More M6 gear grind issues..

[BadSport340]

Originally Posted by booneSS13

Now it's mainly 3rd gear. When I granny shift it into 3rd, the shifter goes into gear and it grinds for a moment and as it's grinding when I give it gas it revs up like it's in a neutral state (Almost like an automatic transmission that won't move the car when the gear is going out) then after maybe 5 seconds it engage and moves the car. Praying that this transmission isn't toast

There are only so many things that can cause a transmission to grind. You just have to find out if it's caused by something internal (such as bad synchros) or something external (clutch not disengaging, bad shifter, etc.).

If the pressure plate wasn't disengaging the clutch, then you likely wouldn't be able to put it into gear with the motor running. The clutch and input shaft need to spin freely in order for the synchros to function properly. If the clutch is still spinning with the motor, then the transmission input shaft and gear cluster will be spinning with the motor too. Grinding happens when there is an RPM difference between the dog teeth on the side of the gear, and the collar that's trying to slide over those teeth. A seized pilot bearing can have a similar effect because it causes the input shaft to spin with the motor even when the clutch is disengaged.

Now.. some questions...

-When did it start grinding?
-Is the grinding getting worse/changing?
-Does it go into first easily?
-Are you SURE the shifter is FULLY engaging the gear?
-How does it act when shifting quickly/firmly and also normally at low RPM's?
-How does it act when shifting quickly/firmly and also normally higher RPM's?

Try to keep things simple. If you're only having problems under certain conditions, then what about those conditions would cause the problems you're having? If you can drive around town normally with no issues, but it grinds going into 2nd at redline, then your synchros probably aren't grabbing like they should. Issues like a bad pressure plate or shifter might be more apparent all the time or in other conditions.

Anyways, just food for thought Good luck on figuring this all out.

[BenningJ]

I have the Hurst Pro-Billet Short Throw in my car. Had it since I took delivery of the car. I now have 52,000 miles on the car. At first I was having issues with the 1st-2nd shift only. When I did my cam swap I went with Redline D4 ATF in the transmission and couldn't be happier. Very rarely do I get the 1st-2nd grind and if I do I chalk it up to a mistake by me.

[acammer]

Originally Posted by BenningJ

I have the Hurst Pro-Billet Short Throw in my car. Had it since I took delivery of the car. I now have 52,000 miles on the car. At first I was having issues with the 1st-2nd shift only. When I did my cam swap I went with Redline D4 ATF in the transmission and couldn't be happier. Very rarely do I get the 1st-2nd grind and if I do I chalk it up to a mistake by me.

I think a big piece of it is learning to "drive" around it. The only time I grind the 1-2 is when I make a hard/fast 1-2 on "auto-pilot" - ie. paying close attention to something else and relying on muscle memory without any brain input to the shift routine. Then I pull the gear with the short-throw faster than I get the clutch in and pull a grind. If I give even a fleeting though to the shift I remember not to rush it, and it can still be quick and grind free.

It's frustrating because I feel like I'm re-learning how to shift hard/fast with this car. I've had a bunch of other stick cars including a T-56 equipped '96 Z28 and never once had this problem. I'm definitely going to try the Redline D4 ATF and an IdealGarage master cylinder to see if I can resolve it completely, but for the most part, mine just requires some intentionality to not rush the shift and out-run the syncro.

[booneSS13]

Originally Posted by BadSport340

There are only so many things that can cause a transmission to grind. You just have to find out if it's caused by something internal (such as bad synchros) or something external (clutch not disengaging, bad shifter, etc.).

If the pressure plate wasn't disengaging the clutch, then you likely wouldn't be able to put it into gear with the motor running. The clutch and input shaft need to spin freely in order for the synchros to function properly. If the clutch is still spinning with the motor, then the transmission input shaft and gear cluster will be spinning with the motor too. Grinding happens when there is an RPM difference between the dog teeth on the side of the gear, and the collar that's trying to slide over those teeth. A seized pilot bearing can have a similar effect because it causes the input shaft to spin with the motor even when the clutch is disengaged.

Now.. some questions...

-When did it start grinding?
-Is the grinding getting worse/changing?
-Does it go into first easily?
-Are you SURE the shifter is FULLY engaging the gear?
-How does it act when shifting quickly/firmly and also normally at low RPM's?
-How does it act when shifting quickly/firmly and also normally higher RPM's?

Try to keep things simple. If you're only having problems under certain conditions, then what about those conditions would cause the problems you're having? If you can drive around town normally with no issues, but it grinds going into 2nd at redline, then your synchros probably aren't grabbing like they should. Issues like a bad pressure plate or shifter might be more apparent all the time or in other conditions.

Anyways, just food for thought Good luck on figuring this all out.

Thanks a lot. It does it not matter what rpm I'm at. If I try to shift quickly from second to third it completely blocks me. Sometimes with no grind. Almost as if I didn't even push the clutch pedal in. But if I hang the shifter there or pull it out and put it back it it goes in eventually. I've noticed over the past couple days I don't have this problem with granny shifting at any rpm. This started maybe 600 miles ago

[booneSS13]

Originally Posted by BenningJ

I have the Hurst Pro-Billet Short Throw in my car. Had it since I took delivery of the car. I now have 52,000 miles on the car. At first I was having issues with the 1st-2nd shift only. When I did my cam swap I went with Redline D4 ATF in the transmission and couldn't be happier. Very rarely do I get the 1st-2nd grind and if I do I chalk it up to a mistake by me.

it's mostly 2nd to 3rd for me same here I'm going to have to assume user error when I was having issues before from 1st to 2nd. I'm going to try the redline d4 next week and see

[booneSS13]

Originally Posted by acammer

I think a big piece of it is learning to "drive" around it. The only time I grind the 1-2 is when I make a hard/fast 1-2 on "auto-pilot" - ie. paying close attention to something else and relying on muscle memory without any brain input to the shift routine. Then I pull the gear with the short-throw faster than I get the clutch in and pull a grind. If I give even a fleeting though to the shift I remember not to rush it, and it can still be quick and grind free.

It's frustrating because I feel like I'm re-learning how to shift hard/fast with this car. I've had a bunch of other stick cars including a T-56 equipped '96 Z28 and never once had this problem. I'm definitely going to try the Redline D4 ATF and an IdealGarage master cylinder to see if I can resolve it completely, but for the most part, mine just requires some intentionality to not rush the shift and out-run the syncro.

Yeah I've been driving around it too lately it's really frustrating. As long as I granny shift it into 2nd-3rd it's fine but like you say if I try to go too fast it will lock me out 100% of the time now. I don't understand because this has just started 3 or so weeks ago. This is definitely frustrating.

[acammer]

Originally Posted by booneSS13

Yeah I've been driving around it too lately it's really frustrating. As long as I granny shift it into 2nd-3rd it's fine but like you say if I try to go too fast it will lock me out 100% of the time now. I don't understand because this has just started 3 or so weeks ago. This is definitely frustrating.

If yours started suddenly and is rapidly getting worse I think that points to a transmission failure of some sort, syncro related. If it was all gears, I'd blame the clutch, but it's it's special to just the 2-3 shift, there's your problem. I'm afraid my 1-2 shift will turn into a more serious issue some day. I gotta stop banging into it and it'll probably be fine. Let us know what you find.

[lkurek]

I vote for the throwout bearing wasnt verified/shimmed properly. This must be done or the clutch wont release properly......and that means grind time. Which will KILL your trans in no time. Get this fixed ASAP

[booneSS13]

Originally Posted by lkurek

I vote for the throwout bearing wasnt verified/shimmed properly. This must be done or the clutch wont release properly......and that means grind time. Which will KILL your trans in no time. Get this fixed ASAP

if that was the case wouldn't it effect all gears?

[acammer]

Originally Posted by booneSS13

if that was the case wouldn't it effect all gears?

Exactly - if it's only one shift that's experiencing the problem, you can pretty much rule OUT the clutch.

[booneSS13]

Originally Posted by acammer

Exactly - if it's only one shift that's experiencing the problem, you can pretty much rule OUT the clutch.

Yeah hopefully I don't have to pull this transmission. I'll change to redline and see what happens

[booneSS13]

Here's a video of what I'm talking about to make it a little more clear. No grind just like I hit a wall when trying to go to third.


https://youtu.be/11d0gE02_Tw

[lkurek]

I didn't realize it was only one gear having this issue. If it's only third this happens with...definitely a synchro or bent fork issue. The aluminum forks have a tendency to bend with one or two missed shifts.

Only thing I can think of...and fluid won't help it, unfortunately

[butch2000]

Or the pads are off the fork ? so you will not get a full engagement from the fork , I have had a few cars with the tremec and none of them like being power shifted , it chews up the teeth on the sliders ?