I see this question pop up A LOT on all forums and I've never seen someone simply make a thread that answers the question before it's even asked. Therefore, I shall answer the question once and for all to the best of my knowledge in this post.

Why re-gear? Well, my dear friend, that answer is simple. When you put bigger tires on your vehicle, you are changing the overall ratio that your axles spin at, which in turn changes your transmissions ratio, which in turn affects how your engine is spinning and how hard it is working to get your vehicle moving. Sounds complicated right? It isn't at all! You simply need to change the ratio so that your torque is replenished at the wheels. This in turn brings back and in some cases improves MPG and increases the drive-ability of your vehicle.

I heard I can see negative effects from re-gearing? You can see some negative effects in some cases. If your axle is already weak and you add more weight to it (the tires) and then reapply the full amount of torque to that axle, you may run the risk of breaking something. However, this is not an issue in most applications. The other situation may be if you gear too deep (4.88, etc.) you start losing the amount of material used in between each gear tooth which can weaken the ring and pinion themselves. This however, is once again not a risk in most applications. There are little to no risks when re-gearing in 95% of cases. In fact, it will save you some clutches in both manual and automatic transmissions since you won't have to rev them to the moon to get moving.

What gear ratio is right for me? Well, that depends on your tire size, transmission, engine, etc. honestly. However, I will give you a chart that I believe will help you choose the typical gearing that is needed.


Now, you can go up or down a size without having much negative affect. Some prefer to gear deep (I prefer deep gearing for offroading, towing, etc.) and some don't but this is pretty much the benchmark for gear ratios when it comes to XJs. You may want to modify it a little based on your engine or terrain.

Hope this helps! I'll let everyone chime in on their experiences and recommendations just in case I missed something. Feel free to ask questions!

 

i like deeper gearing myself. i used to run 5.38s with 35s and the only drawback was i wasnt comfortable cruising at 85 mph for hours at a time. loved it otherwise. you always hear of people complaining about not going deep enough. but almost never complaining about going too deep.

 

Yeah, I didn't include 5.XX gears mainly because you can't run them in the stock D30 as far as I know?

 

you can in low pinion dana 30's. but nobody wants to run a low pinion 30 lol

 

Lol, can't say I've never had one under a rig.

 

great contribution dood!!

 

I generally see the same ratios recommended no matter which tranny, but I know the TJ guys always suggest 1 step deeper for the manual transmissions. That might be because of the 3-speed auto though.

Not too familiar with the AW4.

 

I have some good links on NAXJA, but site's down right now

by "deeper", do u mean go numerically higher?... from what i have understood, u would go 1 step numerically "lower"... example, use 4.10's for 33's on a 5-speed, instead of 4.56's on an AW4

 

This is what I think, since the AX15 has a lower first gear. 5 speed XJs come with 3.07 and autos come with 3.55 so that makes sense

 

with a 5 speed you have much better control with the deeper gears offroad however. and the final drive ratio is close enough to keep the rpms around the same as an auto.

 

I started with the stock gears in my 96 5 speed with 31s, it was a dog on the highway (5th was useless) and 1st gear was meh at best. Did an axle swap out of a 2000 auto and drove around for a bit with the 3.55s in 2wd (only swapped the rear axle) and off the line acceleration didnt feel much different. Highway manners were much better with the 3.55s and 31s in terms of being able to maintain speed in 5th gear and even get up to speed faster (of course).
I then regeared both front and rear axles to 4.10s with my 31s, and they're awesome. I will say that first is more or less useless on the road unless you like to take the RPMs up over 3k which i don't, but I have acceleration pretty much on demand no matter what gear i'm in. Offroad, the 4.10s are awesome. I probably won't regear when i go to 33s because 90% of my driving is on the road/highway speeds.

 

Yes sir, that's what I mean.

I've also seen that some people will go lower for the 5-speed, but considering my preferences I don't really recommend any different.

 

I have a question. Where's the cheapest place for gears? I want 4.56s for a D30 and 8.25

 

i want 4.88s but i can go higher since i have the low pinion in my 2000?

what would 4.88s cost? is there a better (stronger) brand?

 

4.88 is as low as you can go in the 8.25, D-35's are not worth re-gearing, D-44's can go lower into the 5's