tire size and gear ratio

[dhreeves]

I have the chance to get a set of 31x10.50's and a three inch lift for about $250.00 for eveything but I don't have the money to re-gear. I have an '89 4.0L with a 5 speed so I have 3.07's. Anyone have experience with this combo? I know I will need to re-gear I was just wondering how miserable it will be to drive in the mean time.

Don

 

[LAWNMAN323]

I had 307's with 30X9.5 tires, my truck was pretty quick before the lift- 4.0L, 5spd. No complaints. I don't imagine the 31's would be too bad. You plan on towing anything??

I switched axles to 355 gears with 33's, the price was right.

Scott

 

[Kejtar]

For stick... I'd recommend 4.11's That's what I am running on mine now and it seems just about perfect. If you plan to go any taller (bigger tires) thoguh think about 4.56's

Kejtar

 

[Kejtar]

oh.... I kind of missed the main point of hte post... sorry... I had at one time 235's with 3.07's which was surviveable.. but tall hills and tall climbs on the freeway were terrible

Kejtar

 

[Dirk Funk]

I run 31 MTs with 3.07, 5 speed and 3" lift. It works, but isn't great.

 

[kelly klassen]

I've had the same (5 spd 3.07) but with the newer (98) H.O. engine. 30x9.50s were managable, but I geared to 3.73 with the expectation that they'd be very close to stock when I put on the 31s. I was very happy with this setup over the old 3.07s. While I still had the 3.07s, I tried on my buddy's worn out (slightly smaller) 31s for a day and found it barely adequate. Especially off road with the little bit of playing around in the gravel pit we did. I'd have to agree that you can get away with it, but you won't be happy. With the 5 spd you *should* be running at least 3.73s if not 4.10s. The auto tranny soaks up a lot in torque convertor, but the 5 spd is not very forgiving with gears. The redeeming factor is the incredible torque range we enjoy with our good ole 4.0s. However running so low RPMs, you can expect to increase your carbon buildup. Best of luck.

 

[kelly klassen]

By the way, go for it!

 

[woody]

I've ran 33" with 3.07 an a 5 speed as well as presently with 3.55 and an AW4 (it sucks)

I didn't have a point of reference, since i bought the 5spd jeep with 33s already installed...but when I finally got 4.56 in there, it was like an extra 2 cylinders out of the 4.0.

Can't wait for a few more weeks and I'll be back to 4.56 in the auto-Jeep plus an air-tube/K&N too! Be in hawg heaven I will

 

[thompson97]

i'm in a similar situation. i have a '97 with the 5 spd, 4.10's, and 30's right now. but i'm putting my lift up to 6.5", and will easily be able to clear 33's. my dilema is... should i go all the to 33's(will it feel like stock), or should i settle for 32's which i know would be sufficient. also, i haven't added any performance products, i.e. cat back, intake, tec. but plan to in the future. how much should that be taken into account? thanks.

 

[shizza-my-nizza]

If you are tight for cash you will be fine with 3.07's and 31's. That sounds like a pretty decent deal if I read it correctly. 3" lift and (4) 31's for $250. I have had 32" bfg's with 3.07 gears for at least a year maybe more. I am not saying it is ideal. In fact it is not. But you can get away with it as long as you need to until you get lower gears. 5th gear will be pretty much useless except for a long downhill on the highway. Hopefully I can get my D44 installed and gear the front to match because it has 3.55's still not perfect but better than 3.07's after that will be a detroit in the 44 with 4.56's.

 

[Eagle]

My '88 MJ had 3.07 gears when I first bought it. With 31" tires it was horrible. Lousy acceleration, unable to maintain speed on highway upgrades, and it really makes the clutch work hard. I don't think you'll be a happy camper with that setup. The crawl ratio is worse than terrible.

I re-geared with 3.73s and that puts the final drive ratio exactly equivalent to 3.55s on stock tires. I really should have gone to 4.11s, but I bought the gears with the intention of going with 30" tires, then my brother gave me a half-worn set of 31s so I'm driving them until they die (which may be soon).

 

[red87cherokee]

I run 31 MTs with 3.07, 5 speed and 3" lift. It works, but isn't great.

Same setup I have (except different brand tires). On the road, the biggest difference is that 5th is only really good at freeway speeds, and hills that could be taken in 4th gear with 235/75r15's now require me to lug down to 45 or 50, or downshift into 3rd gear.

As Dirk said "It works, but isn't great." On the other hand, I'm not rushing out to change gears (yet).

Off highway, I find that I am shifting into 4-Lo in areas that I could go with 4-Hi before.

BTW, the only reason I'm waiting to re-gear is I'm trying to decide whether I will be going with larger tires or stay with the 31's.

 

[Larry Shank]

I ran 31's with my 94 5spd and 3.07's for about a year.
Man, I could wind the gears forever.
Even towed my 18' jetboat.
Don't know how I did not burn up my clutch.
Go for it, but the next thing on your mind will be a gear change.
garentee it.

http://www.geocities.com/lancaster_xj/Jeep.html

 

[NMCruser]

i too am in the same dilema

what do you guys think of 31's with 3.73's and a 5spd. I love how she runs with 30's. will there be much of a difference?

 

[Eagle]

31s with 3.73s is a very nice combination for an all-purpose XJ. As I posted above, the final drive ratio is exactly the same as an auto with 3.54 gears and stock tires. Gets decent gas mileage, decent performance, and the crawl ratio is setter than a stock 5-speed with 3.07s.

Nonetheless, if it were primarily (or only) a trail machine I'd recommend 4.10s.