Regearing for 35's

[Walking Tall]

Hello folks,
I have 06 LJ hardtop ( non rubicon) automatic trans. Stock gears in it now 3:73
I'm putting on 35's next week. Next step is regearing , I'be read a lot of posts on here about regearing. I'm getting mixed opinions lol. This is not my Daily driver. Weekends only for off-road nothing to extreme. Don't wanna lose my highway ability so I can get travel to other areas.
My local shop is strongly recommending 4.56 & not to go with 4.88 or even 5.13 or more. They are saying that the gear will be to small & therefore be weak I will have a problem breaking it.Really??? Sounds like a lot of people on here are running gearing in the 5.?? Without issues.
Help please!

 

[Jerry Bransford]

That shop is giving you totally bad information where your Jeep with its 42RLE automatic transmission is concerned.

The ratios they suggested are only appropriate for a manual transmission. 4.88 is actually the preferred ratio for 35's and 5-speed manual transmission. I ran that combination in my previous TJ with its 5-speed manual transmission for years. Perfect on the highway and offroad.

However, manual and automatic transmissions require different axle ratios. What ratio works well with a 5-speed manual transmission would absolutely suck with your 42RLE 4-speed automatic. That's what that shop you went to doesn't get.

Your 42RLE automatic transmission has an extremely steep Overdrive ratio which drops the rpms by 31%. 5.38 is actually preferred for 35's but you can only gear to 5.13 due to your front Dana 30 axle.

After my previous TJ was stolen, I bought a used TJ configured with with 35's, 42RLE automatic, and 4.88 gearing. The 4.88 is good offroad but it absolutely sucks on the highway due to it producing too low of an engine rpm. The engine is always lugging on the highway and I'm always having to turn the Overdrive off to get the engine rpms up enough to stop it from lugging.

Kids in offroad shops normally drive big lifted trucks with big v8 engines built for them by someone else. Few know how to to gear Jeeps properly, fewer yet know how to gear them properly when you have the 42RLE automatic transmission.

Not to mention they're only repeating untrue internet myths where it comes to the strength of gear ratios like 4.88 (which has been an extremely popular ratio in TJs for 20+ years) and 5.13 which was severely tested in the toughest rock crawling trails for years before it was finally released for sale. It too is a very popular ratio on very tough trails where it holds up just fine. That they're claiming they're not strong enough is absolute pure BS. They really (!) don't know what they're talking about.

That shop is so clueless about what would work well on your Jeep with its automatic transmission that I'd find a different shop to work with.

 

[glwood]

Yeah, if I had a dollar for every time I've read 'my local shop said x.xx gears were too steep' I'd be rich. A lot of shops seem stuck on the rpm conversion charts, with no consideration for the engine/transmission factors in real life.

 

[Rob5589]

Jerry summed it up nicely. Don't waste your hard earned dollars on anything other than 5.13's.

 

[mtngoattj]

I agree with jerry

Sent from my SM-G930T using Tapatalk

 

[Walking Tall]

Thanks for the advice , I'll defidently go with the the 5:13 then. Is it the side of the housing on the Dana 30 front that won't let me go with the 5:38's?

Would you guys recommend install lockers at this time to save some money. The (shop)
Is recommending Detroit lockers, simple & nothing to switch on & off like the ARB

 

[Rob5589]

If you are going with lockers, yes, do it all at the same time. I prefer the Detroit locker over the ARB but, both are great and have pros and cons.

 

[Jerry Bransford]

Thanks for the advice , I'll defidently go with the the 5:13 then. Is it the side of the housing on the Dana 30 front that won't let me go with the 5:38's?

Would you guys recommend install lockers at this time to save some money. The (shop)
Is recommending Detroit lockers, simple & nothing to switch on & off like the ARB

I loved my rear Detroit Locker, I still miss it (that Jeep was stolen) years later. However, the Detroit Locker is not a good choice for the front Dana 30 which flexes too much for it to hold together reliably.

I'd probably just go for the less costly Aussie lunchbox locker up front. Works well and holds together well. It does softly click/ratchet a bit when making slow turns when you're in 2wd like in a parking lot. For no clicking, the $100 more expensive No-Slip lunchbox locker from Powertrax like I used to run is silent. At least I couldn't hear it.