Transmission overheated in one of the passes in the Rockies - HELP

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thedoors

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Hi,

My family and I were traveling from Farmington, NM to Montrose, CO.  We encountered two pretty tough passes - under construction too.  They were about 8% grade and at the top of the first pass our 5.3 L V8 Suburban 4wd (~9200 lbs towing capacity) towing a 27ft TT (6500 lbs GVW) just died.  After a quick prayer, a very helpful couple towed our vehichle and trailer up to the top of the pass.  The gentleman told us our transmission overheated and sure enough after a few minutes of cooling we were able to continue downhill and handled the next pass ok.

This gentleman told me just to take it real slow 10-15 mph in first gear at the next pass and I should be ok.  This worked fine for the second pass ... in onther words we did not overheat and die at the top of the pass.

I have 2 questions about this ... 1) shouldn't my vehicle be able to pull at a higher speed than this and not overhead the tranny?
and 2) now that our tranny overheated but ok now, should I be concerned with any damage caused?

Thanks for response.
 

King

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I can't say for sure about your transmission, but I was told that the gear train/ clutches used in the LO or 1st position are different than those used in any drive position.  The LO  setting can take much more torque.  I had a 81 olds diesel toronado used for towing a large boat.  I changed the engine to a 72 455 cu in.  Since the transmission (a 250 turbohydromatic) was rated at 250 ft lbs torque and the engine rated at 400 ft lbs, the tranny didn't last long.  The repair shop guy told me to always start off in LO, and always downshift instead of letting the tranny control the shifting.
It would be good to have the fluid and filter flushed and changed.
 

Ron

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At the very least the Transmission fluid has most likely been degraded.  I would recommend you get the transmission fluid and filters changed.  I would also recommend installing Amsoil synthetic transmission fluid since you are towing.  The transmission will run cooler and the Amsoil fluid will tolerate high heat levels.
 

Gary RV_Wizard

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Damage? Yes - the tranny fluid has been cooked and is no longer suitable for use. Definitely get the tranny fluid changed and use a synthetic fluid to help survive the high temperatures when towing. Synthetic is expensive but well worth it for ehicles that have to endure heavy loads.

Consider adding a transmission oil cooler and/or additional electric cooling fan to the Suburban. It should help somewhat.

Were you using the air conditioner? It adds to the overall heat load on the cooling system and makes it that much harder for the tranny fluid to get cooled.  You also didn't mention how old the Burb is - towing capability deteriotes with age due to wear on the drive train.

Should you be able to tow faster up an 8% grade?  Probably not. Your Suburban is under powered for that much trailer load and you should not expect to cruise up any and all hills.  When they tell you it will pull 9200 lbs, they didn't say how fast!  :(
 

Carl L

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thedoors said:
Hi,

My family and I were traveling from Farmington, NM to Montrose, CO.? We encountered two pretty tough passes - under construction too.? They were about 8% grade and at the top of the first pass our 5.3 L V8 Suburban 4wd (~9200 lbs towing capacity) towing a 27ft TT (6500 lbs GVW) just died.? After a quick prayer, a very helpful couple towed our vehichle and trailer up to the top of the pass.? The gentleman told us our transmission overheated and sure enough after a few minutes of cooling we were able to continue downhill and handled the next pass ok.

This gentleman told me just to take it real slow 10-15 mph in first gear at the next pass and I should be ok.? This worked fine for the second pass ... in onther words we did not overheat and die at the top of the pass.

I have 2 questions about this ... 1) shouldn't my vehicle be able to pull at a higher speed than this and not overhead the tranny?
and 2) now that our tranny overheated but ok now, should I be concerned with any damage caused?

Thanks for response.

Lets run a few numbers.? The first number is that tow rating.? Trailer Life's 2005 tables give your truck a rating of 8100 lbs, not 9200 lbs.? ? You were towing in the mountain west.? ?Because of the altitude degrades your horsepower by 3% per thousand feet and, as you now know, you have to face long steep grades, I recommend lowering your tow rating by 20%.*? ? By these lights, your Burb should only pull 6480 lbs.? ? You have a trailer that you say has a GVWR of 6500 lbs.? ?So you were right at your top limit.

At that top limit, your rig is not going to leap over Colorado's 8 percenters.? Therefore it behooves you to downshift to 1st when you hit the main grade.? ?Setting 1st manually keeps your tranny from searching of higher gears which can overheat it all by itself.? ?Turn on your hazard blinkers and settle in to getting over the hill by keeping your rpms to around 2500-3000 and accepting the slow speed that will dictate.? ? Eventually, you will get over the hill.? Welcome to the RV life? ;D

Is your tranny fluid shot?.? Probably.? Get a power flush and fluid change.? In fact, that should be regular annual maintenance since you are towing.? ?You are way beyond normal service conditions.? ?I do that myself.

[* Going over an 8000 ft pass cuts your horsepower by 24%.  Any internal combustion engine without a blower is going to wheeze at those altitudes.]
 

John From Detroit

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Makes me glad I go over mountains with an 8.1 Vortec V8 using an Allision transmission with aux coolers out the wazoo


I'll second the advice to use a transmission oil cooler or two on the Surburan.  (in addition to changing fluid)

In "Drive" the trans is making decisions, Shift, or don't shift, Ideally it will pick the proper gear for the job you are doing, In LOW it's got no decisions to make, you have done all the work for it, All it's got to do is move power from the front of the bus to the rear wheels.

There are other things you can do too, but downshifting before you hit the grade is about the best bet

Or a 8.1 liter Silverado with an allison 6 speed and the SSC pack or a banks power pack  (If you like power)

That is a bit over 350 truck type horsepower in that pack.. Way more than a Silverado needs without a trailer

Don't forget the transmission coolers though.  Absolute must if pulling more than a couple thousand pounds
 

thedoors

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Thanks for the responses.

While in Montrose, I got our suburban (2001 w/ 88000 mi we just purchased one month ago) full serviced including transmission service.  We had one more pass from Montrose to ColoSprings (Monarch Pass) and per the recommendations was able to defeat it (at 20 mph :).

Thanks again.

Another question though .... with the towing package, isn't a tranny cooler included?  Is it possible to add even another?  Also, can one change the tranny fluid to synthetic without having to take it in for service (the tranny service in Montrose cost me $108).

 

Wendy

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If it makes any of you feel better, we used to get passed by Volkswagens when climbing Colorado passes in our old Class C. Getting passed by a VW is embarrassing, too say the least.....well, for us but not for the VW.
 

Ron

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Since the transmission was overheated and the fluid has been degraded I would recommend have the synthetic installed by a shop that has the proper equipment and expertise to properly flush the transmission system.  Will probably be less cost in the long run.
 

Carl L

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thedoors said:
Thanks for the responses.

While in Montrose, I got our suburban (2001 w/ 88000 mi we just purchased one month ago) full serviced including transmission service.? We had one more pass from Montrose to ColoSprings (Monarch Pass) and per the recommendations was able to defeat it (at 20 mph :).

Thanks again.

Another question though .... with the towing package, isn't a tranny cooler included?? Is it possible to add even another?? Also, can one change the tranny fluid to synthetic without having to take it in for service (the tranny service in Montrose cost me $108).

That is a reasonable price.  I generally find small town service to be both decent and honest -- as long as you are dealing with a good local outfit.  Expect to pay it more or less every year just before the towing season.  If you have already replaced the overheated fluid, wait till next year this time for going to synthetic.  I have been running my 5.0L Ford Bronco on non-synthetic for 11 years.  I also replace the fluid every yearl with a power drain at a Ford dealership that I have had long experience with.
 

Lowell

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My 2005 Dodge 1500 does not have a transmission temperature gauge.  It does have a transmission overheat warning light.  How safe is it to assume the transmission temperature is OK unless the warning light come on?  How difficult is it to have a transmission temperature gauge installed? 
Jake
 

Carl L

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Safe enough.  Most auto transmissions nowadays have a fail safe mode if the think overheats.  It feels like the transmission started making very hard shifts, which it has.  The remedy is to stop and let it cool till it resets.

It has happened to me once in 15 years of towing.  Oddly enough, it happened while we were not towing.  My wife left the OD engaged while driving a windy tho level road leading into Sedona.  The transmission was constantly cycling thru 2nd, 3rd, and 4th as she went around the switchbacks.  The constant uncoupling and coupling caused the transmission overheat. 
 

Gary RV_Wizard

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How difficult is it to have a transmission temperature gauge installed? 

It varies, depending on the tranny. The difficulty is in the temperature sensor/sending unit, which has to be installed somewhere in the transmission or a fluid cooling line immediuately adjacent to the tranny.  Some already have a plug that can easily be be replaced with a sensor.  Others may need a hole driled and tapped into the transmission pan or some sort of tee fitted into a cooling line to allow the addition of the sensor.  Then there is the gauge itself, which mounts in or on the dash board somewhere.
 
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