Re-gear and 4.0L 42RLE

[bmonday]

OK, I have an LJ running 33" tires, 4.0 motor and auto tranny. I upgraded to 4.88s and think it was a great choice. I very nearly went with 4.56 and was talked out of it, thankfully, by the guys over at the JeepsUnlimited boards.

I pull a fairly heavy M416-based trailer, and don't have too much trouble maintaining 60-70 speeds on modest hills.

That said, I also have a supercharger in mine, which skews the results a bit.

 

[titleguy]

My opinion on the 42RLE is if you have one installed from the factory, it's not necessarily a bad tranny, but if I was going to the trouble of doing a swap, it's not what I would use. It's not particularly strong or well supported by the aftermarket (no deep pans available---although that may change with the AA Rubicrawler hitting the market). It's also computer controlled with no standalone computer I know of.

I would go with a 700R4 or a 4L60 (same tranny) non-computer controlled. It has overdrive, a nice low first gear, reliable as hell, tons of aftermarket support, and parts are available everywhere. The only downside is adapters are a bit $$, but you only have to buy those once and if you change your mind down the road you can get most of your money back on pirate because guys are always using them.

 

[86cj]

Most folks on the Rubicon board say 5.13's with 33's and for sure with 35's.
4.88's with 33's is the route I'm going, I have no desire to go to 35's.

It seems to me that 33's w/4:88 ratio would work great, (I like the 4:88 RPM's in 3rd best) but when you shift to the deep .69 O/D, a 5:13 gear ratio gives a final drive ratio of (3:53 vs 3:36) which makes it easier for a stock engine to push a heavy Jeep and it's big tires.

I noticed last trip if I went fast enough to get the RPM's into the mid 2000's in O/D, the transmission could stay in O/D under more load, sort of telling me what it wanted. I am going to try 5:13's and if I can't live with the RPM's on 33's, I will get some 35"s when these wear out.

I am going to go with JK outers on my replacement D44 front axle, the bigger U joints and 12" rotors w/calipers will be nice and will work with my wheels. I can use my TJ style HD Currie tie rods which give no bumpsteer, but I like the crossover style steering of the JK and am looking at my options for the JK knuckles.

 

[trail-explorer]

I wouldn't consider anything less then 4.88s with a 42RLE and 33s.

Here's a pretty decent write up:

http://www.rubiconownersforum.com/phpbb3/viewtopic.php?f=38&t=53777

 

[Jeffb79]

go 4.88s with the 42RLE, you'll be wishing you had if you went with 4.56.

as for the rubi 44 axles only holding 33" tires.... that's kind of a weak statement.
In stock form I wouldn't run larger than 33" tires. With upgraded shafts and u joints it will handle 35s just fine. With trussing, different locker and upgraded outers you can run up 37s without much problem.

 

[86cj]

I wouldn't consider anything less then 4.88s with a 42RLE and 33s.

Here's a pretty decent write up:

http://www.rubiconownersforum.com/phpbb3/viewtopic.php?f=38&t=53777

He has the right Idea, It's all about the Final drive ratio in O/D......

It feels weird gearing my Jeep for optimum Hwy performance and then picking a 5:13......Just Sayin'.........


Thanks for the input everybody...