I have a 1970 Cougar XR7 convertible with 351C that originally came with a 3 speed manual and was converted to a Tremec 5 speed. I just purchased the car and knew it had some light clutch chatter when I bought it so wanted to fix it. I took the transmission out and found some heat marks on the pressure plate and the flywheel needed to be machined. I had the flywheel machined and replaced the 11" clutch that was installed with a new 11" American Powertrain Science Friction 1126F Stage 1 Easy Street Rabco clutch. Now the clutch won’t disengage.
The clutch I took out had three release fingers whereas the replacement eighteen, which I believe will give more uniform pressure than the one with three. Maybe that’s where my chatter was coming from to begin with?
Has anyone had this issue and if so what did you have to do or modify in order to remedy the concern? I have the linkage adjustment all the way at the end and it still won’t disengage. American Powertrain tech hotline had no real solution. Anyone have any ideas?
pics of the old clutch and the existing clutch linkage are on the other site.
My vote is on the wrong throw out bearing height. Measure from the outside edge of the clutch release fingers to the outside edge of the bellhousing where it mates up to and touches the transmission face. (A)
Then measure from the transmission face to the clutch side face of the throw out bearing in relaxed, non extended mode. (B)
You should have 1/4 inch or less of difference in the two measurements.
If measurement (B) is greater than measurement (A) then the clutch would act as if it was partially or fully disengaged.
If (A) is more than about 1/4 inch greater than (B) then you would have the condition you describe. Clutch would not disengage.
How far down does the pedal travel before contacting the pressure plate fingers? If you lay both pressure plates face down on a flat surface is your old one taller? If the new pressure plate is shorter, you’d need to do something like lengthen the pivot point to compensate. Or, if you changed the throw out bearing, how does it compare to the old one?
How much was removed from the flywheel? If an excessive amount was removed, you’d need a flywheel shim to move the flywheel towards the transmission so the flywheel’s surface is in the correct location.
I’ve removed “race” clutches to re-install stock cutches for better drivability.
Thanks guys for your input. I’ve sent pics of my old clutch and linkage set up to American Powertrain and they will hopefully have a solution by the end of the day.
I had a similar situation, the transmission bearing retainer was against the clutch plate hub and would not allow the clutch to disengage cleanly. Did you have any problem with the transmission going all the way to the bellhousing without pulling it to the bellhousing with the bolts?
That being said I’ve had a Centerforce dual friction in my cat for years. No chatter, no slipping.
No real tangible response from American Powertrain yesterday other than to make sure we machined the flywheel which we definitely did. So we took the transmission out again last night and found the release bearing heights don’t match. The fork has got to be a good 1/4" off from the original. Emailed pics to AP, just waiting on a response.
Picture of bearings on mercurycougar.net website.
Well, I found the proper release bearing, both in a greasable and non-greasable variety. Greasable one must be a one shot “grease it before installing” and that’s it cause I can’t see greasing it afterwards. Anyone have any preference from one over the other in their experience?
Also noticed one of the release fingers to be weak on the pressure plate after we took it out again. American Powertrain is air shipping a replacement one to me. Will hopefully have it by Tuesday and start enjoying my cat. Been missing out on a lot of great weather lately! Pic of clutch on other site.
I disagree on where the grease fitting puts grease. In my experience, it also greases the bearing, as evidenced by the grease pushing out between the sleeve of the bearing and the bearing itself. It also greases the trans bearing retainer through a small grease hole.
I thought the fingers looked very odd too. My Centerforce dual friction unit does not stick up like that. BUT, maybe the fingers sit down properly when the the pressure plate and disk are bolted to the flywheel.
I had one other thought about this which might shed some light. If the grease only serves to grease the transmission bearing retainer, can you explain why the TO bearing gets tighter as I grease? It is because the grease is getting down into the bearing and the excess comes out where I mentioned. I turn the bearing and grease until grease has pushed out all the way around the sleeve and then clean up and install.
I probably have an old bearing around I could demonstrate on, Art do you have one so you could try also to see if you what I see?
Thanks for your thoughts guys. I didn’t want to start any disagreements between members on this but it does generate some good conversation we can all benefit from. I was always of the opinion that something greasable is to be maintained over time and I saw no way to re-grease the bearing once installed. Actually, I’d never seen a greaseable one before. I believe either one will do the job! I’ll have another day or two to decide which one to use until my replacement clutch arrives anyway.
Thanks again and I’ll let you know how everything turns out when done.
Yes, you cannot easily re-grease once installed but you can if the trans is removed or a clutch job is done subsequently.
One important thing about any TOB is to make sure the clutch adjustment leaves a little play, just enough to let the TOB pull away from the pressure plate fingers. The bearing will last the longest if this is followed.
Well, the Cat is back on the road…finally! Installed the replacement pressure plate Tuesday night that I received from AP last Friday and installed it with a new proper throw out bearing. With all the chatter I had before I was beginning to think I forgot how to drive a standard after all these years in my daily automatics. It works as slick as silk. Thanks guys for all your insights.
