Question re: Clunky / Grinding Shift
06-08-2015, 01:42 PM
#1
Intermediate
Thread Starter
Question re: Clunky / Grinding Shift
Car details:
- 2K11, GT3 RS
- 4.0PP, t/o bearing, clutch disk installed last year
- 20K KMS, 2K KMS on above parts
- During above service had, coolant lines pinned and vario-cam bolts l/t'd.
When the car is cold, I don't rush the shifts, the gear lever into 2nd, 3rd and 4th is generally clunky.
As things warm up, I can definitely feel things moving a tad more smoothly but the gear change is never what I would call really sweet / clean. I'm assuming this is normal and the nature of the shorter / firmer shift?
THE CONCERN
At a lapping day ~2 weeks ago, coming into a 3rd gear corner from 4th (damp track), put in the clutch, hard on the brakes (ABS), heel / toe to 3rd and have a gear grind.
Go around again, slow the shift on the same corner, same issue (less grind).
As described this definitely sounds like user error / bad timing on lever / clutch for this particular corner.
That said, I'm curious if something was improperly assembled / shimmed during rebuild given the clunky-ness during normal use. Perhaps exacerbated at higher revs under faster conditions? Synchro's? Gear Oil? Ham fisted? Tranny Mount?
What kind of damage can be done during a grind like this?
- 2K11, GT3 RS
- 4.0PP, t/o bearing, clutch disk installed last year
- 20K KMS, 2K KMS on above parts
- During above service had, coolant lines pinned and vario-cam bolts l/t'd.
When the car is cold, I don't rush the shifts, the gear lever into 2nd, 3rd and 4th is generally clunky.
As things warm up, I can definitely feel things moving a tad more smoothly but the gear change is never what I would call really sweet / clean. I'm assuming this is normal and the nature of the shorter / firmer shift?
THE CONCERN
At a lapping day ~2 weeks ago, coming into a 3rd gear corner from 4th (damp track), put in the clutch, hard on the brakes (ABS), heel / toe to 3rd and have a gear grind.
Go around again, slow the shift on the same corner, same issue (less grind).
As described this definitely sounds like user error / bad timing on lever / clutch for this particular corner.
That said, I'm curious if something was improperly assembled / shimmed during rebuild given the clunky-ness during normal use. Perhaps exacerbated at higher revs under faster conditions? Synchro's? Gear Oil? Ham fisted? Tranny Mount?
What kind of damage can be done during a grind like this?
06-08-2015, 01:55 PM
#3
Rennlist Member
When was fluid changed last and how often do you change?
What fluid do you run? Delvac? It's balky when cold, but sweet when hot.
Drop the fluid, inspect the color, inspect the magnet. Should just be normal sediment. No metal chunks on the plug. Metal chunks... drop tranny and ship it off to get opened up.
Regarding the action/feel, could be synchros, could be something in the clutch not releasing right. The 4.0 PP seems to have some issues - I'm putting a new one in mine now as we believe it is warped and not allowing full disengagement of the clutch. Mine has about 25 track days on it. Something in the springs are off alignment getting some sort of heat stress not allowing TOB to slide perpendicular to the guide tube.
Anyway, I'd start with the clutch, specifically: TOB, Guide tube, bushings & shims, shift fork, and Pressure plate. Most likely your flywheel and disk are fine.
If the problem persists good chance its internal and you have a syncho going.
What fluid do you run? Delvac? It's balky when cold, but sweet when hot.
Drop the fluid, inspect the color, inspect the magnet. Should just be normal sediment. No metal chunks on the plug. Metal chunks... drop tranny and ship it off to get opened up.
Regarding the action/feel, could be synchros, could be something in the clutch not releasing right. The 4.0 PP seems to have some issues - I'm putting a new one in mine now as we believe it is warped and not allowing full disengagement of the clutch. Mine has about 25 track days on it. Something in the springs are off alignment getting some sort of heat stress not allowing TOB to slide perpendicular to the guide tube.
Anyway, I'd start with the clutch, specifically: TOB, Guide tube, bushings & shims, shift fork, and Pressure plate. Most likely your flywheel and disk are fine.
If the problem persists good chance its internal and you have a syncho going.
06-08-2015, 02:44 PM
#4
Intermediate
Thread Starter
@ngng
No grinding during up-shifts around town - just aforementioned clunky-ness (gear lever sticky, doesn't consistently slide into gear).
@Spyerx
Fluid was changed during rebuild ~2K kms ago.
It was a lengthy process to get it all together after the 3.8 pp failed. Apparently they had to wait for the right shims. I wonder if the "right shims" never arrived...
No grinding during up-shifts around town - just aforementioned clunky-ness (gear lever sticky, doesn't consistently slide into gear).
@Spyerx
Fluid was changed during rebuild ~2K kms ago.
It was a lengthy process to get it all together after the 3.8 pp failed. Apparently they had to wait for the right shims. I wonder if the "right shims" never arrived...
06-08-2015, 03:17 PM
#5
Rennlist Member
Drop fluid again.
What shims are you talking about? The shims on the throw out bearing?
What shims are you talking about? The shims on the throw out bearing?
06-08-2015, 03:52 PM
#6
Personally, I think it might be the synchros, but I think Spyerx post shows the best order to diagnose the issue.
I had a somewhat similar problem last year with my RS, a little grinding and cables popped off. But they found metal on the drain plug, so the dealership changed the shift forks and gears 1-2, 5-6 (weird cause I found the problem with 3-4, but the problem is totally gone now) under CPO. Synchros were fine, but they replaced them since anytime they change the gears they recommend replacing the synchros.
I had a somewhat similar problem last year with my RS, a little grinding and cables popped off. But they found metal on the drain plug, so the dealership changed the shift forks and gears 1-2, 5-6 (weird cause I found the problem with 3-4, but the problem is totally gone now) under CPO. Synchros were fine, but they replaced them since anytime they change the gears they recommend replacing the synchros.
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06-09-2015, 12:55 AM
#8
@ngng
No grinding during up-shifts around town - just aforementioned clunky-ness (gear lever sticky, doesn't consistently slide into gear).
@Spyerx
Fluid was changed during rebuild ~2K kms ago.
It was a lengthy process to get it all together after the 3.8 pp failed. Apparently they had to wait for the right shims. I wonder if the "right shims" never arrived...
No grinding during up-shifts around town - just aforementioned clunky-ness (gear lever sticky, doesn't consistently slide into gear).
@Spyerx
Fluid was changed during rebuild ~2K kms ago.
It was a lengthy process to get it all together after the 3.8 pp failed. Apparently they had to wait for the right shims. I wonder if the "right shims" never arrived...
Just because they rebuilt the transmission does not mean they replaced anything except basic stuff. Synchros alone would have been 1500ish. PCNA didn't do anything useful when they "rebuilt" mine after my pp failure. I should have pressed for a new one. Check your invoice, or ask the dealer what they replaced.
As Spyerx mentioned, the 4.0 clutch is a bit squirrelly and can develop an issue with full engagement, which could cause grinding. I went into the transmission when mine was acting up, grinding in skip shifts into and out of 3rd...to find that my synchros were worn, but still OK (except for 1st and 2nd).
best of luck!
