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MG MGB Technical - Grinding reverse/clutch

I know this has been beaten to death in the
archives, but here's the story. Just replaced
my old 4 speed with a rebuilt overdrive (car is
a 79B), which works
great. However, I get bad grinding going into
reverse, and I have to push the gearlever pretty
hard to get into first. I didn't have this
problem with the old transmission.

I replaced the clevis pins (one was worn) pushrod,
and slave because I thought it was leaking (but
it wasn't on close examination.) Clutch MC is
a year old.
Bled with the eezibleed, which always worked for
me before. Still get grinding into reverse.

The car doesn't creep forward with the clutch
pedal pressed down, and seems to engage at
the "right" point. I put in a new pilot bushing
(oiled it beforehand), new Borg and Beck clutch
when I replaced the tranny. What on earth
am I doing wrong??? Could this be a transmission
fault?
Ronald

No.Clutch related.If clutch is new and correctly installed, it must be release mechanism.
Ken R
Ken Rich

Ronald. What is the state of the pushrod for the clutch master cylinder. My daughter had a similar problem while in school in Tucson and the fault was traced to a very worn master cylinder pushrod. They are available, as a seperate part, from Moss. The mechanic sent the old pushrod home with her and it was worn to about twice as large as it should be, front to back. Something seems to be limiting the full movement of the clutch. That would have to be master cylinder, bad flex hose, slave cylinder push rod, the throwout bearing fork or leaking seals within the MC or slave cylinder. A thorough system check out and rebuild is in order. Did you rebuild the master and slave cylinders? Did you replace the flex line? Did you rebush the throwout bearing fork? It could be one of these items or a combination working together to reduce the amount of throwout bearing movement. Les
Les Bengtson

Ronald - After going through the "normal" bleeding routine, I have found it helpful to manually push the slave cylinder piston all the way into the cylinder, forcing any air in the cylinder up into the line to the master cylinder and then bleed the system a time or two. This insures that any air trapped in the slave cylinder is all purged. Good luck - Dave
David DuBois

Thanks very much for the comments. The clutch action
was noticeabley better this morning after bleeding last night,
although still get some reverse grind.
This is consistent with previous threads suggesting that air bubbles
to some extent drift upwards and out of the MC, so clutch (and
brakes) are firmer 12 hrs or so after bleeding.

I think I must still have some air in the hydraulics -- hose is
relatively new and stainless, MC (and pushrod) is also
nearly new. Throwout bushing seemed ok.

One other concern -- I got two new Borg and Beck clutches
from different suppliers. However, both diaphragms looked
slightly different in construction from my old diaphragm, and
the clutch disk was of a dark colored instead of yellowish-looking
material. The clutch disk number was the same however.

Does anyone know of a recent changeover in clutch components
supplied by AP (Delphi?) Could I have been supplied the
wrong type of clutch? If so, I would think it wouldn't work at all.
Thanks again.
Ronald

Ronald - if you still have air in the system try reverse filling. After reading many tales of woe I filled my system using a gunsons at very low pressure on the *slave* nipple and watched for the level to rise in the master. Topped off, and had full travel without further ado i.e. no bleeding required at all.

But first check the slave travel to see if the problem is hydraulic or mechanical. you should have 1/2" to 5/8" travel of the slave piston when operated by the clutch pedal. Less than this and there is air in the hydraulics, otherwise it looks like a mechanical problem inside the bell-housing, unfortunately. And I get the impression you reused the throwout or release bearing? False economy, unless the old unit has a known and short history.
Paul Hunt

Thanks for the reverse bleeding tip -- will try this next, since
slave travel seems correct.
My frustration is that I used a new throw-out bearing as part
of the complete new three-piece clutch kit. But I am concerned that
Borg and Beck arbitrarily seems to have changed the diaphragm
and disk for the MGB kits, and wonder if that is part of my
problem. Interestingly, the same "new" type of diaphragm
and disk was found
in two differently-packaged clutch kits from two different suppliers.

Try to look up an AP or Delphi web site -- you would think you
could find cross-references for the actual clutch part numbers.
These large companies have the world's most useless web sites.

My other thought is that the pilot bushing is binding slightly
with the input shaft (based on reading the archives.) But
given the softness of the bushing material, I would think this
problem would go away on its own.
Ronald

This thread was discussed between 07/02/2002 and 08/02/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.