High tranny temp when towing well below rated capabilityI have 2009 CK

[tcfulmer]

I have 2009 CK10543 - Silverado: Short Crew 1500 4WD equiped as follows:

 

LC9 - Engine: 5.3L, V-8, Flex Fuel, SFI

C5W: GVW Rating 7000 Lbs

G80: Locking Differential, Rear

GU6: Rear Axle, 3.42 Ratio

KNP: Transmission Cooling System

K5L: Heavy-Duty Cooling Equipment

Z71: Suspension Package: Off-Road

Z82: Trailering Package

PDU: Power Pack Plus Pkg.

 

I tow a 2008 Outback 21RS trailer, 6,500 lbs gross weight, 375 lbs tongue weight using a Equalizer 10,000 lb WD hitch. I have weighed the truck/trailer at different times and when loaded for a trip it has never exceeded 6,000 lbs. Per the owner's manual and GM fleet web site, the ball/hitch tow rating on this truck is 9,500 lbs which is well over the 6,500 lbs gross of the trailer. There is one mountain pass that I occationally have to drive with the trailer that runs the temperature up to around 255 degrees. Stevens Pass is 13 miles at an average of a 4.7% grade. The last 3 miles is a 7.3% grade. The start of that last three miles is a hairpin curve that you have to slow down for. I have asked my dealer if the 255 degrees is something I need to be concerned about to which they have answer that I am alright up to around 270 degrees. I have been searching for informaton about this on various forums and pretty much everywhere I have been told this is way too hot. I figure there are a few possiblities as to why it is so hot.

 

1) A bad temperature sensor is showing hotter than it really is.

 

2) The HD tranny cooling isn't working correctly.

 

3) Bad tranny fluid.

 

4) I'm taking the pass in the wrong gear. I'm using tow/haul mode and it's usually in 4th gear.

 

5) This is just the way it is supposed to be.

 

I'm hoping that I can get an answer on if this temperature is too high or not and if so is there a recommendation for what I should ask the dealer to look at or if I should tow differently.

[NitroCherokee]

I am not a trans guy, but that is too hot in my opinion. I have seen that Trans Fluid starts to "paste" at 260*. My 08 GMT900 Ex cab short box 4x4 with the 5.3 and 3.42:1 gears towing my travel trailer (8500lbs) going down the road and my trans NEVER went over 200* and I dont drive easy. I did have the 4L60 4 speed tho.

[txab]

What's your engine temp? Are your fans working properly? Radiator and condenser clean and bug free? Feel like the trans is slipping at all? Dealer check trans temp gauge to make sure it is reading accurately?

 

No matter what I'd get a larger cooler. The OEM doesn't supply much more cooling, it's better than nothing. But plenty of aftermarket coolers will do a better job

[Jsdirt]

Your tranny won't last long at that temp ....

 

It's an old chart, but still ...

 

[SouthCo]

I have no helpful info but curious to see what you find out. I have a the 5.3 with 3.42 gears and max trailering package that's supposed to be good for 9500lbs. I've never seen my trans temp get too hot but I haven't towed more than about 3000lbs.

[Jsdirt]

Mine has never gone over 200°. Only time it hit that was towing 6,000 lbs. up a fairly steep grade at 45mph about 6 miles in 90° summer heat. As soon as I crested the hill, the temp immediately dropped down to 180°. Usually stays around 150° to 160° on level ground with that load.

[SouthCo]

To the OP, I'd make the dealer put it in writing that you are good up to 270 with the info that's been posted so far. That should help down the road if you have a failure. But I'd search out another dealer also to see what the say. Something can't be right. I know you suggested that the gauge could be wrong, so what temp are you seeing when unloaded?

[gmtech4]

tow in 3rd and see,

 

that is the gear it says in any owners manual i think ,,

 

warranty left ?

 

what Darral said

[markw8]

Dex 6 is synthetic. It should be ok at that temp. That said, you don't want to see that for miles and miles. The grade you describe is a big one. You need to know what gears and when your torque converter is locked and try to stay in that range. When it unlocks it builds heat in a hurry.

 

If your seeing 255 on this, and it drops as you crest the top, your ok. I would certainly change the fluid on the extreme duty interval. Tranny fluid, just like motor oil is much better than it used to be. If it bothers you, have a second cooler installed. Like I said try to keep the TC locked up.

 

Mark

[Z71-K9]

Third gear and TH mode is a must. I am betting third gear alone will drop the temps 25 degrees.

[Z45]

Dex 6 is synthetic. It should be ok at that temp.

Mark

 

 

Which brand? Can't mean the factory fill GM, I says petroleum on the GM MSDS? No where in any GM literature or documentation is it referred to as synthetic. After market products are from some manufactures but to meet the spec it is not a requirement it be synthetic.

 

quote from msds

Section I. Chemical Product and Company Identification

 

Material Safety Data Sheet

Product Name

 

Synonym

DEXRON VI ATF

 

Code

 

RDL-3434, GM Mat. Spec. 9986153

 

DEX6, 460-613

 

Automatic Transmission Fluid for use in General Motors vehicles,

 

requiring the DEXRON VI specification.

Petro-Canada: 403-296-3000

 

Canutec Transportation:

 

613-996-6666

 

P o i s o n C o n t r o l C e n t r e :

 

C o n s u l t l o c a l t e l e p h o n e

 

d i r e c t o r y f o r e m e r g e n c y

 

number(s).

 

PETRO-CANADA

 

P.O. Box 2844

 

Calgary, Alberta

 

T2P 3E3

 

Mixture of severely hydrotreated and hydrocracked base oil (petroleum).

 

 

 

LINK to MSDS

[Jsdirt]

Knowing GM, the hydrotreating probably qualifies it as "synthetic". I recall reading of some change in regulations that allowed oil refiners to sell oil as "synthetic" with inferior base stock that would never qualify as a synthetic in the years prior.

 

That's why I run Amsoil in everything, front to back.

[music]

A few comments:

• Ignore the chart posted above. It was put out by an aftermarket transmission cooler manufacturer *many* years ago, and... even if it was accurate then... wouldn't apply to the newer fluids we have today (like Dex-VI).
  
• Your "high temp" warning light will come, and the truck will go into "limp mode", if the temps get too high. I think that's around 265 to 270F.
  

 

I'm impressed that you're pulling a 8% grade w/ 6000 lbs in 4th. Are you using "T/H mode" with the selector in "M", and it's picking that gear itself? I don't have the 6-spd, so I don't know if putting the selector in 4th in T/H tries to keep it there, even if it shouldnt? The higher rpms of 3rd will pump the fluid quicker, and should cooler better... assuming the torque converter isn't working harder (it shouldn't). The ECM/TCM should be picking the optimal gear though.

 

A few parameters you didn't mention:

1. Ambient temps.
   
2. Normal temps (transmission & ambient) when towing on flatter ground.
   
3. Motor temps (normal or high)?
   

 

I'm towing closer to a 7000 lb camper, and topped 10,000 ft this past summer, plus *many* steep grades from the Grand Canyon to Yellowstone and back home via WY. The highest temp I saw was ~ 230F on a very long/steep pull to ~ 10,000 ft, but ambient temps were low up there. Motor temps actually climbed on me in TX with ambient temps of 105F and 30 to 50 mph head/cross winds, but the transmission temps stayed at ~100F over ambient on those days (as is typical for non-mountain towing). Those days were a much tougher pull than any mountain pass we crossed, in every way.

[markw8]

Most all snnthetics today are hydrotreated/hydrocracked dino oil. This I believe was allowed to be considered synthetic by a judge during a law suit over just what could be called synthetic.

 

Mark

[tcfulmer]

I've been towing in tow/haul but shifted into drive not manual. I have to tow that same stretch of road at the end of August and will try it in manual limited to third gear. I really appreciate all of the input. In past years I would guess that abient temps have been in the 70s. At the top of this run is a large parking area for the Steven Pass ski lodge. No matter what my temp reads when I try it this time, I may pull over there and hit the tranny pan with my infrared thermometer just to see how it compares to the dash readout. The only other place I've had a climb in temp is going over Snoqualmie Pass (I-90) where it didn't get quite as hot.