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MG MGB Technical - Overdrive questions

I have checked the archives, but not found the answers to a couple of questions.

My 69 B started not releasing the OD when hot. Behind the filter I found the pieces of what could have been a brass thrust washer - 1.5" dia. I assume this to be the beginning of the end of the OD - so, my questions:

Can the LH Overdrive be replaced in situ - ie. without removing the engine / gearbox ?

If I disable the OD by removing the oil pump and solenoid etc, will this affect the normal gearbox operation ?

It is a 69 chrome bumper with 4 synchro gearbox.

Thanks,
Glen
G Ward

It sounds like the rear thrust washer has come apart. The unit cannot be repaired while it is still in the car. It is an engine/transmission out of the car job. Disabling the OD probably won't make much difference, since there are probably quite a bit of metallic particles moving about your transmission. A repair or replacement is in order. Sorry. RAY
rjm RAY

Ray, That would be the rear thrust washer from the OD or Gearbox ?
I know that the OD will need replacing, I was just finding out if I could buy some time by disabling it, and stop it engaging at all until I get the time / money to fix.
Glen

G Ward

I have an overdrive which probably needs overhauling, but if one just doesn't engage it, can one put off the evil moment? Mike
J.M. Doust

The problem I have is the the OD comes on without flicking the switch when it is hot - works perfectly when cold - have checked electrics and they're OK. Glen
G Ward

Just going back through the drawings and looking at the parts from the sump, It looks like the pieces bay be from the outer part of the Sun wheel thrust bush.

Some archive threads indicated that a failure in this thrust bush will cause the OD to engage at will.

Any thoughts ?
Thanks, Glen
G Ward

The more you drive it the more parts you will buy, and the farther you will walk home.

FRM
FR Millmore

You certainly can't get away with removing the oil pump as that is operating all the time the car is moving and supplying oil via a low-pressure valve to many parts of the OD for lubrication. As the oil is shared between OD and gearbox there is every likelihood that broken bits will be as well, leading to the cost and walk that FRM mentions.
PaulH Solihull

Paul and FRM, you are right, I have bitten the bullet, setup to remove the engine + gearbox and ordered a replacement OD from Moss-Europe.
They are way cheaper - including freight than local suppliers here in Oz. Plus they can get it here quicker that suppliers from the other side of the country!

Thanks for the advice, people.
Glen
G Ward

Glen,

Sorry to hear of your woes! I went through a full OD & gearbox refurb about 4 years back, it was certainly an adventure. If you are interested I think I may still have an excellent electronic copy of a Volvo manual covering this model of ovedrive used in the P1800 I believe. I assume you are going to pull the gerbox apart to an extent to make sure no goodies are floating around in there also?

Don't throw the old OD - should be able to refurb or sell as is for some reasonable $$.

If I can help please feel free to send an email.

Cheers and good luck!
C Brennan

Chris,

I have emailed this to you directly as well.

Thanks for your advice and offer, it's great to get other perspectives on a problem.

I would very much like a copy of the Volvo manual covering the overdrive, and yes, I intend to partially dismantle and flush out the gearbox.
Plus the clutch etc.

Thanks,
Glen
G Ward

Glen

I have the LH type OD overhaul instructions in WORD format if you're interested. It's a 5 meg file, but I can try to email it to you if you're interested.

Tom
T Lea

I hear this story and I think Sierra 5 speed....
vem myers

Tom, if it's at all possible, I'd like a copy as well, as it'll be useful in the not too distant future.
Thanks
thedotbruntsatwanadoodotfr
Graham

"I hear this story and I think Sierra 5 speed...."

Why swap a 6-speed with 'paddle' change (OK, OD ratios only) for a 5-speed ...
PaulH Solihull

Tom, I would also be interested in a copy of your OD file if possible.
Thanks, Mark
(wellardmatoptusnet.com.au)
M Wellard

On the way Mark
T Lea

Tom,

Please send me the gear box rebuild file. I would be interested in seeing it. If it is not copyrighted, or if we can get permission from the originator, I'll post it on the technical section of my website for others to download. http://www.dbraun99.com

warmly,
dave

dave at dbraun99 dot com (replace the at and dot with the usual glyphs)
Dave Braun

This thread was discussed between 27/10/2011 and 08/11/2011

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