opened the rear diff and a silver shower came out. time for new gears. something i needed to do anyway. 5 speed manual 97 sahara 4.0l with 35" tires. should i be going with 5:13 gears?
Which gears should I go with?
- Thread starter Jon Wildes
- Start date
I loved my '97 TJ's combination of 4.0, 35" tires, and 4.88 gears on both the highway and offroad. 5.13 seems a bit low if it will see much highway time though it'd be great for a mostly offroad Jeep.
OP
OP
Chris according to that chart it said 5:13. That’s what led me to pick those gears. But they are saying 4:88
I would lean towards 5.13 myself. That would be a slightly lower rpm than my current 33s/4.88/5 speed, which I like quite a bit.
OP
Even if it’s mainly a highway Jeep. I wanna go off-roading some but nothing crazy. At least at first.
Mine is a daily driver that does just fine on the highway.
Grimmjeeper.com
I set mine up for 3k rpm at 75mph.
Jerry, when you ran this combination, did you have to downshift much from 5th gear on the highway? Ever tow a small trailer with this combination?
OP
fourmustangs
TJ Enthusiast
is there data showing rpm and shifts with 42rle as this posts says i should be running 5.13 gears for 33" tires currently still have 4.10 gears
That is correct.
My old TJ was a 42RLE with 33s and I installed 4.88 gears. I always ended up regretting that, as 5.13 would have been the better choice.
The 4.88 gears were better than the factory 4.10, but with that horrible .69 overdrive ratio in the 42RLE, the 5.13 is a much better choice.
You'll sit around 2400 rpms at highway speeds, which is where you want to be. The 4.0 should not be below 2000 rpms at highway speed when cruising.
According to Grimmjeeper...
NV3550/34”/4.88 = 2640rpm @ 75mph
NV3550/34.5”/4.88 = 2602rpm @ 75mph
NV3550/34”/5.13 = 2776rpm @ 75mph
NV3550/34.5”/5.13 = 2735rpm @ 75mph
NV3550/34”/4.88 = 2640rpm @ 75mph
NV3550/34.5”/4.88 = 2602rpm @ 75mph
NV3550/34”/5.13 = 2776rpm @ 75mph
NV3550/34.5”/5.13 = 2735rpm @ 75mph
Second this! DO NOT re-gear the 42RLE with anything that will put you below 2000 rpm cruising. I'm on 35's with mine and just purchased 5.38s to be able to keep highway speed. Haven't installed them yet but based on everything I've researched here i'll finally be able to use my OD on the highway!
Second this! DO NOT re-gear the 42RLE with anything that will put you below 2000 rpm cruising. I'm on 35's with mine and just purchased 5.38s to be able to keep highway speed. Haven't installed them yet but based on everything I've researched here i'll finally be able to use my OD on the highway!
You'll like it! I have a 42RLE with 35s and 5.38 gears. On the highway I sit around 2300 rpm or so, which is perfect. Right in the power band where it needs to be.
fourmustangs
TJ Enthusiast
Second this! DO NOT re-gear the 42RLE with anything that will put you below 2000 rpm cruising. I'm on 35's with mine and just purchased 5.38s to be able to keep highway speed. Haven't installed them yet but based on everything I've researched here i'll finally be able to use my OD on the highway!
My 33 and 4.10 I was cruising at 2500 at 75mph this last weekend on a 4 hr trip. It does go into OD early like 45mph and that's around 1500rpm...if I'm not going over 50 I usually turn OD off
In 4lo and 1st gear I have to be on brakes hard to not start crawling.
That's the problem I have, and its driving me crazy about what gear ratio to use. Of my highway usage, it's rare I'm above 65 MPH. The 0.69 OD only helps with highway cruise. Using GrimmJeeper's calculator, and my set up, I will be turning the OD off with 3.73, 4.10, 4.56, 4.88, and 5.13, when I'm driving 45 MPH. I wish I could actually try some different ratios before buying.
With 35's, 5-speed, and 4.88 I'd only have to downshift to downshift to climb a grade or to pass traffic. I was usually towing my pop up tent trailer whenever I was on the highway. It towed so well I literally had to regularly check the mirror to make sure it was still there.
But don't confuse the performance of 4.88 with the 5-speed with the abysmal performance you'd get with 4.88 with the 42RLE 4-speed and 35's.