gear change (5sp/with 33's)

[h.curtis]

Are my calculations right?

Stock:
225/75 R15 = 28.29" tire height
stock gear 3.07

New:
33X10.50
gear needed to be same as stock: 3.58

Is it correct that if I want to be stock I will be running as close to 3.58's as I can get? This doesn't seem right. I am currently running 31's with stock gears and there is plenty of pep.

Curt

 

[OILBURNER]

I take it this is a 5 speed (3.07: gears)
I have always been told that 4.10's feel about right for 33's but they are talking about 33x12.50's. Those are quite a bit heavier than 33x10.50's.

3.55's would be cheap & easy to find, but 3.73's would probably feel better

 

[Vug]

Your math is right but you are assuming that 33's are 33 inchs tall. Most are not. A BFG AT/KO 33x10.5 is 32.7" tall.

(32.7/28.3)*3.07=3.54
3.73's or 4.10's would be better.

Oilburner is right. You want to step down a gear from what is 'back to stock' to conpenstate for tire wieght, amongst other things.

I went to 4.56's with my 32" Swampers and thought it was perfect.

 

[XJEEPER]

OK Curt, brace yourself.........
It's a fairly well know fact that regearing charts lie. Having said that I will explain.

When you regear your rig, it's usually because you've installed bigger tires, in conjunction with a bigger lift, which usually means that you're planning on using your rig offroad so you've installed rocker protection, skidplating, HD front and rear bumpers and even a winch? Not to mention a roof rack, full size spare, HiLift, recovery gear, spare axle shafts, tools, etc.

What the charts can't tell you, is what the effects of all this increased weight, added wind and rolling resistance of larger tires, increased wind resistance of a taller rig, power loss due to altitude changes, poor mileage due to power loss, and most importantly, the actual power applied to the ground.

This stuff is learned through trial and error.......and since you have such a large collection of experienced XJers here at your disposal, many of us have been through both the trial and the error (the smart ones learned from someone elses mistakes ) when it comes to regearing a rig.

Here's the lowdown.
With a 3:07 stock ratio, you must have a 5 speed. And I'll assume you have a 4.0 motor of some flavor, HO or non-HO and you live near sea level elevation.

To run 33's, the optimum ratio that you'll need to run is 4:56. You could get by with 4:10's, but if you live or travel at an altitude of 3000-6000 ft, 4:10's may hurt your mileage and performance. Don't worry about the increased RPM at cruising speeds, the 4.0 motor can run all day at 2800-3000 rpms, it's right in the middle of the power range, and will actually use less fuel because it is working more efficiently.

Bottom line is, trust the advice of your fellow XJers that have been there...done that, over a gear chart or some guy at a parts house that won't mind selling you another set of even lower gears next year.
Does this mean you'll need new carriers? Yes. Should you consider installing a traction device in conjunction with the re-gear? Yes.

Oh yah........did I mention that I've been through 3 gear ratio changes in 6 years before winding up with the perfect setup? A swap from a 5 speed to an auto required the last one, but this way......you only need to do it once.
WOW, look at all the time and money you just saved!

 

[jimbar]

What he said.... 4.56's and 33" in a 5sp and glad I did.

 

[h.curtis]

Thanks for the information. Being that I am running 31's with 3.07's and like it pretty well. I was thinking to go to 3.73's to add to the calculated 3.55's due to the extra stuff you mentioned. I thought about 4.11's and may go there, but now that I have a full Borla exhaust is seems to have a real nice bit of low end torque. I don't think I will add extra weight on my XJ other than tires (had skid plates, full spare stock w/upcountry) I am wanting to be as light as possible. I do like the ARB Bully though with the winch. That is sweet, but too heavy IMHO.

Yes I have a 4.0 HO as well. I gotta say my Jeep is fast and plenty of power. Even with the 130K on it since I bought it new in '96.

I also want to mention that I am not a rock crawler. I do most of my off road in snow and mud. I work at a ski resort. The elevation here isn't high at all. Under 3000 feet.

4.56's seem so steep to me. I like to run 70-75 on the highway. Seems like I would be screaming.

Keep in mind, I am not arguing with anyone here. I am just stating how my jeep will be set up and how I drive for more information. I guess the number 4.56 is messing with me quite a bit. Very steep gear.

Curt

 

[OILBURNER]

I always advise to try & hook up with a fellow XJ'er who has a different gear setup. I am sure if you are not a jerk they would let you drive it & see first-hand the differences.
Couldn't hurt

 

[dennisuello]

I wouldn't go for less than 4.10s with 33s and manual.

 

[Ted Z]

I am running 33x12.50 with 4.56s and a 5 speed and I like it.... I am also averaging about 17mpg....

 

[ChuckD]

I have 4.10 and 33's, I agree 4.56 would be better, but you have to consider what axles you have. Are they worth the $$ to change the gearing.

Either find cheap D30's or D35's that are geared to 4.10, or get at least an 8.8 or D44 for the rear and regear to 4.56.

I found that it is easier and cheaper to find somebodies hand me downs.

 

[Eagle]

I didn't bother to re-check your math, but something's off. I am running 31x10.50s through 3.73 gears, and the overall final drive ratio (as proven by engine RPM at 65 MPH) is exactly the same as stock tires and 3.55 gears.

To get any improvement in gearing you need 4.10s with 31" tires, 4.56 with 32" tires, and either 4.56 or 4.88 with 33" tires.

If you want a copy of my spreadsheet showing tires sizes, gear ratios, and RPM at various speeds, hit me with a PM and your e-mail address. Be sure to let me know if you want Excel or Quattro Pro format, although that's probably a silly question these days.

 

[h.curtis]

To get any improvement in gearing you need 4.10s with 31" tires, 4.56 with 32" tires, and either 4.56 or 4.88 with 33" tires.

Keep in mind there is a big difference in a 5sp and auto. I am running 3.07's with 31's and it is no problem.

Curt

 

[h.curtis]

I found that it is easier and cheaper to find somebodies hand me downs.

Yes, I agree. I am not changing my rearend now, so I will be looking for cheap ring and pinions. I will look for a 44 off an XJ over the next couple of years while I am running my 35c. Gotta do things over time due to the huge $$ I am spending on this lift and tires.

Curt

 

[xj92]

I've got 4.10's with 31's right now and it's great around town, but a little too low on the highway because I like to cruise at 85 on the interstate. I'll be moving up to 33's soon and hope I'll like the combo there. I went to 4.10's because I could get factory axles for cheap with that ratio. Found the rear for $200 and sold my old one for $100. I haven't found a front cheaper than $450 though, and they're rare altogether with 4.10's. If you wanted to do the swap ultra-cheap, people are always getting rid of 3.55 axles (me, for example) for around $100-$200. Just something to consider.

 

[Jes]

4.56's seem so steep to me. I like to run 70-75 on the highway. Seems like I would be screaming.

Curt

This is 4.56 gears, AX15, 33X12.5 tires and a speedo that is about 6 percent over optomistic. I generally get about 18 MPG at 70 MPH and have gotten a best of 25 MPG with this setup.

Jes

NOTE: Professional driver on closed course. Do not attempt. Your mileage may vary. Read all safety warnings before using heavy equipment. Void where prohibited by law. Subject to tax where applicable. All rights reserved.

 

[OILBURNER]

Professional driver on closed course. Do not attempt. Your mileage may vary. Read all safety warnings before using heavy equipment. Void where prohibited by law. Subject to tax where applicable. All rights reserved.

:roflmao:



OT: Hey what package does that leather-wrapped steering wheel come with?

 

[h.curtis]

This is 4.56 gears, AX15, 33X12.5 tires and a speedo that is about 6 percent over optomistic. I generally get about 18 MPG at 70 MPH and have gotten a best of 25 MPG with this setup.

Jes

Dang, I guess that is why they say a picture is worth 1 thousand words. Glad you were on a closed course. :laugh2:

That isn't as bad as I thought. I am going to forget the 3.73's that is for sure. With the 5sp I have an overdrive that would make it better on the highway as well....I think?

Thanks for the picture. I got a kick out of the post all together with the disclaimer.

Curt

 

[Jes]

The AX15 is a 5 speed with a .75 overdrive. The AW4 automatic has a .70 overdrive(I believe).

Oilburner, I have a Sport model of 1993 vintage.

Jes

 

[XJEEPER]

Great cluster shot Jes........4:56's are only scary to those that are afraid of too low gearing....and the Boogie Man .....the rest of us love them! Who was it that decided that 2200 is the best RPM for cruising........dude with a BB Chevy, I think?
Some folks even argue that their 1" t-case drop and YJ slipyoke are as vibe free as an SYE.........step toward the light and be saved!!

Curt, you only think that 3:07's and 31's are OK.....BTDT too. 3:73's were perfect for 31's.....but then I got the 32" tire bug....and along came a cheap set of 4:10's.......much better with the 32's and 5sp, but not using 5th gear that much on the freeway.....underpowered?
Then came the AW4 swap and now the 4:10's were not enough so at last......the glorious 4:56's! :angel:

Good luck with your decision..... the lifeless steed has been pummeled enough.........

 

[David - Atlanta]

Rats! Here I am trying to work a deal on some 32" x 9.50 Swampers because I got a good price on some 4.10 equiped axles and now I'm not sure I'll be happy with the settup.

I have read posts where those with 4.10's LOVED them off-road with 31's but felt they were a little too steep on the road. I was thinking that the 1 inch difference to 32's would still give good off-road performance (aka better than stock) but would be slightly better on road.

I want to have the gearing a little lower than stock (I have the 5 speed & stock gears were the 3.07's) but from what I am reading here would you all say that I would need to stay with 31's instead of the 32's then?