nosajwp said:
It's looking more and more like I will do the same. I love the way XJ's look with 4"+ of lift and big tires, but I'm finding out they can do a lot with stock suspension height, good shocks, and good tires. Plus, I really don't want to spend all the money to re-gear, change my rear driveshaft, etc. (at least not anytime soon).
When you went to 30's, I think I remember you saying you went to 3.73 gears. I have the AW4 and 3.55's...if I go to 30's (29.5" vs. 28.4") do you think I will see much of a performance difference? At least it might bring my speedo back closer to actual!
That's not exactly what I said. remember, I'm the admiral of "the Fleet."
My '88 XJ is still a 5-speed with the stock 3.07 gearing, and I have run that with 30x9.50s when wheeling. Going from stock tires to 30s with the 3.07s really makes a difference. No acceleration, and a lot of downshifting for upgrades, even on the Interstate.
The '88 MJ is also a 5-speed, and came to me wearing 3.07 gears. I was given a set of 31x10.50s (my brother's cast-offs, not a club member's beneficence), so I threw them on to replace the bald stock-size tires that came on it. With that combo, 5th gear was useless.
The 3.73s came about because I had decided I wanted to run that ratio with 30" tires on the XJ. I had purchased the gears, but I had not installed the gears when I got the MJ, so I threw them in that to help compensate for the 31" tires. It was much better, but still not quite right. The final overall drive ratio comes out the same (speed to RPM) as stock tires with 3.54 gears. 4.10s would be a better choice with 31s, but it was quite driveable with 3.73s.
3.54s and an automatic with 30s is a lot better than my 5-speed with 30s and 3.07 gearing, so I think you'd be fine with that combination. Moving only one jump in gear ratio only changes the engine speed a few hundred RPM at highway speed, so IMHO a jump of only one step in ratio isn't worth the money and effort involved. By all means, run your stock gears with 30" tires until you decide to lift it and run bigger rubber, then do the tires and gearing once to make it all match up.