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"Kickdown" Overdrive !!


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Hello,

I have recently developed an interesting situation with my D-Type overdrive on the Vitesse.

It engages and disengages perfectly in 3rd and 4th. However, on a frequent basis if I floor the accelerator the OD will automatically jump out - as if manually disengaged and then if I ease off the accelerator slightly the OD will automatically cut back in.

I'm certain that the issue is not electrical and reading another current topic "Lazy Overdrive" I wonder if my OD issue is the solenoid piston.

Pete mentioned in that thread it will do many uncontrolled engages disengages slips this certainly broadly reflects my situation.  

I should emphasise this only occurs when the accelerator is opened swiftly, producing a "kickdown" situation as you would get in an automatic - hence my solenoid suspicion.

The transmission is going to be checked in September, but thought pitching this may be beneficial.

Oil is Castrol EP90 hypoid which was changed earlier in the year with the fluid level always correct.

Any advice, much appreciated.

Thank you.

Richard.

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The D-type is a little marginal on a Vitesse so it doesn't take a lot to cause the problem you describe. It's most likely low oil pressure causing low clamping force, which allows it to slip (and fall back to the unidirectional clutch) under hard acceleration.

Causes of low pressure on a D-type are as Pete says - low oil level, badly adjusted solenoid, rust or similar causing limited plunger travel - plus, unfortunately, wear and tear. The solenoid operates a shuttle that acts as a valve but relies on tight tolerance fitting of the steel plunger in an alloy casing to provide a seal. I had one (on my GT6) that had been abused (electrical problem causing machine-gun rattle of the solenoid) to the point where that tolerance no longer sealed.It would work when cold but start to slip on hard accel as it warmed up, gradually getting worse until it couldn't engage at all. Hopefully that's not the cause of your problem, as I don't think there's a practical fix for it.

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Hi Richard,

grasping at straws here.

This has been reported a number of times on TR's with the 'A' & 'J' type OD.

I assume you have a switch that turns it ON/OFF.

On the TR's it has often been the thick rubber gaiter at the base of the gear stick.

When you floor it the torque of the engine twists the GB and forces the gearstick into the gaiter.  If the inhibit switches are marginal then the twisting may push the stick and then push the 

selector fork  off the switch plunger. 

Either try and move the gaiter away from the stick or reduce the thickness of the inhibit switch fibre washers.

 

Roger 

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18 minutes ago, RogerH said:

Hi Richard,

grasping at straws here.

This has been reported a number of times on TR's with the 'A' & 'J' type OD.

I assume you have a switch that turns it ON/OFF.

On the TR's it has often been the thick rubber gaiter at the base of the gear stick.

When you floor it the torque of the engine twists the GB and forces the gearstick into the gaiter.  If the inhibit switches are marginal then the twisting may push the stick and then push the 

selector fork  off the switch plunger. 

Either try and move the gaiter away from the stick or reduce the thickness of the inhibit switch fibre washers.

 

Roger 

Or using Uncle Petes advice hold the gearstick when od drops out and if od reengages it’s the inhibitor switch needs re positioning . That’s what happened to me in my Vitesse 

Paul 

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31 minutes ago, Paul H said:

Or using Uncle Petes advice hold the gearstick when od drops out and if od reengages it’s the inhibitor switch needs re positioning . That’s what happened to me in my Vitesse 

Paul 

You just beat me to that, Paul!! Try driving and holding the gearstick so that it can't move about as you accelerate / decelerate; this will eliminate the movement caused by the car's motion and keep the cam against the switch. If that works, you may need to adjust the switch or the bracket on top of the gearbox remote assembly to make a better connection.

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we fitted a uprated pump , cant remember the way  its fitted , but was DIY once you removed an internal locking pin and made a simple threaded tube to drag the piston out 

it fitted ok ,

you cant remove the (from memory) the pump piston without separating the OD cases 

pete

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