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Triumph TR6 - New J type OD

I've just installed a re-built OD unit in the 73 TR6. It is working wonderfully but the driver has a few screws loose. I did not install the reverse inhibitor switch, and left OD on after stopping for lunch. When we set off again, I had reversed and run through the gears before I realized the OD was on all the time.

I've been told that reversing while the OD is engaged will damage the unit. While it seems fine and runs smoothly, I'm wondering if I have already wrecked it. Any thoughts? Thanks in advance.
B Chamberlain

If it is working then probably no damage at all. I presume it kicked into OD on 3rd gear.
As you can see, connecting up the inhibitor is at the very top of your TODO list.
Rick '71 with A type OD
Rick Crawford

I think the inhibitor switches only allow the use of od on the selectors on which they are installed. In the case of the j type, there is only 1 switch on the 3-4 selector and the od wont't operate on the other gears, including reverse. If there is a switch on the reverse selector, it operates the backup lights.
Berry Price
BTP Price

You are absolutely correct. The switch "makes" the circuit and allows the OD to work in 3rd and 4th gears only in the case of the J type.
Sorry I was thinking A Type as there is an "isolator switch" to prevent operation in 1st and reverse.
Rick Crawford

Thanks Rick,I thought maybe I had shot from lip. I think inhibitor and isolator are the same. My old TR3 manual refers to them as isolator switches. Maybe they should be called "enabler switches".
BTP Price

Thanks all. I'll connect the isolator switch this weekend. It appears that, as the car wasn't running prior to backing up, the OD pressure was off and the unit was not engaged. I reversed only a few yards before headed off. All seems fine and I cautiously believe the one-way bearing has survived.
B Chamberlain

Oh no. Now another issue:

I engaged the OD once on the highway and all appeared fine: drop in RPM, smooth operation. After an hour highway driving, I switched off the OD when I pulled off to get gas but there was no change in RPM. Out of the gas station, I switched it on and again, nothing. I can't tell if its stuck on or if its not engaged at all. Its reading 2500 rpm at 50 mph in 3rd and 2500 rpm at 70 mmph in 4th. The solenoid sounds like its moving.

Can anyone help here?

These are my questions:
At the given rpms and speed, is the OD on or off?
Is there a test I can do in situ?
Will the pump pressure ease when the car is stopped to the point where the OD will disengage?
Can I reverse?

Again, any suggestions would be greatly appreciated.

B Chamberlain

My 71 turns about 3000rpm in 4th at 70mph with a non-OD box. Sounds like your OD is stuck on. This is not unheard of in rebuilt gearboxes. The cone clutch has high spots that are getting wedged during engagement. A little use will wear these high spots down and allow proper function.

In the meantime if it's stuck - DON'T reverse!
Don't do any hard acceleration in lower gears with the OD stuck on either. The planetary gears are not rated for that much torque and you may damage them.

Crawl underneath with a lead or rawhide mallet and 'tap' the brake ring on the OD. If all you have is a steel hammer, put a piece of 2x4 against the trans before hitting it! This will normally shock it loose since the hydraulic pressure drops to zero without the shaft(s) turning. All it needs is a little help to free it up.

Best of luck and let us know how you get on.

Tom Sotomayor

This thread was discussed between 07/08/2007 and 13/08/2007

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