Still working on the shake at launch issue I have with my stock 69 Barracuda Formula S 383 4 speed car. Just a question concerning the bell housing. If the Parallelism of the tranny mounting surface or the concentricity to the crankshaft were out of spec. would that cause an intermittent hard shake at standstill take off? Once the car is rolling it's fine. No shifting issues. Just take off shake.

I've done lots of work on this car the past 2 years and still trying to pinpoint this issue. All the obvious stuff and then some. Thinking more out of the box at this point.

Thanks.

Alignment out will cause high rpm vibration. Sounds like clutch chatter to me. I'd check the surfaces if your clutch and pressure plate. Also the disc needs to have good springs and attached to the steel in a way that it has some space in between the two disc. I had a racing disc with solid backing on the material and it would shake terribly. I think it's called the marcell that it's attached to and it is cupped so it acts like a spring or cushion. My best guess.

Here is what I've done so far:

New Mcleod clutch/pressure plate set & throw out bearing from Brewer's.
New super stock springs and bushings.
New pilot bushing.
New tranny front bearing/seal. Ensured tranny shaft didn't have burrs or imperfections.
Resurfaced/ measured pressure plate twice during the removal and re-inspection of the new clutch components.
New rear tranny/motor mount.
Adjustable pinion snubber.
Measured pinion angle. 2.5 degrees negative. Also played around with 2 and 4 degree shims to make more negative.
Ensured correct drive shaft length.
Thoroughly inspected the linkage, 3 times.
Checked the motor mounts. They appear like new. Motor does not move a bunch during hard launch. Also looked at them with the emergency brake set and clutch release to load the motor.

I'm probably missing something but this is most of it. Car does not vibrate at all going down the road. At a rolling start does not shake. Standing still however during light or hard launch you get some degree of shake. I can actually get a violent shake at light launch. Shake that is way more than any clutch chatter I've ran into over the years.

I have added traction bars to it and set the snubbers against the springs. You can drive it with very little to no shake at launch that way. I don't like doing that but it at least allows me to drive the car.

When you say "resurface" in the above statement are you referring to the flywheel or pressure plate ?? And how did you resurface them. I have heard of flywheels developing hard spots from heat that cannot be corrected by surfacing. Your description sure sounds like a clutch, PP, FW issue.

I was referring to the flywheel concerning the resurface. The PP is new. Can the hard spot areas be identified prior to resurfacing?

Where does the shake feel like it's coming from? Back of the car, middle? What type of tire is on the car?
The reason I ask, is I had a similar situation when I swapped tires on my car. I went from a drag radial to a bias ply and had horrible tire shake on a hard launch.

What type of shocks too?

I replaced the shocks all round and have the longer units in the rear to accommodate the super stock springs.

shake feels all over but mostly in the middle. I've got 15" Mastercraft 50's on it now but it also shook with 14" BF Goodrich TA's. Both street radials.

To my knowledge without testing, No. Before the surfacing they visually appear as blued or other color irregularly shaped spots and sometimes cracks. After surfacing the surface may appear fresh and normal but can be very irregular to a friction surface (clutch material). Most clutch manufacturers typically recommend a new flywheel for the above reason.

So to be clear, the flywheel could have hard spots due to overheating that resurfacing can hide. I guess I should pull that back apart and look at the flywheel now after driving the car around for almost a year this way. It may tell me something now where it wouldn't before. The car had been sitting for quite some time and may have been shaking on the previous owner.

Launch issue, what do you mean by launch? Are you talking about a shudder if you feather the clutch from a standstill or a shudder if you "dump" it from a standstill?

read the earlier posts, it does both

keep us posted on what you find.
Myself, I might just put an entire new assembly and flywheel in.
FYI We have had very good luck with the Centerforce dual friction clutches in our own as well as customers cars

Sounds like clutch related vibration, chatter
Did you possibly get some oil or other oil based liquids on either the clutch disc, pressure plate or flywheel?
If so that may be part of the problem

What type of material is the disc face have on it? Certain High Performance materials will grab causing your shutter condition. If it's a stock type rag facing look for broken or weak mounts ,sing bushings or bad shocks

Both.

I've had the Assy. apart twice looking for those things. Non found.

The Hays setup I took out really didn't look all that bad considering all the shake. I put in this McLeod setup based on Wayne Brewers recommendation. This same setup worked great in my 68 Bee a few years ago. Shake the same before and after.

I am considering a new flywheel. I got to get it back apart anyhow but hate to just keep throwing money at it.

You can try this to eliminate some of the components as contributing to the problem.

Replace the driver's side engine mount with a solid mount, or drill a hole through it and bolt a nut with washers through it and or chain the motor down so it can't lift up any more than 1/2".

This will hold the engine from being able to lift from the torque. I've had issues in the past like this. using a solid mount eliminated the changing geometry of my linkage when the engine moved and pointed me in the direction of the aforementioned missing Marcel spring that cushions the grabbing force of the clutch.

Rigid puck style clutches don't typically have Marcel springs and they tend to chatter unless they are essentially dumped at the starting line or the engine trans is solidly mounted. I still have some of those old solid puck clutches laying around.

It wasn't until the Mcloed Street Twin's came out that I was able to have a clutch live on the street with a high output engine with no chatter.

Reading through your struggles and BELIEVE me I've BTDT, I'm wondering if the flywheel has not been the culprit all along
Especially if it has not been replaced. Other than replacing everything, The only other option I can think of is to send the entire assembly into the current supplier (McLeod) for analysis. just my

Silly though just occurred, So one other stupid question ?? any chance the crank has too much end play??

please keep us posted

Chaining that left mount down would be an interesting trial just to see if I have a mount issue. The only thing I've done as far as checking mounts is put the emergency brake on and feather the clutch out to watch the amount of engine lift I get which didn't seem to be allot but it was only visual. Definitely food for thought.

If you get the shudder on a feathered start or a dumped start, I'd start looking elsewhere. On a dumped start the clutch is going to lock up quickly. If you have a shudder after that occurs, how could it be clutch related? It is interesting that putting the traction bars solid against the springs virtually solves the problem. You wouldn't have a broken spring or a loose differential by any chance?

I put new Super Stock springs on and didn't see any difference in shake. As far as the differential goes, I talked to Dr Diff for quite some time about the issue tapping his knowledge about differential operation and his contention was that it would not be the carrier. To go a step further a fella on A Bodies Only site that followed my problem also has the same problem with his 68 383-S car.

I also need to add to this mix that the car does not shake every time you let the clutch out hard or soft. I would say 70% shake if I put a # to it.

Also to answer a previous question, I can't say I've checked crank play but wouldn't you think I would have allot of other things going on to with motor vibration if the crank had an issue like that? It's part of thinking out of the box at this point though which is what I'm trying to do. I very much appreciate all this food for thought.

So this isn't a consistent problem? So what's different between the 30% and 70% cases? Track, weather, time of day, amount of fuel in tank........?

Nothing is consistent.

Any unusual sensations when up or downshifting when let clutch out, or does your quote of no shifting issues cover this?

Any shudder stsrting out in 2nd gear.

Assume transmission mount ok as you have removed it several times.

Does sound like plain old ordinary clutch chatter caused by defective clutch or flywheel surface or motor mounts. Pilot bearing fit of trans mainshaft ok?

What happens when in reverse? If nothing, would suspect again engine or transmission mounts

Don't suppose rear axle posi could cause this???

No issues up or down shifting.

No shudder with 2nd gear takeoff.

New tranny mount.

2 new pilot bushings. Only because I already had it apart and they are cheap.

No shake in reverse.

Dr diff says no on the posi and a contact from A bodies site has a 68 with the exact same problem. He rebuilt his posi. Did not fix.

I think I will chain down that left engine mount side and see what happens.

Was once ok and now is not?

How, when, after what did it start to shutter.

No shutter in reverse sounds like motor mounts or possible cracked K member or chassis. All bolts there torqued properly?

With handbrake on, ease clutch out in low gear. Still shutter? Can you get it on a drive on lift and have someone under car while easing clutch out to perhaps observe what may be occurring?

Driveshaft too long, causing a bind as axle winds up as clutch is released?

The car has shook the two years I've had it. According to the last owner who had it 30 years and it's been on stands for about 15, It has never shaken for him till just before he stored the car away. He got the car running then I bought it but I didn't drive it down the road before hand. He did report the fact he felt it needed a clutch.

During assembly all bolts have been torqued correctly.

I have raised the rear of the car on stands and had someone in the car so I can observe clutch, drive train action. No issues. Car has to be on the ground, taking more torque/resistance to highlight the issue. When handbrake is on, car back on the ground and easing the clutch out, no shake.

Wayne Brewer suggested also measuring the drive shaft. Shaft is the correct length.

Hey...I'm the guy from for a bodies only forum. I have a '68 Barracuda 383, 4 speed, 3:23 sure grip convertible. Unlike Tim's car, my car is not numbers matching. It is an original 383, 4 speed convertible car but it was missing the big block and 4 speed and the big rear end. Anyhow, everything on my has been rebuilt or is new. Had the tranny rebuilt, got all the rest of my 4 speed stuff from Brewers. Had the 3:23 suregrip rebuilt, etc. My car acts exactly like Tim's. I originally thought the clutch was the problem and replaced it (new fly wheel). I recently filmed the rear in slow motion with my phone in my driveway and the leaf springs jump up and down pretty violently which is what the shaking is. I was about to buy new springs when I read Tim's other post and saw that he tried that and it didn't help so I don't know what to do. I put this car together myself and it's super frustrating and embarrassing that I have to take off with no acceleration until the car is rolling or it will shake pretty badly. Someone else must have had this problem before.

Have you talked to Wayne Brewer at all about this? Especially since you got all the 4 speed stuff from him as I did. If you do, tell him you've talked to me as well. He'll remember me from last years Norwalk Monster Mopar. That's the last time I talked to him about mine.

What you describe could be caused by clutch chatter as the assembly grabs/ slips/grabs. As the power is applied the front of the differential raises as the pinion tries to climb the ring gear. how much it raises depend on how much power is being transmitted.
In order for it to act as you describe the power has to be varying for one reason or another or the front of the springs are extremely weak. One could try an adjustable pinion snubber pre loaded to stabilize the front of the differential. Doing so would minimize /eliminate the differential movement , u joint angles changing etc. on a normal take off.
The chatter if being caused by the clutch may be being amplified by the differential movement. It would still be there but should be a lot less noticeable.
I'm still thinking something in the clutch area is at the root of the problem. Another thought that might be a possibility is a bent input shaft.

I almost wish one of the cars was closer as I love resolving issues like this

Another thought I just had would be to check the air gap as the disc is being engaged with say a feeler gauge looking for irregularities. While this would not expose contaminated / irregular surfaces it might expose a bent disc, warped PP, or bent input shaft

I removed the stock snubber & tried a new adjustable pinion snubber. Played around with the setup. As far as the distance from the floor. I even set the rubber snubber against the floor. Still shakes.

Checked the tranny input shaft when I replaced the front bearing. Straight as an arrow.

You mention weakness in the front of the springs. I've already tried installing brand new super stock springs. Still shakes.

Have you tried moving driveshaft yoke as it enters rear of transmission up and down to ensure no slop at this bushing. Unlikely the cause but certainty the cause of unexplainable vibrations from driveline cruising down the freeway.

Slim chance of your problem, good news is easy to check. Should have no movement if all is well and snug.

Back to your original title, has bellhousing been throughly dialed in! Running out of ideas, had considered that, but assumed had already dialed in when replacing clutch. However do not see anywhere that it had been.

Wonder if mainshsft bearing out of transmission into clutch might cause your shutter if sloppy. I believe you said had replaced pilot bushing/bearing.

Are rear of transmission and differential shafts running true and straight left to right? You have mentioned that driveline angles are ok up and down. Am assuming U Joints are in order.

I had missed earlier comment that you had checked driveshaft for proper length.

Are you certain that rear springs are quality products with correct number and positioning of leaves. Rear axle properly positioned in springs?

I would think that a tweaked pinion shaft would cause a wealth of issues besides a shudder in low gear,,,,vibrations, broken u joints etc.

Interesting no issue in reverse,,,takes me back to engine mounts. Is engine setting at proper height in K Member. Not one side higher than other or tweaked so tailshaft from trans is not pointed directly left/right to pinion at rear,,,same as mentioned earlier in this post.

With hood up, can an observer see shudder in engine?

If you just slip the clutch gradually to move forward in low,,,,do you still get shuddder. If let out rapidly with sufficient gas not to stall, will you have shuddder starting in 2nd.

Wonder what you might see on a chassis dyno with full weight of rear wheels on the roller.

Yes I have checked for drive shaft yoke slop as it sets in the tranny. Non there. Compared to my 71 Cuda and it's pretty much the same.

Bell housing has not been dialed in. I wonder though that if that were the cause wouldn't I have other issues going on?

Replaced tranny front bearing.

Checking drive train alignment left to right would be something to pursue. I haven't checked that. U joints are good.

Mopar Performance super stock springs.

Yes gradual clutch engagement will still shake. If you just get it rolling you can boil the tires after that but hang onto your hats if you try this from a standing start.

Don't think we discussed this but does your car also shake in reverse or from a 2nd gear take off?

I am still struggling with the fact that if you set the traction bars up so they touch the springs all is good. If it was clutch chatter, how could setting up the bars affect that. I also go back to the fact that typically Mopar rear springs don't need traction bars just spring clamps. I hate to get fixated on something but this seems to indicate spring wind up. Too bad you don't have another set of springs, even lighter ones, just to see how it will react.

Spring wise though, I put a new set of Super Stock springs on it. It still shakes. Also all isn't good when the bars are set to the springs. That just makes the car bearable to drive. It still has some shake just not violent shake. Shook with my worn out stock springs too.

After doing all that to the rear of the car with the springs, pinion snubber and pinion angle. I believe it is up in that clutch area somewhere, especially since take off is good about 30% of the time. It's inconsistent.

I didn't go back and read every post but early on you state that you got a new clutch set from Brewer. What did you tell him you were going to be using your car for? Did they sell you a Hi performance disc? such as a Kevlar one? Those will grab,not slip on take off and will cause the symptoms you have. Other than that , mounts, motor and transmission. They might look OK but if they have never been changed out there 50 years old. Shocks , the same , they may look good but don't last forever.

Was this before or after all the other drivetrain work? Just trying to establish a time line of what you did and the effects of what you did.

Using wheel chocks or If handbrake works well enough to hold car well, engage it tightly and with transmission in low gear, give it some gas and let out the clutch. Have an assistant view rear springs while doing so. Any shudder or other observations of note in behavior of springs or driveline?

Would certainly be better to be on a drive on lift,,,,,looking for unusual engine and transmission lift or rock.

Reposting this as it may have slipped by,



This can easily be done by adjusting the length of the clutch rod.

Yep this setup Wayne suggested. It just happens to be the same setup I used in my stock 383 4 speed Super Bee a few years ago. Same use, just street. Not one issue with that.

Adding the super stock springs is the last thing I did. I then stuck the traction bars on.

When I was going over the linkage looking for irregularities, I did adjust around on the rod just to see what would happen at various engagement points. It shook at all of them.

I need to do this test again. I've done it once and I'm pretty sure I saw no shake with that. That's what pointed me to the back end and changing the springs.

Could clutch disc when released, not move freely on transmission main spline. I had always checked for this many years ago when was still replacing clutches, did so before bolting pressure plate in place. More than once had found a problem,,,,and a couple of times with a disc not runing true when spun on a smooth bench top surface.

I will post this thought on the other thread of the day suggesting another clutch problem.

Just did another check of my LH motor mount. This car has power steering so it's not the easiest to see but I set the mercy brake on the car and popped the clutch a few times. Had someone watch the motor mount and even took a video. The rubber does separate and is cracked almost all the way across about 1/16th from the top of the mount. It's not all the way thru though cause the motor still does not raise up enough from left to right under torque for the air cleaner to tag the hood. It does indicate a questionable mount. Car does not shake or anything slip while the brake is set and popping the clutch to raise the motor.

Did you check/reset the pinion angle when you put those springs in?

The fact that you said it went away , for the most part , with snubber bars up against the rear springs tells me it's a driveline issue. Pinion angle is the first thing to look at.

Where's Quicktree ?

Yes I did experiment with the angle shims after putting the new springs in. I've looked at this pinion angle allot and tried different negative angles with no success in getting rid of the shake.

Another odd thing to me is that when I set the mercy brake and bump engage the clutch, I get no shake. That test led me to the rear thinking the motor, tranny clutch area was fine.

How about an actual pinion angle reading ? Was negative actually the correct way to go ?

Yes. Negative is where you want to be in relation to the tranny tail. My readings have been anywhere from -2.5 to -8, depending on what shims I had in place.

I see in the latest edition of Hemming's Muscle Machines there is a fella with a 69 Dart 383 4 speed car & 3.23 SG with the same problem that wrote in. His car is original also with the drive train rebuilt. Common theme it appears. He has also replaced the clutch twice. New flywheel and various parts as well.

I have a 69 383 4 speed dart with the original sagging rear springs , I don't remember any issue with either a borg&beck 3 finger or the McLoed Borg&Beck/Long. The stock borg&beck did have a vibration issue in the engine itself but that was caused by the flywheel that was cut at an angle and was hot fully neutral because of it.

Where is Rhinodart in this discussion? No disrespect to anyone who has posted but if anyone knows about this kind of generic problem he should.

I think Rhinodart lives in Illinois as well, not too far from me. Heck I would take the car to him if he didn't mind looking at it for me. I've tried so many things to this point that I'm wondering if it's something I've missed along the way. I've had lots of other eyes on this thing too but I wouldn't call the eyes real experienced on 4 speeds and their setup. I believe that's what this will take.

We are all curious on this one, hopefully if cause is found that finding is posted.

All too often this important close out report does not happpen. Important for those who have posted their ideas,,,and for the next member to experience the same problem.

Absolutely. Responding back with a post will be the first thing I do after figuring this issue out. 40 years of working on these things, mine and my friends cars, and I've never have had a problem I've worked on for so long.

I do plan to replace that motor mount but since it's not cracked all the way thru I don't believe it is the source of the shake.

I had a similar issue with my old Roadrunner. After lots of aggravation and pulling trans down way too many times, it was the flywheel. Mind you I sent it out for resurfacing just to clean it up. Put a dial indicator on it, machine shop screwed it up. Had it cut again, solved.

I've had this flywheel measured after the 1st resurface and it was fine but I went ahead and had it resurfaced again anyhow for more precision by a very good machine shop I use at work then remeasured again. Local Napa did the 1st time but it was within specification. No complaints.

Did you ever get this resolved?