Looking for real life feedback on highway towing with 3.73 gears

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Ferg513

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I have a 2018 JKU Sport automatic 5 speed with 3.21 gearing. I am upgrading to 3.73 next week! I put about 25-30k highway miles driving a year. We camp a lot and Im looking to purchase a 6x12 Vnose enclosed trailer (1250lbs) to convert into a camper. Only adding 400ish lbs of cargo. Driving flat to hilly highways. No mountains.

I am looking for real life feedback on towing a cargo trailer on the highway with a 6x12 - 7x14 cargo trailer with 3.73s? Will these suffice and pull decent at 65-70 mph? It’s mostly a wind resistance issue I would imagine not weight? I don’t want to go to 4.10s preferably if I don’t have to because of the amount of highway driving I do for work without towing. I want to find a 5th gear sweet spot on the highway towing. The 3.21 gears suck. Thanks!
 
I put bf goodrich all terrains but I believe close to stock size 31.5 - 32 inch and I do not plan to lift or put larger tires on.
 
Those are close to stock size tires, i'd think those gears would be better then the 3.21's for towing.
 
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I agree with the 3.73 with the tire size and weight you're describing. However, if you upgrade to a 33 or larger tire and don't plan on much off-roading, you'll probably need to go to a 4.10. You also didn't mention if you have a 2-door or 4-door:

"The (2 door) JK is rated to tow 2000 lbs regardless of gear ratio.
The (4 door) JKU is rated to tow 2000 lbs with the 3.21 gear ratio, 3500 with the 3.73 gear ratio.
Note this is related to street and highway driving with the stock gears and tire sizes."

There's no way I'd tow 2000lbs with my JKU and a 3.21 gear, by the way.
 
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Appreciate that info!

It is a 4 door. I don’t have plans to upgrade tire size. Ultimately looking to pick the best gear ratio for recreational highway towing a few times a month and a set that still runs 2500 rpms or under in 5th gear around 75mph when I’m not towing. 4.10 just seems like it may be more than I want for daily driving but just curious if the 3.73 is enough to still tow comfortably a enclosed trailer cuz the 3.21 is pretty pathetic with any sort of higher speed towing from my little bit of experience.
 
Have you verified that your JKU is, in fact, equipped with a 3.21, by either the build sheet or the tag on the differential?
I think you'll probably be okay with the 3.73, if you have to re-gear it. I don't think you need to go up to a 4.10.
 
Thanks for the feedback!

My research shows the 2018 JKU Sport automatic comes equipped with 3.21. Im going to dig around more but Im almost positive it is 3.21 based off initial research and its onroad performance. Feels like a dog when it tows and around 2000rpms in 5th at 75mph
 
http://www.nathanson.org/davesays/wp-content/uploads/2019/09/jeep-vin-buildsheet.html

You can enter your VIN at the above link and get the factory build sheet.
You can also crawl under and look at the tag on the differential and it will be right there as a "3.21" or whatever it may be.

Here's the other way- little more useful if you have reason the believe the JK was re-geared.
1607105946544.png
 
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Thats great info and a handy site to have too! Appreciated.

Accord to the site is 3.21 on the build sheet
 
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Justcmy opinion...I've towed all my life, with everything from well set up diesel pickups to sadly underpowered, ill equipped undersized vehicles. Our 2018 JKU Rubicon auto with 3.73 gears and stock 32" tires was one of the worse vehicles I've ever towed with. It struggled with a 4x8 flat utility trailer with some pressure treated lumber on it. When I had to haul a motorcycle about 500 miles, it was very sluggish on hills and fuel mileage was pitiful. It worked harder than my old XJ with 31s and a 4.0 hauling a 3/4 ton van on a trailer. The 3.6 sure is NOT a towing engine.

The JK will do it, but I wouldn't want to do it for very far. Enclosed trailers are like pulling a parachute through the wind.
 
This is not an exact match, just sharing my experience.

A few months back we purchased our 2018 Jeep Wrangler 4 Door JK, it has the 3.21 with automatic 6 speed transmission.

We have a 6x12 enclosed v-nose trailer

We took some scrap metal to the junk yard/recycler.

I did not feel comfortable at anything over 70mph on the highway.

MPG was 13.
I agree with nydiesel, I wouldn't want to travel up north 8 hours pulling this trailer, maybe if I kept the speed at 60 mph it would be ok ?

We have a 14 foot aluminum boat.
We pulled it about 1/2 hour to indoor/winter storage.
I'd say our Jeep pulled it so well - I hardly noticed it was back there.

In upcoming May and August 2021, we will be towing our boat 8 hours north.. fingers crossed our Jeep will pull our small boat as well as our Chevrolet Traverse did.
 
Update: After using the link/website that was referenced to look up the details of you vehicle using the VIN code... I found out... "surprise".... I have a 5 speed automatic (not a 6 speed)... apologies on my incorrect post above.

In the VIN details for the equipment listing I saw that our Jeep has an "Engine Block Heater". Shortly ago I grabbed a flashlight, popped the hood, looked around and found the 110 volt power cord. This will come in handy once the snow starts here in Michigan.
 
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I have a 2018 jk 2door with 35s on it pull a 1300 pound camper on hills to the up of Michigan .the jk had low power 6 speed manual had to pull in 4/5 gears all the time the 6 gear would not pull no power . Not sure my gearing but something has to give .recently I pulled my camper out west changed my 35s back to stock and still the same issue with now power this time on some hills 3/4/ gear to even stay up with traffic hard to drive road speed. The set up I would love to have is pull the camper with the 35s on it .I’m sure I need to regear but to what .
 
Chazyon said:
I have a 2018 jk 2door with 35s on it pull a 1300 pound camper on hills to the up of Michigan .the jk had low power 6 speed manual had to pull in 4/5 gears all the time the 6 gear would not pull no power . Not sure my gearing but something has to give .recently I pulled my camper out west changed my 35s back to stock and still the same issue with now power this time on some hills 3/4/ gear to even stay up with traffic hard to drive road speed. The set up I would love to have is pull the camper with the 35s on it .I’m sure I need to regear but to what .
Click to expand...

You will want 4.56 or 4.88's with the 35's. Also a Pedal Commander will help make the throttle pedal more responsive to help getting the JK moving.
 
Tom_H said:
In the VIN details for the equipment listing I saw that our Jeep has an "Engine Block Heater". Shortly ago I grabbed a flashlight, popped the hood, looked around and found the 110 volt power cord. This will come in handy once the snow starts here in Michigan.
Click to expand...
I purchased my JKU a few months back and used the same site to view the build sheet. The previous owner (a friend) had no idea he had the ‘winter package’ which includes the engine block heater, yet he owned the Jeep for 5 years. Pleasant surprise, for sure.
 
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My '10 JK Sahara has the oem towing package which includes 3.73 gears. I don't care for them as I do only highway driving. I can't make any suggestions to you, as I'm interested in advice on gears that are more highway friendly.
 
Ferg513 said:
Thanks for the feedback!

My research shows the 2018 JKU Sport automatic comes equipped with 3.21. Im going to dig around more but Im almost positive it is 3.21 based off initial research and its onroad performance. Feels like a dog when it tows and around 2000rpms in 5th at 75mph
Click to expand...
Don't trust the build sheet. Mi e said I had 3.73's but when I jacked it up I actually had 3.21 gears.
 
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