gears grinding when shifting

[longbridgehealey]

So I had two problems going on at once. I was losing clutch fluid from the master cylinder when shifting, and the gears were grinding when shifting, requiring several pumps of the clutch to shift. So I started with the master cyl, and replaced it last night. Cured the leak, but still have the shifting issue. Gonna replace the slave cyl on Monday. Any thoughts on the grinding of the gears? It can be in any gear, but does not happen all of the time in any gear. Rapid pumping allows smooth shift....
(Oh, 1969 sprite)

Thanks,
Larry

 

[Jim_Gruber]

Air in the line, rebleed, and rebleed

 

[longbridgehealey]

OK, that's what I'll do. I thought I got it all, but probably I didn't. Thanks!

 

[Deleted member 8987]

Quick check on release point. Park nose down on an incline, engine off, first gear......slowly depress the clutch pedal (no pumping) and see at what point the car starts to roll. If it's air or hydraulics, you will probably see two inches from the florboards.

 

[longbridgehealey]

Car starts to roll after maybe an inch of pressure.

We've bled and bled and rebled. Still have the problem
She shifts great for the first ten minutes or so, then after it heats up, it starts to not want to downshift from third to second. I can pump the clutch five or six times, and get pressure up, and then it shifts great again for a minute or two. Also, it will occasionally creep forward from a stop when in first with no brakes. From my non-lbc friends, I'm hearing both "you need a new clutch" and "you need to rebuild the transmission". What I don't understand (amoung a million other things) is why it shifts great for the first couple of minutes. If the gear box or clutch were bad, wouldn't it be bad all of the time?

Thanks,
Larry

 

[JohnnyO]

When was the last time you changed all of your hydraulic fluid? Hydraulic fluid wears down when it gets heated (which is always) and it absorbs moisture over time which also dilutes it's effectiveness. Could be why your system works ok in the beginning, but as it heats up you lose the effectiveness of the fluid. You should drain your whole system, brakes and clutch hydraulics and replace with the highest rated heat index fluid you can find.

 

[longbridgehealey]

Hi Johnny - We've bled the clutch so much over the past couple weeks that I can't imagine there is any old fluid left in there. However you never know, will give it a try...

Thanks!

 

[Gerard]

I can pump the clutch five or six times, and get pressure up, and then it shifts great again for a minute or two. Also, it will occasionally creep forward from a stop when in first with no brakes.

These two descriptions indicate to me that you have a seal not holding pressure. It could be a pitted bore in either the master or the slave or just a seal that is worn past it's tolerance. I've also seen instances where you can get a little piece of debris lodged under the lip seal that will allow pressure to drop. If the "heat issue" is real, that would make me suspect the slave first. You might have just enough heat expansion to make the seal marginal. What you should do is have someone sit in the car with the clutch fully depressed and and you watch to see if the slave push rod slowly moves to the return position (you don't need the engine running for this test). That'll give you your answer if it the transmission or the clutch. From all you've described, my bet is on the latter. I think also that the 1" bore slave in the '69 does not have a circlip retainer. Pull back the rubber dust cup and see if it full of fluid or if at rest. the piston is way at the exit end of the bore

How long since either or both the slave or the master were rebuilt or replaced?

 

[longbridgehealey]

Hi Gerald - Both the master and slave replaced two weeks ago...Had a leaking master cyl and just decided to replace rather than rebuild. We had this shifting problem before master and slave swap. Figured the leaking master was allowing clutch pressure to drop, but I guess I was wrong.

 

[Gerard]

I still suggest you check for push rod movement while holding the pedal to the floor. If it holds steady, then either you have too much free play or your synchros are the problem.

You could also be loosing travel as a result of wallowed out pivot points in the clevis pins at the pedal or push rod. Also, check that you have the correct push rod length, It should be 2 11/16” from hole center to end. Replace the push rod if it is the incorrect length or either the clevis pins or push rod is worn.

 

[DrEntropy]

And check the master cylinder clevis pin and the hole in the pedal it goes thru for ovality, too.

But as Gerard has said, sounds like fluid getting out of the system around a cup or seal. Don't count on "new" being "good" necessarily. If you see no fluid evidence at the slave, the issue most likely is internal to the M/C.

 

[longbridgehealey]

Thanks Doc and Gerald - that's a couple things to check on. I'll let you know how it goes.

Larry