Mixing stock drive ratios

Im pretty sure that my 1988 cherokee has 3.07's because it was 5-speed, and i think auto's have 3.55's (correct me if im wrong). Im swapping to an Aw-4, soo i was wondering what its gonna be like with this combo? Gas-milage? Acceleration? I will be running 31's. Should i look into a re-gear?

I would.

With 31's, 3.07 gears, and running at 50 mph; (assuming you have .75 OD) your RPM will be 1247 according to this handy dandy calculator... http://www.rocky-road.com/calculator.html

With 3.55's you'd be running 1442, not great, but in a better position for cruising. I'd go with 3.73's or even 4.10's.

I didn't regear after lifting my XJ and going to 31" tyres. Mind you, this is with an AW4 and 3.55 gearing - which is liveable, but noticeably down on power compared to when it had the stock 28" tyres. Not to mention that fuel economy's gone from an average of around 15mpg to 12-13mpg; with what I've spent on fuel in the past few months I likely could've paid for gears.

Moral of the story: regear and go to 4.10s. 3.73s will be marginally better than 3.55s, but 3.93 is the equivalent to 3.55 if you're running 31" tyres (assuming you had 28" or thereabouts tyres stock), so you'll still be under-specced. I'm not aware of anyone who makes a 3.93 gearset for the XJ, so just go straight to 4.10s.

If you don't do alot of interstate driving go straight to 4.56's. JIM.

I forgot to mention that I'll be running a 4.6 stroker, if that makes a difference.

If you got the money for a stroker, you got the $ for the gears.

Minimum 4.10's.

I swapped 3.55's in to cover my 31's with a 5spd.

I still don't see 5th gear unless I'm doing about 75 mph.

3.07's,an auto ,and 31's?


If your doing a stroker you should know better.

red91inWA said:

I swapped 3.55's in to cover my 31's with a 5spd.

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Same for me. My XJ never gets above 55; I haven't used fifth gear since March.

red91inWA said:

If you got the money for a stroker, you got the $ for the gears.



I swapped 3.55's in to cover my 31's with a 5spd.

I still don't see 5th gear unless I'm doing about 75 mph.

Click to expand...

i run 3.07s with a 5sp and 32s i can still hold 5th on reletively flat ground at about 70mph. pulling a trailer though is a diffent story and i will need to do something about that. i dont think my jeep will like running 3100rpm for any length of time cause i cant even hold forth unless i am doing about 80mph and floored on flat ground

Well you see, my jeep has a blown motor, and i found a great deal on a stroker/Aw-4. Since my jeep has the Ba10/5, i decided to swap in the Aw-4 because the old BA10/5 wouldnt be able to handle the power. I didnt really think about the difference in auto/manual gear ratios. BTW im only 18 soo i dont have an abundance of money.

If your strocker has a big cam your powerband may be raised over stock, in which case lugging it along at low rpm's with the wrong gears may make things even worse. You need to figure out EXACTLY what you have and then buy the right gears so everything works well together. If you are capable of doing the swap this should be elementary for you.