Are you sure they're transmission lines and not oil? The setup on my '93 SSEI is coolant and oil are cooled in the radiator and the transmission has its own cooler. This won't matter anyway because the thermostat only controls when the COOLANT (only used on the engine) is let back into or out of the block. This whole thing is a cycle. Your coolant starts at your radiator and at a certain temp your t-stat opens up and lets that coolant in. In the meanwhile you have coolant that was in the block warming up to that temperature. As the t-stat opens cold coolant from the radiator comes out and the hot stuff goes in. Now that the block has cool fluid the t-stat closes again and the cycle repeats. Now if you don't give that coolant in the radiator enough time to cool down below the t-stats temperature your t-stat will just stay open and it will flow in a loop slowly warming itself up until your fans kick in and cool the whole thing down. Thats why your car still runs at normal temps when you sit still and runs cool when your moving. Your radiator doesn't cool it unless there is air blowing across it. No air and it gets hot and holds the t-stat open and now you've got a cycle that would overheat your car if not for your fans. Hope that clears a few things up

Just thought about it more..If you read what I had posted in place of this I was wrong. If you didn't read it, I'M NEVER WRONG MUAHAHAHHAHA. haha j/k j/k

Although I have no problem with people running Tranny coolers in their car, I would have to suggest that you not get one unless you drive in harsh conditions. (Consistant temps over 100 degrees, in heavy traffic, lots of stop and go traffic, or you are constantly at the track) Tranny coolers can do more harm than good. This is why I would never get a tranny cooler, unless I was able to turn it on and off at will. I will repeat that you can do whatever you want to your car, it is your car and I can't stop you, but this is my opinion on why I wouldn't do it.

The transmissions in our cars are rated at an operating temperature of 180-230 degrees. If they run colder than 180 degrees it can be damaging, because running the transmission when not warmed up to operating temps car ruin clutches among many other things. If they run warmer than 230 degrees that is also damaging, but I personally have not ever seen a case where a 4T60 or 4T65 has run that warm. If you live in a warm climate, and or experience the conditions above your tranny may run this warm, creating a reason for a tranny cooler, which if I were in that case I would install a switched one so I could watch the temps and not let it go out of operating temps. This is the problem I have with getting a tranny cooler. While monitoring the GTP at the track last week I noticed something. The tranny temps never went above 171 degrees. That is not even at operating temps. The car has no aftermarket tranny cooler, and it was 70 degrees outside. The car is making well over 400ft.lbs of torque, and the tranny is only rated for 280. We did a burnout before every single run to heat up the slicks, and ran WOT until 110 mph every time, and making that much power and doing burnouts, and brake torqueing to 2000rpms, and the tranny was only running 171 degrees at the end of the last run with no aftermarket coolers, and this is after a 1hr. and 30 minute drive to the track with about 20 minute cool down time before running (we had to put on slicks, and do other track prep), and the temp is accurate because it was read using the Autotap Scan Tool, so its not like the guage is off or anything, why is a tranny cooler needed? The problem I have with this is 171 degrees isn't even at operating temps yet. It damages the tranny to run that cold, and it does that with the stock setup. Now if under those conditions the tranny only runs 171 degrees, there would have to be some pretty harsh conditions to make it run hotter than the 230 degree maximum recommended temp. The warmest I have ever personally ever seen the tranny temps is 201 degrees. That was on a 2 lane road after about 1 and a half hours of stop and go driving on the 2 lane road, and 40-80 mph runs (passing people) many times, and while stopping at stop signs (about 20 of them) we just nailed the gas and let the tires spin (which they do up until 45mph). And with driving like that, with all the upshifting and downshifting, I don't see how anyone would have a problem with tranny temps being too hot because that was some pretty harsh driving in a car making a LOT of power, it would take a LOT to get the temps to 230 from what I have monitored. My suggestion is if you are going to install a tranny cooler, put it on a switch, and have a guage in the car so you know where the temps are, and turn it on and off as necessary.

I just hope this helps anyones decision on getting an aftermarket transmission cooler.

Very interesting and informative. Makes me wonder why my 93 SSEI has a transmission cooler though. My main source of info on this is www.pontiacserver.com/ratios.html and they say:
The biggest cause of failure of the original
4T60 (440) is heat. [snip of restricted info] Through
control of shift points and torque converter lockup,
tranmission temperature can be controlled. There is
a temperature sensor in the transmission for the ECM
to monitor. This shows the STRONG recommendation
to add and external air/oil transmission cooler
for 4T60 (440) equipped vehicles.


But the only thing I've found to contradict this is:
http://www.startribune.com/stories/435/924544.html
But they go to the extreme and talk about temps below zero but I guess the IDEA is there.

Do you have links to any info where I can read up on this?

I too would like to know more about this. I was cosidering getting one, but I live in NH where temps around zero and in the teens are commonplace in the winter. Any info woud be very much appreciated.

Well dbtk2 may have a point but I have owned cars long enough to know that you never have too much cooling when it comes to automatic transmissions. The first mod I did was to add a small cooler....it was as big as would fit in such a tight location...and don't have any problems. Look at it as insurance. It does'nt cost much. I have never heard of a trani that has failed because it was too cold. They usually burn up the clutches due to heat and oil that has never been changed when it breaks down due to heat. Or they break gear teeth due to fatigue caused by excessive stress.
I live in Canada too.

Good for you. Like I said, you can put on a tranny cooler if you want, it is your car do what you want, and if you want some "insurance" then there is nothing wrong with that. I was just stating that in my opinion that is why I would never install one because without one the tranny in the GTP and SSEi don't even run at operating temps. I live in Michigan and it isn't exactly warm here either.

Yes no yes no yes no.....
ok now that i can't make up my mind, I live in Louisiana, and it get HOT here, so should I get one for my N/A series 1 with no stock co0ler? Let me know what you think. I have already had my tranny rebuilt before, so I want to keep it as long as I can.

That might be the rating that GM gives them, but I don't believe for a moment that running them colder than 180 can be damaging. Besides the trani cooler is connected in line with your radiator, so it will never run that much cooler than your coolant temperature and will even supplement it to a degree.
Heat is what damages the clutches not cold.
Of course, if it'* too cold the fluid doesn't flow well and that could affect bearing lube and trani fluid flow thru the clutch packs but anything over 130 is fine.
I will still stick with cooler the better.
And if you have an older transmission like your 88 4T60 which used a factor trani cooler with the HD towing package, it'* a must have.
Like I said, it'* insurance, so if you can afford to rebuild your trani every few years or don't plan on keeping it for a while, don't install one.
I don't think dbk2 has much experience with sub zero temperature driving over 30 years.IMO
I do however respect his knowledge when it comes to performance mods on the 3800 SC engine.

what if we have high summer temps and sub-zero winter temps??? :P

Does anyone know how much these coolers really cool the fluid more than stock??? I mean I doubt that they really get the fluid temp THAT low.