Automatic transmission overheating?
Thread Starter
Instructor
Joined: Mar 2015
Posts: 113
Likes: 3
Automatic transmission overheating?
I was at button willow raceway yesterday, and it's my 3rd track day so I'm pretty much still beginner. This time I try to use the paddle shift a bit more aggressively so that there are indeed several times that it's close to the red line, and the vehicle refuse to accelerate without me up-shifting.
It's hot, like 103F on the track and in my last 20mins session (there is 1 hour between sessions), and in those last 5mins, the transmission deny my downshift to 3rd gear even at around 40-60mph. And after I come off the track, I shift to D, but the shifting also jerks.I don't know whether that's a sign of overheating since I didn't see anything on the gauge.
The jerk disappears after I fill the gas and the car cool down a while.
While it's worth noting that my gas was low in my last session (in red zone, but still be around 2 gallon left), don't know whether that causes the shift deny, but it won't make sense for the jerking?
It's hot, like 103F on the track and in my last 20mins session (there is 1 hour between sessions), and in those last 5mins, the transmission deny my downshift to 3rd gear even at around 40-60mph. And after I come off the track, I shift to D, but the shifting also jerks.I don't know whether that's a sign of overheating since I didn't see anything on the gauge.
The jerk disappears after I fill the gas and the car cool down a while.
While it's worth noting that my gas was low in my last session (in red zone, but still be around 2 gallon left), don't know whether that causes the shift deny, but it won't make sense for the jerking?
Racer
Joined: Oct 2004
Posts: 432
Likes: 49
From: Southern Maryland
If your car over heated, you should have seen a warning message in both the HUD and the DIC. The following are what I have seen posted:
engine coolant: 262 deg F
engine oil : 320 deg F
M7 transmission: 325 deg F
I know you have an automatic, I assume it would have the same limit as the M7 (??). Remember, you have two fuel cells, so if you were down to two gallons of gas, the fuel pickup was probably not picking up all the fuel (a possible reason why your car had problems accelerating). I haven't seen a posting describing what you've seen with your transmission. Is your car a Z51 or Z06?
engine coolant: 262 deg F
engine oil : 320 deg F
M7 transmission: 325 deg F
I know you have an automatic, I assume it would have the same limit as the M7 (??). Remember, you have two fuel cells, so if you were down to two gallons of gas, the fuel pickup was probably not picking up all the fuel (a possible reason why your car had problems accelerating). I haven't seen a posting describing what you've seen with your transmission. Is your car a Z51 or Z06?
Instructor
Joined: Oct 2014
Posts: 146
Likes: 25
From: Louisiana
The A8 will start shifting on its own or denying downshifts if trans temps get high. I don't knows exactly what temp but on mine at the track I t was at about 270F. It's not as high as stated above. You will get a message on the display when it gets much higher than that. I cannot remember the exact values but I have gotten the message twice on the track. I don't think low fuel has anything to do with what you saw. Lots of threads on the topic if you search.
Last edited by ap6954; Sep 27, 2015 at 08:39 PM.
Drifting
Joined: Dec 2003
Posts: 1,711
Likes: 90
From: Hillsdale NJ
Once the transmission gets hot it will deny shifts and downshift on its own in manual mode. That happens at about 275 degrees, but assume once you break 270 its going to start happening. I always keep the dash in track mode with the temps displayed and I can tell when the bar is getting in that neighborhood so I can back off before it happens, or at least it doesn't come as a surprise.
FYI: It happened to me the other day after 3 laps with temperatures all of 66 degrees. This problem is going to get fixed over the winter or I'm going to raise hell.
FYI: It happened to me the other day after 3 laps with temperatures all of 66 degrees. This problem is going to get fixed over the winter or I'm going to raise hell.
Racer
Joined: Jun 2013
Posts: 489
Likes: 272
I bought a 2015 Z51 A8 primarily to do track days on. And I can only run 10-12 minutes, even with early upshifting and minimizing shifting to 2 per lap, before the transmission overheats and goes crazy upshifting and downshifting on its own, and a lap later throws a "Transmission Overheat, Idle Car" message.
The only potential fix is a retrofit kit of the 2016 C7 extra transmission radiator. That is likely to cost $2,000+ in parts and labor.
I really would like to know what "raise hell" means. I think a class action may be the only vehicle.
Dazed Confused & Verklemp
Joined: May 2008
Posts: 1,398
Likes: 109
From: Naples, FL & Clear Lake, IA
This subject has been posted to death!
GM claims there is going to be a kit for sale to solve this issue for us A8 owners. Will be an additional profit center for Chevy dealers.....
I'm not holding my breath. Much like the AFM failure issue. They seem to have fixed these issues on the Z06, but the rest of us are SOL....
The "NEW GM" is really just the "same OLD GM".
GM claims there is going to be a kit for sale to solve this issue for us A8 owners. Will be an additional profit center for Chevy dealers.....
I'm not holding my breath. Much like the AFM failure issue. They seem to have fixed these issues on the Z06, but the rest of us are SOL....
The "NEW GM" is really just the "same OLD GM".
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