31's with 3.55's?

[Rod Knee]

I have found, on this board, the "you will be fine" response to ANY question not worth the time it takes to read. Sorry about wasting your time in saying so.

 

[vortex]

SO then another question (seeing as this is all about ON ROAD driving) how will it perform in the mud/clay/snow?

-PJ-

 

[fordtech]

NOTE: I also live above 6000 feet, so figuring a 3% power loss per thousand feet, I've already got troubles. At sea level I notice the jeep pulls MUCH better. But add the altitude and the 30s on 3.55s.... yeah, the jeep hates life in the mountains...

This is a great point. I think people forget this. My 4-cyl YJ was a whole different jeep when I pulled it off the dolly in NY after moving from CO.

 

[winkosmosis]

I have 31" BFG ATs with 3.55 gears and my XJ feels great on the street. Seems like every time I floor it, I'm surprised at how well I accelerate. I have a hard time believing anyone would want to regear for 31

 

[rocknxj]

im not really sure where everyones major lack of power is coming from, i hated mine on 31s and 3.55s until i gave it a tune up, i still had the original plugs and wires and stuff and didnt realize it:bawl: so, after a fresh tune up, im more than happy with the power, i mean, its not my cummins, but still gets along great, i can even pull my 17.5 ft boat with it with no problems. just thinking maybe some of you should check on a tune up if it is as bad as everyone says it is......

X2.

Many things will rob you of power, but in general, I'd still say stick with the 3.55 gears on 31s and buy rocker protection with the money you will save on gears.

 

[KamekLocked]

Fore everyone figuring out thier mpg, have you corrected the speedo with the correct gear? If not your mpg calculations are useless...

I have 31" MTR's and 3.55 gears on my XJ and there is a difference, my brother has 235/75r15 on his XJ and there is a difference.

 

[vortex]

Still wanting to know how this set-up works in the mud, snow, clay....

-PJ-

 

[hanaxj87]

Still wanting to know how this set-up works in the mud, snow, clay....

-PJ-

I think your fine.. Wheel them 31's!!!

Nick

 

[nonnie]

SEE POST #34

I have 31's with an AX-15 and 3:07's.I won't even pass another vehicle unless on a decline. I was hoping to save cash by not regearing but great bald headed G-zuz....no power at all.:bawl: Off road low range and 2nd is my only hope.


'96 2DR,4.0,30/8.25 both open , RC 6.5", SYE, BFG M/T's on 7" factory alloys....running 225/75x15 remould studded winter for the snow...

 

[vortex]

So has anyone ran bias ply buckshot mudders? curious how well they would clean out? My bro has a set on his samurai and i was thinking about buying them just wanted to see if you guys had any experiances to speak of?

 

[89xj]

I have 31" BFG ATs with 3.55 gears and my XJ feels great on the street. Seems like every time I floor it, I'm surprised at how well I accelerate. I have a hard time believing anyone would want to regear for 31

31's with a manual trans(stock 3.07 gearing) IMHO, sucks.

i regeared my 89 with a 5speed and 31's to 4.10 because you should NOT have to "floor it" to have decent performance and the use of 5th gear on an incline.

it not about flooring it, its about having the engine at the right rpm range for the amount of work/load on the engine.

 

[slowjeep]

is there much of a difference from 30s to 31s, I can find used 31s much easier than 30s but am worried about performance since I drive a DD 90 non HO.

 

[vortex]

Well thanks for all the advise!!

-PJ-

 

[casm]

Not really. I did for a couple years. Not really worth the time or money to get 3.73's or 4.10's. Especially on a DD. Speedo should be off roughly 11% depending on what tires u get and it'll feel a little less peppy but other than that it's fine.

Disagreed - I went the same route, and regretted it in terms of fuel economy. Was averaging about 12.5mpg with 31" tyres on 3.55:1 gears; went back up to a more-or-less solid 15mpg on 4.10s.

Is it driveable? Sure. Performance was affected, though, particularly on hills. It wasn't horrible, but it definitely was noticeable. The other side of the coin is that for the extra I spent on gas with the 3.55s, 4.10s would've been a break-even proposition after about nine months. There's really no reason not to do them, IMHO...

 

[94CountryXJ]

I'm going to go with 4.10's but I'm also going up to 33's in spring. But, not until I can do lockers at the same time as well.

 

[vortex]

Well the lift goes on today and the tires come soon!!!

-PJ-

 

[RCP Phx]

I'm going to go with 4.10's but I'm also going up to 33's in spring. But, not until I can do lockers at the same time as well.

Youll like yourself better(later) if you 4.56's!

 

[jeep ride]

What size lift you going with?

 

[pyrotyro]

Disagreed - I went the same route, and regretted it in terms of fuel economy. Was averaging about 12.5mpg with 31" tyres on 3.55:1 gears; went back up to a more-or-less solid 15mpg on 4.10s.

Is it driveable? Sure. Performance was affected, though, particularly on hills. It wasn't horrible, but it definitely was noticeable. The other side of the coin is that for the extra I spent on gas with the 3.55s, 4.10s would've been a break-even proposition after about nine months. There's really no reason not to do them, IMHO...

I would disagree strongly with you! unless your foot is always to the floor, i get 15mpgs out of my auto (3.55) on 32s, mixed driving.

I wont lie, I be doing gears as soon as I get the money, but its not that bigga deal at all!

 

[casm]

I would disagree strongly with you! unless your foot is always to the floor, i get 15mpgs out of my auto (3.55) on 32s, mixed driving.

All I can tell you is that those are the numbers I was getting in mixed driving. Measurements were taken from the overhead console after installing the correct speedo gear in the transfer case; this was in turn double-checked against my GPS unit and fuel receipts for accuracy. The amount of variation between the two was virtually zero.

If you were getting better fuel economy in your particular circumstances, I'm thrilled for you - but your circumstances don't necessarily match mine. Also, how were you determining your fuel economy? Was your speedo corrected after your lift? What year is the XJ you were taking the measurements on? All of these things (and more) affect the overall numbers.

I wont lie, I be doing gears as soon as I get the money, but its not that bigga deal at all!

Perhaps not in your specific case, but that seems to be the exception rather than the norm.