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The TR Register Australia Inc. forum dedicated to Sidescreen TRs and Derivatives
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 Post subject: TR Overdrive
PostPosted: Thu Sep 10, 2020 6:54 pm 

Joined: Fri Dec 20, 2013 7:48 am
Posts: 110
My knowledge of the TR overdrive is a bit sketchy, and during these covid times, I thought it might be interesting to gather together some information from various people about the overdrive units.

What I do know, or think I know, is that the TR2 only had overdrive on top. All early TRs came with the A-Type overdrive. I think the J-Type was on the Spitfire and maybe TR6? Are they interchangeable and is there any benefit in using a later one?

I had my overdrive rebuilt by a guy in SA decades ago and he only set it up on third and fourth. I did ask at the time, but can't remember why but I seem to recall before that, not much difference between 2 overdrive and 3. A couple of other topics to explore:
- What are the things that usually go wrong?
- Who is an OK repairer if you need assistance?
- Has anyone recently had one rebuilt? How did it go and what did it cost?

I would be interested in hearing more and I am sure other people would too.

 Post subject: Re: TR Overdrive
PostPosted: Sun Sep 13, 2020 10:53 pm 

Joined: Wed Dec 18, 2013 5:05 pm
Posts: 326
Hi Nev,

All sidescreen TRs had A type od. The later TR6s had the J type.

The TR2 did only have it on top but putting it on 3rd only required a new switch on the gearbox top so many were modified, my BRG car has been modified. My red TR2 hasn't. Putting it on 2nd required more work and the later od with 2nd had bigger operating valves which the early cars didn't so putting it on 2nd on an early box introduced more issues.

Although it is an early one my TR6 has been retrofitted with a J type. Apart from a smoother operation and a slightly different ratio I can't tell the difference between the one on the 6 and the ones on my TR2s.

The gearbox mounting is different between the two so to fit a J type would require chassis surgery for the mount. There may be other mods needed as well. Many of our members have fitted 2500 boxes with J type so it can be done but is done for the better gearbox not the J type od. I know of a few people who reckon the A type is better than the J type, why I don't know.

Dave Anderson, a Register member, rebuilds them in SA and is the go to person for Laycock od.

The only problem I have had in 45 years in my BRG TR2 is the solenoid, once, and the switch (a quick clean beside the road and it has been fine since.

The od in my red TR2 wasn't working when I got the car back on the road. A Register member, I'll let him volunteer his details, pulled the od apart and we found the clutch plates had seized together after 50 years in the shed. It was freed and now works fine.

The od in the TR6 wasn't working well after I bought the car and it was the solenoid valve, the rubber seals had gone hard over time and lack of use. A new solenoid fixed it.

I've never had a problem with the od itself.

An A type solenoid is pretty cheap as it is just a solenoid, the valve is in the od. The Register has them for about $45. The J type solenoid is a lot more expensive as it includes the valve. Dave Clark had one for about $300 I think.

Servicing them is much the same for A or J type. Change the oil and pull the od filter out via the sump plug (A type) or plate (J type) for cleaning. I've never found debris in the filter except when I blew the gearbox on my BRG car 25 years ago.

Adjusting the A type is pretty straighforward. I'm not sure if the J type can be adjusted as the valve is intregral to the solenoid.

That is just about all I know about od. I await being corrected as necessary.

 Post subject: Re: TR Overdrive
PostPosted: Wed Sep 16, 2020 11:35 pm 

Joined: Mon Jan 06, 2014 10:25 am
Posts: 101
Hi Neville
When I bought my mid 1955 TR2 in 1964 it had overdrive on 2,3 and 4. I don’t know what its history was in those 9 years but the commission number and engine number number match the birth certificate.
After finally getting it back on the road after lengthy restoration 4 or so years ago I found that overdrive wouldn’t engage despite theoretically having been repaired when I had gearbox overhauled.
David Clarke in Rydalmere ran a whole lot of diagnostic tests with the gearbox in the car. In the end the gearbox had to come out. David then sent it down to Bob Anderson who rebuilt the overdrive. It’s working perfectly, just like I remembered from years ago.
Cost all up with David removing the gearbox for me and organising transport to SA and back about $3 K.
Jim Allen

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