XJ gear vs. Tire

[IH8RDS]

I have a 99XJ with 4.0, AW4, 231, 4.56 and 31" tires.

My question is with expedition/overland travel plus pulling a M416 trailer, would it be better to stay with the same size tire or move up to 33". I'm thinking of pulling/torque and I am a little concerned with mpg. Ultimately pulling power outweighs mpg, but a happy medium would be nice.

What would you do?

 

[kjp98TJ]

i would think 33's would be about perfect with the auto and 4.56's....

 

[wADVr]

How do you like the 4.56:1 and the 31s? To me that seems way overgeared. I have been pretty happy with my 4.56:1 and 33s, I would think 33s would offer plenty of pulling power and keep some economy even with the trailer in tow. How much does this trailer weight?

 

[Backwoods Rambler]

I plan on running 33's with 4.56 to start with, but since I pull a pop-up camper (bigger than a chaser style) I am keeping my options open to possibly 4.88's. This would be for better towng power combined with the colorado mtn passes I frequent in the summertime.

FWIW 4.56 & 33's will give you better than stock (235/75 & 3.73's) overall crawl ratio if you want to use that as a way to deterrmine where your RPMS will land.

Good luck with your choice :smiley_drive:

 

[Brett M]

Switch to 33's, you're way overgeared right now.

 

[ExpoMike]

FWIW 4.56 & 33's will give you better than stock (235/75 & 3.73's) overall crawl ratio if you want to use that as a way to deterrmine where your RPMS will land.

For what it's worth, a majority of XJ's came with 215/75-15 and 3.55 gears.

The typical gear vs. tire combo tends to be 31" tires = 4.10 gears, 33" tires = 4.56 gears. Some may adjust to different combos but I would venture a guess that about 90% of people who actually change their gears use the above combos.

YMMV. :hehe:

 

[John90XJ]

I've been running 33s and 4.10s for several years and with a 4700# rig loaded I still get decent pulling power and good MPG at 18+.

4.56s would be ideal with the trailer. I think you're well over-geared now.

 

[IH8RDS]

I wanted to do the gears only once. That's why I went so deep with 31" tires. I never intended on going over 33" tires. I have heard on NAXJA over the years about the gear vs. tire but pulling a chaser trailer is not really addressed. Most people don't look at a Cherokee as a tow vehicle. I appreciate all of your inputs. I will get the 33's when I get a chance.

As far as the trailer goes... I have no idea how much it will weigh. I am guessing around 2000lbs, but I really don't know. Max tow capacity is what? 4200lbs? I think it is in the 4000lbs range at least. I think I will be safe.

I do feel way over geared and I am glad to hear that is the general consensus. Usually you hear of vehicles being under geared. I'm sure the engine with thank me for the lower engine RPMs :hehe:

 

[kjp98TJ]

i have 4.88's in my TJ. i originally built it for 35's (standard). my pavement tires were ~32's. i didn't mind much. came in handy pulling a loaded 416 with 4 people in the jeep for 4 hrs. and the 2nd and 3rd gear starts at stop signs saved shifting . and i rarely drive over 55. virtually zero highway.


now running 33's full time. no idea about MPG's. when it gets low, i fill up.

 

[xr8dxj]

I'm sitting with 4.56's and 37's. Not optimal by any means, but when I origianlly put 33's on I didn't think I would ever need to go higher. And when I went to 37's I decided to stay with 4.56's because the 4.88 ring gear in my 30 would be too thin. So I tried to leave "the weak link" as my axles and axel u-joint instead of the r&p. Thankfully it's worked out. My snapped axels & u-joints to r&p ratio is about 5:0. :wings:

 

[OverlandZJ]

I'm running a 4:56 R&P w/ 33's and auto trans. 2150 RPM @ 65MPH and close to if not 20MPG with a tailwind.

I'm happy with that since many report substantially less MPG than i have experienced.

 

[Sleeps In Jeeps]

So what kind of gears would a 96 SE AW4 come with? My XJ had a 231 when I bought it but Im not sure if that was stock.

I currently have 33's and was wondering if I need to re-gear.

Thanks guys!

 

[John90XJ]

So what kind of gears would a 96 SE AW4 come with? My XJ had a 231 when I bought it but Im not sure if that was stock.

I currently have 33's and was wondering if I need to re-gear.

Thanks guys!

It should be 3.55. That was common from the beginning of the 4.0 motor coupled with a 4 speed auto.

The 231 could very well have been stock.

Running 33"s with that gearing is not optimal. 4.10s or 4.56s would be better choices depending how you use it.

 

[Sleeps In Jeeps]

Just daily driven. Can I be doing any harm to my drive trian if left stock?

Thanks!

 

[John90XJ]

Just daily driven. Can I be doing any harm to my drive trian if left stock?

Thanks!

No, not really. But you're not in the best RPM range for performance and you'd be amazed at how much better it would be if you were.

A nice mod for someone in your spot is to find a pair of axles from a 4 cylinder manual XJ. You'll get 4.10 gears and it's basically a bolt-in swap. One pro is getting a HP D30 if you don't have one. A con is possibly losing the ABS if you have that.

I did this same swap years ago and it was an easy way to get the performance back when I went to bigger tires.