Good tranny cooler locations?

[88 K30]

I recently added a new B&M cooler for my transmission. I mounted it in front of the radiator for good airflow, but it has created a problem: The cooler pulls so much heat from the tranny fluid, it reduces the surface of the radiator that is exposed to cool air, and causes the truck to run hotter than it ever did before (especially on hills) when towing. I have not yet put the Robertshaw 180^ t-stat, but I don't think it's going to help much with the problem. It might mask it, but I really need to reloacte the cooler to prevent it from heating the radiator in the summer. I was thinking of moving it to the drivers side of the core support and punching out the driver's side knockout for airflow, but that will limit it's airflow. The old body style trucks really can't afford to lose any fresh air radiator surface. Where do you all have your external coolers mounted in the early trucks?
Thanks!

[Craig M]

I am facing the same issue on a 89 truck. Existing small transmission oil cooler is in front of the radiator. Am considering buying a cooler with an intergral fan. Then I can locate it anywhere under vehicle, and not in the frontal grill area. I agree that the radiator needs all the cool air it can get. A bunch of cooler in front of the radiator hurt engine cooling.

[HillBilly2]

You may want to pull the radiator and condenser apart and check for debris buildup. This is a problem with these trucks. It shuts off the airflow. I don't think having the transmission cooler out there should make a huge difference. After all, it went thru the radiator before. You might want to space it out from the condenser an inch or so.

FWIW, I was told to run the transmission fluid thru the radiator and then out to the aux cooler and then back to tranny. It dropped my transmission temps about 20-25 degrees.

[88 K30]

I actually checked the space between the condenser and radiator while I was installing the cooler and it was clean. I ran the fluid through the radiator, then into the cooler and back. It is mounted about 1" in front of the condenser. It did go through the radiator before, but that is just a tube and doesn't transfer the heat nearly as efficiently as the external cooler does, which is why the fluid got a little "burnt" and prompted me to finally get that external cooler I had been meaning to add (and is now causing me headaches).

It's a plate-type cooler and seems to be very efficient. I didn't mean that it is really blocking the airflow, rather that it is heating the air going through it so much that the radiator is getting pretty warm air on that side and, since it covers about 30% of the total open space in the core support (80% of the driver's side), it really impacts the already marginal cooling ability of these early-body trucks. Especially on a 90 degree day towing 5500+ lbs with the stock 190 or 195 t-stat and some pretty decent hills.

I looked at the core support and underhood area this weekend and even though I will be installing the 180 t-stat soon, I think I will also be moving that cooler over to the side (or maybe even inside the engine compartment) and removing the driver's side knockout to give it some air flow or installing a small electric fan to cool it, depending on location. Since I will be adding my Banks Sidewinder soon, too, I really don't want any potential cooling issues.

I remember reading about a really heavy duty radiator that someone offered for these trucks. Anyone know who makes such a beast?

[Mikeandwendy74]

Hi I put a new cooler in last winter( 06/07) heres what I did. the lines from my turbo 400 were steel all the way, I chopped them 6-8 inches from the tranny, made some good steel to flex changeover fittings, then ran the lines towards the back and towards the drivers sideof the truck. I mounted the tranny cooler to the underside of the rear transmission crossmember support. The cooler gets blasted with air under the truck constantly. People are reading this saying what the... but I tell ya it works great, I tow a 7900 lb trailer with a half cord of hardwood in the truck 4 adults and zero problems. I've towed like this at least 15-20 times, the fluid in the tranny still looks like brand new. This truck is my daily driver also, I put at least 40 miles per day under normal conditions. Thats about 15,000 miles since the cooler went in not including the towing days.

[DennisG01]

Hi I put a new cooler in last winter( 06/07) heres what I did. the lines from my turbo 400 were steel all the way, I chopped them 6-8 inches from the tranny, made some good steel to flex changeover fittings, then ran the lines towards the back and towards the drivers sideof the truck. I mounted the tranny cooler to the underside of the rear transmission crossmember support. The cooler gets blasted with air under the truck constantly. People are reading this saying what the... but I tell ya it works great, I tow a 7900 lb trailer with a half cord of hardwood in the truck 4 adults and zero problems. I've towed like this at least 15-20 times, the fluid in the tranny still looks like brand new. This truck is my daily driver also, I put at least 40 miles per day under normal conditions. Thats about 15,000 miles since the cooler went in not including the towing days.

Not crazy at all! The service manager at a good, local fuel injection shop did the same thing. Said it worked great and never had any problems.

[97-6.5TD-F]

I agree to check for dirt and debris buildup, my 97 ran very hot when I got it all the time. Pulled the rad and pressure washed it from the fan side, then washed out the condensor from the engine bay. Now the temp never goes over the middle bar, even when towing 10k.

[HillBilly2]

There are two issues that come to mind with mounting a cooler under the truck. First is the danger of a rock bouncing up from the road and puncturing it. Second is just mud and other debris clogging it up. Both could be overcome with proper placement, so let us know your solution. I considered doing this but ended up with it in front of the radiator an inch or so. fwiw I do drive on dirt roads enough to have a more or less permanent coating of mud underneath.

[Robyn]

If the cooler is causing that much difference in the engine temp I am suspect that the radiator may be close to the end of its life.

A good radiator thats clean along with a fan/clutch thats working properly should cool the little beast real easy even with the added tranny cooler. Get the tranny cooler as far forward of the radiator as possible to allow as much air to mix in the area and flow though.

I do agree, under truck mounting is a harbinger of disaster.

These coolers are fairly rugged but will not take a hit from a rock well and then there is the mud issue.

I was watching some off road stuff with Hummers on You Tube last eavening and those folks had those Hummers up to the windshields in crap.
A cooler under the truck would be fouled with mud in a heartbeat and then the heat would bake it solid as a rock.

If your radiator is the original I would be having a look at it. Also be sure that there is not a bunch of crud between the AC condenser and the core.
Airflow airflow airflow and more airflow is the key as long as the coolant can pass its heat to the radiator fins your set.

If the fan clutch is not working well then this can be a big issue.
Check the fan clutch bimetal spring, if there is oil seeping out the front and this is all clogged with dirt then the fan clutch is ready for the bone heap.

The spring reacts to the heat in the airstream and varies the control valve in the clutch to raise or lower the fan speed.

Now if the spring is all skanked up with oil and dirt this will insulate the spring and retard the needed action of the valve, possibly even stopping it from working properly.

Check these things and see if your problem can be rectified without moving the cooler.

I have never seen any issues with a tranny cooler causing issue with engine temp unless there are other problems.


best

Robyn

[rustyk]

All good advice, to which I'd add, flush and clean the cooling system - the amount of crud from city water is incredible (I ALWAYS used distilled water). I got a cup of sludge out (just out of the block) of my Ford diesel van when I got it, and when an M-B mechanic, can't remember how many water pumps I replaced because the crud had eroded the aluminum impeller down to nothing.