4L60e running at 200-210F at operating temp.

[Pinger]

Heat always flows towards cold (less heat). Theoretically both fluids are the same temperature before start up. Both start flowing immediately. The coolant is going to start getting warm first, as it's cooling combustion. The ATF is just heat by friction. Since the coolant gets hot faster, the heat will flow into the ATF at the transmission cooler.

But the coolant is cold in the rad until the thermostat opens. After it opens there will be heat flow from coolant to ATF but for the initial period the ATF will be giving up its heat (no matter how marginal) to the coolant rad.

Saddle cooler?

Oil cooler incorporated into coolant radiator. Brit speak that never made it across the Atlantic!

210F is a little high, are you sure it's not just your gauge?

Possibly a touch high and/or inaccurate gauge but as it is just on the cusp of the temp water boils at at atmo pressure and is in a sealed (pressurised) system designed to avoid boiling I'm not overly concerned.

The transmission cooler is on the cool side of the radiator, even if engine temperature (taken at the head) is 210F, that side of the radiator should be quite a bit less.

If it left the rad at 85C (185F) then that's still on the high side for cooling ATF - no?

 

[GMTMark]

If you want to put a cooler on it you won’t hurt anything. You might help. 210 at the pressure hole doesn't sound too bad. I would imagine it would be a little cooler in the pan.

 

[zetros]

There is a bit of concern regarding the lack of transmission heating ability given I had bypassed the saddle cooler entirely.

That being said, I live in Georgia where it is very hot a good portion of the year, and even then, I drive this thing like a granny in general but especially when it is cold and has not warmed up yet.

Also, FWIW, it is about 90 degrees outside and the tranny only reached 165. Absolutely no leaks either, 2 days later. I think I can call this a success, and once again, thank y'all for the help.

 

[alpinecrick]

I really don't see how it can. There is no heat in the coolant rad until the coolant thermostat opens and all that time the trans fluid is shedding its heat into the coolant rad - not drawing heat from it.
There seems to have been a shift away from saddle coolers to heat exchangers (often found at the base of the engine oil filter) that see coolant circulated through them immediately on start-up as in effect, connected to the same circuit as the cabin heaters. That type can warm the trans fluid.



OP is concerned with 'high' trans fluid temp of 210F - the same temp as the coolant in my Vortec runs at.
Even the saddle cooler's ability to cool the trans fluid is debatable when its cooling medium (engine coolant) is at a higher temperature than desirable trans fluid temps.

Pinger,
That’s why it’s a heat exchanger, it works both ways.

Vortecs came with 195 degree thermostat, unless the truck was destined for very cold climates. I don’t think the northern hinterlands of the British Isles qualify as that kind’ve cold.
Any good reason you’re running that warm of a thermostat?

Note the ATF first runs through the auxiliary cooler, then through the external cooler-when equipped—for further cooling.
When I used a infrared temp gun on the trans outlet line I was getting somewhere around 210. I suspect on sustained climbs or towing the ATF exiting the trans can become significantly warmer. This why I’m still a little suspicious the test port might be the coldest spot in the trans.

 

[L31MaxExpress]

Pinger,
That’s why it’s a heat exchanger, it works both ways.

Vortecs came with 195 degree thermostat, unless the truck was destined for very cold climates. I don’t think the northern hinterlands of the British Isles qualify as that kind’ve cold.
Any good reason you’re running that warm of a thermostat?

Note the ATF first runs through the auxiliary cooler, then through the external cooler-when equipped—for further cooling.
When I used a infrared temp gun on the trans outlet line I was getting somewhere around 210. I suspect on sustained climbs or towing the ATF exiting the trans can become significantly warmer. This why I’m still a little suspicious the test port might be the coldest spot in the trans.

The hottest fluid is the outlet of the torque converter and that is what leaves the cooler line headed to the cooler. Can easily hit 250°F and beyond on a hard long pull. Which is why the in-radiator cooler is so important.

 

[thegawd]

so am I just lucky nothing has happened in the last 6-7 years. why would a shop warranty a brand new rebuild if it was a concern?

I get the idea but I dont buy it. I dont care either because it ****** me. twice. not guna happen again.

Al

 

[L31MaxExpress]

so am I just lucky nothing has happened in the last 6-7 years. why would a shop warranty a brand new rebuild if it was a concern?

I get the idea but I dont buy it. I dont care either because it ****** me. twice. not guna happen again.

Al

Lucky or you don't work your truck hard. Unless you have some form of instrumentation you would never know if you are overheating it or not. Long hard pull in 2nd gear at 50-60 mph will have the converter unlocked and overwhelm even a Trucool 40K with heat.

I bypassed the in radiator cooler on my old G20 van years ago with a Hayden 679 and it burned the fluid in a couple of months. I put the radiator cooler back into the loop. Luckily the trans lived.

I have not once seen that problem on a good quality radiator or a GM factory radiator.

Factory Nissan 4.0L trucks have that problem throughout many years but a good quality aftermarket radiator like a Koyo practically guarantees it will never happen.

 

[alpinecrick]

After 6-7 years you haven't saved up the pennies to buy a $170 radiator?

How do you manage to put gas in that thing?

 

[thegawd]

tank is full and the rad passes a pressure test. I have 6 kids and different priorities.

 

[thegawd]

ok heres a damn good question,

how are you ever guna tell if your rad starts leaking coolant into your transmission?