Triumph Repair: downshift clashing, dot4, hydraulic line

Question
I have a 1980 Spitfire, and I have rebuilt the transmission, replaced the clutch, and replaced the leaking slave cylinder. About half the time the gears clash terribly when I downshift (almost never on upshift)--when it goes into the lower gear, not when I release the clutch. I've been told there is air in the hydraulic line. I removed the slave cylinder today to re-bleed it (because I was told it would work better that way). I put an entire jar of DOT4 through it with nothing but clear fluid coming out. When I closed the bleeder valve, before replacing the slave into the bell housing, the pedal wouldn't budge. So I reinserted the slave--pushing it as far forward as it would go, and drove it around the block. Still getting the harsh downshift. Anything else I should be looking for?

Answer
Hi Tom,
Your clutch does not know if you are upshifting or down shifting so I doubt you have a clutch problem. The most common is incorrect procedure in down shifting and the second is the use of thick gear oil in the transmission which makes the syncros not work too well. You did replace the syncros when you rebuilt the gearbox?

Down shifting is a lost art today. Any time you down shift you should depress the clutch all the way to the floor and rev the engine once quickly just as you push it into the next lower gear. (Never go down two gears) When it is done correctly and you release the clutch to decelerate, there should not be a jerk in either direction but just a smooth transition to deceleration. It takes practice. Many times in the dealerships I worked in we changed from the gear oil that BLM recommended to engine oil to make the syncros work better.

Here is a test for the clutch. With the car warmed up and at idle (below 1000 RPM) depress the clutch pedal all the way to the floor and put the shift lever into first then pull it into neutral and shift into reverse. If the gears do not clash going into reverse the clutch is ok as far as it's release. The Spitfire and the TR-6 both did not release except with the pedal all the way to the floor even when new.

Let me know,
Howard