Triumph Repair: overdrive or clutch slipping, cone clutch, clutch pressure plate

Question
Jim, I resently bought a 1980 spitfire, it had a new clutch, pressure plate and bearing, something is slipping in the drive line. I replaced the clutch master and slave cylinders, still slips. The over drive seams to work ok, I can feel it up shift and down shift and see it on the tach also. I have tied diffent tests to isolate the probem, like first gear, it will spin the tires with out slipping but when shifting to second it slips badly. I tryed starting off in third gear and it seamed to not slip, the longer I drive the car the less it seems to slip then when cold. I have not checked the oil level in trans nor clean any of the trans filters, solenoid valve. I have checked for oil leak on the floor for maybe the main bearing leaking, I don't see any thing, I live in NW arkansas not a lot of British techs around there, I did talk to a trans guy, he asked me if it had a stepped flywheel. being someone could have turned the main face down only thus reducing pressure to the disk? I'd like pin point the probem before pulling the trans and sending it off. What do you think Jim ?

Answer
HI Jim,
There are three clutches in an overdrive car. The main engine clutch and two cone shaped clutches in the overdrive unit.
The overdrive is a two speed auto trans with a cone shaped clutch. When you are not in overdrive the cone clutch is spring loaded to a metal cone attached to the out put shaft and is just direct drive. When you put it in overdrive, an oil pump pushes the cone clutch in the opposite direction and locks into a different metal cone attached to the case and that starts a set of sun gears turning to give you a higher gearing. The clutch lining on each side of the cone are independent of each other so it is unusual to ware out both at the same time. This means if it were slipping in direct drive (out of OD) it is unlikely to effect the drive in OD. So if you note slippage when you are in OD and out of OD it is most likely an engine clutch problem and not an overdrive problem.

However, a faulty clutch hydraulic release system can hold a clutch partially disengaged to make one slip too. So first make sure you have a little free play in the clutch pedal.
If all of that is ok, you do have to remove the clutch to find the problem. A transmission can not slip so you don't need to send it off anywhere.

Howard