I have a 99 XJ that I'm looking to put a 4.5 lift and either 32 or 33" tires. Thi is my daily driver and I'm wondering if I'm gonna have to regear. If I don't regear how bad is this going to effect my fuel economy and power? Please help!! Thanks!!

 

For 33s you want 4.56. To not regear could be the difference of I'd say between 3 and 8 mpgs. All rigs are different so it's hard to say exactly

 

Hmmm... nice to know

How about 31" ?

I have 3.55 gears D30 & D35- do I need a higher ratio?

So that's why I get 17 MPG highway....? \

1989 4L AW4 NP242

 

I would just suffer through that. total cost of regear is over $1000 by a decent chunk
regear isnt worth it unless you're running 33's or bigger
and you would need to swap out that rear D35 because you'd be retarded to spend any money building it
both axles actually, might as well get the reverse D30 while you're at it

 

I run 32's and had to regear to 4.10's. The power loss of trying to climb hills was terrible. I was having to drive around in 3rd gear all the time and if I towed just my small popup camper to hunt out of it would go all the way down to 2nd gear trying to climb the hills. Regearing was expensive but well worth it to me. some guys don't mind the power loss, but I pack my Cherokee out. After regearing, I towed a 5,000 lb. trailer with ease. Regearing was the best thing I've done to my Jeep. 32's for me needed the 4.10 ratio. 33's would need the 4.56's.

 

Ok thanks what's your opinion on 32's? If it gonna make a difference I'll get 32's.

 

Auto tranny = 3.55 stock
Manual tranny = 3.07 stock
Tires = 28" tall stock

33/28 = 1.18 X 3.55 = 4.18:1
1.18 X 3.07 = 3.62:1

4.10 or 3.73 gears get u very close to stock mechanical leverage using 33" tires. Just change the numbers to re-calculate.

 

it depends on your rear axle and whether or not you are a4 or m5

I have 33s and the stock 3.07s, but the M5 makes it manageable.

I once calculated it somewhere on here, and 3.6ish was as close to stock ratio as possible, I would agree with the above, 3.73 or 4.1/4.11 is best

 

I'm so torn to regear or not when lifting and getting some 31x10.50s on my C8.25 3.55. I assume going to a 3.73 would bring back the torque and gas mileage. If I did decide that was best I'll probably go with the ford 8.8 with the 3.73LS

 

And another regearing thread??????

 

Ok thanks man. About what gas mileage are you getting fliyingstick?

 

Going to 32's in my 5.9 the power loss was noticeable. Gears are ALWAYS a good investment

 

While all this math is sound, it does not take into account the additional rotational inertia of the larger tires. While 33's & 4.10 gears might calculate close to stock specs, it definitely won't "feel" like stock. The common understanding is that (with the AW4) 33's should get 4.56 gears, 32's -> 4.10, 31's -> 3.73 (although I question if that is worth the price), etc....

 

I think you mean rolling resistance, because inertia will go up with the higher weight.

 

Yep, equivalent to stock mathematical leverage won't compensate for the extra weight, rolling resistance, etc.,......that's a given.