RusherRacing

I am using the Redline D4 ATF in the trans and Redline 75w-90 in the diff.

During the Big Bend Open Road Race my trans temps got up to 285 give or take 5 deg. The high temp warning light came on and it gave me a temp. Air temp was ~90 Deg.
I checked the fluid on both the trans and the diff. Both were full and the oil didn't look contaminated or dirty in anyway. I called Redline and they said there oil is good for temps alot higher than that. (400 range)

I went to Hastings for a little Corvette Days Open track thing Jun. 6th and 7th. On Saturday towards the end of the day I was pushing the car fairly good and the high trans temp light came on again but this time would not give me a temperature which I thought was weird. Anyone know why?

It was ~30 degrees hotter than a C5 FRC running a little faster lap times (no coolers on trans or diff.) based on case temp right when we pulled off the track.

Is the Redline causing increased trans temps? I didn't have this issue last summer using stock fluid. Will over filling the transmission/diff help? Any suggestions on how to bring down the temperatures.

Honestly I can't afford to do a cooler setup right now, nor can I afford a transmission. If I am not hurting the tranny much and everything should be fine then i will continue to run the way it is. (aka seals etc are designed to operate up to 300 deg.) Will another fluid help something less viscus? or am I done racing until I can afford to do the oil coolers?

froggy47

The Redline is probably saving you a lot of grief, I say wrap the exhaust where it passes the tran/diff with header wrap. That's where your heat is.

MungoZ06

Was running Seat Time Fri at Summit Main - every hour on the hour for 25 minutes, so effectively, 30 minutes cool-down. It was moderate - ~ 80 degree ambient.
9:00; 10:00; 11:00 - end of that session I got a high trans temp warning as I took the checker for cool down lap. I was already letting up - temp read 277, so the warning must trigger @ 280.
First time I've had the warning; also first time I've run that close back to back to back sessions. So ... we had a lunch break; went out at 1:00, took a bye on the 2:00 and ran the 3:00. No recurrence.
Running Amsoil in the trans and diff.

drbenne

tranny cooler time. I wrapped my exhaust and this helped, but if you are planning on driving the car hard especially if the ambient temps are high, I would do the tranny cooler. I tried to avoid putting one in, but I just couldn't avoid getting the tranny temp warning within a 30 minute race.

The oil (red line, royal purple) may be able to withstand high temps, but the transmission is not designed to see those type of temps.
Transmissions are mucho expensive to replace or fix.

longdaddy

the fluids you're running are not causing higher temperatures, it's your driving

RusherRacing

Any reason why it wouldn't read out the temp like it did the first time?

I will not run back to back again 20 minutes on 20 minutes off until i get coolers. If those damn 12v oil pumps weren't so expensive. I will switch to straight pipes and mount the coolers where the mufflers are currently with some duct work and fabrication. But don't have the coin now probably will need to be a winter project.

C66 Racing

Way back when I was running DEs in my car when it was stock, I got a similar warning (interestingly had Red Line D4 ATF in my car as well at the time). The tranny temp warning comes on at something like 280F and I believe if it is hotter than that it will display the temp. Once it cools down below the setpoint, it won't display the temp anymore. I'd guess that the second time it came in right at the setpoint, you probably backed off quickly and it cooled down to just below the setpoint so you couldn't see the temp.

As for your original question, I don't believe that there is any specific temp that you can say for certainty, below is okay, above is bad. The fluid's viscosity will drop in an exponential decay as it heats up. A typical Dexron III ATF fluid will have a viscosity of about 39 cSt at 100F, 7.5 cSt at 212F and probably under 3.0 at 300F. So to say that the fluid is okay to 400F is misleading. The fluids basestock might not breakdown and it might not catch on fire, but what damage is that really low viscosity causing your synchros, gears, etc.?

Finally, I suspect that the primary difference in tranny temps between one driver and another is his rpm which varies by gear selection and obviously how fast he is going. If you want to try to run longer, try using a higher gear when possible (5th vice 4th, etc).

Last C5

Wrapped mine and haven't seen a tranny temp warning since.

You can also switch from D4 to Redlines' new High Temp ATF too. I used to use D4 but I switched to the High Temp to see how it would work about a year ago. No problems and 20 + days on the track.

longdaddy

this is odd because I had my trans temperature display the day aftert I had the warning (i.e. turned on the car in the morning, see readout "trans 60F"). I believe it will stay on as long as you do not change DIC screen, may be varied over model yearts, etc.

Slalom4me

mikahb posted photos of exhaust heat damage to the load floor area
of his tub early this year that may be of supplemental interest
.

2MCHPWR

is the tranny temp sensor on z06's only?
i have base c5 and curious if I have this sensor. thanks.

The Spark

Base C5 does not have a sensor.

I installed DRM tranny and diff coolers before the Big Bend Race.
I added oil temp gauges for both. Due to location the sensors are on the return lines before going into the trans or diff.

I was in the 130 mph class and temps were about 210*. I use Royal Purple oil BTW.

yakisoba

I overheated the trans (new trans, RPM) and decided on a trans cooler thereafter. Ran a test this weekend, at 100degrees F air temp. Ran 25 minutes on a short twisty track, mostly second and third gear work. Pushing hard. No issues. I'm sold. Heck even with a cool shirt, I got pretty hot.