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DeepVee
03-28-2006, 16:54
Anyone else having problems with the durability of the slave and master cylinder used with the GM ZF transmission? I'm going on my 3rd hydraulic system, courtesy of GM.

31,236 miles, new slave & master due to soft pedal. Also a new clutch disc and pressure plate due to a heat checked pressure plate.

40,717 miles, new slave & master due to a soft pedal and trouble getting into gear.

41,130 miles new clutch disc, pressure plate & flywheel, clutch would not disengage.

Currently at 58,300 miles and now the pedal is soft again and very difficult to shift after the system gets hot. The truck is back at the dealership for a new slave & master; we'll see if this fixes it. I called customer service to complain about what seems to be an ongoing problem and also since my GMPP expires in two weeks. So far Customer Service seems willing to listen and is waiting for the outcome at the dealership.

I feel this is a heat build up issue; the GM ZF just seems to build and retain too much heat which eventually kills the clutch components. GM and the dealership have always been very good about fixing the problem but it seems to be a temporary fix and always comes back. I believe my only solution now is to install an external circulation pump and cooler on the transmission and see if it helps. I just feel there has to be a reason why Ford felt an oil cooler was necessary on their version of the ZF 6-speed.

BTW, this truck tows 5,000 lbs a couple times a year.

crafty
03-29-2006, 10:16
I've got over 65000 miles on mine and the only trouble I've had is the flywheel and throwout bearing. I've done two flywheels (one in 2002, the other in 2005) and the throwout was done last year as well. I've never had an issue with the slave amd master cylinder.
I tow 11,000 lbs four or five times a year and the rest of the time is just straight city/highway driving. I'm quite hapy with mine.:D :D :D

jackrabbit
03-30-2006, 10:17
Well, everything I have read has said that going to a SMF has solved the problems that you have described for the Dmax trucks.

In your case you have the 8.1 gas and I believe this already has a SMF in it.

That being the case, I haven't seen any posts until now on with that combination (8.1/6sp) that had these issues.

As a guess, it sounds as if the pressure plate is not assembled correctly and allowing the clutch to partially slip. Since you don't tow anything, I wouldn't think that you would need the external cooler.