New 4 speed - clutch slipping - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jjames · 08-20-2010, 10:38 AM

All - please help!

Just finished the swap from a 3speed to a M20 4 speed - everything went together perfect, etc.. Clutch only had 5,000 miles on it looked good. Did replace the throwout bearing.

Problem - the clutch is slipping VERY bad. feels like a rubber band in all gears.

It drives and shifts and dis-engages without issue, but feels like it is never fulling engaging and there is some slope in the clutch peddle that wasnt there before.

I am clueless - any ideas?

Lee H · 08-20-2010, 10:44 AM

How far off the floor does it engage? What application is the bell housing, clutch, & throw out bearing? Did you own and or put the 5K miles on it? Did you have the flywheel turned?

jjames · 08-20-2010, 10:50 AM

I'll check the engagement height

As for the rest - the bell housing was from the Sigsaw 3 Speed that was in it - the M20 should have been a bolt in replacement for it.

The clutch was in the truck when i bought it - put around 2,000 miles on it. was 100% solid before the transmission switch.

The throwout bearing was a replacement for the type that was in it (the long type).

jjames · 08-20-2010, 01:11 PM

checked and played with the linkage - no idea

it engages 100% about 1.5 inches from the floor and then only comes up about 1/2 travel.

the top half is compeltely loose.

Lee H · 08-20-2010, 02:36 PM

New throwout bearing with this install or one with the 5K miles? 1.5 inched is a little close to the floor but the free travel half way down is the bigger issue I think. How much travel was there before your swap?

jjames · 08-20-2010, 03:23 PM

I fixed the travel and engagement issues by playing with the linked adjustment (adjusted it all the way out)

I still have the rubber band effect issue.

The throwout bearing is brand new with the new transmission install.

the clutch is slipping under heavy load. Anytime i step on it in 1, 2 or 3 it slips and in 4th just about anything more than coasting it slips (can smell it bad).

Wrenchbender Ret · 08-20-2010, 03:41 PM

Check to see if the TO brg is too long & backing up against the bell houseing.

jjames · 08-20-2010, 04:04 PM

ya - that is my next step - just trying to avoid having to pull the transmission again.

The TO is the long type, which is what was in it. But the clutch is the kind with many fingers, which I always thought meant it took the short type bearing and that only the 4 big finger style pressure plate took the long style bearing.

Well - I will go pull the drive shaft and transmission (again) and see what i see....

Lee H · 08-20-2010, 04:04 PM

Assuming you matched up the throwout bearing with the old one and it matched, I suspect that it was installed incorrectly on the clutch fork or the clutch and or the fly wheel, pressure plate surface was marginal and just can't hold. Afraid your going to have to start over with a new clutch kit. Have the fly wheel turned and pay special attention to the new throw out bearing install directions. It's easy to get those on wrong. Also test fit the pilot bushing to make sure it fits the muncie end shaft.

jjames · 08-20-2010, 05:04 PM

just pulled the transmission - everything looks fine.

The throwout bearing doesnt have any wear on any surface (as I would guess it would if there was contact with the retainer bearing).

I test fitted a short type TO as well - it wont work - so the long style is the type needed.

As for the installation of the TO bearing, guess I could use the training on that - when i removed the old one, i just installed the new one by aligning it on the fork and then sliding the input shaft and transmission back into the bell housing.

Wrenchbender Ret · 08-20-2010, 06:20 PM

I wanted you to look up in side before you pulled it to see if the bearing was backed up against the bell housing.
There are 2 kinds of diaphragm type clutches used. The older model has the fingers parallel with the disc & flywheel. It uses the long TO brg. The later model often used as a replacement has the fingers extended rearward & are about even with the outer surface of the pressure plate, commonly called a beehive clutch. It uses the short brg. There is hardly any way you could have gotten it in wrong. The brg. slides on the trns brg. retainer. The fork goes in the grooves. Some brgs have a lump or pin to keep it from turning.

jjames · 08-20-2010, 07:29 PM

Well i think have it figured out (thanks for the suggestions!)

I put it all back together again with the long bearing and then did just what you suggested. From underneath I checked the play between the bearing and the pressure plate (its the type that has the fingers angled towards the rear).

Once you tighten the transmission down, the retainer bearing presses the throwout bearing against the pressure plate. The book (factory manual) mentions that you need 1/16th to 1/8th play between the plate and the bearing.

In my case I have none and it would seem that the bearing is being pressed hard enough to engage the clutch (hence the slipping).

So, now my question is, what can i do?

Option 1 - This is a new transmission (M20), i guess the retainer bearing is just a little thicker than the 3speed i had. - Can I change the retainer bearing to a thinner one?

Option 2 - I already tried using the short type bearing, its too short (at least with the current fork and fork ball that I have) - Can I get a different clutch fork, fork ball and shorter type bearing?

Option 3 - Is there some sort of adapter or spacer plate to move the transmission back a little?

Option 4? - ???

raycow · 08-21-2010, 01:42 AM

The bent finger pressure plate is supposed to be used with a short bearing. I have no clue how you got that setup to work with the old transmission. Even more mystifying is why it worked with the old transmission and not the new one.

You don't have any choice on forks, but there is an aftermarket ball stud made for dealing with problems like this. I think McLeod might have it. If you don't have any luck finding the ball stud, you might want to see if the bearing retainer has enough material so it can be machined to clear the throwout bearing.

Also, you may have another problem that hasn't presented itself yet. What year is your bellhousing?

Ray

jjames · 08-21-2010, 08:19 AM

The bell housing is stock - '71 3speed with an inline 6. (I think1)

Last owner put in a new (not so mild) 350 - but left the 3 speed.

ts71281 · 08-21-2010, 11:02 AM

Someone correct me if I'm wrong but your M20 has a smaller flange in the front while your 71 bellhousing is setup for a large bore trans. This change happened sometime around 68. I remember something about this since years ago when I did the M20 swap, I remember wanting only a 67 bellhousing. Anything newer and I would have had to use an adaptor ring between the bellhousing bore and the flange on the trans. Make sense?

jjames · 08-21-2010, 11:24 AM

The trans guy corrected this by putting a large (truck style) retainer bearing on the transmission (5 1/8" diameter) which matched the bell housing and the 3 speed that I removed.

raycow · 08-21-2010, 12:45 PM

Quote:

Originally Posted by jjames

The trans guy corrected this by putting a large (truck style) retainer bearing on the transmission (5 1/8" diameter) which matched the bell housing and the 3 speed that I removed.

Ok, that's what I was going to ask about, so the diameter mismatch was already taken care of. However, it does sound like the replacement bearing retainer might stick out farther than the one on the Saginaw, which puts a bind on the throwout bearing.

Ray

jjames · 08-21-2010, 12:55 PM

So i guess my next step is to take to my transmission guy (www.KajunJon.com) and see if

1 - i can swap the retainer bearings from the 3 speed to the 4 speed
2 - if he was a different thinner styler retainer bearing or
3 - ?

raycow · 08-21-2010, 01:29 PM

Quote:

Originally Posted by jjames

So i guess my next step is to take to my transmission guy (www.KajunJon.com) and see if

1 - i can swap the retainer bearings from the 3 speed to the 4 speed
2 - if he was a different thinner styler retainer bearing or
3 - ?

I'm not sure if the Saginaw bearing retainer will bolt to the Muncie case (I'm thinking the Muncie uses a larger bearing), although it certainly couldn't hurt to try it. If that doesn't work out, then you might want see if it is possible to machine the Muncie retainer for clearance.

Ray

redneck6 · 04-12-2012, 03:04 PM

any up dates on this ?

RustyBucket · 04-12-2012, 03:53 PM

If you've got both transmissions put 'em side by side and compare their snouts. Gotta be frustratin'.... new 4spd. to play with and you can't go blast around.

08-20-2010, 10:38 AM	#1
jjames Registered User Join Date: Aug 2010 Location: Chester, IL Posts: 17	New 4 speed - clutch slipping All - please help! Just finished the swap from a 3speed to a M20 4 speed - everything went together perfect, etc.. Clutch only had 5,000 miles on it looked good. Did replace the throwout bearing. Problem - the clutch is slipping VERY bad. feels like a rubber band in all gears. It drives and shifts and dis-engages without issue, but feels like it is never fulling engaging and there is some slope in the clutch peddle that wasnt there before. I am clueless - any ideas?

08-20-2010, 10:44 AM	#2
Lee H Registered User Join Date: Jun 2010 Location: Upland Ca Posts: 4,147	Re: New 4 speed - clutch slipping How far off the floor does it engage? What application is the bell housing, clutch, & throw out bearing? Did you own and or put the 5K miles on it? Did you have the flywheel turned? __________________ 1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703

08-20-2010, 10:50 AM	#3
jjames Registered User Join Date: Aug 2010 Location: Chester, IL Posts: 17	Re: New 4 speed - clutch slipping I'll check the engagement height As for the rest - the bell housing was from the Sigsaw 3 Speed that was in it - the M20 should have been a bolt in replacement for it. The clutch was in the truck when i bought it - put around 2,000 miles on it. was 100% solid before the transmission switch. The throwout bearing was a replacement for the type that was in it (the long type).

08-20-2010, 01:11 PM	#4
jjames Registered User Join Date: Aug 2010 Location: Chester, IL Posts: 17	Re: New 4 speed - clutch slipping checked and played with the linkage - no idea it engages 100% about 1.5 inches from the floor and then only comes up about 1/2 travel. the top half is compeltely loose.

08-20-2010, 02:36 PM	#5
Lee H Registered User Join Date: Jun 2010 Location: Upland Ca Posts: 4,147	Re: New 4 speed - clutch slipping New throwout bearing with this install or one with the 5K miles? 1.5 inched is a little close to the floor but the free travel half way down is the bigger issue I think. How much travel was there before your swap? __________________ 1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703

08-20-2010, 03:23 PM	#6
jjames Registered User Join Date: Aug 2010 Location: Chester, IL Posts: 17	Re: New 4 speed - clutch slipping I fixed the travel and engagement issues by playing with the linked adjustment (adjusted it all the way out) I still have the rubber band effect issue. The throwout bearing is brand new with the new transmission install. the clutch is slipping under heavy load. Anytime i step on it in 1, 2 or 3 it slips and in 4th just about anything more than coasting it slips (can smell it bad).

08-20-2010, 03:41 PM	#7
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,229	Re: New 4 speed - clutch slipping Check to see if the TO brg is too long & backing up against the bell houseing.

08-20-2010, 04:04 PM	#8
jjames Registered User Join Date: Aug 2010 Location: Chester, IL Posts: 17	Re: New 4 speed - clutch slipping ya - that is my next step - just trying to avoid having to pull the transmission again. The TO is the long type, which is what was in it. But the clutch is the kind with many fingers, which I always thought meant it took the short type bearing and that only the 4 big finger style pressure plate took the long style bearing. Well - I will go pull the drive shaft and transmission (again) and see what i see....

08-20-2010, 04:04 PM	#9
Lee H Registered User Join Date: Jun 2010 Location: Upland Ca Posts: 4,147	Re: New 4 speed - clutch slipping Assuming you matched up the throwout bearing with the old one and it matched, I suspect that it was installed incorrectly on the clutch fork or the clutch and or the fly wheel, pressure plate surface was marginal and just can't hold. Afraid your going to have to start over with a new clutch kit. Have the fly wheel turned and pay special attention to the new throw out bearing install directions. It's easy to get those on wrong. Also test fit the pilot bushing to make sure it fits the muncie end shaft. __________________ 1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703

08-20-2010, 05:04 PM	#10
jjames Registered User Join Date: Aug 2010 Location: Chester, IL Posts: 17	Re: New 4 speed - clutch slipping just pulled the transmission - everything looks fine. The throwout bearing doesnt have any wear on any surface (as I would guess it would if there was contact with the retainer bearing). I test fitted a short type TO as well - it wont work - so the long style is the type needed. As for the installation of the TO bearing, guess I could use the training on that - when i removed the old one, i just installed the new one by aligning it on the fork and then sliding the input shaft and transmission back into the bell housing.

08-20-2010, 06:20 PM	#11
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,229	Re: New 4 speed - clutch slipping I wanted you to look up in side before you pulled it to see if the bearing was backed up against the bell housing. There are 2 kinds of diaphragm type clutches used. The older model has the fingers parallel with the disc & flywheel. It uses the long TO brg. The later model often used as a replacement has the fingers extended rearward & are about even with the outer surface of the pressure plate, commonly called a beehive clutch. It uses the short brg. There is hardly any way you could have gotten it in wrong. The brg. slides on the trns brg. retainer. The fork goes in the grooves. Some brgs have a lump or pin to keep it from turning.

08-20-2010, 07:29 PM	#12
jjames Registered User Join Date: Aug 2010 Location: Chester, IL Posts: 17	Re: New 4 speed - clutch slipping Well i think have it figured out (thanks for the suggestions!) I put it all back together again with the long bearing and then did just what you suggested. From underneath I checked the play between the bearing and the pressure plate (its the type that has the fingers angled towards the rear). Once you tighten the transmission down, the retainer bearing presses the throwout bearing against the pressure plate. The book (factory manual) mentions that you need 1/16th to 1/8th play between the plate and the bearing. In my case I have none and it would seem that the bearing is being pressed hard enough to engage the clutch (hence the slipping). So, now my question is, what can i do? Option 1 - This is a new transmission (M20), i guess the retainer bearing is just a little thicker than the 3speed i had. - Can I change the retainer bearing to a thinner one? Option 2 - I already tried using the short type bearing, its too short (at least with the current fork and fork ball that I have) - Can I get a different clutch fork, fork ball and shorter type bearing? Option 3 - Is there some sort of adapter or spacer plate to move the transmission back a little? Option 4? - ???

08-21-2010, 01:42 AM	#13
raycow Registered User Join Date: Mar 2003 Location: San Francisco, CA USA Posts: 2,454	Re: New 4 speed - clutch slipping The bent finger pressure plate is supposed to be used with a short bearing. I have no clue how you got that setup to work with the old transmission. Even more mystifying is why it worked with the old transmission and not the new one. You don't have any choice on forks, but there is an aftermarket ball stud made for dealing with problems like this. I think McLeod might have it. If you don't have any luck finding the ball stud, you might want to see if the bearing retainer has enough material so it can be machined to clear the throwout bearing. Also, you may have another problem that hasn't presented itself yet. What year is your bellhousing? Ray Last edited by raycow; 08-21-2010 at 01:57 AM.

08-21-2010, 08:19 AM	#14
jjames Registered User Join Date: Aug 2010 Location: Chester, IL Posts: 17	Re: New 4 speed - clutch slipping The bell housing is stock - '71 3speed with an inline 6. (I think1) Last owner put in a new (not so mild) 350 - but left the 3 speed.

08-21-2010, 11:02 AM	#15
ts71281 Registered User Join Date: Apr 2003 Location: Maple Grove, MN Posts: 497	Re: New 4 speed - clutch slipping Someone correct me if I'm wrong but your M20 has a smaller flange in the front while your 71 bellhousing is setup for a large bore trans. This change happened sometime around 68. I remember something about this since years ago when I did the M20 swap, I remember wanting only a 67 bellhousing. Anything newer and I would have had to use an adaptor ring between the bellhousing bore and the flange on the trans. Make sense?



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08-21-2010, 11:24 AM	#16
jjames Registered User Join Date: Aug 2010 Location: Chester, IL Posts: 17	Re: New 4 speed - clutch slipping The trans guy corrected this by putting a large (truck style) retainer bearing on the transmission (5 1/8" diameter) which matched the bell housing and the 3 speed that I removed.

08-21-2010, 12:55 PM	#18
jjames Registered User Join Date: Aug 2010 Location: Chester, IL Posts: 17	Re: New 4 speed - clutch slipping So i guess my next step is to take to my transmission guy (www.KajunJon.com) and see if 1 - i can swap the retainer bearings from the 3 speed to the 4 speed 2 - if he was a different thinner styler retainer bearing or 3 - ?

04-12-2012, 03:04 PM	#20
redneck6 Registered User Join Date: Jul 2009 Location: sparks nv Posts: 142	Re: New 4 speed - clutch slipping any up dates on this ? __________________ 64 chevy c10 swb fleet small back window , in progress 454/400 swap , disc front disc rear , and just geting it on the road . 09 ford f350 cc swb 4x4 6.4l , to haul the others home . 2011 chevy hhr not mine but love the milage ..

04-12-2012, 03:53 PM	#21
RustyBucket Registered User Join Date: Jul 2009 Location: Space Coast, Fl. Posts: 1,055	Re: New 4 speed - clutch slipping If you've got both transmissions put 'em side by side and compare their snouts. Gotta be frustratin'.... new 4spd. to play with and you can't go blast around. __________________ Dad always said, "Son, WISH IN ONE HAND, and ......." -------------------------------------- -------------------------------------- Current toy trucks: '71 GMC 1500 SUPER CUSTOM short/step, orig. dk. blue, 350/700r, ps,pb, A/C '72 Blazer 2wd, ochre & white, 454, tremecTKO 500 5spd. ps, pb, A/C, tilt Last 10yrs of hobby vehicles, had a FEW more in the 50yrs. before these: '66 Plymouth Belvedere City of Miami cop car clone. '70 Nova 406"sb, 13.5-1, solid roller, Brodix, p.glide/t.brake, back halved, 9" Ford, spool 4.88, cage,ladder bar/coilover, 10.5 tire....... SOLD!! '67 C10 short/step side mount spare -- SOLD!! '72 Jimmy 2wd, 350/350, ps, pb, fun driver, lots of bondo & a shiny red paint job..... SOLD!! '69 Nova 350, 4spd, A/C, ps, p.b, ...SOLD!!

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