dkbug
Well-Known Member
Hello all,
I am at wits end with an issue I have been experiencing for awhile, and I hope that I can tap into the wisdom from the experts here at FABO. Preferably, I do not want to redesign the car and throw a ton of new parts at it without being sure that we have found the culprit. There are a couple posts from people on FABO explaining the exact same issue with no prevail. I will try an explain the issue in as much detail as possible. Starting off, I will drop all the specs I have.
Motor:
1971 440 - Stock stroke
Howards roller hydraulic cam
max wedge spec 906 heads
FAST EFI
Trans:
1965 A833 (Low mileage, not rebuilt)
Factory A body big block bell housing (Brewers)
Brand new McLeod clutch assembly from Brewers (Ceramic both sides)
Brand new flywheel (I resurfaced it even though it was new since I do not trust parts stores)
New pilot bushing (Brewers)
New throw-out bearing (Brewers)
New clutch fork (Brewers)
Misc:
Drive shaft converted from ball/flange to slip yoke (New shaft made / rebalanced)
Brand new Moog u-joints (shaft was balanced with the new joints)
TTI 2" headers
TTI Z Bar and bracket
Mounting:
Schumacher /6 to RB mounts
Motor mounts are brand new rubber mounts from the parts store... for diagnosis only
Trans mount is brand new rubber mount from the parts store... again, for diag only
Suspension/Rear:
8 3/4" A body factory width rear
3:23 sure-grip rear
Factory pinion snubber
Super stock springs (all the rear leafs are still clamped)
Springs moved inboard
Pinion angle is right at -2* from the drive train angle
Problem: The drive train violently shakes when taking off from a stand-still. Before I put my scoop on, I could watch the motor rocking back and forth with the shudder. The problem seems to only occur when I am on a hill. (Basically under a load..) Taking off when the car is facing downhill and the shake isn't there. The higher the RPM, the worse the shake. However, if I dump the clutch everything seems perfect. If I lug the motor, the shake is almost non-existent. Taking off in second - The shake is there, but hardly noticeable. All the other gears are perfect, including reverse! I spoke with Dan over at Brewers (The guy is a blessing btw... He is extremely helpful and I refuse to do 4-speed business with anyone else) and he is confident that the drive line angles are to blame. I have tried some 6* shims in addition to 2* shims and the problem didn't seem to be much different between the two. I replaced the trans mount as the one I had looked to be defective, and the problem is more bearable, but something still isn't right. I do know the difference between clutch chatter and a shudder, this one is definitely a shudder. The clutch is pretty aggressive, so I do expect to have some sort of vibration when the clutch engages.
I talked with McLeod directly, and the tech seemed to think that maybe I glazed the clutch during break-in. He suggested that I go do some higher RPM clutch dumps to try and de-glaze it... No change after many many tire frying take-offs.
Things I have tried:
New motor mounts
New Trans mount
Clutch fork adjustment (in/out)
Pinion angle shims both 2* & 6*
Let me know your thoughts.
I am at wits end with an issue I have been experiencing for awhile, and I hope that I can tap into the wisdom from the experts here at FABO. Preferably, I do not want to redesign the car and throw a ton of new parts at it without being sure that we have found the culprit. There are a couple posts from people on FABO explaining the exact same issue with no prevail. I will try an explain the issue in as much detail as possible. Starting off, I will drop all the specs I have.
Motor:
1971 440 - Stock stroke
Howards roller hydraulic cam
max wedge spec 906 heads
FAST EFI
Trans:
1965 A833 (Low mileage, not rebuilt)
Factory A body big block bell housing (Brewers)
Brand new McLeod clutch assembly from Brewers (Ceramic both sides)
Brand new flywheel (I resurfaced it even though it was new since I do not trust parts stores)
New pilot bushing (Brewers)
New throw-out bearing (Brewers)
New clutch fork (Brewers)
Misc:
Drive shaft converted from ball/flange to slip yoke (New shaft made / rebalanced)
Brand new Moog u-joints (shaft was balanced with the new joints)
TTI 2" headers
TTI Z Bar and bracket
Mounting:
Schumacher /6 to RB mounts
Motor mounts are brand new rubber mounts from the parts store... for diagnosis only
Trans mount is brand new rubber mount from the parts store... again, for diag only
Suspension/Rear:
8 3/4" A body factory width rear
3:23 sure-grip rear
Factory pinion snubber
Super stock springs (all the rear leafs are still clamped)
Springs moved inboard
Pinion angle is right at -2* from the drive train angle
Problem: The drive train violently shakes when taking off from a stand-still. Before I put my scoop on, I could watch the motor rocking back and forth with the shudder. The problem seems to only occur when I am on a hill. (Basically under a load..) Taking off when the car is facing downhill and the shake isn't there. The higher the RPM, the worse the shake. However, if I dump the clutch everything seems perfect. If I lug the motor, the shake is almost non-existent. Taking off in second - The shake is there, but hardly noticeable. All the other gears are perfect, including reverse! I spoke with Dan over at Brewers (The guy is a blessing btw... He is extremely helpful and I refuse to do 4-speed business with anyone else) and he is confident that the drive line angles are to blame. I have tried some 6* shims in addition to 2* shims and the problem didn't seem to be much different between the two. I replaced the trans mount as the one I had looked to be defective, and the problem is more bearable, but something still isn't right. I do know the difference between clutch chatter and a shudder, this one is definitely a shudder. The clutch is pretty aggressive, so I do expect to have some sort of vibration when the clutch engages.
I talked with McLeod directly, and the tech seemed to think that maybe I glazed the clutch during break-in. He suggested that I go do some higher RPM clutch dumps to try and de-glaze it... No change after many many tire frying take-offs.
Things I have tried:
New motor mounts
New Trans mount
Clutch fork adjustment (in/out)
Pinion angle shims both 2* & 6*
Let me know your thoughts.
Last edited: