Replaced Broken Trans, Now Clutch Slips

mike000

Well-known member
Joined
Jun 11, 2012
Location
Hartford, CT
TDI
1Z TDI swapped '90 Jetta
About 10,000 miles ago, I did a clutch job on my Passat 1z/02A, using an OEM SACHS VR6 clutch, as recommended on the forums. The car ran flawlessly for years. The differential eventually developed excessive backlash, and cracked the transmission case, creating a very slow seep of oil out from inside the bell housing, though never enough to get any residue whatsoever on the flywheel, pressure plate, or clutch disk. I just changed the transmission to a MK3 Jetta TDI unit (also a CTN code, just like the trans I took out), and reused the clutch. New OEM hardware was used, as they're torque-to-yeild bolts, and everything went together smoothly. First time giving it more than half throttle in 4th gear, the clutch slipped, and even worse in 5th. I have absolute no clue why, as the thing grabbed like an animal beforehand, and never had a single issue. I just pulled the transmission back out, assuming I must have made a mistake, or the trans came with a bent clutch level or something, but everything looks to be in tip-top shape. This is not my first time doing a clutch or transmission install, so I'd like to think that I didn't make a dumb user-error, but anything is possible! Help before I start throwing new parts at it without a proper diagnosis :confused::confused::confused:
 

mike000

Well-known member
Joined
Jun 11, 2012
Location
Hartford, CT
TDI
1Z TDI swapped '90 Jetta
I'd also like to note, that as soon as I took the car out of the garage, I noticed the clutch grabbing high on the clutch pedal, but just attributed it to being a mental thing, having not driven the car in months (my other car grabs very low).
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
My bet is the clutch got oil on it.

My last B4 was purchased very cheap, because the PO replaced the clutch and it slipped. They blamed the flywheel, dropped the trans and replaced the flywheel. Same issue, so they blamed the transmission and put it up for sale.

I pulled it apart, cleaned and sanded the PP and disc and bolted it back together.

It's been fine, since.

-Todd
 

tripl-e

Veteran Member
Joined
May 22, 2006
Location
Basking Ridge, NJ USA
TDI
b4 sporting a new ET 6th gear!
The high clutch pedal is key! Something is amiss in the release hardware, the pressure plate is not applying full clamping force to the disc. Somehow the throwout bearing and the release arm are not able to retract fully.

Try opening the bleed nipple on the slave cylinder to see if hydraulic fluid is trapped. If an 'open' hydraulic circuit does not change anything then the problem must be mechanical and is likely ( sorry to say) inside the bellhousing.

Good Luck!
EEE
 

GCBUG00

Veteran Member
Joined
Jun 9, 2013
Location
Hartsville SC
TDI
2000 Beetle
The high clutch pedal is key! Something is amiss in the release hardware, the pressure plate is not applying full clamping force to the disc. Somehow the throwout bearing and the release arm are not able to retract fully.
Try opening the bleed nipple on the slave cylinder to see if hydraulic fluid is trapped. If an 'open' hydraulic circuit does not change anything then the problem must be mechanical and is likely ( sorry to say) inside the bellhousing.
Good Luck!
EEE
What he said, I like it.

Adding when the slave cyl is removed note the position of the fork. If its all the way up against the case (away from engine) that's not right. Fork has now applied excessive pressure to bearing.
 

mike000

Well-known member
Joined
Jun 11, 2012
Location
Hartford, CT
TDI
1Z TDI swapped '90 Jetta
Thanks everyone for the input!

Before pulling the transmission for the second time, I pulled off the clutch slave to feel if there was tension on the clutch fork, and I was able to wiggle it freely, so it was not bound up, and when the trans was removed, it was seating fine on the pivot ball with the retaining spring still in place. However the one part that I haven't tried replacing is the clutch slave cylinder, mainly because I didn't think to. It's worked fine for years, and isn't visibly leaking, but I suppose it's the next step.

The high clutch pedal is key! Something is amiss in the release hardware, the pressure plate is not applying full clamping force to the disc. Somehow the throwout bearing and the release arm are not able to retract fully.

Try opening the bleed nipple on the slave cylinder to see if hydraulic fluid is trapped. If an 'open' hydraulic circuit does not change anything then the problem must be mechanical and is likely ( sorry to say) inside the bellhousing.

Good Luck!
EEE
I'm glad someone else thought this was a key symptom as well. I wasn't sure if it was my imagination (having not driven the car for two months), but as soon as the clutch first slipped, I figured there had to be something to it.

My current dilemma is that the transmission is out of the car for the second time, and very hopefully the last time. Do I assume it must be related to the clutch hydraulic system and reinstall the trans with the plan to bleed and potentially swap out the slave cylinder upon reinstallation of the trans, or should I replace the clutch disc while I'm in there under the possibility of oil contamination or something? I'd rather not spend money I don't have to when the disc has 80% life left, but I REALLY don't want to pull this transmission a third time :confused:
 

mike000

Well-known member
Joined
Jun 11, 2012
Location
Hartford, CT
TDI
1Z TDI swapped '90 Jetta
So after pulling the trans and evaluating everything in the clutch assembly, I concluded everything was well within spec and in perfect working order. I scuffed the clutch disc, pressure plate, and flywheel, before reinstalling the trans. The slipping remained. I changed out the slave cylinder in favor of a known-good spare with the same part number, though the slipping still exists with no change. At this point, I've just accepted that my Malone tune and larger nozzles were close enough to the [claimed] 300ft/lb torque rating of my VR6 clutch, causing the massively premature failure. I just ordered a "Stage 2 Daily" Southbend clutch kit, rated at 330ft/lb of torque at the wheels. This transmission replacement job has gotten more costly than I originally anticipated, but things happen, I guess. What a hell of a coincidence than 10,000 miles on this clutch without as much of a hiccup, until 10 miles after replacing the transmission.
 
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