Holy crap..after about 300-400 miles at 80 plus..the clutch pedal goes to the floor..and the engagement window becomes about the bottom inch of pedal travel...pumping the clutch helps..as does cruisng below 80 for extended time. I hear it might be related to the fluid level. Does not slip in normal and heated occurences.

Sounds like boiling clutch fluid.

Holy crap..after about 300-400 miles at 80 plus..the clutch pedal goes to the floor..and the engagement window becomes about the bottom inch of pedal travel...pumping the clutch helps..as does cruisng below 80 for extended time. I hear it might be related to the fluid level. Does not slip in normal and heated occurences.


I should get mine back in a day with a tranny cooler. Once I put the HJAT at 5 on I will let you know if still slips and pedal gets hard. My bet; it will.http://www.dieselplace.com/forum/smileys/Cry.gif

A cooler fr the ZF6..do they install in the PTO plates?? I also hear changing to DOT 5 helps

I don't think DOT5 is compatible with the seals in the hydraulic system. You may start leaking like a sieve. Sounds like air got in somehow...


How would a tranny cooler affect the clutch?


I am starting to think the clamping force needed to keep the disc on the flywheel just isn't sufficient. I can cause a hard pedal in mine by 'getting on it' while in 6th. I cannot sense the slippage though as the vehicle speed increase seems to track with the engine speed increase.


Either that or the geometry of the entire setup is getting tweeked by the power (torque) and does not return to normal until the clutch is depressed. Things are just getting in a bind....


Later....

JP is right. cooler is just a GM rep requirement. the tech is not convinced it will fix it. have already changed to Dot 4 and changed the hydro slave cyl twice. Should get it back tomorrow and will test it over the weekend.


BTW, they gave me a '04 bowtie gasser 1500 truck to use until my HD comes back. the vortec has great acceleration but the truck drives and feels like my wife's old Buick LeSabre . . .http://www.dieselplace.com/forum/smileys/Ermm.gif

What does the dealer do when he sees all the gauges and big exhaust and all that?


Do they ask any questions, or do they know that they wont get anywhere if they do?

My dealer has not asked any questions at all. The did tell me and charge me $99 extra when they pulled the tranny to replace the flexplate due to the compression bars on the lift kit. This morn they called about a plate i installed with the bumper extension (3" to give room for big tires). I dropped by and told them to take it off and put it in the back. They have been good and have not had any problems with my mods. Of course, the HJAT is removed before the visit. No questions about the rolled up and tied pyro probe wire..http://www.dieselplace.com/forum/smileys/Approve.gif I think they just do what the rep tells them. Then they bill GM. They have only seen 3 manual diesels at this dealer, so far. . . I use them because they treat me well and are within walking distance of my office.

Sure would be nice to have a decent dealer. I called mine a few weeks ago to chat. I wanted to see what they thought of an extra fuel filter. The guy was an ass. Told me that GM designed it fine. http://www.dieselplace.com/forum/smileys/Dead.gif


I hung up and called the chevy dealer. They were much better, but still no use. Mine is a GMC, and they are so close, they cant work on the other guys brand.


Neither had ever seen (or knew of) a 6 speed. I just hope my flywheel goes out at a good place.


It is feeling kinda funny. Engages at the very bottom of the pedal. Kinda mushy.

How many miles do you guys have? On my last long trip two weeks ago I was suprised I didn't have a hard pedal after running 300 miles/4 hrs straight. I have 27K on my truck and while I don't believe the trans is getting too hot to cause this problem stanger things have been true. Maybe the trannys are that tight and run hot until you get a bunch of miles on them. I'd be interesting to put a temp probe in the drain plug to see.

Why can't GM solve this issue. Perhaps it is a difficult problem to solve, but perhaps they should just clean the slate and redesign a clutch setup. We may be a minority, but those of us who drive the manual transmission trucks tend to be very loyal to choosing gears on our own.





GM, are you listening???????

Why can't GM solve this issue. Perhaps it is a difficult problem to solve, but perhaps they should just clean the slate and redesign a clutch setup. We may be a minority, but those of us who drive the manual transmission trucks tend to be very loyal to choosing gears on our own.





GM, are you listening???????





It costs money (a lot) to do a redesign and a recall and then replace the parts. They have already redsigned (slightly) the flexplate. I had one installed a couple monthes ago. New P/N. Don't know if it is strong enough to handle a beefy aftermarket clutch. Even if it could the heat may still cause the hydraulic fluid in the clutch system to boil and then cause a hard pedal. I expect to get my truck back today. The dealer will be testing the tranny cooler this morning. I don't expect that it will solve the clutch slippage problem . . .http://www.dieselplace.com/forum/smileys/Ermm.gif

It only happens if I cruise above 80mph for longer than 4 hours ish.

How many miles do you guys have? On my last long trip two weeks ago I was suprised I didn't have a hard pedal after running 300 miles/4 hrs straight. I have 27K on my truck and while I don't believe the trans is getting too hot to cause this problem stanger things have been true. Maybe the trannys are that tight and run hot until you get a bunch of miles on them. I'd be interesting to put a temp probe in the drain plug to see.


I got mine back. The electric 'Cool-Man' tranny fluid pump made by 'Shureflo' kicks on at 200*F and circulates the fluid thru a 'radiator' behind the grill tha is about 12" x 18". The this morning on the way in to work, with HJAT4, the pedal went hard even before the engine was up to normal operating temp. http://www.dieselplace.com/forum/smileys/Angry.gif http://www.dieselplace.com/forum/smileys/Throw Up.gif


Exactly what I expected. I got a PM this am about a member working on a single mass flywheel who is getting close . . . I hope it will work. http://www.dieselplace.com/forum/smileys/Thumbs Up.gif


My truck has 40K miles. I had this problem before the big tires were installed. Does not seem to be a problem with out the chip set at lvl 3 or above.