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

[TonyC]

Hi Robert, a fellow member has had pretty much the same problem. His OD would engage but not dis-engage until everything cooled down again. Turns out the solenoid was fouled with a lot of sludge/ debris. The chap who fixed it cleaned the solenoid, withdrew the overdrive sump filter ( both the rectangular version on the inside of the sump plate, and the cylindrical version removed with a special two pronged tool). I would suggest you focus in the solenoid. Easy removed from underneath the car with a 1” AF crowfoot spanner. That special tool you need for the cylindrical filter once you remove the OD sump cover can be fashioned out of an angle grinder disc removal tool. 

Hope it helps.

TonyC

[TonyC]

Sorry Robert forgot to mention - reversing with OD engaged is a definite No No. Severe internal damage can result.

BTW there are three cylinder plugs which you see when the OD sump is removed. The filter is in the one adjacent to the nameplate riveted to the outer housing. Check the Moss catalogue for more detail.

TonyC

 

[Nigel Triumph]

I've had very similar failure to disengage when hot from a J- type overdrive. It was a sticky solenoid, just as Tony has described.

Nigel

[rwest]

Thanks TonyC & Nigel, I'll take a look at the solenoid and see if it can just be cleaned or whether it'll need replacing.

Cheers, Robert

[rwest]

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

[RogerH]

Hi Robert,

 

Penrite GB40 is a good oil for the OD/GB.  I think TRiumph actually states SAE 90.

Not sure but there may be air in tge oil and could take time to pickle out.  I'm sure there may be a better answer winging its way here

 

Roger

[Drewmotty]

GB40 is actually a 25W/70 oil so a bit less viscous than SAE90. It’s the best I’ve found for our overdrive gearboxes. 

[stuart]

I take it youve rechecked the oil level now its been run for a while?

Stuart.

[Steve-B]

As a newbie-ish owner, I've been told that one should always push the clutch in before engaging the OD(or disengaging it). Is this an old wives story or true?

I've only got the shop manual and not the original owners manual so can't seem to get an answer via google...

[RobH]

12 minutes ago, Steve-B said:

I've been told that one should always push the clutch in before engaging the OD

Bad advice - completely unnecessary and just what you should not do.

[Hamish]

1 hour ago, Steve-B said:

As a newbie-ish owner, I've been told that one should always push the clutch in before engaging the OD(or disengaging it). Is this an old wives story or true?

I've only got the shop manual and not the original owners manual so can't seem to get an answer via google...

Steve

whilst I sprint and hill climb my car it is used on the road and both on road and track I can change up using A type OD at big revs and full throttle

[TRTOM2498PI]

Using the clutch is not required for a standard o/d unit.  It is certainly not required if on full throttle at say circa 6500 RPM + on flat chat, you can just engage o/d and off you go. In fact, a competition can be that fast and fierce, that if you use the clutch, o/d will be activated before you even release the clutch pedal !

[stuart]

Always keep your foot down when changing in and out of overdrive, never use the clutch, thats the whole point of electric overdrive being instant gear changes.

Stuart.

[Rod1883]

Interesting Stuart.

The J type on the Stag changes in, and especially out, far more smoothly if the throttle is eased off at least a little. The A type on the TR2 performs more smoothly with a bit of throttle - both in and out.

[Mike C]

5 hours ago, Hamish said:

Steve

whilst I sprint and hill climb my car it is used on the road and both on road and track I can change up using A type OD at big revs and full throttle

+1

[Steve-B]

 thanks guys, a myth I thought was actually is, well done all