TR6 J-Type overdrive will not disengage when warm

[rwest]

My J-Type overdrive has been playing around recently. When the gearbox was cold everything would be fine, the overdrive functioned correctly and there was no hesitation either engaging or disengaging. However, after 10-15 minutes, disengaging would be hesitant and would sometimes re-engage before disengaging correctly.

On my last trip it did not disengage at all, and I had overdrive in all forward gears (and presumably reverse, although I was careful not to even try).

Having left the car overnight it appears that it is working again, although I was only brave enough to try it with the rear wheels off the ground.

I had already drained the gearbox oil and refilled it with Penrite GB40 gearbox oil prior to the final run.

I've read that it can be the solenoid that could be at fault and am looking for a second opinion as I'm not a gearbox expert (but will have to become one as I now live in France).

Also, looking at the drivetrain, I would assume that the unidirectional clutch would be ruined even if I try pushing the car backwards with the gearbox in neutral as the propshaft, and therefore overdrive, would still be rotating. Can someone confirm or deny?

Thanks you all for reading this long email, but I wanted to be as descriptive as possible.

Cheers, Robert

 

[mastaphixa]

A friend with a J type OD in his TR6 was experiencing the same thing. I removed the solenoid and was able to duplicate the fault by connecting the solenoid to a battery and checked the temperature of the solenoid. After it got above 175 degrees (about 15 minutes) the plunger would no longer retract. If allowed to cool it would retract. I removed the C clip in the end of the solenoid, made sure everything was clean, replaced all the seals and tried again. No help. I stretched the return spring and viola it worked after being on the battery for 45 minutes at a temperature just over 200 degrees. Getting that little C clip out is a right treat and I ended up mangling it on both the solenoids I repaired this way. Mcmaster Carr has a C clip that isn't exactly the same (thinner) but works well. The PN is 99142A330. Hope this helps.

 

[rwest]

Thanks for the info - everything seems to be pointing at the solenoid as being the culprit. It's well over 25 years old, it might be time to buy an new one. I'll update when I've swapped it over.

 

[Sarastro]

Before you buy a new one, it might be a good idea to look at it in operation and make sure that is the problem. There are a lot of things that could cause what you are seeing; a sticking solenoid is only one. I realize this isn't as easy as with the A type, but you still should be able to tell if it's operating. At least, you could check the voltage to see if it's being switched properly.

 

[rwest]

A friend with a J type OD in his TR6 was experiencing the same thing. I removed the solenoid and was able to duplicate the fault by connecting the solenoid to a battery and checked the temperature of the solenoid. After it got above 175 degrees (about 15 minutes) the plunger would no longer retract. If allowed to cool it would retract. I removed the C clip in the end of the solenoid, made sure everything was clean, replaced all the seals and tried again. No help. I stretched the return spring and viola it worked after being on the battery for 45 minutes at a temperature just over 200 degrees. Getting that little C clip out is a right treat and I ended up mangling it on both the solenoids I repaired this way. Mcmaster Carr has a C clip that isn't exactly the same (thinner) but works well. The PN is 99142A330. Hope this helps.

Sorry for the late reply, things just kept getting in the way.

I replaced the overdrive solenoid and everything is now working fine. I also cleaned out the two filters in the overdrive sump and created the "special tool" needed to remove the cylindrical filter out of an old 9/16 socket.

Just one question. I used Penrite GB40 gearbox oil when refilling the gearbox and the overdrive now takes up to 1 second to engage, it seemed much quicker before. It disengages instantaneously, it's just the engagement that feels slightly sluggish. Someone on one of the other forums suggested that GB40 maybe a bit too viscous for our overdrives, does anyone else agree and if so, what oil would you suggest?

Many thanks to everyone's help on this, I'm just so glad that it was external to the overdrive

Cheers, Robert

 

[Sarastro]

Might be the difference in oils, but it might also be the actuator valve adjustment. The valve, on the right side of the OD, should open about 0.030 inches--lots of opinions on what the exact value should be, but the 0.030 seems to work well for me, at least.

 

[mastaphixa]

Sarastro, you may be thinking of the A type overdrive with the valve on the right side. This is a J type and the solenoid/valve are on the left side.

 

[robertrudolphi]

I was told to use non-synthetic 80-90 weight oil, in trans with overdrive

 

[Sarastro]

Sarastro, you may be thinking of the A type overdrive with the valve on the right side. This is a J type and the solenoid/valve are on the left side.

Arrrgggh!! I missed that simple point. I was indeed thinking A-type.