Violent Take-Off Shudder

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dkbug

dkbug

Well-Known Member
Joined
May 11, 2011
Messages
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Location
Norman, Oklahoma
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.
 
Last edited:
You have a very aggressive clutch disc. Not sure how you ended up with that, but it is what it is.

You’ll likely have to reduce the plate load (spring pressure) some to get the disc to not just grab the flywheel and in doing so, beat the crap out of everything.

If you have a diaphragm pressure plate I have no clue how to accomplish that.
 
dkbug said:
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.
Click to expand...
There has been alot of chatter on the forum lately regarding driveline angles, most of which a wrong.
What are your current angles set at? Both at the trans output shaft and at the pinion yoke?
So let me get this straight the shudder is there al the time, say at highway speeds? Or just when you take off?
 
512Stroker said:
There has been alot of chatter on the forum lately regarding driveline angles, most of which a wrong.
What are your current angles set at? Both at the trans output shaft and at the pinion yoke?
So let me get this straight the shudder is there al the time, say at highway speeds? Or just when you take off?
Click to expand...


Here is what I started with. Sorry for the crappy representation, but its what I have to work with. All angles were read at the flange face both on the diff and the trans.

5243_n.png?_nc_cat=101&ccb=1-3&_nc_sid=ae9488&_nc_ohc=Yb9NrWmQYKkAX_2pgI5&_nc_ht=scontent-dfw5-1.png


Note: The 2.4* is POSITIVE 1* from the drive line angle. I threw some 6* shims at it to make it -5*. Didnt help, but introduced vibration at highway speeds. I swapped out the 6* shims for some 2* shims to make it -1*. No change to the shudder, but the highway is quite pleasant now.

From the OP, the shudder is at take-off only when under a load. I.E. a hill.
 
dkbug said:
Here is what I started with. Sorry for the crappy representation, but its what I have to work with. All angles were read at the flange face both on the diff and the trans.

View attachment 1715738889

Note: The 2.4* is POSITIVE 1* from the drive line angle. I threw some 6* shims at it to make it -5*. Didnt help, but introduced vibration at highway speeds. I swapped out the 6* shims for some 2* shims to make it -1*. No change to the shudder, but the highway is quite pleasant now.

From the OP, the shudder is at take-off only when under a load. I.E. a hill.
Click to expand...
Leave the angles where they are they are pretty close.
If it's not shaking at highway speeds your angles a OK.
You have a clutch issue.
I had this issue on my Vette years ago when I trashed a brand new pressure plate.
Just for ***** and grins, have you measured your current crankshaft end play?
 
As YR pointed out you have a clutch material issue.
Believe him, and you will be on your way to solving the problem.
 
512Stroker said:
Leave the angles where they are they are pretty close.
If it's not shaking at highway speeds your angles a OK.
You have a clutch issue.
I had this issue on my Vette years ago when I trashed a brand new pressure plate.
Just for ***** and grins, have you measured your current crankshaft end play?
Click to expand...
TrailBeast said:
As YR pointed out you have a clutch material issue.
Believe him, and you will be on your way to solving the problem.
Click to expand...

Well, that sucks. Pulling the trans out of this car is an absolute nightmare. Here is a video of how much it is shuddering. The shudder translates all the way to the wheels.

 
dkbug said:
Well, that sucks. Pulling the trans out of this car is an absolute nightmare. Here is a video of how much it is shuddering. The shudder translates all the way to the wheels.

Click to expand...


That could be caused by a problem with the dampener assembly in the center of the disc.
Still a disc problem though.
 
512Stroker said:
Leave the angles where they are they are pretty close.
If it's not shaking at highway speeds your angles a OK.
You have a clutch issue.
I had this issue on my Vette years ago when I trashed a brand new pressure plate.
Just for ***** and grins, have you measured your current crankshaft end play?
Click to expand...

I had the bottom end built in a machine shop and he did measure crank play. I do not have a recorded value, but he said that it was within spec. I trust my machinist quite a bit. Pretty stand up dude.
 
dkbug said:
Well, that sucks. Pulling the trans out of this car is an absolute nightmare. Here is a video of how much it is shuddering. The shudder translates all the way to the wheels.

Click to expand...

That is severe
Time to get the wrenches out.
 
dkbug said:
Well, that sucks. Pulling the trans out of this car is an absolute nightmare. Here is a video of how much it is shuddering. The shudder translates all the way to the wheels.

Click to expand...



Yeah, that’s a clutch issue. I don’t know what your spring load is but it’s got to come down or you need a different disc. My off the top of my had guess is anything over 2000 pounds and it’s going to shake like a dog pooping peach seeds. It will probably take less.

I’m not a big fan of ceramic, velve-touch, dual friction or any of that trick of the week Crap for a street car. Either use a nice, high performance rag disc or you need to step up to sintered iron. And the issue with sintered iron is the exact same issue you have...it can’t stand high plate loads.

You’re kinda stuck. Do you remember what the pressure plate is?
 
dkbug said:
I had the bottom end built in a machine shop and he did measure crank play. I do not have a recorded value, but he said that it was within spec. I trust my machinist quite a bit. Pretty stand up dude.
Click to expand...
Replace the clutch before you tear up the crankshaft thrust bearing.
May be a good idea to measure it and the flywheel runout while you have it apart.
Good luck
 
I had the same problem, it turned out that the he clutch
Disc was soaked in oil? Don’t know if ceramic will repel oil ??
 
Put the snubber up against the floorboard an try again (if it's not already)..... If you still get a shudder, then I'd say for positive the clutch has to be the issue.
 
mopar head said:
Bad shudder was always pilot bearing in my experience.
Click to expand...

Loose pilot bearing ^^^^ clutch disc goes off center, shudder, shudder, shudder.

Could have been wrong size pilot bearing upon assembly. Should be able to pull the clutch inspection cover and look at the position of the clutch disc between the flywheel and pressure plate. Then rotate by hand 180° without stepping on the clutch and check again. 3 /16th" off on the 2 checks is a lot.

That is a seriously bad shudder you have there, something is seriously wrong.

Should be able to have the shift in neutral, idling, clutch and trans quiet as a mouse.

Noisy loud exhaust does not favor trying to listen for clues.

Ever put the clutch disc in backwards????
 
I had the same problem, very bad shudder going into 1st, checked pinion angle, added shims, same problem, the new clutch I got from brewers turned out to be bad, I changed to an OEM style 3 finger clutch and fixed the issue, brewers refunded the purchase price of the clutch. I know it’s hard to Believe that a brand new clutch could be bad, but it does happen. I got the replacement clutch from rock auto it was a perfection clutch
 
Lefty71 said:
Put the snubber up against the floorboard an try again (if it's not already)..... If you still get a shudder, then I'd say for positive the clutch has to be the issue.
Click to expand...

This made a difference. I wedged a couple 2x4's between the snubber and the floor board and the shudder is virtually gone. What does this mean if my pinion angle is at -2* relative to the engine centerline?
 
dkbug said:
I wedged a couple 2x4's between the snubber and the floor board and the shudder is virtually gone. What does this mean if my pinion angle is at -2* relative to the engine centerline?
Click to expand...

I'm not a chassis expert, but if you could get 3" of wood blocks in there, then your snubber was for looks if you know what I'm saying. When you use a snubber on a drag car, there is virtually no space when the car is at rest. The rear should rise anyway if all works well. The other thing I would do is double check your angles, maybe get a Mopar chassis book to help, and also, check the clutch because so many other folks said they had experienced those issues as well.
 
dkbug said:
This made a difference. I wedged a couple 2x4's between the snubber and the floor board and the shudder is virtually gone. What does this mean if my pinion angle is at -2* relative to the engine centerline?
Click to expand...


That’s not the right fix. That clutch is a parts breaker. Fix that part of it. I have BTDT and you are just wasting time and money until you fix the clutch.
 
yellow rose said:
That’s not the right fix. That clutch is a parts breaker. Fix that part of it. I have BTDT and you are just wasting time and money until you fix the clutch.
Click to expand...

I'm not going to doubt you as you definitely have more experience than me, and you are likely correct because of said experience. However, I am going to ask for you to elaborate on your thought about why the fact that eliminating axle wrap essentially eliminates my original complaint isn't the source, but the clutch is. I am a mechanical engineer by trade, so please excuse my questions. I genuinely would like to understand the thought process.

Sitting in idle, the clutch is very quiet. Shifting into any other gear is perfect and quiet. Reverse is perfect and quiet. Its only when taking off in first gear that I am seeing the majority of the action happening at my rear diff. The clutch only has 800 miles on it by the way. Its not gotten any worse/better. When I put that 3" worth of wood above the snubber, ALL shudder disappeared.
 
the snubber was just flopping with the clutch grabs. My vote is for the clutch replacement. Snubber should be like 1" at rest to do any good on the strip. Imagine that snubber holding still and reducing the overall shudder and you only have -2.5 down? Id go 5 down on the pinion angle in relation to the output shaft as its gonna wind up to maybe 0 under load, depending on what spring rate you have. If you do use a snubber riding on the floorboard, the shudder will stop because the rear end will no longer load and unload with the clutch chatter, it will be solid. It may cure the shudder but youll be riding a buckboard with that pinion hitting the floor over every bump and youll probably end up breaking a perch or something.
 
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Also, I watched the video I posted. 99% of the noise that is heard is the hood shaking and the exhaust hitting the bottom of the car. The clutch doesn't make hardly any noise.
 
Tend to agree with the clutch disc diagnosis. However I have to ask a couple of things. Was block align bored? Was bell housing alignment checked during the build-up? What first gear is in the tranny? Years ago I was talked into installing a metallic disc clutch behind my 440. It was very hard to take off smoothly from idle. The problem resolved itself when the clutch disc came apart while driving back from lunch one day. I didn't replace it with another one! Good luck!
 
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