Towing and Gears

[jimstj]

Hey Guys

I have read a lot of posts about towing, but mostly related to weight. Not so much with regards to gears.
I have a 2002 TJ 4.0L 5spd. I currently have 31s now (2.5in lift), but will be getting 33s.

I was all set to re-gear to 4.10s but then as I consider pulling a trailer I am thinking the 4.56 might be better. I don't want to spin too high down the road as I usually drive to my destinations as far as Oregon (from Los Angeles) so was thinking go with 4.10s. I did the grim jeeper gear calc (attached) to compare the RPMs at different speeds and the 4.56s don't seem bad. So can anyone comment if there is a material difference between the gears when towing in town and / or hwy between these two gears?

Probably worth noting, I don't do a lot of crawling, but spend a lot of time off-road getting to fishing and hunting places, and great places to camp.

lastly, since I am going to re-gear I think I will put in an LSD. I do spend a lot of time in the snow and rain. Question is, is there a brand people recommend and should I put the LSD in both the front and rear? Or just the rear?

Thanks guys

 

[never monday]

4.56 is the better option.

 

[jimstj]

thanks @never monday, feel free to elaborate

 

[bromel]

If you're going to 33s, you want at least 4.56 regardless if you're towing.

 

[never monday]

Yup, gear ratio choice is to restore hwy driving. Target about 2800 rpms for a cruise speed in top gear. The engine will be happier with a little spin going on.

 

[RubiconRic]

Are the long highway trips with the trailer or without? It's hard to tell from your post if you're towing in LA or up to Oregon and back. I have 4.88 in my '03 with the 5 speed and I believe I'm around 3k RPM on the highway with 33's, which I'm ok with (this is without a trailer). For you, even without a trailer, I would think you'd enjoy 4.56 better than 4.10 if there are any sort of hills. Another thought, if your highway speeds rarely exceed 65mph-ish then you may also want to consider 4.88 if you're doing lots of towing in hills/mountains.

 

[jimstj]

Yup, gear ratio choice is to restore hwy driving. Target about 2800 rpms for a cruise speed in top gear. The engine will be happier with a little spin going on.

Sounds good and thanks. I was thinking I should keep it with the lower RPMs. So good to hear spinning it up a bit is okay.

 

[jimstj]

Are the long highway trips with the trailer or without? It's hard to tell from your post if you're towing in LA or up to Oregon and back. I have 4.88 in my '03 with the 5 speed and I believe I'm around 3k RPM on the highway with 33's, which I'm ok with (this is without a trailer). For you, even without a trailer, I would think you'd enjoy 4.56 better than 4.10 if there are any sort of hills. Another thought, if your highway speeds rarely exceed 65mph-ish then you may also want to consider 4.88 if you're doing lots of towing in hills/mountains.

thx Ric
The highway trips with the trailer could be short like a few hours, or all the way up to Oregon. During the warmer weather I usually take a few days to get up there and camp along the way.
I'm not usually in a hurry when traveling in the jeep, so typically in the right lanes, but on occasion I need to get somewhere so would like to be able to cruise closer to 70+. Having said that there are plenty of times I will tow in the hills like the Eastern Sierras or some of the northern grades.
Putting the 4.88 in the gear calculator appears to result in rpm's and optimal speeds. Damn. I think 4.10s are out and now I need to decide between 4.56 and 4.88. Is there anything I need to modify or is there any increased wear and tear with the 4.88s?

 

[J&M’s ICON]

My opinion only, as I’m typing this response my Jeep is getting regeared from 4:88 to 5:13.

4:88 are great with the 6spd manual transmission for 90% of the time and especially for the Jeep’s overall performance.

I am going to 5:13 for one reason only, towing!

Living in Colorado, where there are a lot of mountains/passes, your always on an incline. My off road trailer is right at the 1800lb - 2000lb limit so for me, 5:13 is the way to go.

My opinion, if your going to regear, NO LESS than 4:88.

 

[Jerry Bransford]

Sounds good and thanks. I was thinking I should keep it with the lower RPMs. So good to hear spinning it up a bit is okay.

The very slightly higher rpms of 4.56 vs. 4.10 are what you need and they are still more than highway-friendly, you're not going to be worried about them at all. 4.56 is the optimal ratio for 33's, 5-speed and 4.0 engine. I ran 4.10 with 33's years ago and I just hated it, the rpms were a tad too low and I had to downshift for even very minor uphill sections. You won't regret 4.56 in the least.

 

[BugoutJeep]

Don't worry about spinning your engine too fast. However, if you aren't doing a lot of towing you could run the 4.56s and just run 4th gear when towing in more hilly environments. I've towed a Willy's Jeep on a 2k lb trailer for 45 hilly and twisty miles with my TJ running 31s and 3.07s and ax-15 manual 5 speed with the old 4.0L. It was awful, but worked.

Just make sure you're solidly in your peak torque curve when picking gears. I'm running the R2.8 now and with 33s, 3.07s, AX-15, that gearing sucked even with the diesel, but I could tow just because you can always tow something. I did 3k lbs locally a handful of times and the Jeep brakes were a MAJOR issue. I swapped to ~27.5" diameter tires and towing was SO MUCH better, but I could get my speeds and peak torque which happens at 1,800 rpms match so driving was much better, as was fuel economy.

I just finished the regear so I don't have enough information yet, but I plan to run 33s for our rainy season and then 31s for the summer, where I do more towing. It's mostly about towing with plenty of room above you peak torque so you don't get bogged down when you hit hills or you can just shift more often.

 

[jimstj]

My opinion only, as I’m typing this response my Jeep is getting regeared from 4:88 to 5:13.

4:88 are great with the 6spd manual transmission for 90% of the time and especially for the Jeep’s overall performance.

I am going to 5:13 for one reason only, towing!

Living in Colorado, where there are a lot of mountains/passes, your always on an incline. My off road trailer is right at the 1800lb - 2000lb limit so for me, 5:13 is the way to go.

My opinion, if your going to regear, NO LESS than 4:88.

Thanks J&M, I understand there are considerations between the manual and auto transmissions. Would the 5.13 auto be the same as 4.88 manual?

 

[Jerry Bransford]

Thanks J&M, I understand there are considerations between the manual and auto transmissions. Would the 5.13 auto be the same as 4.88 manual?

The automatics used in Wranglers require different gearing than for our manual transmissions. And early TJ automatics require different gearing than for later automatics. What's good for one transmission/engine combination is seldom appropriate for a different transmission/engine combination.

 

[jimstj]

The very slightly higher rpms of 4.56 vs. 4.10 are what you need and they are still more than highway-friendly, you're not going to be worried about them at all. 4.56 is the optimal ratio for 33's, 5-speed and 4.0 engine. I ran 4.10 with 33's years ago and I just hated it, the rpms were a tad too low and I had to downshift for even very minor uphill sections. You won't regret 4.56 in the least.

Thanks Jerry. I found that I cannot get a decent trailer without getting close to that 1800 to 2000 lbs range. So that is probably where I will end up. would you still go with the 4.56 or go up to 4.88?

 

[jimstj]

Don't worry about spinning your engine too fast. However, if you aren't doing a lot of towing you could run the 4.56s and just run 4th gear when towing in more hilly environments. I've towed a Willy's Jeep on a 2k lb trailer for 45 hilly and twisty miles with my TJ running 31s and 3.07s and ax-15 manual 5 speed with the old 4.0L. It was awful, but worked.

Just make sure you're solidly in your peak torque curve when picking gears. I'm running the R2.8 now and with 33s, 3.07s, AX-15, that gearing sucked even with the diesel, but I could tow just because you can always tow something. I did 3k lbs locally a handful of times and the Jeep brakes were a MAJOR issue. I swapped to ~27.5" diameter tires and towing was SO MUCH better, but I could get my speeds and peak torque which happens at 1,800 rpms match so driving was much better, as was fuel economy.

I just finished the re-gear so I don't have enough information yet, but I plan to run 33s for our rainy season and then 31s for the summer, where I do more towing. It's mostly about towing with plenty of room above you peak torque so you don't get bogged down when you hit hills or you can just shift more often.

Thanks bugout. I has often occurred to me that I do not really know what my power band is on my jeep as it is or with the new tire size and gears. any suggestions?

 

[Jerry Bransford]

Thanks Jerry. I found that I cannot get a decent trailer without getting close to that 1800 to 2000 lbs range. So that is probably where I will end up. would you still go with the 4.56 or go up to 4.88?

I'd stay with the 4.56 which will be fine for towing too. The 4.0 has zero problem with that 2000 lb. load, the only reason for the limitation to 2000 lbs. is the TJ's short wheelbase. The same engine/transmission but in the longer wheelbase Unlimited is rated to tow 3500 lbs.

You will barely notice that 1800-2000 lb. trailer's weight. I tow an 1800 lb. pop-up tent trailer a lot and I literally have to look to make sure it's still there behind me on the highway.

 

[J&M’s ICON]

Thanks J&M, I understand there are considerations between the manual and auto transmissions. Would the 5.13 auto be the same as 4.88 manual?

I run 35” tires, you running a smaller diameter tire, as Jerry said, 4:56 will probably be ok. Personally, I’d go with 4:88 if your Jeep can be regeared to that with no additional mods being needed.

 

[never monday]

O’d amend my recomendation to 4.88 if your spending a significant amount of time over 5000’ elevation.

 

[jimstj]

While we are on this topic, I plan to add a LSD and thinking of the Detroit Truetrac only in the rear. Any thoughts? I am in rain and snow mostly and desert roads.

 

[RubiconRic]

Others will offer better advice, but seems to me if you're going down that road, plus regear, and assuming you're paying someone else to do the install, you may want to broaden your search to consider fully assembled, bolt-on Dana 44 packages. Obviously more expensive, but you seem committed to investing in your Jeep.