[Mgs] Overdrive Diagram

riverside at southslope.net riverside at southslope.net
Fri Jan 18 14:38:18 MST 2019


Quantum mechanics used to recommend 30W
non detergent oil and it always worked well for us.
We are putting together a TR6 w/ Odr and I decided 
to check in to see if that had changed and their new
recommendation is Redline MT 90   75w90  GL4.

drove the car once and the OD shifted well. 

art at riverside sports cars.

From: Jack Wheeler via Mgs 
Sent: Friday, January 18, 2019 10:32 AM
To: Osborne, Paul 
Cc: Mglist 
Subject: Re: [Mgs] Overdrive Diagram

Hi Paul.  You are correct, I removed the low pressure valve, NOT the pump assembly.  I was looking at the manual and the parts which came out appeared to be closer to those shown as the pump assembly, but neither was the same as mine.  That's how I assumed it was the pump assembly.

So, now that I have the low pressure valve installed properly, the overdrive still does not engage.  The other thing I changed was the gear oil.  I always used straight 50 Wt. motor oil in my overdrives, and that worked fine.  Based on a recent article in the Tech Issue of "MG Driver" magazine, I switched to EP 85/90 GL-4 gear oil.  Do you think this could be causing the problem?

Thanks for your help.

Jack


On Thursday, January 17, 2019, 10:38:25 PM EST, Osborne, Paul <paul at ece.rochester.edu> wrote: 


Hi Jack, hum, a few things I might be a able to help. I have been build/repair the Laycock OD units and transmissions for a some time, for MGS and Triumphs and Jaguar. I have seen a good number. I do not claim to be the last word on these.   Some info about your unit may help. 1971 MGB is it  orig to the car?  
If so it should be a black label LH unit mated to a full synchro 4 Spd trans. The pump assy. Is located in the sump, not visible from the outside housing unless the sump is removed. All have a roller in the end as that is running on the input shaft which has a pump cam. Is that what you removed? If that is not what you removed, but you removed the large nut just nest to the solenoid cover(black label) that is the pressure valve. There is not roller on that plunger.  Let’s stop there for now and let me know if this is what was removed.  

Paul




  On Jan 17, 2019, at 2:13 PM, Jack Wheeler via Mgs <mgs at autox.team.net> wrote:

  Does anyone have a good exploded diagram of the overdrive unit used in a 1971 MGB, that you could send to me?  I am particularly interested in the pump assembly.  I changed the oil in my gearbox this week, using EP 85/90 GL-4 gear oil, as recommended in a recent article in the MG Driver magazine.

  While the car was up in the air, I noticed a leak around the plug which holds the pump assembly in place.  So, I removed the pump, careful to keep all the pieces in the order in which they came out.  I cleaned everything up, and reinstalled the pump assembly and plug (part number 466-315 in the Moss catalog), with a new gasket.  I thought I had all of the pieces of the pump assembly (items 62-66 in the Moss diagram) in the right order when I reinstalled it, but when I took the car out for a test drive, the overdrive would not engage.

  In addition to trying to keep the pieces in the order in which they came out, I also used the exploded diagram in the Moss catalog (Page 41) as a guide.  The Moss diagram, however, is different than my overdrive unit.  Moss says their diagram is for cars from 1968 to 1980, but apparently, some things were changed during that time frame.  I can't believe the engineers would let anything go unchanged for 12 years!  It looks like the plunger (Moss part number 466-305) shown in the Moss catalog diagram has a roller on the end of it.  My plunger does not have a roller on the end of it.  Maybe this will give you a lead to which diagram I am looking for.


  So, that leaves me looking for a good exploded diagram of the unit used in a 1971 model.  Can anyone help with that, or does anyone have any suggestions as to what I might have done to make the overdrive not work, when it has always worked fine.  Thanks.

  Jack Wheeler

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Paul Osborne
Department of Electrical and Computer Engineering
University of Rochester
201 Hopeman Building RC
Rochester, NY 14627

585-275-5226





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