Page 2 of 2

Overdrive clutch type

Posted: Thu Jun 20, 2019 7:55 pm
by Old and Slow
AFAIK overdrives are built with "sun and planet gears" and are switched in by a solenoid operating a brake band. If there's no brake band the drive passes straight through. however if there's some debris in the O/D then this might put your trip to France at risk. I wonder if flushing out with a couple of oil changes might be a quick solution, not to get the O/D working, but to minimise the likelihood of something else going wrong.
Greater experts than me might have a view on this.

Overdrive clutch type

Posted: Thu Jun 20, 2019 8:24 pm
by Oldconn
My understanding is that the overdrive has a double cone clutch. One face at a time is engaged, while the other face is free to spin. If either face is worn out, you can experience slip , whether in direct drive or in O/D. Mine is beginning to slip slightly in direct, but not in O/D. So if you lose one side of the lining entirely, I would imagine you would lose drive completely. Could you piece of debris be a segment of a cone-shaped band of clutch friction material?

Overdrive clutch type

Posted: Thu Jun 20, 2019 8:34 pm
by gtcse8
Sorry Phil but you can`t "Flush" an OD unit, not in the way you can Flush an engine by replacing the oil after running the car.

The OD picks up the oil from the GB and then pressurises it through an eccentric pump driven by the gearbox outpout shaft, the oil does not get splashed around, as it does in the engine by the crankshaft.
The oil then drains back through the casting of the OD back into the GB.
Mark

Overdrive clutch type

Posted: Thu Jun 20, 2019 9:12 pm
by jag12
The overdrive uses the gearbox oil not engine oil :D

Overdrive clutch type

Posted: Fri Jun 21, 2019 7:48 am
by gtcse8
EDIT :roll:

I had engine on my mind with reference to "Flushing after running.
The point I was trying get over was that the engine oil has a far harder life than the GB oil.
The engine oil is sent to the top of the heads and then flows back into the sump, hitting the camshaft and crankshaft and being violently thrown against the inside of the block, thereby washing any contaminates into the sump.

The GB oil has a far easier route, and is only "Stirred up by the gears in the GB section.
The bit that is collected by the eccentric pump is then pushed through the hydraulic clutch at the rear of the box, then it simply drains back into the bottom of the box. :lol:

Overdrive clutch type

Posted: Fri Jun 21, 2019 9:43 am
by Rev Light
Just to note - I did actually send a picture to the specialist mentioned in a previous post, but have not yet had a response.

Overdrive clutch type

Posted: Fri Jun 21, 2019 12:29 pm
by halfpenny
Give him a call; he's very reasonable, but you will have to contact him

Overdrive clutch type

Posted: Fri Jun 21, 2019 4:47 pm
by Old and Slow
Thanks to all above for clarifying my initial (inexpert) comment. I don't think I'd risk the trip to France then. :cry:

Overdrive clutch type

Posted: Sat Jun 22, 2019 10:24 am
by Rev Light
I am the eternal optimist. I will be cruising on the lesser roads at lower speeds.

Mark is going to supply me as used overdrive, which will keep thing simple when it is time to change. More ducks to line up.

Steve.

Overdrive clutch type

Posted: Sat Jun 22, 2019 3:24 pm
by David Tew
When you change the OD make sure you fit (or make) the correct gasket with an oil-return hole at the bottom. I've seen them assembled with a plain gasket which causes oil to collect in the OD rather than doing it's job in the gearbox. :wink:

Overdrive clutch type

Posted: Sat Jul 06, 2019 10:29 am
by Dennis Nicholas
Rev Light
Have a look at http://www.buckeyetriumphs.org/technica ... 1/JOD1.HTM
All will be revealed.
Bear in mind that Scimitar GTE Overdrive introduced from Chassis No. 932478 incorporated gearbox and overdrive units of a new design.
Also google J type Laycock overdrive units. Popular motoring did a good strip/overhaul article (Nov 1977).
Also Moss Europe have a good exploded diagram for J spares for Triumph Spitfire.

That will keep you busy for a while :)

Dennis

Overdrive clutch type

Posted: Sat Jul 06, 2019 11:05 am
by Dennis Nicholas
Looks like buckeyetriumphs have changed their webpage set up. Try https://static1.squarespace.com/static/ ... Part+I.pdf

There are subsequent parts 11 and 111. Just search on their site "J type overdrive".