Hey all,

Gear Grinding while parked. When I push the clutch in, I can hear everything spin down, but when I go to push it into gear (Reverse, 1st) I can FEEL two surfaces grinding as I push it into gear, and it DOES grind, even though the clutch is bottomed out. I JUST replaced the Brake master, reservoir grommets, blue hose, Clutch Master, AND clutch slave. The Clutch Master I received was actually the old style WITHOUT the longer spring and stem. I bled the system with a power bleeder from the slave while pumping the pedal per WSM, and even did the cockpit burp on the Clutch MC. Can't figure out why something is still spinning under there when the clutch is depressed to the floor. ANY help would be great. Thanks guys.

 

Did it grind before you did the work you just completed, or is this a new problem?

 

When I received the car it had so many issues it'd be easier to list what still worked rather than problems, but yes. Getting it to the house was an issue as it ground in 1st and 2nd going down the road, but didn't notice the fine grinding until I had finally replaced the entire hydraulic system. So issue persisted. As far as if it is better than it was, that's hard to tell...

EDIT: Worth mentioning that if I force the car into Reverse/1st through the grind, taking it out of that gear and into any gear after that does not cause grinding UNTIL I release and reapply the clutch, then grinding into gear starts again.

 

The synchros in your transmission are hating what you are doing. They just asked me to ask you to please stop and repair the problem, before you destroy them, any further.
Review the work you just performed:
Is the blue hose running continuously downhill from the reservoir to the clutch master? (The blue hose should "pass" along the side of the power brake booster right a the "3 o'clock" position. If you left the new hose long (as almost everyone does) it will be below this position, the result of which allows the hose to drop below the clutch master. There is forever be a trapped bubble in this hose, if this is the case.....making bleeding very difficult.
I haven't "seen" a replacement clutch master for a dual disc clutch with the proper length plunger and spring.....for over 15 years. I question this, but perhaps someone finally grew a brain cell and has cured this issue at the manufacturer's level. (I'm very doubtful.)
Bleeding these system is a genuine...bitch. The easiest solution is to buy my custom clutch hose, which eliminates the metal line above the starter and the flexible hose to the sway bar attachment and "reverse bleed" the system. This turns an agonizing job into a 4 minute process. At any rate....you need to make sure the system is completely bled and there is no air in the lines from the master to the slave.

If the gears still grind, after the above is absolutely perfect, you have a clutch "issue".

 

I ran the new hose down and right up against the booster to the supply line nipple on the MC, so there are no dips, but I'll double check. Could you send me a link to your custom hose?

Also, could it be the syncos are already shot? Previous ownership maintenance was non-existent (drilled screws through interior panels to keep them up, never serviced transaxle (done now, no metal shavings), etc. Do these syncos kick in at idle, parked?

 

Yes, most of these transmission have "synchro problems", usually in 1st and 2nd....sometimes third.
There's no synchro in reverse, in your car, so reverse is a great way to judge clutch release. You should be able to push the clutch down, count slowly to 2, and engage reverse, without grinding.

Sorry, my website is decades old.
There's a debate between my wife, my son, and me that we actually have the time to increase our workload.
My custom clutch hose has been discussed, on this Forum, many times. I'll see if I can find you a link to one of those discussions....if someone doesn't beat me to it.

 

Did you replace the release arm bushing?



Greg Brown clutch flex line in the gray

 

Release arm bushing? Not sure which that is. Haven't replaced any bushings though.

 

you will have to remove the air cleaner base to see the top of the release arm,
the bushing is between the pivot ball and the release arm,
I like to use a dremel to open up the bushing so its easier to press onto the ball

 

Just read up on release arm bushing replacement. Seems fairly straight forward. It's a pain to drop part of the exhaust to get in there, but if it needs to be done, it is what it is. Also, big fan Merlin. Have read many-a-post where your solutions have solved the problem. Here's to hoping. Bushing on order, hopefully I can get a link to that flex hose for the slave later.

 

A failing pilot bearing and dry (un lubricated) or worn stub shaft splines can also contribute to these symptoms.

 

When I got my '79, the low gear synchros were shot. Couldn't downshift into second without double-clutching, even upshifts would occasionally grind without a very long pause in neutral on the way between gears. Had a supercharged engine that should have resulted in a fast car, but because of the transmission, couldn't take advantage of the powerplant benefits. Scrapped it and put in a Corvette Z06 6-speed transmission and it made a world of difference. Not only can I shift the car like a normal MT, but the gear ratios of that trans and having an extra gear make much better use of the power added to the motor. I can now cruise at 85 or 90 MPH at 2,000 RPM in 6th gear.

Obviously try to get what you have working properly, but if it turns out to be an internal transmission issue, weight the costs of fixing the MT against going to something more modern that shifts better, even compared to a properly working 928 MT, which is still fairly notchy and slow, even when not grinding.

 

Check out some of threads under my username from the past 8 to 12 months. I went through a full clutch rebuild, TT rebuild, and trans swap (due to the original trans having grinding issue in 2nd). Hopefully some of what I went through, and the excellent advice offered in those threads by Greg/MrMerlin/Rob/Ed/etc might help you out.

What I’ll tell you is that I thought all I needed was to swap the trans to fix my issue. But my clutch was somewhat in shambles when I dug into it all. It’s incredible how well the car drove prior to my work despite all of the issues hidden beneath the surface. These cars are tanks imho.