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A-Type Overdrive and slipping


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I am getting close to getting the TR6 re-registered and back out there on the road.

 

A few cursory test drives around the block highlighted a few things to sort out, but the most worrying is that I get what feels like clutch slip but only in 2nd gear.

 

Having used the search function, the worst case seems to be that it could be the uni-directional bearing is shot but the overdrive was rebuilt not long before the car went off the road and the diagnosis was all OK in the overdrive and box. Its probably done < 5,000 miles since. Clutch was replaced at the same time and there are no noises or anything that would suggest a problem.

 

I havent had an opportunity to do the basics like check G/B oil levels since its been re-fitted, but out of the car (prior to mating it up to the engine) the level was checked and no noticeable leaks have occurred since.

It didnt do this before it went off the road either.

Are there any other checks I could do before stripping the box out again to replace the uni-directional bearing?

 

Could it be the A-type clutch being dry after 4+ years of inactivity and drying out?

 

Breaking it to me gently, but what else could it be?

 

Thanks for any advise.

 

Andrew

Edited by AndrewP
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Hi Andrew,

Might as well be the normal clutch.

Does the clutch mechanism fully release?

Check the fork on side of bell house.

Cheers,

Waldi

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I'd assume that the clutch doesn't slip with the OD off.

 

2nd imposes huge torque loads on the OD- that's why it seems to have only allowed by Triumph on early TR6's with A type OD's. Some may argue it wasn't a roaring success even then.

 

I'd check things that have been disturbed during the reinstallation- wiring and solenoid adjustment. And make sure you don't have super slippery GL5 in the gearbox- the torque of a rebuilt engine may be enough to make a previously functional OD start slipping.

 

I've never heard of a problem with the clutch drying out- but if it is the cause it may improve with use.

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Thanks for the replies.

 

I`ll go through the basics and see what it throws up.

 

I may drop the filter off the OD and see if there are any worrying bits.

 

I have checked that all the inhibitor switches work and that the solenoid clicks in and out smartly, so Im happy that if the UD bearing is knackered its more old age rather than reversing and damaging it.

 

Never a dull moment!

 

Andrew

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Forgot..one question/clarification.

 

So if whilst driving it slips with no OD engaged (so all the power being transmitted through the OD clutch) and no slip when in OD...this indicates its the OD clutch lining on its way out?

If I drive and lightly press on the clutch pedal and it slips (or flooring it in 4th) then it's the main clutch (engine to gearbox)

What would a test for the uni-directional (sprag) bearing be?

 

Thanks

Edited by AndrewP
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I've never pulled my A type apart but I'd I'd agree slippage in 2nd when the OD is "off" is probably the inner lining of the cone clutch or its springs.

 

If you get clutch slip in top (with feet off the pedal ) but not in the lower gears it's probably the main clutch.

 

Can't think of any test for the sprag bearing other than a close examination of the particles attached to the OD drain plug magnet!

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I've never pulled my A type apart but I'd I'd agree slippage in 2nd when the OD is "off" is probably the inner lining of the cone clutch or its springs.

 

If you get clutch slip in top (with feet off the pedal ) but not in the lower gears it's probably the main clutch.

 

Can't think of any test for the sprag bearing other than a close examination of the particles attached to the OD drain plug magnet!

Hi Andrew,

 

Maybe my above comment on the cone clutch is incorrect. This article discusses the operational modes of the OD and under mode 2) the cone clutch can't slip in forward gear unless the sprag clutch slips:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&ved=2ahUKEwjpv9HY3cPdAhWLUrwKHSO8Cx8QFjAFegQICRAB&url=http%3A%2F%2Fobswww.unige.ch%2F~wildif%2Fcars%2Ftech_talk%2Foverdrive_frame.htm&usg=AOvVaw29EKkNl1wbWda4FXxe_nmu

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Hi Mike,

Many thanks for taking the time to reply with the info. The OD is one of those items that makes 95% sense to me, but it's the operation of the sprag bearing that confused me.

I admit I'm not 100% clear in my mind but I'll assume the statement that it's so that engine cannot speed up during the OD is engaging.

Somewhat reassuringly the statement of " If your engine is able to speed up when you engage the OD, then the sprag clutch is not working" in my case sounds like it may be the OD lining rather than the sprag bearing chewing itself up as it's when the OD is disengaged and accelerating in 2nd in my case.

Either way a few more drives should assist with a bit of diagnosis.

 

Thanks again

 

Andrew

Edited by AndrewP
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Just a minor update,

I had another chance to take the car round the block yesterday and to somewhat my relief it slips in all gears.

Further checking showed that the slave rod was way too far protruded and not returning back fully and I can only assume loading the clutch.

Then..further checks show the master weeping, and so its a complete clutch hydraulic system strip and rebuild :(

Fingers crossed it will fix the issue and Im able to test when Im next able to get it out.

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Hi Mike,

Agree, but it's slipping in all gears.

I think what's happened is for whatever reason the slave has gone beyond its limits and can't return fully as even with the arm disconnected, I can't push the slave rod back.

Probably a strange bit of luck as well finding the master was leaking too before it did damage to the paint.

Anyway, a night or two in the garage will see it fixed and hopefully fully functional again.

Cheers

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