a must for 35s and bigger, 5.13s would be perfect. You gain mpg, all your power and some and it keeps you from burning up a tranny.