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MG MGB Technical - What is this piece I found in my overdrive?

Hello All,
I'm partially dis-assembling an overdrive gearbox to go in my '77 B.
Firstly, the overdrive unit did not want to slide away from the overdrive adapter as the manual said it would.

It would only move about 1/2 inch. It did eventually come free and I found a piece of what looks like a thrust washer laying on the overdrive adapter (see photo).

I have looked over the exploded view of the overdrive unit in my manual and cannot find anything that seems to match.

Any ideas where it came from or what it is? The ends are not clean so it may have been in there for some time.

Thanks in advance,
David

David Steverson

From the Parts Catalogue it *could* be the snap ring that goes between the sun wheel and the cam that drives the pump - 37H 1908. Item 22 in the Workshop Manual, item 10 in Haynes?

Is this an unknown quantity i.e. new to you? Even if you have found the above parts it may be an old one with the bits not fully cleaned out from a previous breakage.
Paul Hunt

Hi:

If it is bronze, then it could be part of the steady bushing on the input side of the o/d unit, check to see if it is broken-up; if so then it must be replaced.It also could be part of the rear bronze thrust washer.

Good luck, Rich Boris
67 B roadster
R. Boris

I found similar mysterious bits in my diff when I stripped and rebuilt that.

http://asciimation.co.nz/pics/page6.html

Never did figure out what it was. I thought maybe some kind of hard, caked grease or something perhaps. Maybe that's what happens to the fiber washers when they get ground up and the paste ends up floating about in there?


Simon
Simon Jansen

That is one the fabled "Oh Sh-t" parts. You know, the kind that when you open up the case you just have to make that exclamation.
Bruce-C

Bruce! were you listening in or something??
David Steverson

If it is bronze it pieces of the thrust washer that stops the sun wheel wearing its way throught the alloy casing that holds the actuating pistons. A common problem on post 74 models. They are only held in by peening over the alloy around the outside & with time come loose & break up. You will need to get a new one made. preferably from Microid bronze. I hold them in place with short 3/16" Whitworth allen grub screws. A competent engineering shop should be able to do this.
Garth
Garth Bagnall

It is definitely the thrust washer which has broken.

They were GLUED on originally!

Best fix is to have the earlier type of lubrication bush fitted - ORS in the UK will do that for you on original tooling - otherwise get a local machine shop to make up a bush, it has to be frozen and fitted to a heated casing to get the necessary interference fit and then machined in place.
Chris at Octarine Services

A fellow MG'er who has some experience with overdrives stopped by.

It appears I have a new-ish thrust washer in place. We think this is a piece of the old one that was missed.

So, onwards and upwards on the refurbish!!
David Steverson

Hi,

I am working on my OD and have the same problem with the broken washer. I cannot find the part number in any diagrams.

Anybody have that number? Thanks
Todd

This thread was discussed between 29/01/2009 and 04/02/2009

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