[Fot] A-type OD leaks

[Henry A. Morrison]

My current overdrive rebuild went so well with me replacing a variety of linings and washers that were shot or just not installed by the previous rebuilder.  I thought all the pressure producing bits looked good so mostly left them alone.  I did the pressure test when I got it all back together and it was close to where it was supposed to be.  I drove the car once and it seemed to work, drove it again and it dropped into overdrive whenever I lifted off the gas and dropped out again when power was re applied.  This is pretty much what the thing was doing when I started the project and I'm sure was the reason for my slower than they should have been lap times at the Cup!

Any suggestions on what to do next?

Cheers, Henry Morrison

________________________________
From: Fot <fot-bounces at autox.team.net> on behalf of Glenn Franco via Fot <fot at autox.team.net>
Sent: Thursday, September 21, 2023 2:57 PM
To: Nick Black <vintagenick42 at yahoo.com>
Cc: Joe Boruch <jaboruch at yahoo.com>; FOT Triumph <fot at autox.team.net>
Subject: Re: [Fot] A-type OD leaks

I have to chime in on issues with the A type overdrive. Thankfully I have NO more A types to overhaul since they are a P.I.T.A. to do.
The hardest part, as stated, is lining up the 2 splines that will allow the mainshaft to nest into the Planetary Gearset and Overrunning Clutch. You basically need at least yourself and a helper to put it together. I probably did 10-12 of these 2 or more years ago. First time we did one we split the adapter plate pulling the O/D on to the transmission. Unfortunately it was welded back together and the repair was a weak spot. If you force the O/D onto the trans when pulling it back together with the 2 nuts on the O/D studs it will break or bend the plate.

The fasteners (6) that hold the plate to the back of the transmission are drilled for safety wire. I used stainless safety wire on those after torquing. Make sure you repeat the way the wire is routed through the bolt heads. I had a couple transmissions leak because I didn't follow the routing  properly. I mistakenly routed some of the wire near the base of the plate fouling the gasket which resulted in an embarrassing 3 comebacks on one transmission due to leaks.
Took awhile to figure it out, dumb mistake.

Glenn 74 TR6 Restored, 68 TR250 Frame Off in Progress, 73 BMW 2002


On Thu, Sep 21, 2023 at 4:04 PM Nick Black via Fot <fot at autox.team.net<mailto:fot at autox.team.net>> wrote:
Joe
I agree, it’s the bolts that hold the od plate to the transmission. I recall that the torque on these bolts is about 25 lbs. the bolts are totally soft and will stretch forever with one or two additional pounds… throw them away and use Allen head bolts drilled for safety wire. The stock bolts stretch and the plate gets loose and leaks.

Sent from the wilds of NorCal

On Sep 20, 2023, at 8:52 PM, Joe Boruch via Fot <fot at autox.team.net<mailto:fot at autox.team.net>> wrote:


I have a leaky a-type OD in my street TR4 that looks like it's leaking from near the adapter plate.  I have never taken one apart.  Can I just separate the OD from the trans and replace the gaskets or the adapter plate (I've heard that Quantum Mechanics sells an uprated plate and am checking with John to see if he has one) and then reassemble without needing to take the OD apart further?  There is a youtube video that shows an OD being separated and it looks like it is do able.


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