Sorry, it's a long one, so TLDR; I'm having transmission cooling issues and was wondering if anyone here has had any experience with this.
Okay, so on Wednesday, I opened up the transmission filter for a routine service (last I did was in December) and found some metal chips (see attached photo). After some analysis and consulting with other technicians, we resolved to simply do a full transmission service and check the oil content after a few test drives. That didn't end well as I ended up changing the gearbox after a very spirited test drive during which I got a P2787-4b: Clutch temperature too high DTC in the TCM (note: this does not trigger a check engine light).
Some backstory... when I first got the car, I occasionally used to have the well-known "Gearbox Fault" message where the transmission is stuck in park on fresh ignition cycles until after a few ignition toggles which eventually clears it. We tried updating the TCM software and other things mentioned in the forums but had no luck.
Because I'm technically inclined, I was able to do some investigation with my scanner and noticed that the message usually came up alongside a P0658-11 code on the transmission control module (Actuator supply voltage A - circuit low).
I figured this occurred after prolonged high-stress driving and started monitoring certain parameters on every drive. In particular, I was looking at:
- Transmission oil temperature
- Actuator supply voltage
- Control module supply voltage
- Control module voltage
- Control module internal temperature
- Engine coolant temperature
What I discovered from observing these values was that the DTC always got registered on the TCM when the transmission oil temperature was relatively higher than that of the engine (roughly around 10-30 degrees)... when this happened, the actuator supply voltage also reduced significantly obviously as a result of high resistance caused by heat internally.
Before thinking of a solution, my workaround was to clear the error whenever it came up after a drive and wait for the temperature to normalize while the car is idling before switching it off — this worked for the longest time and I never had to worry about the car being stuck in park on startup until the day the gearbox really took a beating and the TCM got fried this time (actuator supply voltage had a steady zero-value) before I could even clear the code and repeat my usual procedure.
We changed the TCM and while at it, did a full transmission service (oil + filter). After configuring the new module everything worked as usual, but I kept running into the Clutch temperature too high DTC.
It wasn't really a huge concern considering how aggressively I shift in manual and the car always gets driven hard, but still we changed the transmission oil cooler and did another full service just to be safe. Guess what? The error still always occurred after extremely hard driving, and just this Wednesday, after servicing the transmission and doing a test drive, the new TCM I installed in December got fried.
So I decided to change the transmission altogether with the hopes that there was some mechanical fault or damage inside the clutch (mind you, I never had any erratic shifting or slipping or selecting issues), so we did that — full transmission + torque converter replacement, configured the new module and went on a drive to perform the adaptation procedure.
After a few rounds of hard driving, boom — clutch temp too high again. Remember, this is a new gearbox and torque converter. Engine temp was around 100, transmission oil temp was reading 130s, but everything was fine still – just cleared the code afterwards and allowed the car sit idle before turning off.
In case you're wondering, my background is with stricter German cars (BMW, Audi, Porsche), so I have a habit of following specifications (or where applicable above spec): original JLR antifreeze (STJLR.651.5003 spec) w/ 50:50 mixture, all original parts including the transmission oil cooler, ZF Lifeguard Fluid 8 etc. Also, I've never had engine cooling issues on this car as I did a cooling system overhaul (seals, pipes, hoses, water pump) as soon as I got it.
At this rate, I might need to have backup TCMs sitting around in case the new one gets fried again haha. Seriously though, what I’m thinking now is that either the oil cooler or JLR coolant isn’t optimized for ZF8HP in areas with relatively high ambient temp.
Couple questions:
- Has anyone ever run into a similar issue?
- Is there any other cooling component between the engine and the transmission I might be missing?
- Is there a performance transmission oil cooler for these cars?
Okay, so on Wednesday, I opened up the transmission filter for a routine service (last I did was in December) and found some metal chips (see attached photo). After some analysis and consulting with other technicians, we resolved to simply do a full transmission service and check the oil content after a few test drives. That didn't end well as I ended up changing the gearbox after a very spirited test drive during which I got a P2787-4b: Clutch temperature too high DTC in the TCM (note: this does not trigger a check engine light).
Some backstory... when I first got the car, I occasionally used to have the well-known "Gearbox Fault" message where the transmission is stuck in park on fresh ignition cycles until after a few ignition toggles which eventually clears it. We tried updating the TCM software and other things mentioned in the forums but had no luck.
Because I'm technically inclined, I was able to do some investigation with my scanner and noticed that the message usually came up alongside a P0658-11 code on the transmission control module (Actuator supply voltage A - circuit low).
I figured this occurred after prolonged high-stress driving and started monitoring certain parameters on every drive. In particular, I was looking at:
- Transmission oil temperature
- Actuator supply voltage
- Control module supply voltage
- Control module voltage
- Control module internal temperature
- Engine coolant temperature
What I discovered from observing these values was that the DTC always got registered on the TCM when the transmission oil temperature was relatively higher than that of the engine (roughly around 10-30 degrees)... when this happened, the actuator supply voltage also reduced significantly obviously as a result of high resistance caused by heat internally.
Before thinking of a solution, my workaround was to clear the error whenever it came up after a drive and wait for the temperature to normalize while the car is idling before switching it off — this worked for the longest time and I never had to worry about the car being stuck in park on startup until the day the gearbox really took a beating and the TCM got fried this time (actuator supply voltage had a steady zero-value) before I could even clear the code and repeat my usual procedure.
We changed the TCM and while at it, did a full transmission service (oil + filter). After configuring the new module everything worked as usual, but I kept running into the Clutch temperature too high DTC.
It wasn't really a huge concern considering how aggressively I shift in manual and the car always gets driven hard, but still we changed the transmission oil cooler and did another full service just to be safe. Guess what? The error still always occurred after extremely hard driving, and just this Wednesday, after servicing the transmission and doing a test drive, the new TCM I installed in December got fried.
So I decided to change the transmission altogether with the hopes that there was some mechanical fault or damage inside the clutch (mind you, I never had any erratic shifting or slipping or selecting issues), so we did that — full transmission + torque converter replacement, configured the new module and went on a drive to perform the adaptation procedure.
After a few rounds of hard driving, boom — clutch temp too high again. Remember, this is a new gearbox and torque converter. Engine temp was around 100, transmission oil temp was reading 130s, but everything was fine still – just cleared the code afterwards and allowed the car sit idle before turning off.
In case you're wondering, my background is with stricter German cars (BMW, Audi, Porsche), so I have a habit of following specifications (or where applicable above spec): original JLR antifreeze (STJLR.651.5003 spec) w/ 50:50 mixture, all original parts including the transmission oil cooler, ZF Lifeguard Fluid 8 etc. Also, I've never had engine cooling issues on this car as I did a cooling system overhaul (seals, pipes, hoses, water pump) as soon as I got it.
At this rate, I might need to have backup TCMs sitting around in case the new one gets fried again haha. Seriously though, what I’m thinking now is that either the oil cooler or JLR coolant isn’t optimized for ZF8HP in areas with relatively high ambient temp.
Couple questions:
- Has anyone ever run into a similar issue?
- Is there any other cooling component between the engine and the transmission I might be missing?
- Is there a performance transmission oil cooler for these cars?
