One day while at work with the Gm books in front of me I found a part number for the 3500 HD trans cooler and then searched for the part number for the stocker that is OEM for most of our trucks. The HD cooler is about 45% larger (just a bit smaller than the oil cooler) than the stock trans cooler. The upgrade cooler part number is GM 15974686, you will also need the upper bracket GM 15968707. This upgrage takes all of about 15 minutes to install with a phillips driver, a 7mm nut driver and a 10mm socket on a 1/4 drive ratchet. Once installed you will have to add about 1 1/2 quarts of trans fluid. I'll keep you posted if there is any reduction in trans temp ands also a increase in coolant temps.

nice find. I'll be paying attention to this thread.

Man nice find, any luck on letting me browse that book? JK

I wish I could bring them home, but we still have some GM trucks in the fleet. So at work they have to stay :(

Is the "upper bracket" installed in the pic? I would think it would be similar to the one you took off but with a different length. I just don't see anything in the pic.

Yes, the new upper bracket is shorter than the original. the new bracket cost me $5.11 so it wasnt worth my time to cut, bend and drill two holes and hopefully did it right the first time :)

Well took the burb out for a drive around town (honey do's) after I got the replacemnet oil cooler lines in (bastad engineers, they just love to get you completely oiled up). Around town the temps just hovered 155* about 20* lower than before. Todays temp was around 86*. Down the freeway with the converter locked up temps droped to 110*-120* gauges lowest reading is 100* so lower reading are hard to tell without scanner hook-up. I'll keep y'all posted when I hook up the trailer and do some towing.

Is there a larger oil cooler?

Is there a larger oil cooler?

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No, this is the largest GM offers for our body style of truck. Derale may sell one that is larger but I do not know if the fittings are compatable of if there will be grill clearance issues.
GM should of just installed the largest cooler possible on these trucks to begin with.

GM should of just installed the largest cooler possible on these trucks to begin with.

And blocked even more of the radiator?

I wonder at what point the factory cooler can't provide enough cooling?

This is the largest factory cooler, just for the 3500HD models. If any more cooling is needed one can be installed underneath the vehicle. Also with asking all of the drivers that operate the fleet GM vehicles (also diesels) what their coolat temps were, they all stated nothing above 210 continuous, loaded on the hottest days and with the A/C on.
The biggest culprit to poor air flow isn't the coolers, it is the lack of maintenance and not cleaning them out annually.

The larger transmission oil cooler you have shown was also available on 1500 chassis trucks, too. You might do a search further, but I'm guessing it's available on them all in any combination, not just the 3500HD.

My wife's '94 K1500 Suburban was equipped with that larger cooler from the factory. Since hers is a people hauler and mine is an equipment hauler, I swapped them both out over a year ago just for the added surface area and cooling benefits.

It was an easy swap - same fittings, brackets swapped perfectly and done.

Nice find, though. It would be an inexpensive upgrade. (mine just happened to be free)

The larger transmission oil cooler you have shown was also available on 1500 chassis trucks, too. You might do a search further, but I'm guessing it's available on them all in any combination, not just the 3500HD.

My wife's '94 K1500 Suburban was equipped with that larger cooler from the factory. Since hers is a people hauler and mine is an equipment hauler, I swapped them both out over a year ago just for the added surface area and cooling benefits.

It was an easy swap - same fittings, brackets swapped perfectly and done.

Nice find, though. It would be an inexpensive upgrade. (mine just happened to be free)
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Your absolutely correct about the cooler being available for all models, it is just an options option kind of deal. The majority of the trans coolers on the 1500-2500 series are the smaller one and the 3500 and 3500HD are standard with the larger one.

It would be a good time to upgrade to 5/8 lines. They are standard on 99/2000 2500/3500 trucks.The intent was to increase oil cooling by extra flow ,IMO. Engine Oil cooler appears same size as earlier trucks.

It would be a good time to upgrade to 5/8 lines. They are standard on 99/2000 2500/3500 trucks.The intent was to increase oil cooling by extra flow ,IMO. Engine Oil cooler appears same size as earlier trucks.
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I hope thats a typo. 5/8" lines? :)

Yes, the engine oil cooler is the same size through out the truck line. Exact same cooler that is on my 95 that came factory on my blazer (well of a 1980 K-5 blazer) minus the trick fittings.

Are the fittings the same on all years?

DSG markets a bigger oil cooler kit with shorter bracket than that oil cooler. The filler piece under the grill has to be trimmed. Long mfg makes them for multiple companies B&M for one. I bought the OE sized oil cooler with 1/2 NPT. I think there are some AN fitting options too but none of them I have seen are OE GM fittings.

Since the engine oil cools the bottom of the engine too the hit to the cooling capacity is not too detrimental.