Anyone running 5.38 with 35" tire and a auto? The shop thats going to do my gears said the 5.38 are way too tall. He wants to put in 4.88. I have 4.10s now. Would 5.13 be a better choice? Why is the sky blue? How does a duck quack? Does the Chinese joint downtown really serve cat meat in the daily special? Hell I'm just going nuts trying to figure this out. I almost want someone to tell me what the hell to do.

Wow . . . Thats better now . . . OK, not really, just a bit more info would be nice.

Thanks

 

bump, help a brother out.

 

I did a ton of research and read that 5.38 is too tall for the D30. I was further advised to go with 5.13s for my auto with 35" tires. If you think about it, there really isn't a large difference between 5.13 and 5.38 anyway.

BTW, HUGE difference between my stock 3.73 with 35" tires and my 5.13 + Flashpaq! Feels like a completely different vehicle. Haven't had a chance to try out 4 Lo, though ... should be interesting!

 

well in all your research I hope you also found that noone makes 5.38 for the JK D30 anyways, 5.13's as tall as you can go

 

I went with 5.13 gears on mine and very happy with the out come. It's worth every penny.

 

Is regearing really necessary when getting 35s? One thing I never hear people talk about is....does regearing affect the vehicle's warranty? Say something goes wrong with the Jeep. Is the dealership going to give me a hard time about covering or servicing any type of job because I lifted and regeared my vehicle?

 

Good thread. I plan on regearing to 5:13 with Dana 44's but I was wondering about the break in period as well. Thanks everyone.

 

I just installed 5.13's in my 44's with 37's and I am very disappointed with the highway speed and not being able to go above 60-65 and hold it in Overdrive on my Automatic on the flat 60 fwy. I wished I had gone 5.38 and they do not have the programming ready for the 2010 JK yet.

I did do the Intake.

Chido

 

Black-X----Just about any mechanical mod you make on your Jeep has the potential of impacting your warranty. Most of all it depends on your dealer, mine is not mod friendly and looks for any reason not to honor the warranty and good luck getting any help from Chrysler itself, They will tell you their dealers are independent and they have no control over them.

 

Just for clarification.....as you didn't reprogram, are the speeds you are trying to reach (mentioned above) based on what the speedometer says, or based upon a gps, etc?

I ask, because with 37's, your speedometer is off by ~ 13.5 % or more (Depending upon what tires your's was calibrated for...), so you're really going closer to 75 when the speedo says 65 mph, etc.

And - you don't say whether the speed was hard to reach because the engine was winding out (RPM too high), or because it was too weak to even get the rpm to climb, etc.

For example, with 32's, 60 mph is around 2k rpm in 6th

37's would drop that rpm to ~ 1,730 rpm at 60 mph

5.13 gears would then RAISE that rpm by ~ 27.3 %, back UP to ~ 2,202 rpm at 60 mph

This means 5.13's have more than compensated for the 37's as far as final drive ratio...


...and you are now just fighting the extra drag and rolling resistance of the larger tires in addition to the gearing issues.

And - when your speedometer is telling you you're going 65 mph, you're actually going ~ 9.2 % more (After the tires and gears are corrected for...) or ~72 mph.

So, IF the above were correct, its 72 mph you are trying to maintain in the same way that you WOULD have tried to go 65 mph...making the jeep seem slower, etc.



If you did 5.38's instead of 5.13's, that would ADD ~ 4.6% to your rpm at any given speed, and make the speedometer off by that amount more than it was already off by.

IE: You'd be at 2,308 rpm instead of 2,202 in the above example....a difference of only 106 rpm.