Stock tranny cooler...good enough?

[TJ35]

I'm new to this site and am very impressed. The information found here is great. Recent posts in this section have got me thinking about my pickup. I drive a 2004 GMC Silverado with the tow package that includes the factory external transmission cooler. I tow quite a bit on hot days (100+) sometimes up steep grades. The trailer I tow can weigh up to 7ooo lbs.

My question...is the external cooler that came from the factory up to this usage. I am within the factory limit, but I was wondering if anyone had/heard of problems that would suggest this is not good enough.

Also my owners manual says the transmission fliud is dexron III. Is this stock coolant good enough for a 25k OCI at this usage?

Thanks in advance.

 

[1maniac]

When I tow I absolutely MUST have an external cooler and high quality synthetic ATF.

 

[OiledMustangGT]

how big is the stock cooler?

i would want one at least 12"x12"

 

[olympic]

The only way to know for sure if your stock cooler is adequate is to install a transmission temperature gauge. Barring that, keep an eye on the condition of the fluid. If it starts to darken or smell burnt, it's getting too hot.

If you can keep the ATF temps down, 25k should be no problem. A good synthetic like M1 or Amsoil is good insurance though and highly recomended.

 

[Rhymingmechanic]

I have a 2001 Silverado with the trans cooler. It seems small, even compared to the engine oil coolers on the previous generation GM trucks. The size is about 11 or 12 by 6 or 8 inches and 3/4 or 1 inch thick. It is not a stacked-plate--it's designed like a small radiator, with alternating rows of cooling fins and flat tubes.

I can't say how well it cools, and I've done very little towing. The fluid looked fine at 35k miles when I switched to Mobil 1--2 pan drains and then a filter change.

A trick, if expensive, way to get a trans temp gauge is to swap in the instrument cluster from a truck that has the gauge. In my case, the cluster from a Denali up to 2002 will fit. All the wiring is there, but some trucks just get a delete panel. The downside is that you need to have the new odometer reprogrammed at a dealer or speedometer shop.

 

[mechtech]

$50-$75 dollars for a great trans cooler [anybody's].
What do you have to gain, and what do you have to lose?
Towing with an auto trans - I'd get the best.
Not towing with an auto trans - I'd get the best.

 

[TJ35]

I looked closer at the transmission cooler that I have and it is only about 11 x 6 x 1. That seems a little smaller that what I would like. I think that a larger cooler is definately the way to go. Will getting a diferent cooler than stock affect my factory warranty at all? Same question regarding switching to a synthetic ATF, can this void a factory warranty? I temp gauge should be on the truck this week, but I figure better safe than sorry.

 

[ULVER]

Good to check with GM about the warranty question. That being said:

Working with fleets of police cars over the years, I have found the factory transmission coolers a bit on the "light" side. We had some Ford Crown Vics with the factory cooler, that was rated for a 7,500lb. vehicle. Adequate but... You can freely go for overkill, with transmission coolers. Believe me! We now run Hayden coolers rated for a mobil home, towing a vehicle!

"Tube & fin" designs suck. If that is indeed what is on your GM, it's time for the "stacked-plate" design which is wildly superior. A synthetic fluid is a fine idea, as well. I like Royal Purple, but Amsoil and Mobil 1 are excellent.

Your demands sound...ah...

demanding!!! I would absolutely say you are ripe for a stacked-plate cooler, and 100% synthetic fluid.

It's cheap peace-of-mind.

 

[noodlerooney]

I second that stacked-plate cooler and 100% synthetic fluid. Another nice thing about this design is that when transmission fluid is cool (viscous) it bypasses the cooler and as it heats up (less viscous), more of the transmission fluid is diverted through the cooler, ie.low pressure drop. Also, not fragile like the fin & tube design. As long as you install it after the OEM cooler (correct way), any warranty will still be in force.

 

[mzugg]

You might look more closely at the cooler you have on there stock. The newer vehicles I've seen are equipped with a stacked plate cooler that has the small radiator like fins between the plates. These are reputed to be very efficient coolers. I believe most of them are made by Dana Corp's "Long Manufacturing."

Heres a link to Long's catalog: http://www.longmfg.com/web/longwebf...cc05256c650003652a/$FILE/LNG013_Cat_Final.pdf

If you want to get an idea what your trans temp is, I've found that using an inexpensive digital cooking thermometer (Walmart), and holding the full length of the metal probe against the bottom of the transmission pan with a thick wad of rag, gives a reading within a few degrees of an in pan sensor. A quick check during hard use would tell you if you need to worry.

A proper trans temp gauge would probably be a good idea for your type of use though. Hopefully, you could pick up on a developing problem before it smokes your transmission. Plus, I've seen more than a few vehicles burned to the ground when the first sign of a seriously overheated transmission was a big burp of fluid out the fill tube and onto the exhaust.