Clutch slip after engine rebuild

scrivyscriv · Posted: Wed Apr 22, 2015 2:30 pm Post subject: Clutch slip after engine rebuild

My clutch is slipping slightly in 3rd and 4the gear on hard acceleration, in my 1971 bus. Just rebuilt the engine - flywheel was resurfaced and the depth is about 21.5mm, but I reused the pressure plate and disc (disc thickness checked good) from my previously running beetle.

Is the slipping normal while the clutch disc breaks in? What's the best thing to do right now? I hate to change the clutch since I had the engine balanced. I just don't want to be stuck on the side of the road. Either way I just don't know whether I need to replace it or not.
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catahoula lou · Posted: Wed Apr 22, 2015 4:00 pm Post subject:

Do you have the recommended 1/2" (or any) clutch pedal play? May be too tight...
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Dauz · Samba Member Joined: January 05, 2010 Posts: 1790

Do you have proper "play" in the pedal? Maybe you just need a clutch adjustment.

gt1953 · Posted: Wed Apr 22, 2015 4:06 pm Post subject:

clutch is miss adjusted. Weak pressure plate possibly.
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modok · Posted: Wed Apr 22, 2015 4:28 pm Post subject:

Happens a lot! Problem is the engine is making more torque! isn't that good tho??
You might have balanced a tired pressure plate.......that's a bummer.

Try a centerforce or copperhead clutch disk. About 20-30% more holding power than the average stock disk with the same pressure plate.

Dauz · Samba Member Joined: January 05, 2010 Posts: 1790

kamesama980 · Posted: Thu Apr 23, 2015 10:39 am Post subject:

Sure the resurfaced flywheel is exactly right? Sure the pplate isn't worn a little too? .020" (.5mm) is enough on an old toyota to be the difference between towing 6klbs and not getting over 30 mph.

Found that out with a bad-used flywheel for my Cressida that was resurfaced without the .020" step. few years later put it my truck and pulled 6klbs (way more than it's rated) 300 miles...twice over 3 years/30k miles I had it.
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vwsb74 · Posted: Thu Apr 23, 2015 11:06 am Post subject:

Oil leak from the tranny or flywheel or during installation
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scrivyscriv · Posted: Thu Apr 23, 2015 7:56 pm Post subject:

I think I'd be willing to spend the extra money on a Copperhead disc if it would give me a good shot at NOT replacing the pressure plate yet (Let me stress, this is 100% due to wanting to keep the engine balanced!).
Honestly, I did not really understand pressure plate clamping pressure, disc thickness and flywheel-to-pressure-plate depth very well when I sent my parts out for balancing. If I had known better, I would have just spent the extra hundred up front and put a new Sachs clutch kit on, instead of wasting my time balancing a weak used PP.

I think either way, even if I end up replacing the PP anytime soon, the Copperhead disc looks like a good part to have on just a stocker bus engine.

The clutch looks like it has a little more freeplay than it needs, eyeballed at the pedal.. the pedal is definitely not releasing too high.
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Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help.

scrivyscriv · Posted: Sat Apr 25, 2015 7:58 am Post subject:

After doing some more research, I think my flywheel is the problem..
I measured .844" from the pressure plate mounting surface to clutch surface, which is almost .5mm deeper than the 21mm spec.

Seems like no matter what I do now, the engine balance WILL be jacked up.. so should I take the flywheel back and have them cut the .5mm step down? I didn't measure the flywheel depth before I took it in so I don't know how much material they actually removed.
I went ahead and ordered a Daikin street disc and a Brazil Sachs plate.
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Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help.

modok · Posted: Sat Apr 25, 2015 12:46 pm Post subject:

That is not enough to make a difference really, as disks and pressure plates vary as much, or more.
Flywheel book says .830-.835"

Get the new disk and bolt the pressure plate on, and observe the ANGLE of the springy fingers. You want them near flat. If the middle is pointing outward then cut the flywheel some more, of they are almost flat across or slightly inward, leave it.

scrivyscriv · Posted: Sat May 09, 2015 1:30 pm Post subject:

I'm not familiar with how clutches can fail, but I did not expect to find what I did today... The disc lining had something like a gummy consistency. Left smear marks around the inner contact area of the flywheel. Y'all ever seen this before?

Image may have been reduced in size. Click image to view fullscreen.

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Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help.

scrivyscriv · Posted: Sat May 09, 2015 6:08 pm Post subject:

I bolted up a new Daikin street disc with a new Brazil Sachs pressure plate and the difference is night and day. Accidentally barked tires twice downshifting from 4 and 3!
Thanks for the direction and input yall.
_________________
Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help.

Dr OnHolliday · Posted: Sat May 09, 2015 9:05 pm Post subject:

Glad its working but that flywheel surface is substandard, especially considering the other new parts.
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modok · Posted: Sat May 09, 2015 10:35 pm Post subject:

Not perfect but probably good enough. I think the disk was his main problem, looks like its reaction to hard use was SMEARING into a mess LOL

scrivyscriv · Posted: Sun May 10, 2015 9:00 am Post subject:

Yeah it sucks that my flywheel got abused because of the disc slipping. I had it turned and balanced during the build. The resin came off but there are some small burn marks.
_________________
Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help.

jfats808 · Posted: Sun May 10, 2015 9:34 am Post subject:

Unless you're running a bus, that flywheel is too heavy. Call a shop and get a balanced German vanadium crank that's 13bs or less.
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scrivyscriv · Posted: Sun May 10, 2015 9:36 am Post subject:


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