Transmission oil in radiator:better watch for it

93TS 3800 with dual transmission loops in main radiator (no towing package, no external cooler, no engine oil pass).
For all those surviving TS, keep an eye on this. I had read about it on this forum...but now I experienced it. Some transmission smell came from the radiator cap together with a brownish film on top and greasy top. Not much in quantity...and absolutely no sign of contamination in transmission oil....just like it was a really small one way leak. Anyway, I had already bought an external cooler in anticipation of that event and will install it within a few days...; as I was away from home, I have just disconnected the hoses coming from transmission near radiator bottom and plugged them together so as to bypass the oil cooling pass . WIth outside temperatures really down now, I can get back home without problem and no fear of seeing the condition worsening.

Good thing you caught it early. You do not want any anti-freeze getting into your transmission. If transmission fluid could get out of the cooler it is only a matter of time before the hot pressurized coolant seeps into the transmission fluid when you shut the engine down. Probably some got in. If you haven't recently it might be a good idea to change the transmission fluid.

yeah..really clean on the dipstick, but will drop the pan anyway, as any water will sit at the bottom. That was fresh new fluid from last year, complete with filter. Seeing the way it behave in the radiator, these two fluids do not seem to mix easily.

I will have to keep an eye on that... My TS has the Dual trans coolers like yours, but I have my Heavy Duty AUX cooler plumbed in line after the internal coolers..

External cooler installed now, but..coming back home (140 miles) without any cooler surprised me somewhat: although the ride was "benign", small load, cool outside temperature, speed between 60 and 70mph, and I was specially cautious to avoid hard or long accelerations, I was surprised the temperature switch in the transmission tripped and prevented 4th and TCC to operate. I was aware of that feature, but did not think it would set in such non strenuous conditions. After all, transmissions in the past would function normally without any cooler at all......but ...well....may be they should have had one....at least two of them were fried under my command.
I think the limit on that temp. switch is rather conservative, and that is OK anyway. Once car cooled down, all went back to normal and with the cooler installed now, no problem.

The switch may trip in the 230-260F area... Thats pretty hot by any means..

My 95 when it was on the original PCM monitored the Trans temps and at 260F it would be sent into limp home mode as the trans would try to protect its self.. The OBDII PCM that we used does the same and monitors the trans temp as well.. I noticed that even with a standalone HD Trans cooler the trans would still get hot.. So I went to a larger HD cooler and when I did my engine swap I went to the dual cooler to get some cooling effect then to the AUX cooler.. So far so good..

One of the most common failures on these vans is that the trans simply burns up.. 3700-3800 Lbs is a lot to move no matter how you slice it, and put that trans behind a torquer 3800 and heat will come...LOL

LMP would you happen to have Traction Control?

I always wondered if a fully-synthetic transmission fluid would be better at preventing a transmission from frying-up than an extra ATF cooler.

I'm still using the classic setup with original radiator and factory transmission cooling system but I took the risk to load it up with Mobil 1 Synthetic ATF and it does feel more torquer now at high temperatures + changes more softly.

Negative about traction control.
'93 does not have transmission temperature externally monitored: the 7thpin of the connector is not used as in more recent years.
THis incident shows two things: the internal "limp mode" does work, and cooling IS required.
I think that during my trip back home, it just barely went over the temp limit, as at one time, it reverted to full operation on all gears for a limited time, but shortly after fell back in limp mode until home; after a relatively short rest period, it reverted to full operation.
The transmission fluid suffered no color change, still totally translucent, and no burnt smell either, so I think the transmission is saved. I left the lines to the original cooler "opened" but no sign of coolant exiting...yet, a probable sign the leak was minimal. I thought the transmission cooler circuit was at a rather low pressure...it is probably higher than I thought as it was able to use an "hairline" crack that is not exploited by the 13psi coolant pressure... probably because transmisison pressure tries to open the crack from the inside, while coolant pressure acts to compress it closed; I'm going to test the twin coolers with compressed air, looking for bubbles exiting the radiator. Will report findings when available.

I always wondered if a fully-synthetic transmission fluid would be better at preventing a transmission from frying-up than an extra ATF cooler.

I'm still using the classic setup with original radiator and factory transmission cooling system but I took the risk to load it up with Mobil 1 Synthetic ATF and it does feel more torquer now at high temperatures + changes more softly.

I'm sure your synthetic fluid is fine but I think it's best to use Dexron VI since all the previous Dexrons like III are no longer regulated or licensed. Dex VI is a much higher standard than the previous ones and is backwards compatible for all previous Dexron standards. Some Dex VI are synthetic or blends anyway. The important thing is to never allow your trans fluid to get too hot in the first place, because even if you had a synthetic that can handle the heat, the heat is still damaging to the trans clutches and internal parts.

I'll check what type I poured in last year....
I tried compressd air....but no bubble went through. Air pressure was quite low though, as I blocked the circuit with my thumb on one side, and loosely applied the air gun to the other end..as I have only two hands....probably no more than a few psi were used... the leak was very tight, as I can see for now...a few remaining oil drops still come to the radiator cap...
I'm always suspicious of all cleaning and magic concoctions...and I feel the barely oily coolant might not be that detrimental after all, but I would pay due consideration to suggestions in that matter.....

I'm sure your synthetic fluid is fine but I think it's best to use Dexron VI since all the previous Dexrons like III are no longer regulated or licensed. Dex VI is a much higher standard than the previous ones and is backwards compatible for all previous Dexron standards. Some Dex VI are synthetic or blends anyway. The important thing is to never allow your trans fluid to get too hot in the first place, because even if you had a synthetic that can handle the heat, the heat is still damaging to the trans clutches and internal parts.

I have Dex 3 in my van, made or sold under Penzoil.. Van shifts off kilter when the trans warms up.. I will use Dex VI when I change the fluid again.. After so far I have a bit over a year since I did the rebuild.. I used the Dex VI when I changed the fluid on my 03 Bonneville and it shifts smooth and nicely all of the time... But I would still like to add a cooler..

Heat is heat, and I agree just because the fluid will withstand the heat doesn't mean the Rubber lip seals and O-Rings in the trans will... I am replacing a 4T60E in a Lesabre... Owner was on the way home from work and Poof no movement.. I am positive it popped that Lip seal.. Happens with heat and age.. It was 1 year ago that it recieved a cooler..

I live here in FL and have seen a battry of the THM440-T4( 4T60 ) and 4T60-E's fail due to heat related causes..

I have Dex 3 in my van, made or sold under Penzoil.. Van shifts off kilter when the trans warms up.. I will use Dex VI when I change the fluid again.. After so far I have a bit over a year since I did the rebuild.. I used the Dex VI when I changed the fluid on my 03 Bonneville and it shifts smooth and nicely all of the time... But I would still like to add a cooler..

Heat is heat, and I agree just because the fluid will withstand the heat doesn't mean the Rubber lip seals and O-Rings in the trans will... I am replacing a 4T60E in a Lesabre... Owner was on the way home from work and Poof no movement.. I am positive it popped that Lip seal.. Happens with heat and age.. It was 1 year ago that it recieved a cooler..

I live here in FL and have seen a battry of the THM440-T4( 4T60 ) and 4T60-E's fail due to heat related causes..

Yeah I totally agree heat is the worst enemy of an AT no matter what fluid you have in it. You can't do much better than keeping the tranny cool and using Dexron VI fluid. It's the only fluid I'd use now.

You convinced me to buy an extra trans-cooler as soon as possible.

That type of cooler functions only when the van is in motion or is it cooled by the radiator fan also?

LMP, do you have any pictures with an actual setup of this cooler?

Not that it will help.. But I installed my cooler like this.. I later went to a slightly larger cooler..
http://img.photobucket.com/albums/v294/Jr3800/1995%20Pontiac%20Transport/95TransportTrannyRemoval055.jpg