Gearhead Jim

Well, it's supposed to work in the radiator tank as a cooler when the tranny is hot, and as a heater when the tranny is cold.

But really, it doesn't seem to have much effect. Today I got stuck in stop-and-go (mostly, stop) traffic for over 30 minutes. When things first really slowed down, my coolant was 220' and tranny was 170'. After 30 minutes of creeping along, the coolant was still 220' and the tranny had increased to 209', still less than coolant temp despite the long period of converter slippage.

And when I start having fun with lots of throttle and rpm and shifting with the paddles, the trans temps goes up rapidly also. So it doesn't seem to work all that well as a cooler, either.

Has anyone tried installing a pair of sensors, one where the trans fluid goes into the radiator and one where it comes out, to see how much the temp changes as the fluid goes through the radiator tank?

dennis50nj

its the same as any automatic trans cooler in the radiator

Gearhead Jim

Well, I suspect there is some difference from one type of car to another. Does anyone have enough experience with automatic trans temperatues on other vehicles to see if they are any better? Of course, higher stall speeds on the converter, or towing etc, will tend to give higher temps if everything else is equal.

HOXXOH

Personal experience has shown the trans fluid will get real hot (as in 230+) in a hurry, if not going through the OEM radiator cooler. I've been to 235 with the engine also at 235 while driving in the mountains using the OEM cooler. I've also been to 235 with an aftermarket cooler that bypassed the OEM in similar conditions. BTW, at 235 I pull off the road and let it cool off before I kill it.

However, in cooler ambiant temps, I have a tough time getting the trans temps up to a normal working range with just the aftermarket cooler.

Ideally, the temps should be in the 160-190 range. If the A6 gets below 140 it will affect the shifting at WOT along with slippage. Anything over 200 shortens the life between rebuilds. When you get into the 250-275 area, it's closing in on sudden death.

I'm about to run through the aftermarket cooler and then the OEM cooler before it goes back to the trans. I'm hoping that will provide a more balanced temp.

Gearhead Jim

Thanks for your numbers, please be sure to post when you put the extra cooler in before the radiator.

B&M claims their stacked plate coolers have somewhat of a thermostat effect, with cold fluid bypassing most of the plates. Did you have something like that, or different?

dennis50nj

i have a hayden 12x12 stacked plate mounted independent dead center right behind the vararam it heats up fine in the winter and stays cooler in the 95 degree heat, it stays under 185 on the fourth hot lap driving to the track 3800 converter, the only time it was cold and affected shifting was when i trailered to the track but stop and go and turnpike it stays bet ween 140-185 winter or summer and the water temp is between 156 and 181 and oil temp is 150-225 depending on what rpm and outside temp but i have a4

cclive

Most cars with automatics run the fluid through the radiator in an enclosed cooler...this is not unique to the Corvette. The majority of the heat generated is in the shearing of the fluid inside the torque converter. The exchange of heat is simple, the heat goes from the higher temp fluid to the lower temp fluid.

Gearhead Jim

In a really effective system, the coolant and trans fluid would run almost the same temps.

But as noted in post #1, there doesn't seem to be much transfer going on in mine; whether the trans fluid is "too" cold or "too" hot.

I'm looking forward to HOXXOH's results when he installs the extra cooler before the radiator cooler.

cclive

Exactly, if the cooler was 100% efficient, the two fluids would run at the same temp. I think that without the cooler, the trans would naturally run at higher than the 200 to 210 that the radiator runs at...so overall, the trans is being cooled. Around 170 would probably be a healthier temp for the trans though.

jpee

I ran mine just the opposite as your going to do... I ran mine from the trans, to the OEM cooler, THEN to the aftermarket Stacked Plate cooler then back to the trans.... My thinking is..

If the trans is at 230 and you run the fluid to the OEM cooler it will drop the trans fluid from 230 to the engine temp (190 or so) then the fluid that is NOW 190 - 200 will go through the aftermarket cooler and cool it further.. My trans never gets over 200 in traffic.. at the track I have to break stall it to bring the trans temp UP to 160 for my run..

If you run the fluid as you say, (example temps) say its 230 leaving the tranny, it then goes to the After Market cooler and get cooled to 150.. then it goes to the OEM which is 190 (water/engine temp so your heating the fluid UP after the After Market cooler has cooled it....

I think anyway... Cartek agrees w/me and set mine up that way..

dbratten

I asked much the same question and Tom DeWitt replied --

Remember that running fluids of any kind through the radiator will increase or decrease each other's temperature. Having cooler trans fluid enter the radiator will lower the water temp slightly.

Plus, I've never seen the trans temp higher than the water temp during autox or HPDE so running it first through the radiator will add temp.

--Dan

dennis50nj

that's why its best to bypass the rad and run the trans cooler independent i have been doing it for at least 6 years

Gearhead Jim

Seems like you guys have been getting different results...

CGZO6

Points to ponder - The engine coolant temp is taken from a sensor at the front of the drivers side cylinder head. The trans cooler is in the passenger side of radiator. The drivers side of radiator is where the hot water enters the radiator and the passenger side is where it goes back into the engine. During normal driving the coolant on the passenger side of radiator will be significantly cooler than the engine coolant temp reading on the dash/dic. This would explain why the trans fluid temp doesn't seem to rise as high as the engine coolant temp. Also would explain why it eventually rises to above 200 when in stop/go/idling for prolonged periods. The radiator fan doesn't come on until the coolant temp gets to 220, if I recall correctly (unless the a/c is on). So when idling/stop/go for a long time the coolant on the passenger side of radiator will be alot hotter than when driving at normal speed (causing trans temp to rise).

HOXXOH

There's a lot of difference between ambiant temps and topography in NJ vs AZ.
I'm quite sure that if Dennis was driving uphill in the AZ mountains in 110+ temps, he'd see the same overheating issues.
He also saw the results at MIR recently when his fluid was too cold. While the car can be driven normally with low fluid temps, WOT produces problems with erratic shifting and over revving.
I think Dennis runs a 4000 converter in an A4 and mine is a 3600 in an A6. They both need better cooling than the OEM cooler can provide. I have my fans coming on at 192 and full by 201. I'm sure Dennis has his set somewhat similar.

HOXXOH

The temperature sensor is in the valve body, so the fluid temperature going to the cooler is nearly the same as what the DIC reads. By the time the fluid reaches the cooler, it has already dropped several degrees in the lines. It'd be a really rare occurance to have the trans temps at 230 while the engine is at 190.
Since you have to brake stall at the track to get the temps up, you have the same problem I do in bypassing the radiator. You're cooling the fluid too much.

dennis50nj

Tom i have to drive up a 33ft. hill to get to atco i have to drive it far enough to warm up to shift right and my fans come on 100% at 181

Gearhead Jim

Excellent post, thanks.
Duh, why didn't I think of that stuff?

Does anyone know how much the coolant temp drops from exiting the engine until it arrives in the right side tank?
Probably a lot while driving at 70 mph, not so much idling in traffic with only the fan for airflow.
Numbers would be nice...