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How to disassemble black-label overdrive?

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Filigree Avatar
Filigree Silver Member Eric Frazer
Woodinville, WA, USA   USA
1969 MG MGB GT "Mr.Bean"
I want to take apart my bought-on-ebay black-label overdrive transmission... I took off most of the external nuts that seem to hold the overdrive to the main unit, and I took off the access plate and removed some weird piece of metal that looked like a pincer, and unscrewed the set nuts that keep the selector forks attached to the poles. And a weird wired-on bolt that was inside the access hatch. I also took out the overdrive cylinder/pluger and related stuff. The overdrive won't budge. Now what? Anybody have a rundown on this variant of overdrive? The MGB service manual ain't no help. Pointer to online docs, anyone?

thanks!

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converse212 Avatar
converse212 Eric Morgan
Atlanta, GA, USA   USA
1958 MG MGA
1970 MG MGB "Daily Driver"
1970 MG MGB GT "Rusty"
1971 MG MGB GT    & more
Stop, stop, danger Will Robinson!

What manual are you using that doesn’t talk about disassembling the overdrive? Find a copy of the factory manual. There’s a pdf floating around online, some site called “geo-matique” or something like that. I prefer a hard copy but I still keep the pdf.

The factory service manual has all the information in it you need.



Daily driving a '71 MGB

Resurrecting a '58 MGA

Ken Plumstead Avatar
Smithers, BC, Canada   CAN
1965 MG MGB
1968 MG MGC GT
Everything you ever wanted to know about MGBs.

http://www.geomatique-liege.be/MGJP/DocumentsPDF/MGB_Workshop_Manual.pdf

Ken



MG: Transforming gasoline into Fun!!!

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Gary E Avatar
Gary E Silver Member Gary Edwards
Kernersville, ,N.C., USA   USA
Why on earth did you want to take it apart. Most people change the seals under the access plate and then just bench test it for function.



Gary

converse212 Avatar
converse212 Eric Morgan
Atlanta, GA, USA   USA
1958 MG MGA
1970 MG MGB "Daily Driver"
1970 MG MGB GT "Rusty"
1971 MG MGB GT    & more
In reply to # 3717614 by Gary E Why on earth did you want to take it apart. Most people change the seals under the access plate and then just bench test it for function.

Seals don’t always solve the problem...nor tell the whole story. There are also seals that can’t be accessed from under the access plate.



Daily driving a '71 MGB

Resurrecting a '58 MGA

Filigree Avatar
Filigree Silver Member Eric Frazer
Woodinville, WA, USA   USA
1969 MG MGB GT "Mr.Bean"
The manual I have is the "MGB Workshop Manual", publication part No. AKD 3259, 14th edition. 417 pages long. it describes the overdrive for the "D" type, which (I do believe) is not the type I have.

Gary E Avatar
Gary E Silver Member Gary Edwards
Kernersville, ,N.C., USA   USA
I have had 2 od trans and I changed those seals and bench tested it and was good to go. He never said it did not work.



Gary

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Filigree Avatar
Filigree Silver Member Eric Frazer
Woodinville, WA, USA   USA
1969 MG MGB GT "Mr.Bean"
*sigh*. never mind, it was farther down in the manual. Doh! Anyhow, the instructions on how to separate it are terrible and/or don't work. :-)

ohlord Avatar
ohlord Gold Member Rob C
North of Seattle, N.W., USA   USA
1957 Land Rover Series I "EYEYIYI"
1971 MG MGB
1971 MG MGB "Bedouin 2"
John Twist has a video.
However why take it apart? Absent of testing and finding it broke, it can be totally serviced from below, o rings replaced, filter screen gasket renewed, magnets cleaned, system flushed, electrics tested , 20w50 oil changed
Tested for operation.
What to you hope to discover by ripping it apart ?eye popping smiley



"I'm a long way gone down this wild road I'm on
It's gonna take me where I'm bound
It's a long way around"



"These are the days that must happen to you"

RD2 Radar/ Electronic Warfare Technician
Vietnam 1969-1972

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Filigree Avatar
Filigree Silver Member Eric Frazer
Woodinville, WA, USA   USA
1969 MG MGB GT "Mr.Bean"
You have a point... I thought there might be worn bushings or shims inside there, but maybe I'll just leave it alone. Isn't there anything inside the overdrive unit that I should look at? bushings, shims, friction plates, planetary gears, etc?

Ahmed Avatar
Ahmed Silver Member Ahmed EL Abasiry
Chestermere, AB, Canada   CAN
1958 MG MGA
1972 MG MGB
1979 MG MGB
I went through this a couple of months ago. No need to take apart the gearbox or the OD unit completely. Just separate the gearbox, the intermediate housing and the OD unit.

1- Replace front and rear oil seals on the gearbox
2- Check the shims under the front oil seal cover. I bet they will be chewed. Replace as necessary (factory manual has the instructions)
3- Replace all paper seals between the 3 sections of the gearbox (main housing, intermediate housing and OD unit)
4- Replace the paper seals of the remote control unit (where the gear shifter is mounted) and the seal of the side inspection window
5- Replace the O-rings of the OD unit. See John Twist video for details
6- Replace the filter screen and the square paper seal on the OD unit. Clean the magnets from any metal shavings
7- Replace the seal of the speedometer drive cable (under the knurled nut)

Moss has an OD gearbox seal kit (BGK104) which contains all the paper seals necessary. It does NOT contain any O-rings for the OD unit, which have to be bought separately. Moss has them too.

I used a smear of gasket silicone dressing on the paper seals. No leaks so far. I bench tested the unit and all was good. See this video I posted earlier testing the gearbox after refurbishing.




"... the motor car, after woman, is the most fragile and capricious thing on earth." - London Daily Mail 1908

Filigree Avatar
Filigree Silver Member Eric Frazer
Woodinville, WA, USA   USA
1969 MG MGB GT "Mr.Bean"
Yeah but I can't seem to separate the OD from the main housing, or the intermediate housing. they're stuck together big time. something's binding it up. I need to be pointed to a write-up, or a video, or better instructions than this factory repair manual.

converse212 Avatar
converse212 Eric Morgan
Atlanta, GA, USA   USA
1958 MG MGA
1970 MG MGB "Daily Driver"
1970 MG MGB GT "Rusty"
1971 MG MGB GT    & more
If you have the equipment to bench test, then you can get away without disassembling the unit and looking at everything. Do the easy stuff, bench test, and plug it in. If you don’t, then disassemble it completely.

Personally I think it’s a good idea to disassemble an unknown overdrive anyways. There’s no telling what’s been happening in there without looking at it. There are also o rings you can’t get to from the bottom, as I said before. And it’s the best way to really fully clean it.

I’ve never had an issue with taking the overdrive off the box itself. Just pull hard, as best I remember.



Daily driving a '71 MGB

Resurrecting a '58 MGA

MGB 1976 Avatar
MGB 1976 Silver Member Mark Turechek
North of Boston, MA, USA   USA
1976 MG MGB "The Never Ending Project"
The best way to take it apart is to put it on a pallet and send it to Dick Moriz with a check for rebuild/bench test services.

dickmoritz Avatar
dickmoritz Platinum Member Dick Moritz
Philly 'burbs, PA, USA   USA
Your black label overdrive is a Type LH overdrive, which is quite different from the earlier D-type overdrive as used on the 3-synchro cars. Operating pressures for your overdrive are quite high; spec is 400-420 psi. And there are many pitfalls for a first-timer. If you're having trouble removing the overdrive unit from the main gearbox, it's probably because the interlocking arm or selector lever is not disengaged.

If your overdrive is working, I'd suggest you either carefully replace the externally-replaceable seals, gaskets, o-rings, etc., or just leave it alone. And if it needs repair, I recommend having the work done by someone who is very familiar with these units.

Dick



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

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