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Old 07-11-2008, 07:30 PM   #1
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question on towing

hi all
ok i have a few problems with my 93 grand cherokee when iam towing
my tt on the highway my temp goes up to 235 degrees
but when i get off the highway the temp goes back down normally any
idea why I do have a trans cooler and new radiator warter pump my jeep has v8 in it if that helps . also on the highway shound over drive be off or on.
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Old 07-11-2008, 07:53 PM   #2
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Are you running with OD on when on the highway?
What does your Tow Vehicle's Owners Manual say about towing wrt using OD or not?
A trani typically will run hotter with OD on.
I'm not familiar with Jeeps and their engines.
Our previous TV was a Ford with a 5.4L engine. I used the 55mph rule. If under 55mph no OD. If over 55mph (and no head wind, flat land, etc.) OD on.
Sorry I canít help more. Iím sure someone here will have better advice and suggestion for you.

Hutch
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Old 07-11-2008, 09:01 PM   #3
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Hi jabfd32

Iím not a Jeep wizard but letís see if we can find something that is adding up to your problem.

1. Has the Jeep always done towing this since you had the TT or did it just start? Trying to find out if this new just started or not indicating a different problem.

Here are some generic things about automatic transmissions. Tell us which fit your situation.

2. Pulling a TT is a lot like pulling a large solid brick wall down the road. You get both weight and a lot of surface area. The area of the TT outside the outline of the Jeep creates wind drag. This drag takes power to pull. The faster you go, the more power. The more power, the more heat in the transmission.

3 The torque converter on your TV creates high heat when it is not fully locked, we call this slipping as the fluid coupling, the torque convertor, is actually slipping shearing oil creating heat. This action is normal when going slow and or shifting gears. The point being, slipping = heat.

4. When a transmission shifts in and out of a gear, like OD to 3rd, that shift creates some heat. When you do a lot of shifting in and out, that heat adds up faster.

5. Heat management in a transmission is critical to longevity of the transmission. The term ďheat killsĒ truly applies in this case when it getís too high, too long.

6. TV manufactures generally size a transmission cooler to a certain size heat load that comes from a certain size pulling load. They rate the TV by what they call, Gross Combined Weight Rating, (GCWR) meaning the manf stated limit for max engine, transmission and rear axle rating pull limit. To the transmission anything in the truck or hitched to it creates weight. If the GCWR is say, 11,000# and the Jeep weighs, say 5,500# loaded then 11,000 - 5,500# = 5,550# is left for pulling before hitting the rating. However each TV maker rates using slightly different factors. Like pulling a boat that cuts thru the air easy is sort of just weight with low wind drag. But towing a TT, has high wind drag plus weight. I have not yet found a TV maker who adds in wind drag of a TT in there GCWR. There may be some, I just have not found one and I have looked at.

7. If the TV shifts into 2nd gear a lot and hangs there pulling, the Torque convertor (TC) will be slipping and pumping out heat. Long hills one after another in 2nd gear with the TC slipping can rise the tranny pan temps since it canít get ride of it fast enough for the heat load created, then the pan temp's rise.

8. A blocked/restricted radiator can be an issue. Especially on hot summer days. The heat canít get out.

9.Do you know what your GCWR is for your Jeep? And have you ever weighed the TT and TV the way you go camping? If you are close to or over this limit with a TT, tranny heat can and will come.

10.Speed and hills both create heat. Towing 55 to 60MPH is a lot easier then 65 to 70 for heat and I do not recommend towing 65 or over as a main towing speed for other reasons.

Towing in OD can cause problems pending the actual transmission. Like Hutch said check your owners manual. On a small TV, 3 speed with OD, dropping it in 3rd and leaving it there is a common thing and often recommended. 3rd is generally a direct drive gear and the clutches are heavier then the OD clutches. Even if the tranny is rated to tow in OD, if towing conditions dictate that you are going in and out of OD, drop it in 3rd until things smooth out. Towing with cruise control on can and will most times create a lot of shifts which is a problem due to the heat.

OK so which of these applies in your case?

Hope this helps

John

PS if the tranny pan temps are reaching 235, what is the engine temps? Are they rising above your normal 195 or 210 Mark?
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Old 07-12-2008, 07:01 AM   #4
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which temp is getting up to the 235 deg. tranny or engine
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Old 07-12-2008, 08:04 AM   #5
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What speed do you drive at on the highway. Air friction is not linear with speed, but rather exponential. Friction goes up rapidly with speed. Going from 45 to 65 doubles the drag due to air friction. This may explain the difference between highway and non-highway driving.

Other than hills I'm surprised that you get a temperature rise.

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Old 07-13-2008, 08:08 PM   #6
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hi every one thanks for the replys . I normally drive with over drive on and my speed is 65 to 70 the temp gage is the engine temp i do not have a trans temp gages . I do not know the gcwr of the jeep but i called the dealer said it can tow 5000lbs . I just got tt. and i only towed a small boat and i never had a problem and a car trailer but that was in the winter so i had no temp problem.

thanks for the help guys hope i answer all the question jeff
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Old 07-14-2008, 08:06 PM   #7
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Quote:
Originally Posted by rich2500
which temp is getting up to the 235 deg. tranny or engine
On the Jeep it will be a water temp, unless he has a thermostat on the tranny.
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Old 07-14-2008, 08:16 PM   #8
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Re: question on towing

Quote:
Originally Posted by jabfd32
hi all
ok i have a few problems with my 93 grand cherokee when iam towing
my tt on the highway my temp goes up to 235 degrees
but when i get off the highway the temp goes back down normally any
idea why I do have a trans cooler and new radiator warter pump my jeep has v8 in it if that helps . also on the highway shound over drive be off or on.
OD off.

Sounds like you might have a thermostat hanging partially open/closed. When the radiator and water pump was put on, was the system flushed?

I would also check the fill level both in the reserve tank and the radiator make sure you do these cold (let the motor cool for a good two hours before checking or check first thing in the morning before you start the Jeep).

IIRC, the í93 ZJ has a motor driven fan, which will have a fan clutch instead of an electric fan. This is another item to check. If you are interested let me know and I can give you tips on how to check this.

Does it cool only if you are moving at speed, or if you slow down does it also cool as it should?

Do you happen to know the gears in the rear end and which transfer case you have (if 4x4)? If you donít know the TC model, look just behind the shifters and tell me what it says, IIRC it should be Quadra-Trac or Quadra-Drive. For the gears you can go to www.jeep.com and click on the contact us and give them your VIN #, name and current mileage and they will send you what is called a build sheet which will tell you everything that was on it when it rolled off the line.
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Old 07-14-2008, 08:29 PM   #9
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Two more questions for you, when was the last time you have the transfercase and tranny serviced (both time and mileage)? Mileage on the Jeep?
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Old 07-15-2008, 08:29 PM   #10
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jabfd32
hi all

the jeep has v8 373 gears i replace the fan clucth with water pump
coalant is full transfer case oil was changed 10,000 miles ago trans oil changed about 24,000 miles ago the jeep fulltime 4wd let me know if you can think of any thing else also the has 233,000 miles on the motor and still runs very good with exception of temp when towing tt



thanks for help
jeff
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Old 07-15-2008, 09:01 PM   #11
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Did you flush the system when you did the h20 pump?

what about the thermostat?

When you did the radiator did you put in a 1, 2, or 3 row?
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Old 07-17-2008, 04:41 PM   #12
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hello

i did flush the system out the radiator is at least a 2 row but i got it at auto zone . the termostat was changed in febuary

thanks 4 the replies
jeff
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Old 07-17-2008, 05:46 PM   #13
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There is no way that 1550 should be causing your V-8 Jeep to over heat, there has to be a problem.

I towed a 1660 with a '99 GMC V6 Jimmy all out west, and in the summer with AC running it's really hot out west, I was even on the beach of the Pacific Ocean and never had an overheating problem.

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Old 07-17-2008, 08:36 PM   #14
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I had similar problems when I had my 1998 T1950 pulling it with a 98 Jeep Grand Cherokee in the summer (4.0 6 cylinder). My jeep had a 195 degree thermostat and with the A/C on pulling the trailer in hot weather it would raise the water temp that high and the A/c would shutdown so as not to overheat the engine more. This was a good Jeep vehicle but , I think the combined conditions was just to much. Instead of improving it's cooling performance I changed tow vehicles and got a bigger trailer also. but if I hadn't I would have gotten a bigger radiator, better fan and better coolant. The jeep must run near 200 degrees to perform properly , it just couldn't handle the extra load of towing in the summer. I still have the jeep but do not tow a trailer. dave
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Old 07-18-2008, 05:22 AM   #15
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jab when the thermostat was replaced was it replaced with the stock temp(195) if so you could always go to a cooler thermostat 180 or 160 and see if that helps,sounds like you pretty much tried everything else.
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