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A type overdrive issue


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Hi

 

I have been getting inconsistent issues with my A type OD, Solenoid always clicks, but delay in OD engaging, but it always would, today, engage OD, and it either does nothing, no drop in rpm... or no drive at all which seems to happen now 90% of the time, but normal service resumes with OD off.

 

Oil levels are ok...

 

Any ideas, or pointers appreciated.

 

Thanks

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The A-Type has an oil collector where oil under pressure is stored for the moment

the switch is pressed to let the oil immediately swap behind the pistons to transfer

the cone clutch to the other side.

 

If there is a delay the hydraulic area is suspicious, often the collector is scratched

due to debris in the oil from gearbox. That makes scratches on liner and piston

and also makes defects on the piston rings.

 

Also pump and valve should be checked like switch pistons and filter cleaned.

 

To verify this the pressure at the switch valve should be measured before the

gearbox is taken out of the car!!!

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Read the Buckeye articles:

http://www.buckeyetriumphs.org/technical/AOD/AOD1/AOD1.htm

 

The OD is much easier to work on than the gbox.

 

Try a pressure gauge:

https://www.flickr.com/gp/90670218@N04/G90135

 

Thats interesting, I have rebuilt many TR / Stag type gearboxes, but have never tackled an O/D perhaps I should next time (hope there won't be a next time)

 

Bob.

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If we are still talking about the A-Type it makes sense to look after

the OD when gearbox is refurbished.

 

There are two reasons: Other than the J-Type many hydraulic parts can

not be accessed that easily from underneath/outside.

The other reason is that the A-Type always provides pressurized oil to switch

immedeately what needs a constant pressure in the hydraulic system.

 

This causes more wear on the pumping system and the accumulator piston

moves always during drive.

When the gearbox looses some debris that is not catched by the filter it will surely

find its way into the accumulator causing scratches and wear there.

 

So a worn gearbox in front of an A-OD is always a hint to take a look inside the OD.

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There are a lot less parts in an O/D than a gbox.

You need a few "special tools" but these can be improvised from bits of pipe and such:

 

I'd say this is a practical overhaul for many keen mechanic-types.

 

It's easy to make a rig to test it before you fit in the car.

This can save a load of work.

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