T56 Hydraulic Throwout Bearing problem (?)
01-23-2009, 10:09 AM
#1
Launching!
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T56 Hydraulic Throwout Bearing problem (?) I am going to be the first to admit that clutches (et al) are not my strong suit to begin with and the T56 and hydraulic TOB in the '67 is the first one that I have ever done (besides servicing in my old WS6).
That said, as a lot of you know I was having issues downshifting the car car at the Optima challenge - the car would upsift fine but when I tried to do higher speed/rpm downshifts the transmission wouldn't slip into gear. Heck, it wouldn't be forced into gear either... some times it would go with a little more aggressive blip but not always.
Opinions at the time ranged from transmission (doubtful - new by Rockland), to fluid (it was full), to clutch/TOB engaugement (possible), and hardware issues (but after inspection nothing is loose, backed out or missing).
So, out comes the transmission. At first look everything appears to be ok - nothing is loose or appears unusual. So, following some instructions I found on the RAM site I take some measurements to see if maybe the TOB needs a shim (which was one of the more common suggestions up front).
For the record:
McLeod SFI LS bellhousing
McLeod RST dual disc clutch
McLeod aluminim LS flywheel
Stock GM hydraulic throwout bearing (new but maybe refurbished)
Rockland Standard T-56 - Son of Tranzilla
I measured the distance from the clutch fingers to the bellhousing mounting surface - 2.25".
I measured the distance from the compressed TOB bearing surface to the plane of the transmission mounting surface - 2.4"
It would seem to be (and as admitted, I am a far cry from an expert here) that the TOB isn't compressing enough and that based on these measurements there is pressure on the clutch fingers all the time.
so...
Does anyone have any suggestions, ideas, or recommendations on what these measurement mean and what remedy there may be?
My first thought was maybe bad TOB? Or I need an aftermarket TOB? or?
Any help would be appreciated.
Thanks,
James
That said, as a lot of you know I was having issues downshifting the car car at the Optima challenge - the car would upsift fine but when I tried to do higher speed/rpm downshifts the transmission wouldn't slip into gear. Heck, it wouldn't be forced into gear either... some times it would go with a little more aggressive blip but not always.
Opinions at the time ranged from transmission (doubtful - new by Rockland), to fluid (it was full), to clutch/TOB engaugement (possible), and hardware issues (but after inspection nothing is loose, backed out or missing).
So, out comes the transmission. At first look everything appears to be ok - nothing is loose or appears unusual. So, following some instructions I found on the RAM site I take some measurements to see if maybe the TOB needs a shim (which was one of the more common suggestions up front).
For the record:
McLeod SFI LS bellhousing
McLeod RST dual disc clutch
McLeod aluminim LS flywheel
Stock GM hydraulic throwout bearing (new but maybe refurbished)
Rockland Standard T-56 - Son of Tranzilla
I measured the distance from the clutch fingers to the bellhousing mounting surface - 2.25".
I measured the distance from the compressed TOB bearing surface to the plane of the transmission mounting surface - 2.4"
It would seem to be (and as admitted, I am a far cry from an expert here) that the TOB isn't compressing enough and that based on these measurements there is pressure on the clutch fingers all the time.
so...
Does anyone have any suggestions, ideas, or recommendations on what these measurement mean and what remedy there may be?
My first thought was maybe bad TOB? Or I need an aftermarket TOB? or?
Any help would be appreciated.
Thanks,
James
01-23-2009, 10:23 AM
#2
T/0 Bearing James,
Are you using the stock line from the clutch master to the T/O bearing? I have read that there is a restrictor in the line that can be drilled out to allow the fluid to move between the master and the T/0 bearing more quickly. Can you see the gap between the clutch disc/pressure plate and flywheel? I have a C5 bell housing that allows me to remove the bottom half so I can see the gap when the clutch petal is depressed. You could disassemble the clutch master and shorten the metal stop on the end of the piston, this will allow more fluid travel and allow the clutch to open a little farther. I did this on my 968/LS1 and is solved my issue.
Good luck!
BTW-Your car is Killer!
Are you using the stock line from the clutch master to the T/O bearing? I have read that there is a restrictor in the line that can be drilled out to allow the fluid to move between the master and the T/0 bearing more quickly. Can you see the gap between the clutch disc/pressure plate and flywheel? I have a C5 bell housing that allows me to remove the bottom half so I can see the gap when the clutch petal is depressed. You could disassemble the clutch master and shorten the metal stop on the end of the piston, this will allow more fluid travel and allow the clutch to open a little farther. I did this on my 968/LS1 and is solved my issue.
Good luck!
BTW-Your car is Killer!
01-23-2009, 10:36 AM
#3
Launching!
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The end of the stock line is there... my setup comes out of the Tilton MC via a -3AN braided line to a -3/-4 junction to the stock line with the factory quick disconnect. I'm going to double check the "fully compressed" TOB measurement tonight with the bleeder valve open just to be sure that there isn't any hydraulic pressure keeping it from compressing further.
