what gears to run?

[xjmonkey]

Hello, I am sure this topic has been on here MANY, Many times.. I am new to this forum so sorry, but help or opinions would be great! I have a 2000 xj and want to gear it for some more power and better mpg.. It has the 8.25 rear and dana 30 front. What gears would work best with 33's? I dont care if my top speed is 70, but want good power gains and better mpg. (will possibly be pulling a small trailor soon. atv/waive runner. I was thinking some 410's or 456? any one had any experience with what would be better, and where is best place for price and to get installed.

 

[Fester]

You can determine what your RPM will be by using this formula:

RPM = (MPH x AXLE x TRANS x TCASE x 336)/(TIRE DIAMETER)

MPH = speed say 65 mph
AXLE = ratio, probably 3.55 right now and you want 4.10 or 4.56
TRANS = 1:1 in drive or 4th, not sure what they are in OD, maybe around 0.7?
TCASE = 1:1 in 2wd
336 = correction factor
TIRE DIAMETER = 33 in. (probably closer to 32)

So right now with 33's and 3.55's at 65 in fourth or drive it should probably be taching around 2350. Change to 4.10's and it'd jump to 2714, and 3018 for 4.56's.

For install my brother just had Spikes A & D in West Jordan do his stooper doodie and was very impressed. I've had Spike do some alignments and he does great work at a reasonable price. His shop is out by Tuff Country suspensions.

 

[mbryson]

Unless someone has dumped some 4.88 gears on the market in the past few months, 4.56 is your limit with the 8.25. Should be an excellent match for your 33" tires and will work OK with 35" if you decide to go there.

 

[xjmonkey]

Thanks for the info, am I going to have a noticable difference in power driving on road, and also crawling slow? Has anyone experienced better gas mpg? Just want to know if its enough improvement to fork out the money?!? I am thinking 456 gears!

 

[Jinx]

Thanks for the info, am I going to have a noticable difference in power driving on road, and also crawling slow? Has anyone experienced better gas mpg? Just want to know if its enough improvement to fork out the money?!? I am thinking 456 gears!

Increased Power and inceased MPG is unusaul unless you are talking about a diesel.

You might be better off to ask who is running what gears and what tires and what mpg are you getting. That way you can compare to what you currently get and make a decision.

Good luck. I used to run 4.10s in a cj without an 5 gear and 33s worked pretty good. But when I went to 35s my crawl ratio was a little high, freeway is great though. I am thinking the 4.56s would have been better with 35s and the T 18.

 

[mbryson]

Thanks for the info, am I going to have a noticable difference in power driving on road, and also crawling slow? Has anyone experienced better gas mpg?

I can't speak to your exact combination (assuming you're running an AW4) as I ran 4.10 with 33" SSR and 4.88 with 35" MT/R. I did get about the same mileage out of the 35"/4.88 combo that I got out of the 33"/4.10 setup. Both were very acceptable on-road performance as I towed my tent-trailer to Moab at that time with the XJ.

I believe I got about 19-21 mpg on the highway with my 215/70 stockers with 3.55 gears. I went to 32" MT/R and 4.10 gears and stayed around 18-19, 33" and 4.10 gears about 16-18 and stayed there if I kept it under 70 with the 4.88/35" tires. Above 70 with the 4.88 and the mileage fell off a cliff and the whole drivetrain heated up like you wouldn't believe (backlash on my D44 gears was a little tight but within spec).......... ...............if I ever built another Cherokee, I'd stick with a 4.5" RE short arm lift, 4.10 gears and 32" tires with selectable lockers. That car did EVERYTHING well, just nothing exceptional.

Just want to know if its enough improvement to fork out the money?!? I am thinking 456 gears!

You'll want gears for sure, so I'm not sure what you mean here. I think the 4.56 and 33" tire will be a good compromise for low range (you'll want to be slightly lower geared) and a good compromise for high speed (I bet you can run up to 75 mph without issue).

 

[Jeromy]

For install my brother just had Spikes A & D in West Jordan do his stooper doodie and was very impressed. I've had Spike do some alignments and he does great work at a reasonable price. His shop is out by Tuff Country suspensions.

Spike is a great guy

 

[XJEEPER]

4:56's and 32's-33's are a good fit for the multi-use XJ platform. My take is that 4:10's aren't enough for a tire bigger than a 31.....because I did, and they weren't.

Please don't base your gear ratio selection on the RPM/Gearing calculator charts because they will never factor in the increased drag from larger rubber, increase wind resistance (drag coefficient) from 4-6" of lift (face it, the XJ is as slippery as a brick in the wind), added weight from HD bumpers, FS spare, armor, winch, etc. They get you close, but they always, always....did I mention ALWAYS? error on the tall side....not low enough gear to overcome the above mentioned mods.

I've run 285's for a few years now (33" equiv.) with 4:56's and even with my tired 89, almost-200K mile non-HO motor and the AW4 Auto, I can cruise at 75mph all day long (turning 2800 rpm which is right in the sweet spot of the 4.0 power range) and pull down 16-18 mpg on the freeway with the AC blasting.

 

[VANDALL]

I would do 4:10's in the future u can do a 4 to 1 in ur t-case an still drive on the highway but still have a great low range.


VANDALL.

 

[XJEEPER]

Disagree V, the big question is...... how low a crawl ratio is really needed in a daily driver? I regularly run 4+ trails with an open front and an Auburn out back with a stock ratio t-case and have never wanted for a lower crawl ratio, but then I still run a disco-D30 with a Posilock cable so I get simple 2Lo......guess I'm from the old school, but it's seems to have worked for the last 9 years. Someday I'll lock the front........

I get better mileage with 4:56's than I did with 4:10's. Stock gear ratio calculators may say 4:10's for 33's......but the rig ain't stock anymore with 4-6" of lift, bigger tires, added weight...and remember, the monkey wants to pull a trailer too......I've never met anyone that wished they'd gone with taller gears so they could run smaller tires. ;>)

 

[xjmonkey]

"the monkey" ha ha haha ah....... Funny stuff. Thanks for the info, I am pretty sure I will get the 4.56 gears.. when ur on the freeway does ur jeep like to shift down to 4th and back to 5th a bunch.. I know this will happen no matter what on large hills, but if 4.56 would make it have a little more go, I would love it. I do have a 6" lift on it, so yea, it isnt exactly wind friendly.. What brand gears do you recommend, and where to buy? oh yea, how hard is self install? I have done all my other work, but heard gears is a pain the the a$$! oh yea, I only talk about freeway, but like to go wheelin too. My low has never been a prob so far, but I am still a newb.. (I will admit it). oh yea, and I want some type of locker/limited slip in the rear.. I dont wanna spend a arm and leg, but might as well get something when getting geared. Is limited slip worth a sh** of road? And what is cheap but works well?

 

[MOODY]

I am curious as well about the same question. I want to run 33x10.50's on 15" wheels, and I plan on a ltd. slip or a locker in the rear. I, too have heard from people who have done it that 4.56 gears are the way to go. Does it make the 4-lo even lower? Or no change? I have about 2k to spend....any ideas????????/

 

[MOODY]

Oh, mine is a 95 4.0 HO w/ 4" lift, 31 in tires, bumpers, roof rack, etc.

 

[JoeT]

I've got a 89 with 33" MTR's, that eventually I'll run 4:56's on. I've done a lot of research on this myself. This subject has been beaten to a pulp on JU. 4:10's are fine for 31"s to 32"s. 4:56/4:88 for 33"/35".

 

[xjmonkey]

I am for sure going with 4.56 at this point.. But still wanna know if limited slip or locker would be better. I have been in friends that have fully locked rear, and for a daily driver, I dont want it locked 100% of the time.. but then arb's are costy.. Any other ideas?

 

[mbryson]

I am for sure going with 4.56 at this point.. But still wanna know if limited slip or locker would be better. I have been in friends that have fully locked rear, and for a daily driver, I dont want it locked 100% of the time.. but then arb's are costy.. Any other ideas?

Selectables are SWEET!!! If you don't like the ARB, the Eaton is a nice design. I was pretty happy with my ARBs in my XJ (the D30 housing is suspect to bending and the ARB wasn't real thrilled with that--happened a couple of times to me)

 

[xjmonkey]

anyone have any experience with a "powertrax" limited slip?

 

[MOODY]

I had one in my 82 CJ-8 Scrambler. It seemed like it would only work when it felt like it. Made some odd noises at times too. I have been looking at doing a detroit truetrac in my 8.25 rear, I have talked to a guy in Australia that did one f/r and loved the performance, though he has yet to try them on Moab rock...

 

[xjmonkey]

I hear good and bad about L/S.. I am thinking about getting a detroit in the rear.. I want to be sure the thing is going to work. I just hope it doesnt eat rear tires to fast...