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TJ Flat Towing Mystery

Sandy Johnson

Sandy Johnson

Harry Member
Joined
May 19, 2020
Member Number
247
Messages
2,809
Loc
Spreckels, Ca
Got a 98 TJ that we occasionally flat tow behind our RV. It works great BUUUUT... Nearly every time I do, it smells like the serpentine belt is burning when I go to unhook it from the back of the RV. Everything else seems to be fine and it fires right up and runs down the road with no issues after. The smell is gone after that first drive. I've touched the belt after towing and it's not hot. The burned belt smell is stronger if I open the hood and stick my nose over the belt for a sniff test.

I follow the instructions in the manual for flat towing: Key turned, but not on, transfer case in neutral, manual transmission in gear (I usually use 4th because the idea of the transfer case popping out of neutral at 60 mph terrifies me).

What the heck is going on?
 
Take the driveshafts out.
 
crazybluerider said:
Any chance your front alignment is off and your smelling tire?
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I thought maybe that as well. I'm pretty familiar with the smell of hot or burning tires, but I did the sniff test around the tires anyway- it's stronger right over the belt when I pop the hood.


The only potential theory I'm working with is the stock fan is spinning while I'm running down the road and "peeling out" on that small section of the belt. I haven't had a chance to test the theory since it occurred to me in the shower last night a few hours after we got back.
 
Harry Johnson said:
I thought maybe that as well. I'm pretty familiar with the smell of hot or burning tires, but I did the sniff test around the tires anyway- it's stronger right over the belt when I pop the hood.
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The engine would have to be turning for anything with the belt to be hot. Sure you have the Tcase in N and not 4H? :flipoff2::laughing:
 
SLOWPOKE693 said:
The engine would have to be turning for anything with the belt to be hot. Sure you have the Tcase in N and not 4H? :flipoff2::laughing:
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haha, yeah. I'm super paranoid about that especially since I started noticing this. Once I've got everything hooked up and set, I fire up the motor and make sure it doesn't move when I let out the clutch. I've started doing the same thing when I go to unhook it just to see if it has somehow popped into gear.
 
Harry Johnson said:
haha, yeah. I'm super paranoid about that especially since I started noticing this. Once I've got everything hooked up and set, I fire up the motor and make sure it doesn't move when I let out the clutch. I've started doing the same thing when I go to unhook it just to see if it has somehow popped into gear.
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I flat tow mine when we aren't doing harder offroad stuff too. The transfer case falling into gear is the thing of nightmares. It causes me so much anxiety. I do the same thing as you. Once it's all hooked up I throw it in drive and rev the engine. I finally trained myself to shut it off before shifting it back into park. The park pin gets super pissed if you don't. lol

However, thousands of blue hairs all over the country are flat towing vehicles as we speak without any issue. So...
 
Has to be the tires. Next time you road trip check all four tire temps as soon as you stop. I'm gonna guess the front will be hotter than the rears.

Is it possible it's not the Jeep at all and it's the RV causing the smell? Anything stuck to the exhaust?
 
crazybluerider said:
I flat tow mine when we aren't wheeling too. The transfer case falling into gear is the thing of nightmares. It causes me so much anxiety.

However, thousands of blue hairs all over the country are flat towing vehicles as we speak without any issue. So...
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I keep telling myself that. I really want to make some sort of little metal or plastic bracket that I could shove under the t-case lever for towing to hold it in place.
 
SLOWPOKE693 said:
Has to be the tires. Next time you road trip check all four tire temps as soon as you stop. I'm gonna guess the front will be hotter than the rears.

Is it possible it's not the Jeep at all and it's the RV causing the smell? Anything stuck to the exhaust?
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Gonna have to check tires. Definitely not the RV as I've noticed this behind two different types of motorhome.
 
total newb said:
The fan is assumably stock with a clutch hub. That fan would have to be spining pretty fucking fast to lock it up and burn the belt.
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Aren't the stock fan clutches heat activated? The one in this thing is the 24 year old original. I think it takes something like 180* to lock them up normally, but maybe when they start to wear out they lock up sooner? Say 90*?
 
total newb said:
The fan is assumably stock with a clutch hub. That fan would have to be spining pretty fucking fast to lock it up and burn the belt.
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I don’t suppose it would have to “lock up” to drag in the belt some. Could be even if it is just turning the clutch, it makes heat that smells. I would try putting a tie rap on the fan blade. Just don’t forget to remove it.
 
Buy a trailer.

Flat towing is bad for your tires, hard on your front suspension, and terrible on your transfer case - especially a chain driven case that relies on pressure lubrication. The cage bearings on the main shaft / output shaft are not designed to be spun at freeway speeds for endless hours. You also can't backup with the vehicle flat towed.
 
FordFascist said:
Buy a trailer.

Flat towing is bad for your tires, hard on your front suspension, and terrible on your transfer case - especially a chain driven case that relies on pressure lubrication. The cage bearings on the main shaft / output shaft are not designed to be spun at freeway speeds for endless hours. You also can't backup with the vehicle flat towed.
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Welp, this one pretty much pulls light duty wheeling and dingy behind the motorhome duties. We flat tow it to avoid having to figure out where to stuff our flatbed trailer when we roll in to the KOA with the kids.

Horses for courses and all that, but we are thinking about swapping it out for something with 4 doors and a truck bed like a new ranger maybe. Just having a hard time justifying getting rid of it since my dad bought it new and now to the kids, it's officially "Grandpa's Jeep".

This
1659979894240.png




vs that
1659979813454.png
 
crazybluerider said:
NP231J cases run the pump on the output, so they are being lubed while towing.
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Yes, correct. The point I was making is that the entirety of the wear is occurring on quite possibly the smallest bearing in the entire case. There is no scenario in low range where this bearing is ever spinning that fast vs running at 70MPH.

Screen Shot 2022-08-08 at 11.07.49 AM.png
 
FordFascist said:
Yes, correct. The point I was making is that the entirety of the wear is occurring on quite possibly the smallest bearing in the entire case. There is no scenario in low range where this bearing is ever spinning that fast vs running at 70MPH.

Screen Shot 2022-08-08 at 11.07.49 AM.png
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Good point, I hadn't thought about the pocket bearing between the main and output spinning.
 
FordFascist said:
Yes, correct. The point I was making is that the entirety of the wear is occurring on quite possibly the smallest bearing in the entire case. There is no scenario in low range where this bearing is ever spinning that fast vs running at 70MPH.
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Does that bearing spin when it’s driven at 70 under its own power? Or do Jeep’s not go 70?
 
I've flat towed for 25 years, parents flat towed for longer. Zero issues with it as long as you maintain your vehicle. I towed with a NP231 for at least 10 years, and my Atlas II for four. No problems. I change the Atlas fluid every other year. I keep the speeds under 70 just because my rig has 5:13 gears and 35" tires. Buddy left his rig in 3rd and forgot to put his Atlas in neutral. Towed it for 200 miles with no damage. Only issue I have is wearing out my mud tires quicker than I would like but it still doesn't equal the cost and hassle of a trailer, especially at a RV park.

OP: Check or replace your serpentine belt tensioner. It shouldn't let the fan turn if the clutch locks. I also replace my fan clutch every 10 years or so as a maintenance item.
 
probably dumb question... as I've never flat towed anything.

If you think air flow is possibly causing the fan to move... would putting a piece of cardboard in front of the grill (or one of those fancy flat tow car bras) stop enough air?
 
WaterH said:
Does that bearing spin when it’s driven at 70 under its own power? Or do Jeep’s not go 70?
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No. It doesn't spin when the Jeep is high range.

For the cost of tires + the vehicle wear and tear you will be ahead with a trailer. They aren't that expensive.
 
FordFascist said:
No. It doesn't spin when the Jeep is high range.

For the cost of tires + the vehicle wear and tear you will be ahead with a trailer. They aren't that expensive.
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Harry already alluded to this... but I understand that a lot of camp grounds don't really make it feasible to use a trailer...
 
FordFascist said:
No. It doesn't spin when the Jeep is high range.

For the cost of tires + the vehicle wear and tear you will be ahead with a trailer. They aren't that expensive.
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rockota said:
Harry already alluded to this... but I understand that a lot of camp grounds don't really make it feasible to use a trailer...
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Yeah, I own a 16' trailer already. It's easier to find a campsite at rv campgrounds that can accommodate a 27' rig and a spare vehicle than it is to find a site that will fit a 43' rig and spare vehicle. If space isn't an issue, then it goes on the flatbed... shoot, just for the convivence of being able to back up, trailering makes it worth it.
 
Harry Johnson said:
I'm guessing it's one of the newer ones that are designed to be flat towed?
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No, standard output. When I got my Atlas the flat tow output was only for electronic speedo's. I need a cable speedo. Even Advanced Adaptors says in their literature that the only issues they have had with flat towing the standard output have been because the customer didn't follow the break in for the case. Friends have towed thousands of miles over many years with Atlas cases before they made a flat tow output.

Mine is in a 1994 Explorer with a 700R4 trans, 3.8 Atlas II. Looking at a NWF ibox.. I called NWF and they didn't see any issues with flat towing with a iBox.

I also don't have any room for another trailer. Maybe when I move all my stuff to the shopdominium if it ever gets built. Already have a 35' coach, a 20' boat, horse trailer, 2 cars, 2 trucks and the Explorer. I can't shuffle any more stuff around whnever I want to use something.



I still think it's the belt tensioner.
 
BDK said:
No, standard output. When I got my Atlas the flat tow output was only for electronic speedo's. I need a cable speedo. Even Advanced Adaptors says in their literature that the only issues they have had with flat towing the standard output have been because the customer didn't follow the break in for the case. Friends have towed thousands of miles over many years with Atlas cases before they made a flat tow output.

Mine is in a 1994 Explorer with a 700R4 trans, 3.8 Atlas II. Looking at a NWF ibox.. I called NWF and they didn't see any issues with flat towing with a iBox.

I also don't have any room for another trailer. Maybe when I move all my stuff to the shopdominium if it ever gets built. Already have a 35' coach, a 20' boat, horse trailer, 2 cars, 2 trucks and the Explorer. I can't shuffle any more stuff around whnever I want to use something.



I still think it's the belt tensioner.
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Definitely gonna check belt tensioner AND fan clutch when I get a chance. Gonna pull the T-case to add an SYE in the near future and I've got a whole list of maintenance items I want to do on this thing while it's sitting there.
 
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