A type overdrive missing intenal part

[Adrio]

I decided to try and move an A-type overdrive unit from an early TR3 gear box to a late TR3 gear box so that I can use it on my TR4A. Starting with the disassembly of the early box (since it is a spare and not doing anything) everything was going along fine until I discouvered that inside the O/D unit was nissing the cam. This is the part the manual calls the eccentric. It is the part that slides on to the main shaft aft of the gear box and it drives the pump in the overdrive unit.

Does anyone have any idea why this part would have been removed from a gear box overdive unit? If this was a common "solution" to some problem in the past, I would not want to buy a new cam, do all the work of moving the unit to the other gear box only to find out the O/D unit has some fatal flaw in it.

This piece is fairly large and I can't see having "lost it" while taking the thing apart. I remved the O/D unit with the gear box standing on its nose so the cam would have had to travel all the way up the main shaft before falling down and going undetected. Now the 8 springs on the other hand, departd the work bench, but I have found all those.

Any help and/or advice would be great.

thanks,

 

[Keoke]

Hi Adrio, Without the "eccentric" the overdrive will not work as it is this CAM that drives the pump.However, I don't have a clue as to why it was missing.--Fwiw---Keoke

 

[piman]

Hello Adrio,
I hope this link will help, www.overdrive-repairs.co.uk/index.html,
you should be able to order a new pump cam and being relatively small will not cost a fortune to post to you.

Alec

 

[Dave Russell]

Hi Adrio,
You can get a pump cam from Moss for about $77. Item #4, here:
https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=29134#top

If the pump cam truly is missing, & you didn't just lose it, the OD obviously did not work before. I would very carefully compare your parts to the diagrams & see if anything else may be missing or wrongly installed. The OD is full of tiny bits that all have to be there & installed correctly for it to work.

If you wish, I can send a very detailed & complete writeup of the overhaul on the A type OD.
D

 

[Adrio]

[ QUOTE ]

If you wish, I can send a very detailed & complete writeup of the overhaul on the A type OD.


[/ QUOTE ]

Dave,
That would be great. There were signs that this O/D had been opened up before (a few of the studs seemed to have been broken, the end of the tranny main shaft was a bit "mangled" but only a bit, and the cam was missing), so I do not have much faith in the whole thing. I do not want to go down a road that will end up costing me as much as buying a rebuilt tranny with O/D plus a ton of work on my part. This was suppose to be a "quick" swap of parts between the two spare transmissions I had so that I could get O/D into my TR4. It has turned inot a lot more and I want to guard aginst it turning into way too much more.

My web site has my email address if you need it.

 

[Adrio]

I was able to source an eccentic cam locally today and I have it in my hot little hands. Thanks to Dave I am ready to start work on this overdrive adventure again. I expect that this weekend I will be up to my elbows in overdrive and tranny parts. If anyone has any words of advice before I move the guts of an early TR3 overdrive gearbox into the body of a late TR3 non overdrive gear box they would be most welcome. I am taking pictures and will document the fiasco on my web page.