Question About Transmission Temps

prerunner · December 6, 2007

I installed a Hayden 679 trans cooler yesterday on my 08 Silverado and hooked up the boat for the first time.

Just driving around normally before installing the cooler would get me temps of around 180.

I got around the same temps after installing the cooler with the boat hooked up (approx. 4300-4400 lbs).

At the ramp we had a couple of issues getting the boat straight on the trailer and I had to back up and pull out a couple of times. My truck is 2wd with an open diff, so plenty of brakes were needed to keep the tires from spinning. My trans temp hit about 250 by the time we were done. We waited until the temp got back under 200 before leaving and once rolling the temp quickly dropped down under 180.

Is there a serious problem hitting 250 degrees for a very brief time, and the truck will not be driven at these temps. I hope this was an isolated incident and that I won't hit those temps again, but can't be certain.

I normally change my transmission fluid every 30,000 miles, but never towed over 2500 pounds with my last truck.

Thanks

wlvrn1215 · December 6, 2007

250 seams a little high In my opinion. I tow and have the stock tranny cooler and my temp never really goes past 180 give or take a few degrees...even when towing 3000 plus pounds....What gears do you have and how much were you braking while giving it gas.

Bish · December 6, 2007

I agree it is high. I would consider flushing the fluid or drain/refill the pan a couple times. Heat ruins trans fluid pretty quickly. I would have thought the bigger cooler and the fan would have kept it cooler during your pull.

C & A s Dad · December 6, 2007

Chris, I have exactly the same cooler you have and something does not sound right here. The 180 temps without the cooler with normal drving sounds fine. Once the cooler was installed, these normal driving temps should have dropped somewhat, say to 150 to 160 area.

The temps of under 180 once you were on the road towing are also ok. Mine runs 160s to low 170s on a 95+degree day with a 6500lb Camper behind me. Even with me stabbing the camper in a camp site and having to go back and forth a few times, it has never gone over 175.

You did not bypass your internal cooler did you? The fluid should run from the trans through the internal cooler to the aux cooler and back to the trans. I am sure you did this, but I had to ask.

If this is the route you took, I have a theory. I am afraid your 250 temps while on the ramp are a result of your Electric Fans. I am not exactly sure at what temp they kick in but my bet is around 220 and off again around 200. They are likely running just long enough and pulling enough air to cool the engine temp and then turning off leaving the trans temps high. I realize E fans have a purpose in keeping the HP going to the wheels but I have never been comfortable with them for real HD towing use. Unless they recently changed, mfgs still use very large manual fans with clutches on 3/4 ton and 1 ton trucks. I am sure others with E fans can offer more info here. Just my .02.

Is 250 too high for a brief period? I think you are ok. It is my understanding your warning light does not come on to 250 and remember, you have full syn fluid in your truck which will take more heat. I would not want it to remain anywhere near 250 for long but for a few minutes you should be ok. Imagine where the temps would have been without the aux cooler.

xsports33 · December 6, 2007

i would say 250 is pretty high and i'd drop the pan and change the fluid just in case. In addition to what C&A had to say, going back and forth on the launch ramp and constantly braking your torque converter never locked up which added to the heat.

I would also look into getting a larger aux cooler and a deep transmission pan made of cast aluminum w/fins. The larger capacity and cooling effect of the pan will help keep the temps down

C & A s Dad · December 6, 2007

The aux cooler he bought is a stacked plate cooler and is 11" x 11 5/8" and they really do not get any better or bigger. The deeper finned pan would help.

I am not sure where he is located but if he has winter temps in the teens or below, he really does not need to add much more cooling capacity. If he is in a warm climate, the deeper pan would not hurt a thing.

He could also add a "mister" by Hayden. It allows for cool water to be sprayed in a mist on the radiator or in this case he could direct the spray to his aux cooler.

I still belive his problem is a lack of airflow at idle. Aux coolers operate from air to surface contact and I feel he was not getting enough air across the cooler.

xsports33 · December 6, 2007

It's the one i have. I like it

http://www.bulkpart.com/Merchant2/merchant...Product_Count=4

Zembonez · December 7, 2007

WOW! 250

I was scared when mine just went over 200 pulling my boat through some long hills. I think any driving near the 250 mark wouldn't be good but yours was for such a short time I would not worry about it. I might rethink my boat removal method or find a ramp that wasn't so steep maybe...

exracer · December 7, 2007

nothing heats up a trans more than brake torking....install a locker in the rearend

....250 is pushing the limit and I wouldnt do that to offen

millinmike · December 7, 2007

the problem was not that you were towing a trailer but that you were up on the torque converter. 250 is hot but not a huge problem. just think how many people would hit temperatures like that and wouldnt ever know it because they dont have a gauge to tell them. i know that a drag car will hit those temps and above in a matter of seconds sitting on a 2 step rev limiter at the line. if you think about it they have hundreds of horsepower just being eaten up by that converter and well the energy has to go somewhere and unfortunately that poor fluid has to take all of it. btw your a daring man towing a boat with a 2wd open diff truck

C & A s Dad · December 7, 2007

It's the one i have. I like it

http://www.bulkpart.com/Merchant2/merchant...Product_Count=4

Now that is a trans cooler, 22" long, WOW.

I have not seen this with my own eyes but from what I have been told by a reliable source, Ture Cool supplies every other vendor, including Hayden, with their SP coolers. Again, I have no proof. Someone else told me that Borg Warner was the first to develop the design but later sold the patent rights.

When I was deciding on which one to use, I had a chance to speak with an engineer from Hayden and I asked him why they did not offer the 1 1/2" thick models. He said they have found them to be less efficient than the 3/4" models due to less surface to air contact. Of course in the case of the one you have, that is not an issue becuase you have 22" x 8" of surface. What he told me was that if you compare a 3/4" thick model to a 1 1/2" thick model and both have the same frontal surface area, the thinner one will do a better job. I am not engineer and I certainly cannot prove what he said, just passing it along.

He also reminded me that prior the the 800 series GM trucks, GM used a 1 1/2" thick cooler from the factory. With the intro of the 800 series, they moved to the thinner 3/4" thick model for the reasons he gave.

You must be located in a pretty warm climate or I would guess your temps in the winter would be very low.

prerunner · December 7, 2007

I'm in Miami, so yes our climate is usually a little hot. Our "cold front" the other day meant is was 60 degrees before the sun came up, and hit almost 80 by noon

I spoke to a cousin of mine who is a master tech and former service manager at a chevy dealer about it. He told me hitting that temp once will not cause any harm as long as the fluid doesn't discolor or smell. He did tell me not to do it again though.

This hopefully was an isolated case.

The problem was getting the boat straight. We've never had that much problem before, but we also don't usually load the boat back on the trailer at midnight.

My friend said we actually ended up pulling the boat out 4 times I'm sure if we had lined it up straight the first time I wouldn't have been anywhere near those temps.

I probably won't be towing the boat too often, my friend has a 03 Silverado 2500 that we normally use.

Braking, open diffs, spinning tires is a way of life at the boat ramps here in Miami. For the most part us Hispanics are very hard headed and want to do things our way, even if its the wrong way.

Thanks for the help

xsports33 · December 7, 2007

It's the one i have. I like it

http://www.bulkpart.com/Merchant2/merchant...Product_Count=4

Now that is a trans cooler, 22" long, WOW.

I have not seen this with my own eyes but from what I have been told by a reliable source, Ture Cool supplies every other vendor, including Hayden, with their SP coolers. Again, I have no proof. Someone else told me that Borg Warner was the first to develop the design but later sold the patent rights.

When I was deciding on which one to use, I had a chance to speak with an engineer from Hayden and I asked him why they did not offer the 1 1/2" thick models. He said they have found them to be less efficient than the 3/4" models due to less surface to air contact. Of course in the case of the one you have, that is not an issue becuase you have 22" x 8" of surface. What he told me was that if you compare a 3/4" thick model to a 1 1/2" thick model and both have the same frontal surface area, the thinner one will do a better job. I am not engineer and I certainly cannot prove what he said, just passing it along.

He also reminded me that prior the the 800 series GM trucks, GM used a 1 1/2" thick cooler from the factory. With the intro of the 800 series, they moved to the thinner 3/4" thick model for the reasons he gave.

You must be located in a pretty warm climate or I would guess your temps in the winter would be very low.

Actually, i have heard the exact same thing. That Tru Cool is the bulk supplier to many other aftermarket vendors for coolers. Also that the thinner models have a better surface area to contact ratio for convectional heat exchange. Sounds like we're on the same page

I live in a very steady climate, Southern California, where we have 2 seasons: hot and not so hot. We could basically wear shorts year round and not get funny looks. I was a little apprehensive about getting such a large cooler, but after talking with numerous transmission shops and builders it's almost impossible to "over cool" a transmission. I go to the snow about 4-5 times a year and i try to not let my TC lock up until i get the trans temps up a little bit.

C & A s Dad · December 7, 2007

Our cliamates are similar. I think I have had a light jacket on once. Although we had some nights this week in the mid 30s. Brrrr I hate winter.

Today it is a beautiful sunny day and is about 80 degrees.

I agree with the overcooling thing and my research turned up the same info. The fluid does need to ge warm enough to flow well but that does not take much. The only thing I read was that in really cold climates, it would be possible to see the fluid cooled to a point where it would become thick. I would imagine you would have to be in near zero or sub zero weather and have a large cooler for this to happen.

pm26 · December 8, 2007

I'm in Miami, so yes our climate is usually a little hot. Our "cold front" the other day meant is was 60 degrees before the sun came up, and hit almost 80 by noon

I spoke to a cousin of mine who is a master tech and former service manager at a chevy dealer about it. He told me hitting that temp once will not cause any harm as long as the fluid doesn't discolor or smell. He did tell me not to do it again though.

This hopefully was an isolated case.

The problem was getting the boat straight. We've never had that much problem before, but we also don't usually load the boat back on the trailer at midnight.

My friend said we actually ended up pulling the boat out 4 times I'm sure if we had lined it up straight the first time I wouldn't have been anywhere near those temps.

I probably won't be towing the boat too often, my friend has a 03 Silverado 2500 that we normally use.

Braking, open diffs, spinning tires is a way of life at the boat ramps here in Miami. For the most part us Hispanics are very hard headed and want to do things our way, even if its the wrong way.

Thanks for the help

One reason for the boat not getting straight on the trailer is that you may have backed the trailer too far into the water, or your trailer floats. Many aluminum trailers with dual axles and large vertical wood bunk boards will partially float.

I had this problem with my trailer, and I solved it by bolting pieces of used square axles under the cross braces of the trailer. No problems since then. Back you trailer into the water so that the tops of wheel fenders are barely submerged, no more.

My boat/trailer weighs about 4,500 lbs and of course I have no issues whatever pulling it out of water. I have a 4WD plus locking rear differential and in 4LO the truck pulls the boat out of water without any effort at all, and without as much as chirping a single tire. I believe I could

pull out a 10k lbs boat/trailer out of water without any difficulty.