clutch slipping

[technogon]

Just replaced clutch in 72 Z. Still slipping. Readjusted master cyl rod and slave rod. Has small amount of freeplay when released. So linkage is OK. Old clutch was smoked due to improper master cyl rod adjustment not allowing fluid return. Slips most in 5th (5 spd added long ago). Holds in 1st and 2nd. Common problem? Do I need a better pressure plate? Recommend? Motor is stock 72.

[Rob]

I ran my 260Z with a 180B (I don't know what that is stateside but it was a 1.8 litre four) clutch for a long time with absolutely no probs so it isn't like the clutches are weak.

There are a few different of release bearing carriers (the lengths vary), and if the one you use is too long for your clutch it will not let it engage fully and it will slip.

Check if the carrier (not just the release arm) has freeplay. If it doesn't then wander off to your friendly wrecker and see if you can find a shorter one.

Good luck.

[Alfadog]

heh sorry I cant help, erm but would you mind explaining what exactly "clutch slipping" is? :cross-eye

[hmsports]

Clutch slipping is where the clutch isn't completely sandwiched between the flywheel and pressure plate and it is allowed to slip as the engine rotates. The result is less HP getting transferred to the transmission and a glazed clutch disk and a lot of stink. This is usually caused by weak springs on the pressure plate, a worn clutch disk or improperly adjusted slave cylinder. When this happens you will smell a distinct burning odor (kind of like that of brakes when you forget to take the emergcy brake off any drive for a while). Also, when you rev the engine it will seem like you aren't getting anywhere fast but the engine is revving quite high. Hope that makes sense.

[Mr Camouflage]

heh sorry I cant help, erm but would you mind explaining what exactly "clutch slipping" is? :cross-eye

Ah, Alfadog. So young and so much to learn.

Hmm, Yoda you seek. Teach you he, will in the ways of automechanics.

Yep its when the clutch plate (the round discy looking thingo made out of brakepad type stuff, I recommend you pull your gear box off and have a look at it.... no not really) slips because there isn't enough clamping force (from the pressure plate against the flywheel) to stop it from slipping. You see the clutch plate is the only thing conecting the engine's rotational force to the input shaft of the of the gearbox (by clamping it agaonst the rotating fluwheel), and if that's slipping you may as well be driving an automatic with all the rpm your wasting.

Note: clutch plates (sometimes/usually) have a wrong way and a right way to be installed. i.e. they have a side that must be facing the fylwheel and a side the has to face the pressure plate, because sometimes the sprocket thingo that the geabox input shaft goes into usually protrudes more from the pressure plate side than the flywheel side. Am I right? That what I remember from my celica and my mazda. Not sure if datsuns are the same, as I never replaced the clutch on my Z, but I suspect they would be.

Not sure what would happen if you put it in the wrong way around either.

Mr C.

[Mr Camouflage]

"by clamping it agaonst the rotating fluwheel"

I sound like the english spy in 'allo 'allo

Should be "against" and "flywheel".

Mr C

[hmsports]

The clutch will not work if installed backward. If you lay the clutch plate flat on the ground, the center (metal part) will be raised on one side. The four springs act as dampers to take up some of the shock when the clutch is engaged. This I believe is the rear facing side . In order for the clutch to be aligned correctly, you must use a clutch alignment tool - if you don't you will most likely never get your transmission to line up . The pressure plate springs do get soft over time and may be the cause of the slippage . Whenever you replace the clutch or pressure plate it is always a good idea to replace the throw-out bearing too

[Mr Camouflage]

And if you dont have a clutch aligning tool, you can get the clutch plate as central as you can, by using a dowel (or piece of round wood, even better if you turn it on a lathe to match the input shaft), leaving the presure plate just tight enough for you to be able to move the centerplate, but hold it in place. Then slide the gearbox on to check you can get it on, then rip it off again and tighten the pressure plate bolts back up.

If you leave the gearbox in gear you can turn the input shaft by rotating the other propshaft end of the gearbox. Hey it always works for me.

and if you going to all this trouble, replace the spigot bearing also.

That's the little bearing in the flywheel. pack it full of grease, and using a dowel thats a tight fit in the hole, hammer the dowel in. The hydrolic force will push out the bearing.

I'm sure hmsports has a picture of one to post

Mr C

[hmsports]

Ok, so I'll always accept a challenge... :classic:

All I could find was this from a Toyota-Chevy V-8 conversion - but it gives a general idea - although the Z's have a much thinner version

[Dave Sommers]

Technog,

I think Rob has got it nailed as to why your new clutch is slipping like an old one. if you are running a 5psd then someone has obviously made some changes from stock to probably include the clutch housing and throw out bearing sleeve. The clutch housings (pressure plates) have slightly different distances from the flywheel to the spring fingers that the bearing engages and that requires the different bearing sleeves. Therefore the match must be between the clutch housing and the length of the bearing sleeve, and it doesn't really matter whether a 4 or 5 spd is used.

Solution is to check the new clutch housing against the old one and make sure they are of the same height, if not you must find a combination that allows the throw out bearing to fully disengage.

Don't feel bad as this issue has caused more than one transmission to be removed many times.

Good luck on it.

[Alfadog]

Geez guys thanks for the explaination! I think I might have a bit of that ? When flooring it, every here and there it seems to stop pulling for a bit... could this be clutch slipping ?

[halz]

Alfadog, if you've got it floored and your foot is off the clutch pedal then a slipping clutch will mean the revs will rise without the car accelerating as much as it should.