Transmission temperature questions

I have a question about the 4T65-E transmission temps.

I have a 1999 Oldsmobile Eighty Eight LS which has a 4T65-E transmission. I also have a 1995 Oldsmobile Eighty Eight Royale LS that has a 4T60-E transmission.

After driving each car for about 30 minutes, if I get out of the car and just stand next to the engine bay, I can feel that the 99 is MUCH HOTTER than the 95. Also, the temp gauge in the 99 always sticks around maybe 210-220F, where as in the 95, the temp gauge NEVER goes above 210, even on the hottest days.

I was wondering if this was due to the different transmissions, and whether or not the 4T60-E runs much cooler than the 4T65-E. The cars obviously have the exact same engine (3800 GenII). I've been reading around on forums and have seen plenty of discussion but never a solid consensus on whether or not to run a trans cooler; I'd rather not, but if it's going to give me longer net life on my transmission, I would do it.

I'm not racing my car or anything, just using it as a daily driver. I just finished replacing all the solenoids in the trans (unbelievably hard job), and the car is running fine now. The 99 has all new fluids and a new trans fluid filter. I also flushed and got rid of the crap Dexcool and replaced it with regular green, and installed a 180 thermostat. I admit I have not programmed the PCM for the 180F fan trigger temps. Also, I'd like to know how to tell if my rad is working properly and not suffering from any type of possible blockage.

Thanks!

First of all, a 180 thermostat is not such a great idea. The electronic controls use coolant temp as one of the inputs in determining fuel mixture. If the stat opens at 180, instead of the programmed, stock 195F, then the electronic controls may think the engine has not fully warmed up. It may likely richen the mixture slightly to attempt to compensate, which wastes fuel, increases emissions and reduces engine life slightly.

Engines are supposed to run hot. So long as the coolant is not boiling and the oil is not breaking down, a hot-running engine is more efficient and wears out more slowly.
I would suggest putting the 195F thermostat back in.

FWIW, factory temp gauges are often somewhat inaccurate. They are good for telling if your car is running hotter than normal but are lousy at giving you an accurate temp reading. Aftermarket temp gauges, particularly the mechanical ones are much better. However, if the engines never boil over, chances are they are not over heating. If possible, look inside the radiators. Usually blockage due to corrosion is visible, as white deposits around the inlets and/or outlets for the radiator fins. If in doubt, a decent radiator shop can chemically clean out corrosion from radiators. But, as noted above, I do not think you have a problem.

Transmissions do not produce much heat on their own, especially compared to an engine. I doubt a cool or hot transmission would make much difference in what you feel. However, they do absorb heat...... from the engine block, from the air flowing through the radiator and from the exhaust system.

One very significant source of engine compartment heat that you feel is from the exhaust system. Your '99 may have a different system design or be missing heat shields etc, which is radiating more of the heat that you feel.

It is reasonable to assume that your '99's transmission is absorbing more heat from the hotter engine compartment and would benefit from a cooler.

Personally, I think coolers for both your cars are cheap insurance. I always install coolers in my vehicles. They are not very expensive and are easy to install.

Sometimes auto parts shops will try and sell you a cooler based on the GVWR or weight of the car. This means they will sell you a smaller cooler to you because you are not towing anything. Ignore them. Buy the biggest cooler that will fit on your radiator. Within reason, there is no such thing as overcooling a transmission.

Keep in mind too, that if you sell or scrap a car, you can remove the cooler, keep it and reinstall it in another car in the future.

Hmm, great info. The funny thing is that this is degenerating into exactly what I stated earlier: a debate. I've posted questions on other forums, and they are tending to say some of the exact opposite to things you are saying, much like what I've been reading.

Not saying anything is wrong with your advice, it's great. Now, having said that:

First of all, a 180 thermostat is not such a great idea. The electronic controls use coolant temp as one of the inputs in determining fuel mixture. If the stat opens at 180, instead of the programmed, stock 195F, then the electronic controls may think the engine has not fully warmed up. It may likely richen the mixture slightly to attempt to compensate, which wastes fuel, increases emissions and reduces engine life slightly.

I asked some guys at Intense Racing and they said that the easiest fix would be for me to go to a 180F thermostat instead of the 195F. I would lose about 1MPG, which is no problem, but not really do anything else worse to the car in terms of performance loss, or earlier part failure.

One very significant source of engine compartment heat that you feel is from the exhaust system. Your '99 may have a different system design or be missing heat shields etc, which is radiating more of the heat that you feel.

This very well may be the case. I can tell you with 100% certainty that the 99 has a radically different exhaust design, from the exhaust manifold to the cat converter. I should also mention that it is MUCH QUIETER.

It is reasonable to assume that your '99's transmission is absorbing more heat from the hotter engine compartment and would benefit from a cooler.

I was told that both my cars already have trans coolers in them.

Debates are what forums are all about :)

As for Intense Racing's advice.... a cooler thermostat will not stop your car from overheating - that is, boiling over or running too hot. If it overheats or runs really too hot, it will do so regardless of the thermostat setting. The thermostat does not increase cooling system capacity.

Their advice is good for some cars in some situations, but just not yours.

A 180F stat is fine in a non-computer carbureted car. Some of my older cars and trucks have 180 stats in them.
Almost all older carbureted and TBI cars have coolant circulating through the intake manifold. This is required to provide intake manifold heat, which helps keep the fuel-air mixture in suspension. In these engines, a 180 stat often provides a slight increase in power over a 195 stat, because the fuel air mixture in the intake manifold is slightly cooler and slightly more dense.

But a 180 stat is simply not ideal for a late model computer-controlled (ECM) car, like yours, which has a dry intake manifold (with no coolant heat for the incoming air). It will not provide you with any benefit, but it will waste your fuel.

GM has spent $$$ millions over the years engineering electronic systems. The ECM is designed to run with the 195 stat. Yes, it will work okay with a 180, but it is not ideal.... and isn't that why you are here at AF, to make your cars ideal?

Trust me, if GM felt the 180 stat was better, in terms of economy, low emissions and longer engine life, the 180 stat would be in there when they built the car..

BTW, one of my automotive textbooks includes data from International/Navistar which shows that engine wear is inversely proportional to coolant temp. The hotter the coolant, the lower the wear rate, up to 195F. Beyond that, any improvement is negligable.

As for the trans cooler...... maybe I should have made this more clear...... I was writing about auxillary coolers, not the stock ones.
Auxiliary coolers are seperate small radiators that go in front of the car's main radiator and cool fluid with moving air, like the car's main radiator. They work in conjunction with the stock trans cooler to cool the trans fluid even further.

Virtually all automatic transmissions have a stock cooler placed in the radiator tank at the cool side of the radiator. You can see the small steel lines that run from the transmission into the cooler. These direct a small amount of transmission fluid into a cooler that is surrounded by engine coolant.

The problem with these coolers is they have limited capacity. They depend on hot engine coolant for a cooling effect. At that end of the rad, the coolant is still at approx. 130-160 F. This means your trans will have to be significantly hotter than that to receive any benefit.

Transmisison heat is insidious. A little too much heat will not destroy your transmission right away, maybe not next month or next year. But is is bad for some softer parts, such as bushings and washers made of nylon, brass etc. and decreases their lifespan. It also decreases the fluid lifespan. So, ideally cooler transmissions last longer.

Stock coolers are fine for light-duty use, such as highway driving, especially in cooler weather. But anything else - city driving, hot weather, a heavily-laden car, trailer towing etc. will benefit from an auxiliary cooler.

I have driven many cars both with and without auxilliary coolers. I have overheated a couple of transmissions (no auxiliary coolers) with fairly normal use, yet others have been just fine. However, every auxiliary cooler-equipped transm has been trouble - free.

However, since it sounds like you, like me, care about your cars and want them to last a long time, installing an auxiliary cooler is prudent.... not essential... but prudent.

Here's a pic so that you guys can get a better idea of what I'm trying to convey.

http://img4.imageshack.us/img4/411/0625091742.jpg

Is this normal?

Was that idling or as you were cursing? Thats a Bit hot and the fans should have been on if you were idling..

Was that idling or as you were cursing? Thats a Bit hot and the fans should have been on if you were idling..

You mean cruising, right??? :rofl:

That was idling, BTW.

Yeah... I have some Brain Fry going on...LOL

It depends on what the PCM is seeing for temps.. I wonder how far off the dash gauge may be.. If thats 220F then it would be normal to get that hot while idling... Hard to say..