Transmission Oil Cooler

[Iplayfarmer]

Warning: This is a long winded post!

I put in a tranny oil cooler last night. I thought I'd post a few things I learned here for anyone attempting it in the future.

I had a friend help me. If he hadn't been there, I'd have looked all day for the oil lines. I never would have expected the transmission oil line to be coming out of the radiator. (I went back later and saw that this is clearly spelled out in the instructions.) On my truck the line I needed was right at the top of the radiator on the passenger side.

The cooler ties into the return oil line. The instructions suggest opening the lines to see which one oil flows out of to determine the pressure vs. return line. Remember that if you pick the right line, the oil will come out of the radiator not out of the hose. My friend realized this as he was carefully holding the hose over a bucket to catch the fluid and got a hot bath from the fluid spraying out of the radiator. (Note to self: buy some glass cleaner for the windshield.)

I think that no matter what additional parts are in the kit, the best and easiest way to tap into the line is to just cut the tube about halfway between the radiator and the flexible rubber hose. We opted to cut the tubing with bolt cutters rather than with a hack saw to avoid the risk of metal filings getting in the system. After we "smushed" the tubes back open with pliers and screwdrivers there was a cosequent flare on the open ends that I think will even help hold the hose on the tube.

I got the biggest Hayden cooler that Checker auto sells. The price difference between it and the smaller one was about $6, and I figured it was worth it. The drawback to this is that the coil is big enough that it doesn't easily fit anywhere. I have a '99 Silverado 1500. There is an "A" frame in front of the A/C coil that supports the hood latch. This frame effectively splits the face of A/C coil so that there is no surface big enough to attach the oil cooler coil. Anyone contemplating a tranny oil cooler might want to get and idea where it is going to go and what kind of space you have before you buy the biggest unit you can find.

Putting the tranny cooler coil between the AC coil and the radiator is less effective, but even at that, I couldn't see any way of getting my hands in there to attach the little two piece zip ties that they give you to hook the coils together.

After a half hour of goofing around and cursing the tight spaces, I took the grill off the front of the truck. It amazes me how easy that was. There were a few cam lock type fittings on the bottom of the grill, one bolt right by the hood latch (10 mm wrench), and some spring clips on the sides. From the time I thought of it to the time I had the grill sitting on the garage floor was about 75 seconds. (It has probably taken you longer to read this paragraph.)

Once I had the grill off I easily secured the transmission oil cooler coil to the "A" frame itself with plenty of padding at any potential wear point in the form of friction tape covered by electrical tape. I used zip ties to secure it. It seems pretty secure there and allows enough air flow through and around it.

After finishing, I checked the fluid level and added a half quart. At lunch today I drove around a bit and checked the fluid again. It was down another half quart. I'm sure that the coil doesn't hold a quart of fluid. Most of that quart that was missing probably either went home on my friend's shirt or is still on the driveway under where the truck was parked. I was surprised that the fluid was down that far the second time I checked. I'm planning to check the fluid level again tomorrow to make sure it hasn't changed again.

[crashz]

Thanks for the play by play. I too have a GM 1/2 ton and you just saved me an oil bath!!!

BTW - I installed a trans temp gauge on my truck since it has the "standard" tow package transmission oil cooler. I wanted to get a base line of what temps were seen during various driving conditions. So far I have not seen any temps above 180 degrees so I've not seen the need for an additional cooler. That may change if I tow more regularly.

Funny enough, the transmission rarley gets warm until the ambient temps are above 60. Even then its stays around 150 degrees. Only A/C and stop and go driving in 80 degree + weather will bring the temps past 150 and then I haven't yet seen trany temps go beyond 180.

I run Mobil1 synthetic Dextron III H, but I'm having a tough time finding it now. The new bottles only say Mercon V and are compatible with Dextron, but the new Dextron VI is recommended. Anybody see the new Mobil1 Dextron VI?

[Bird]

It's been a long time since I installed a Hayden transmission oil cooler; more than 30 years anyway. I put one on a 1970 Olds 88 sedan with the 350 engine, then later on a 1972 Chrysler station wagon with the 440 engine when I was using them to pull an 18' travel trailer. They worked well, and back then RVers sometimes debated whether you wanted the auxilliary cooler intake on the line going to the radiator or on the line going from the radiator. In other words, did you want it to go through the auxilliary cooler before going to the radiator so the ATF was cooled a bit and less likely to cause the radiator to overheat, or did you want it to warm the radiator coolant, then the ATF be cooled to the maximum before going back to the transmission.

[Iplayfarmer]

Originally Posted by crashz

Funny enough, the transmission rarley gets warm until the ambient temps are above 60. Even then its stays around 150 degrees. Only A/C and stop and go driving in 80 degree + weather will bring the temps past 150 and then I haven't yet seen trany temps go beyond 180.

I've never seen any symptoms of a warm transmission until I start pulling a load that is approaching the rated towing capacity of my truck.

[Stimw]

A trans cooler should go on the pressure line. The stock radiator cooler does two things. I cools the trans fluid on a warmed up vehicle and it warns up the fluid on a cold vehicle. Transmissions work better warm but not hot.
If you put it on the return line you have put the heat into the radiator first when hot and cooled the fluid that was warmed up in cold weather.
I had this argument with a ASE Master. The same ASE Master who couldn't figure out why his B&S lawnmower would quit when hot with 5-30 oil in it. ????? 10 certs and he dosen't understand air cooled engines. ?????

[Iplayfarmer]

Originally Posted by Bird

...RVers sometimes debated whether you wanted the auxilliary cooler intake on the line going to the radiator or on the line going from the radiator. In other words, did you want it to go through the auxilliary cooler before going to the radiator so the ATF was cooled a bit and less likely to cause the radiator to overheat, or did you want it to warm the radiator coolant, then the ATF be cooled to the maximum before going back to the transmission.

I read some of that debate before I installed mine. The other take on putting the cooler before the radiator is that in the winter the fluid is warmed by the radiator helping it to come up to temperature quicker.

I chose to install it after the radiator for maximum cooling effect and because that is the recommended installation from the manufacturer.

[Skyco]

Originally Posted by Stimw

The same ASE Master who couldn't figure out why his B&S lawnmower would quit when hot with 5-30 oil in it. ????? 10 certs and he dosen't understand air cooled engines. ?????

Well clue us in ....why would an air cooled B&S engine quit when hot with 5W-30 oil in it? I see no reason that would be true, B&S even sells a 5w-30 oil rated for all temperatures in their engines.....
Staying on topic- I too always put the trans cooler after the radiator in the return line.

[schmism]

tube and fin or plate stack style?

in the future you an also get a half-n-half trans oil and engine oil cooler, simply add a fixture to the oil filter attachment is the easyest.

[arrabil]

Originally Posted by Iplayfarmer

I've never seen any symptoms of a warm transmission until I start pulling a load that is approaching the rated towing capacity of my truck.

Never driven a Ranger or Explorer with an A4LD, eh?

[Highbeam]

Even with the OEM HD towing package on my 98 half ton chevy, which includes a decent sized aux trans cooler, I have pushed my trans fluid past 200 while towing at the GCWR max and climbing big grades (Blewett Pass) in 95 degree weather with the AC on. To be fair, the engine coolant was also in the 210 range so the coolant was heating the atf.

While towing my trans normally runs about 70-80 degrees above ambient.

The wife's 2001 tahoe has no atf cooler and is similar to Iplayfarmer's situation.

Everyone should have a trans temp gauge on a auto equipped tow vehicle. It isn't hard to plug in a scangauge which digitally displays the actual fluid temp that your on board computer already knows.