Kastiron

I have been searching for an explanation to this question. Somehow the math doesn't line up for me, or maybe it is the logic.

According to page 350 of my owner's manual, the 3.21 geared unlimited with the manual transmission has a towing capacity of only 1,000 lbs in comparison to the 3,500 pounds that the 3.73 and 4.10 ratios can handle.. Does .52 make that much of a difference, and if so why doesn't the 4.10 have a higher rating yet?

I am searching for a popup camper that fits into the 1,000 range, and am having VERY little luck.

I have the stock 225's for tires with no immediate plans to upgrade. Even then, probably not higher than a 245. I really did not want to re-gear just for limited camper pulling use.

Heck, it is worse than a 2-door..

ronjenx

It wouldn't seem .52 is a lot, but it represents a 14% difference. That's a pretty big chunk.
There are lots of theories here why the JK towing limit is so low.

09rubicon

This has been discussed several times in this forum, even got input from several Jeep engineers. In the case of the tow rating two factors came into play, and neither of them is your engines ability to tow!! First is engine and tranny cooling ability, the radiator on the jeep and lack of one on the trany cause high heat build up. Lower gearing will allow the engine to pull more without working to hard, but as you can tell by your manual not much (3500lbs really isnt a lot of weight, my trailer alone weighs 2800lbs). The second realy limiting factor is the actual weight of the jeep. It is a realitivly light vehicle and it really wouldnt take that much weight swinging off the ass end to make you loose control (couple hundred lbs swinging back and forth).
So here is the bottom line, your jeep is more than capable of towing a rather heavy trailer, but doing so is unsafe and could very easily cause your Jeep to overheat causing serious internal damage.

ronjenx

The tranny has a cooler, although an additional one does wonders.

Liberty, weight 4269 lbs., tow capacity 5,000 lbs.
Wrangler, weight 4180 lbs., tow capacity 3500 lbs.
That's just 89 lbs. difference in vehicle weight.

I lean toward aerodynamics being the limiting factor. More air under the vehicle = less air through the radiator.

Like I said, there are lots of theories. The engineers have repeatedly said engine cooling is the limiting factor for the Unlimited (ironic, huh?)

Kastiron

I can understand the engine or transmission cooling being the isssue, it just seems that if the 4.10 and 3.73 ratios can handle 3500lbs that the 3.21 should be able to take more than 1000.

Guess I will be looking to regear so I can pull a 1400lb pop-up camper.

tango3065

Where is located on a Jk? Also I noticed there is no transmission overheat light like most vehicles, did Jeep integrate this in the check engine light or do they just not let you know if the tranny is getting hot?

ronjenx

The automatic tranny cooler is part of the tranny cooler/AC Condenser assembly, in front of the radiator. When the tranny overheats, it trips a code and sounds a chime.

JKJeremy

there are several threads on this but from a real world experience i tow a 2800 lb hybrid travel trailer that is probably pushing the 3500 lb limit when loaded for a trip with my rig that has the 4.10 and 32s and there is no way i would pull anything heavier or even the same thing with less than the 4.10s....it tows great, just sluggish on the uphills and slow from a stop, nothing a downshift can't handle and you can forget using 6th gear,,,,it's not that you can't tow something heavier, it's just that you will be hardly moving and its a safety factor...i've read elsewhere that the same setup in europe is rated for 5,000 lbs so i wouldn't sweat it for pulling something slightly heavier if i had to but not regularly...i porbably wouldn't tow much more than the 1,000 lbs with the 3.21s though if you expect to be able to get out of your own way....manual tranny certainly helps....

tango3065

So no light and a ding that you have to hear over the radio and then try to figure out if that ding is your tranny melting LOL.

ronjenx

It may illuminate the check engine light, but I don't know for sure.