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Triumph TR3 - Overdrive Problems

I am looking for solutions to a problem with the overdrive in my 1961 TR3A. The unit has been rebuilt and works fine in all 3 gears when the car is first driven, but as the overdrive warms up it fails to engage in 2nd, shifts in and out in 3rd and will finally fail to engage in 4th. Also does anyone know of a good manual for this overdrive. Thanks Jim
J.W. Herbert

Jim-Sounds like the oil pressure maybe low. Try this site for detailed troubleshooting and description of the A type
Go to the technical articles and A type OD.

Roadster Factory and maybe Moss have a very nice soft cover instruction manual about 3/16" thick that Standard Triumph printed with Laycock back in 1958 or so, Laycock are the manufacturers of the overdrive. It is excellent and complete.

Someone on the internet sells a hose and a pressure gauge that is filled with oil to dampen the vibrations. On the other end of the flex hose is an adapter perhaps with a ball check valve in it and you connect it to the top right hand side of the overdrive after removing a hex nut. After putting the rear end up safely on jack stands, you rev it up and read the oil pressure produced in the overdrive. In the year 2000, mine read 325 to 340 psi with Valvoline 20W50 in the gearbox and overdrive.

Don Elliott, 1958 TR3A
Don Elliott

Hi Guys:
It certainly seems that low pressure is JW's problem.
When I was checking the pressure on the OD I intend to put in this winter I noticed that the spec (either Laycock or Triumph)called for 380 to 400 psi which seemed very high so I contacted OD Spares in the UK and they advised that the pressure is much better between 340 and 350 as it is much easier on the whole drive train.
I used a similar set-up as Don describes for testing.


Jim - Have you tried a thicker oil ? The pressure I wrote about was right after a complete O/D re-build. I was in Portland Oregon at VTR at the time and the O/D has been fine ever since (more than 32,000 miles on it since August 2000). The shop that did the job had the pressure gauge. Maybe there's a British Car Shop shop with a test gauge (Volvos still use the same overdrive) in your area.

Don Elliott, 1958 TR3A
Don Elliott

Jim-In re-reading your original post, I noticed that your OD had been recently rebuilt. Was there a problem from the beginning or did it appear later? The first place to start would be to check the operating valve adjustment. The articles on the Buckeye site include parts of the Laycock manual, but are much more detailed. The 5 part epic is about 75 pages and is well worth printing.
Berry Price

Thanks you the input. When I first put the car on the road last spring I was using Castrol 30 in the transmission as per the manual. I did switch to Castrol 80 as per the TR-4 manual, this switch had little effect on the shifting problem when hot. I have checked the operating valve adjustment but I haven't checked the operating pressure. I checked out the Buckeye site and found it very informative. They listed several other things to check out that will keep me busy while the white stuff covers the drive way. Thanks again Jim
J.W. Herbert

This thread was discussed between 27/10/2003 and 29/10/2003

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