J Type Overdrive - Advice requested

[tr-idr]

Hi,

I have a problem with a J Type overdrive.

At start of a journey, the overdrive will work a few times in the normal manner, but after that it will not disengage. I'm judging that on the rpm for a given speed, and also I know not to use reverse gear when in doubt if the overdrive is engaged. It will sometimes disengage itself, but I can't give an explanation of when that happens. I've checked out all the wiring and interlocks. A test lamp across the solenoid works perfectly in the appropriate gears. I've also removed the solenoid just to have a look at it, and to operate it on the bench. It takes the expected 2A current, but I was surprised at how little movement there was visible within the valve part. Visible movement was less than 0.5mm. I haven't taken out the circlip yet, but it all looked very clean. I've reinstalled it for now, but would welcome anyone's comments on what movement to expect. Failing any progress I intend draining the oil, and checking the filters. If I find nothing wrong then, I guess a new solenoid is the 'cheapest' starting point. Can anyone advise? Thanks.

 

 

[stillp]

Are you saying the solenoid only moves 0,5 mm? If so there's something seriously worong, it should be more like 5 mm.

 

Pete

[tr-idr]

Yes, there is only a tiny bit of movement. 5mm is more like what I would have expected to see. Sounds like I need to get that circlip removed to see what is jamming it up. Thanks for your input.

[Ol Boys]

i have a 1965 TR4A , when in 3rd if i put into overdrive all is fine but if i come off the revs it comes out of overdrive on its own, oddly not in 2nd or 4th, and my apologies i'm not sure what overdrive type ie J type etc, cheers , ol boys

[JochemsTR]

Your OD is working in 2nd gear? Are you sure you have a J-OD?

Jochem

[RogerH]

Hi OB,

the usual OD for the 4A is the 'A' type. This has the OD solenoid on the lafthand side sitting vertical.

 

As mentioned on the other thread the 3rd gear OD fault may simply be the gearstick gaiter pressing on the stick.

 

Roger

[peejay4A]

Your OD is working in 2nd gear? Are you sure you have a J-OD?

Jochem

If he's replaced an A type with a J type or even wired a J type as for an A type then it's quite possible - as I have done although I've never needed o/d in 2nd. I know you're not supposed to have o/d available on 2nd with a J type but I've done it nonetheless. You just need an A type top cover for the gearbox.

[JochemsTR]

Hello Pete,

my understanding is that Triumph Engineers omitted 2nd Gear OD on J-OD due to lack of torque in 2nd gear....

Adding OD to 2nd gear may be possible....however, I have not seen many TR Drivers actually doing this....that was the reason for my questionmark.

Jochem

[Lebro]

TOO MUCH torque I would have thought

 

Bob.

[peejay4A]

I've heard that story too which is why I referred to it in my post but I chose to connect it up as per A type anyway. If for some reason I swap to an A type, unlikely, then I don't have to change anything.

[AndrewP]

to the OP's question..I had a J-type on my Sprint and it used to do a similar trick...engage when cold, then slip/drop when hot.

 

i ended up giving the OD a service which included removing the cover plate off the bottom of the OD unit, removing, cleaning and replacing the O-rings in each of the 3 'pots' and finally stripping down the solenoid and replacing those o-rings as well.

 

As a tip to getting those plugs/pot screw covers off I used a angle grinder pin spanner (you can get adjustable types) and they all came off without any hassle.

 

Then replaced the gearbox/OD oil and it worked flawlessly.

 

Hope it helps and not the easiest fix but worked for me.