31" on 4.56

[georger]

This has probably been asked before, but it's time to go through my axles for bearings etc. Does anyone have experience running 31s on 4.56 gearing? I've been wanting to re gear, so it's now or never the time. I' currently running 31s with the stock 3.55 ratio. My tires are probably good for another year, so i want to see them run through and then upgrade to 33s, bigger lift, flares, etc. The question is, are 4.56 gears too deep for 31s until the upgrade? My XJ is my DD for now, I put about 40 miles of freeway driving a day. I probably get 4 wheeling a couple of times a month, with some bigger trips planned for the summer.

Other info: 2001 4D, 4.0, Auto, D30, 8.25,

 

[90 waggy]

a little deep for 31's but would work great for the future 33's. i went to the junkyard and got a 30 with 4.10's to match my rear and they work great for 31's but if u plan on getting 33's id go for 4.56's and deal with the high revs on the highway for now. just my .02

 

[MrShaft696]

a little deep for 31's but would work great for the future 33's. i went to the junkyard and got a 30 with 4.10's to match my rear and they work great for 31's but if u plan on getting 33's id go for 4.56's and deal with the high revs on the highway for now. just my .02

Its not even neccesary to say its your .02, because its just a fact that the 40mi of highway is gonna suck, thats just all there is to it really. Everyone says oh the xj loves to cruise at 2500rpm+ but you try it and see. It will be awsome around town & on the trail. You will feel alot better when you get to 33's.

 

[90 waggy]

well some ppl get bent outa shape. so i figured id add that lil bit in there so ppl know im just a tard and know nothing about jeeps..... oh and by the way the jeep l6 does not like revving high for long periods....at all

 

[doublestack]

I run 33's with 4:10's and I can run 65 to 70 pretty decent with out beating it to hard. I think 4:56's would be a good choice.

 

[89xj]

This has probably been asked before, but it's time to go through my axles for bearings etc. Does anyone have experience running 31s on 4.56 gearing? I've been wanting to re gear, so it's now or never the time. I' currently running 31s with the stock 3.55 ratio. My tires are probably good for another year, so i want to see them run through and then upgrade to 33s, bigger lift, flares, etc. The question is, are 4.56 gears too deep for 31s until the upgrade? My XJ is my DD for now, I put about 40 miles of freeway driving a day. I probably get 4 wheeling a couple of times a month, with some bigger trips planned for the summer.

Other info: 2001 4D, 4.0, Auto, D30, 8.25,

are the bearing that bad that you cant wait until you get larger tires?

i have 4.10 and 31's with a five speed and i feel its perfect. 4.56 and 31's would be a little deep, but i dont think it would be too much. i would do it. i would not drive 90 miles an hour.

look at it this way, the difference between 4.10 and 4.56 is only .46 more rotations of the driveshaft for every rotaion of the tire and 1.01 rotations more over stock gearing of 3.54. when i went from 3.07 to 4.10, that was 1.07 more rotaions of the driveshaft and it put it in a perfect rpm range for my 5spd.

so in conclusion, is 1.02(3.54 to 4.56) more rotations too deep for the I6 with an auto trans? i say no its not too much. will it be a bit high, yes, but too much, no.

in my 89 5spd, i can cruise all day at 80mph which is around 2900 rpms.

 

[ktm racer 419]

well some ppl get bent outa shape. so i figured id add that lil bit in there so ppl know im just a tard and know nothing about jeeps..... oh and by the way the jeep l6 does not like revving high for long periods....at all

ive done 3000 rpm for 5 hours before

she loved every second of it

 

[90 waggy]

yup im sure she did. :yelclap:

 

[Lightfoot]

http://lightfootxj.webs.com/index.htm
not the easiest thing to read, but its gives a good idea of what your rpms will be with different tire sizes/ gears. Its not totally accurate because your actual tire diameter will be a little different than the advertised size. You get to decide what you think is too high. Under 3k at 80mph doesnt really seem that bad. Its not like youll be turning 5k at 65. Your highway mileage might not be great, but I doubt it will be that bad.
As far as it being bad for the motor, jeep speed guys turn 3500 all day without a problem. Its not a very well guarded secret that the 4.0 likes to spin.
IMO turning 3k-3200, really isnt hell. My motor is smooth enough, and exhaust quiet enough that I can turn those numbers on the highway, and forget to put it in a higher gear. Before I had a tach, I did half of nebraska that way before I noticed. Got about 15mpg.
Gears arent cheap. If you plan to run bigger tires within the next year, go for it. Just expect your fuel bill to go up.
The other option is to find some junk yard axles, either let your bearings run for a year ( if they can), and build your axles out of the jeep, or if they are real bad, put in the junk yard axles, and build yours up for when you get new tires. No sense in setting up old gears with new bearings If youll have to do it again.
The OP asked for peoples opinions. Its a good idea to make sure people actually agree with you before you shoot down someone elses opinion like that, or you end up looking like the clown.
Just my .02 cents

 

[sunburned]

This has probably been asked before, but it's time to go through my axles for bearings etc. Does anyone have experience running 31s on 4.56 gearing? I've been wanting to re gear, so it's now or never the time. I' currently running 31s with the stock 3.55 ratio. My tires are probably good for another year, so i want to see them run through and then upgrade to 33s, bigger lift, flares, etc. The question is, are 4.56 gears too deep for 31s until the upgrade? My XJ is my DD for now, I put about 40 miles of freeway driving a day. I probably get 4 wheeling a couple of times a month, with some bigger trips planned for the summer.

Other info: 2001 4D, 4.0, Auto, D30, 8.25,

I have 4.56's and 32's and I drive 80 miles a day for work, mostly highway going 70+. You'll be running at least 2500 rpm at highway speed. Not too bad, but you'll be golden once you swap to 33's. I plan on going with 35's.

 

[MrShaft696]

http://lightfootxj.webs.com/index.htm
not the easiest thing to read, but its gives a good idea of what your rpms will be with different tire sizes/ gears. Its not totally accurate because your actual tire diameter will be a little different than the advertised size. You get to decide what you think is too high. Under 3k at 80mph doesnt really seem that bad. Its not like youll be turning 5k at 65. Your highway mileage might not be great, but I doubt it will be that bad.
As far as it being bad for the motor, jeep speed guys turn 3500 all day without a problem. Its not a very well guarded secret that the 4.0 likes to spin.
IMO turning 3k-3200, really isnt hell. My motor is smooth enough, and exhaust quiet enough that I can turn those numbers on the highway, and forget to put it in a higher gear. Before I had a tach, I did half of nebraska that way before I noticed. Got about 15mpg.
Gears arent cheap. If you plan to run bigger tires within the next year, go for it. Just expect your fuel bill to go up.
The other option is to find some junk yard axles, either let your bearings run for a year ( if they can), and build your axles out of the jeep, or if they are real bad, put in the junk yard axles, and build yours up for when you get new tires. No sense in setting up old gears with new bearings If youll have to do it again.
The OP asked for peoples opinions. Its a good idea to make sure people actually agree with you before you shoot down someone elses opinion like that, or you end up looking like the clown.
Just my .02 cents

The opinions are great so start here http://www.naxja.org/forum/showthread.php?t=46901&highlight=gearing then search the other 100 threads a week everywhere on it. Then go here
http://www.naxja.org/forum/showthread.php?t=95375&highlight=axle+gear+chart

The facts are the facts that page sucks for even a clown to read, so read it like this its alot simpler...

RPM's at 65 MPH/105 KPH w/ 3.55:1 axle gears running 28's: 2,076 RPM
RPM's at 65 MPH/105 KPH w/ 3.55:1 axle gears running 30's: 1,938 RPM
RPM's at 65 MPH/105 KPH w/ 3.55:1 axle gears running 31's: 1,876 RPM
RPM's at 65 MPH/105 KPH w/ 3.55:1 axle gears running 32's: 1,817 RPM
RPM's at 65 MPH/105 KPH w/ 3.55:1 axle gears running 33's: 1,762 RPM
RPM's at 65 MPH/105 KPH w/ 3.55:1 axle gears running 35's: 1,661 RPM

RPM's at 65 MPH/105 KPH w/ 4.10:1 axle gears running 28's: 2,398 RPM
RPM's at 65 MPH/105 KPH w/ 4.10:1 axle gears running 30's: 2,238 RPM
RPM's at 65 MPH/105 KPH w/ 4.10:1 axle gears running 31's: 2,166 RPM
RPM's at 65 MPH/105 KPH w/ 4.10:1 axle gears running 32's: 2,099 RPM
RPM's at 65 MPH/105 KPH w/ 4.10:1 axle gears running 33's: 2,035 RPM
RPM's at 65 MPH/105 KPH w/ 4.10:1 axle gears running 35's: 1,919 RPM

RPM's at 65 MPH/105 KPH w/ 4.56:1 axle gears running 28's: 2,668 RPM
RPM's at 65 MPH/105 KPH w/ 4.56:1 axle gears running 30's: 2,490 RPM
RPM's at 65 MPH/105 KPH w/ 4.56:1 axle gears running 31's: 2,409 RPM
RPM's at 65 MPH/105 KPH w/ 4.56:1 axle gears running 32's: 2,334 RPM
RPM's at 65 MPH/105 KPH w/ 4.56:1 axle gears running 33's: 2,263 RPM
RPM's at 65 MPH/105 KPH w/ 4.56:1 axle gears running 35's: 2,134 RPM

RPM's at 65 MPH/105 KPH w/ 4.88:1 axle gears running 28's: 2,855 RPM
RPM's at 65 MPH/105 KPH w/ 4.88:1 axle gears running 30's: 2,664 RPM
RPM's at 65 MPH/105 KPH w/ 4.88:1 axle gears running 31's: 2,579 RPM
RPM's at 65 MPH/105 KPH w/ 4.88:1 axle gears running 32's: 2,498 RPM
RPM's at 65 MPH/105 KPH w/ 4.88:1 axle gears running 33's: 2,422 RPM
RPM's at 65 MPH/105 KPH w/ 4.88:1 axle gears running 35's: 2,284 RPM

 

[JAS]

I am on 31 and 4.88 gears... I have no problems running 65-70 MPH.

I do not wish to drive much faster than that. You will be fine on 31 and 4.56 for a year.

 

[georger]

Thanks guys, you've pretty much validated my thinking. I may even move up in tire size as early as this fall, so it might not be a whole year. My main focus for this summer, however, is reliability.

Now, do I dare start another locker thread? I'm thinking Powertrax, but I have some reservations about winter driving. opinions?

 

[3XJFamily]

Yeah, I drove 31" tires and 4.56 for a year, 40 miles round trip to work. It was no issue. Now that I'm on 33's, I kind of miss the power!

 

[sgtmack]

I have 4.56's. I run 33's on the trail and in the snow, 31's in the summer. It has more power with the 31's, and has been all over the country. The first trip from IN to AL on the 31's at got 18mpg. The same as it did stock. And I was in a hurry. I run it on 2 hour trips twice a month, and I get 2 mpg better with the 31's. I wish I could have gone 4.88's when I did my gears.

It's been 3 years and 40,000 miles since I re-geared. I have been watching the engine performance with my scanner. I have TRXS MT's, which are not very efficient highway tires. They are hard to push down the road. In my Jeep, with the 33's, at 65 the map reading drops far enough to put the PCM in to power mode for the fuel map. It gets sucky mileage because the computer thinks I'm towing something, or going uphill, so it runs rich. This is why larger tires with stock gears kill mileage. The engine has to work harder to keep you moving, so the mileage goes down.

I think if I get the ambition to build an adjustable map sensor I could get some of the mileage back. In the mean time, the 31's work better with the 4.56 gears for me.

So, IMHO, 31's and 4.56 gears work very well.

 

[the_weirdo]

I loved 4.56 gears with 31" tires. Now that I have 33" tires I wish I had 4.88.

 

[xcm]

I loved 4.56 gears with 31" tires. Now that I have 33" tires I wish I had 4.88.

x2

 

[georger]

Nice info guys, thanks for all the input. I actually like the simplicity of the 31s, they work great with my RE 3.5" lift. No rubbing, no steering issues. I'm leaning heavily on pulling the trigger on the 4.56s.

 

[Flyfisher]

Sheesh...after reading all the replys...technical and opinion...got to add mine. I've got an '89 XJ...originally 3.55:1 gears. Running 33's (BFG AT's) and now have 4.56:1...according to my GPS...the combination is very close to stock final drive ratio. Only about 3 mph off at 65 mph...

So...running 4.56:1 with 31's...will be a little low, but good for the short run.

 

[BGDG280]

This has opened My eyes a bit, thanx all for sharing.....

I must have 4:56's in Mine then because with a 33 I'm turning right around 2200 in 5th. It has decent power, but I feel it could have more.