engine/trans shake when burning out

I built a 1950 chevy pickup hot rod with a bb402 and 5 speed trans and ford 9" rear. I've always had horrible problems if I tried to spin the tires on dry pavement with what I thought was axle hop. I have a tri 4 link with coil overs, and I recently did a lot of work to the rear and added a panhard bar and rear sway bar. So after all that I went out thinking I solved the problem and still had major problems.
I asked a buddy of mine to come out with me one day with his camcorder and film my car doing a burn out so I could watch the axle in slow motion to try and figure out what is wrong, and I learned that the axle isn't moving at all, but from inside the car it shakes horribly. The whole cab starts shaking so violently that I can barely even hold onto the stick, and I immediately get off the gas so as not to break something.
I guess the issue is the engine/trans shaking when doing a burnout, but it is mounted properly and I've checked all my welds and mount points and nothing is bent or cracked.
Does anyone have any idea what I can do, or what the actual problem is here????

How's about a picture of your setup so we could have a visual to go by? or put up a link to the video your friend took.... The obvious things would be a cracked flywheel, bad clutch disc or pressure plate....

Have you checked your transmission mount and tail shaft to be sure nothing is broken?
Did you check the motor mounts? (both sides)?
Have you checked all of the body mounts to be sure they are tight?
Have you checked the frame 100% for cracks?
Do you have a pilot bearing/bushing in the crank? If there is one, is it any good?

What starts shaking first? I.E. Does the shifter start shaking first and then the body?

Does it drive fine even when you are running the same rpm that you are at when the shaking happens when you are doing a burn out?

Just a few thoughts off of the top of my head.

You got rubber mounts on your 4 link?

I'll see if I can link the video when I get home, I don't have it here, but unfortunately you can't see anything. My friend was actually confused at first because he thought nothing happened, and from outside it looks fine, all this time I just assumed it was wheel hop because from my perspective I just felt shaking.

yes I have checked all of those things and they are all good.
I have a needle bearing pilot in there and it was new just 6000 miles ago.
The weird part is that it runs perfectly smooth at any rpm, just as long as I'm not spinning the tires. It starts shaking immediately as soon as I have the clutch out if I'm on it hard enough to break the tires loose, I can get on it as hard as I want with no problems as long as I don't break those tires loose.
The trans is what starts to shake back and forth, and since it's a truck I have a big long stick coming all the way up from the floor and it starts bouncing back and forth sideways so violently I always get right off it.

I do have a 3600, so it is a full bed, and my driveshaft is over 70" long. Are there any rules of thumb for max driveshaft length? I know I've been looking at our full size trucks here at work, and both of them have intermediate bearing supports and two piece shafts instead of one long shaft.
My driveshaft angle is very mild, so it's not like I have crazy U joint angles or something, the truck is very low so it's just a few degrees on each end.

May want to check and see if any of the balance weights fell off the driveshaft. With a shaft alomst 6ft in length, you may have alot of whipping at RPM and if any balance weight has fallen off, that will lead to big time vibrations.

try it on wet pavement as well .. john force type burnout ..

Seems to me that if you have no vibration at any rpm/speed with moderate throttle you've ruled out component balance from the list - it would be shaking somewhere in the rpm/speed range if it were a balance problem. What are your rear tires? Are you trying to crank some massive pro-stock meats? I like Hoss's idea about a wet burnout - what does it do on wet pavement? How stout is your driveshaft? Did you have it built for the HP & torque, or are you using an OEM or cut down OEM? I'm leaning towards a clutch/pressure plate/flywheel problem, or maybe the driveshaft wrapping up and going harmonic under maximum torque. Personally I don't like needle bearing pilots, but that's just me. Bronze provides known support, is rugged enough to withstand stabbing the tranny with minor mis-alignment of the clutch disc, and will wear before the input shaft regardless.

I switched the poly link mounts to heim joints because I thought I was getting flexing back and forth in those maybe, so now they are solid as a rock.
I had the driveshaft made custom, and there is no vibration even at 65 mph, which is the fastest I've ever turned it, so as spears said I def don't think there could be a balance issue.
I would hope the shaft is not wrapping, but I guess I can't be positive about that. The only thing is, I would think there would be less torque on the shaft after the tires cut loose than if I kept them planted, and there are no problems at all at full throttle in 1st gear as long as they don't slip.
I did try a burnout here at work, concrete plant, which is like wet conditions because there is a coating of dust on the pavement surface that makes them really slippery, and had the same results.
I wish I could mount a camera under the car to watch the trans when this happens.

You said it's a tri 4 link, is that a 4 link with the two top bars close together like a Chevelle or is it a tri link (1 upper bar)?
What's the IC of the rear suspension? Could be the 4 link / tri link geometry is off & only shows up under power. Bottom bars at the wrong angle? Just thinking out loud. Hard to tell without watching it and seeing what the set-up looks like. Could be the rear end is binding & unloading as the tires spin, Causing a clockwise/counterclockwise rotation of the rear end housing. That may not be noticed from outside the car. I don't know if I'm explaining what I mean right.

I think pro is on the right track if the rear is to tight it could be trying to go both ways at same time trying to remember where I read a post on just that topic. Might have been right here

it is a triangulated 4 link, so I have the two top bars angled inwards and the bottom bars are parrallel. I also added a panhard bar last month when I was attempting to solve the problem.
I'll find the pics I have when I get home of the rear before I put the bed on the truck so you can see it clearly, and I'll also post those video's if I can figure it out, but I've watched those things many times and I can't see any movement at all of the axle.

Also check your pinion angle. If it is too light and going past parallel with the trans, it could be bouncing around.

If the bed is not in place, it should be easy to see if the rear axle / suspension is flexing or binding.. yes/no?

Quote:

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Originally Posted by 34_40

If the bed is not in place, it should be easy to see if the rear axle / suspension is flexing or binding.. yes/no?

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I think the bed is installed now, he has old pics. of the bed off.

You changed from rubber mounted bushings to heims in a day?
Ok, so now what is it doing?
I'm with Bug, pinion angle. It sounds like you have positive pinion angle where the pinion is pointed upwards in relation to the driveshaft. When under power the driveshaft wants to run straight and true so it pulls the pinion downward and that effect tries to lift the tires off the ground.

Quote:

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Originally Posted by pro70z28

I think the bed is installed now, he has old pics. of the bed off.

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AH.. Got it, thanks.. This is a strange one, can't wait for a solution!

Check this out about pinion angle and vibration.
Does pinion angle =vibration - Team Camaro Tech

Attachment 50186I didn't change to heim's in a day, I wish. Last month I lifted the bed off the frame and added a panhard bar, a sway bar, and changed from poly ends to heim's. It took me about 5 weeks or so. The sway bar addition was solely to help with the fact that my truck handled like a boat, but the panhard and the heim's were supposed to solve the shaking problem. I was focused on modifying axle components because I just assumed the shaking was coming from there.
Unfortunately after all that work I had the same problem.
I'm going to try to attach the 2 video's my buddy took from two different perspectives. They aren't the greatest and you can't see the whole vehicle in the framing, but it definitely got me thinking in a different direction. You can't see much of the cab in the video's, so you'll just have to take my word for it that from inside there was significant shaking.
-attached should be a pic of the suspension set up long ago before I even got it on the road, but it is still the same except now it has a panhard and heim's.
I can't see how to attach video's. They aren't showing up the way they do to attach pics. So for now here is just the pic, I'll keep looking on how to do video's.

Probably the easiest way to attach the video is to upload it to youtube then copy & paste the code in the message box here.

http://www.youtube.com/watch?v=nGga0HjpsXg

http://www.youtube.com/watch?v=GNhyH1UY9C4

I know the videos are terrible, there is a tiny portion of time where the wheels are actually slipping, but the reason I so quickly got off the throttle is because of how much the trans starts shaking and how bad it seems inside the cab.
I wish I got a video from inside the cab too.

Also, my axle pinion at ride height is point slightly down in relation to the ds, I think about 3 degrees, and the trans shaft is pointed above the ds about the same degree, so as accurately as I can tell they are basically equal and opposite angles.

Looks like you've done a good job and alls' about where it should be, the suspension geometry and pinion angle. Not shown is the panhard bar and an antiroll bar? I don't much care for a panhard bar and it can cause some binding with that type of suspension - but it isn't affecting anything at launch. The antiroll bar, is it one of those kit types similiar to competition engeering? Did you adjust it to neutral on both links with a driver behind the wheel, fuel etc so that it is at starting line weight? By neutral, i mean can you rattle both links that drop down to the rear housing? They should be loose so that you can slide the attachment bolt in or out?
The one thing that i thought odd is that at low rpm, not much power at all there is smoke coming from the tire - try throwing some weight in the bed, a couple hundred pounds of sand in bags and see what happens.
I tubbed a pickup and tried to drive it out of my shop without the bed on it. It got stuck at the curb in front of my rollup door to keep rain water out of the shop - i had to back up and get a running start. There isn't much weight at all in the back of a pickup and maybe that that is what you're seeing the results of.

right, the sway and panhard are not shown in that pic only because that pic is from 5 years ago and I just put those on last month. I chose that pic anyway because it was the best picture to show the suspension.
The sway bar wasn't from a kit, I had to make it custom. I did not actually check it was completely neutral with me in the cab, 99% of the time I am single handed so that stuff is tough, or if I'm really in a pinch I ask my wife for help and listen to her complain the whole time. It was definitely neutral with nobody in the cab because I checked that.
but yes, in the video from the rear perspective you can see smoke come up right away with only a few revolutions of tire spin. I did re-locate the fuel tank behind the rear axle so there is at least a little more weight back there, but it is still light.
I do think the video does show that the axle is very stable, and from inside it feels like the trans is going to launch to the moon.

Sorry - read the post wrong....

If the truck is smooth at any speed or rpm while cruising, should pretty much rule out driveshaft, U-joint, and alignment issues on the rear.... Other considerations could be a bad shock or shocks that are wrong for the application. Do you recall what weight the springs are? I've seen many instances on cars-trucks that are light in the back where the springs were way too much for the little bit of weight. I can't tell from the pic what coilovers you have, but if they're the generic 'one shock valving fits all' your problem could be there. With something light in the back, takes different valving and light springs to make it work right. Just because you can't see the tires hopping, doesn't mean that the coilovers are doing their job correctly......

As OJ mentioned, you might try adding a few hundred pounds to the rear, and along with that drop your tire pressure down to about 20 psi and try it again. Could be your coilovers are doing the hopping!!!!

Quote:

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Originally Posted by Dave Severson

If the truck is smooth at any speed or rpm while cruising, should pretty much rule out driveshaft, U-joint, and alignment issues on the rear.... Other considerations could be a bad shock or shocks that are wrong for the application. Do you recall what weight the springs are? I've seen many instances on cars-trucks that are light in the back where the springs were way too much for the little bit of weight. I can't tell from the pic what coilovers you have, but if they're the generic 'one shock valving fits all' your problem could be there. With something light in the back, takes different valving and light springs to make it work right. Just because you can't see the tires hopping, doesn't mean that the coilovers are doing their job correctly......

As OJ mentioned, you might try adding a few hundred pounds to the rear, and along with that drop your tire pressure down to about 20 psi and try it again. Could be your coilovers are doing the hopping!!!!

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Not taking credit for your post Dave,but darn if you and I was thinking the same thing.LOL-kind of scary isn't it??.

I want to x2 the thought of a marginal pinion angle where until you apply heavy torque to it,it's effect doesn't show up with normal driving.

Stick shift burnouts are hard on drive-line components.A clutch that is grabbing and releasing-chatter,would have a heavy vibration during a burnout and there again "could" operate normally.Question is do you have a line lock on it??.

From the pictures I saw,it seems the four link doesn't have adjustment holes for you to set the instant centers.Any chance given the light wt rear end and a instant center set to bite too hard??.If you raise(and I really don't want you to break parts in doing so)the RPM's,would that make it wheel hop for you could see it better??.

Maybe find somebody with one of these & mount it under the truck.
http://gopro.com/cameras/hd-hero-960-camera/
get a real time view of what's going on under there under power. under 200 bux

I was thinking like 1Gary, clutch chatter, suspension doesn't appear to flex and it's smooth under "normal" driving. Problem seems to be torque overloaded components.

How much room do you have with the yoke going into the transmission? Are you getting movement of the rear end clockwise and bottoming out the drive shaft?

Not for nothing,but the off road/monster truckers have proven that you don't have to have the drive line in line with each other as long as it is the same degree angles under power.Looks weird as all get out,but I guess it works.

There is a lot of slip room on the trans yoke. I forget exactly what I set it up with, but I just used a standard recommended amount, I'd guess maybe 1.5 inches or so.
Now I'm trying to post a current pic with sway bar and all.

Attachment 50192

very difficult to see everyting in this pic, I had the bed hanging from my garage roof trusses right above my head when I was doing this work, so it was impossible to get a good picture.

Nice set up, sorry to hear of the problems, I,ve built mine out of spare junk, and came out ok. I also was wondering about the yoke travel distance. 1.5 seems like a lot but may be correct, I would imagine that would change with suspension travel which I would assume you do not use alot of. Like you its been awhile since I set mine up., all I did was add a gear vendors, shortened driveshaft, etc. now don't hold me to this, but I believe the yoke travel was setup at .75. Maybe it is as mentioned before driveshaft wrap up if that is even possible.Anyways just following this thread. Interesting.

I could be wrong, but that panhard bar is really going to put things in a bind as you get any suspension movement. If it is set up neutral at static ride height, considering the arc of travel it is going to pull the center of the rear end over toward the drivers side putting your triangulated 4-link joints in a considerable bind. I don't believe it has anything to do with this shake problem, but I believe that you introduced a new problem by installing that panhard bar, just my opinion.
If it were mine I would drop the tranny and check the clutch for evidence of chatter, and the pilot bearing to be sure your needle bearings aren't toasted.

Probably not part of your vibration problem, but the panhard bar seems short. Looks like it could cause the rear end to move side to side as the suspension goes through it's travel.

Roger you beat me to it. lol

well your absolutely right about that panhard binding during suspension travel. As you can see in that photo it isn't even bolted up in that position because the suspension is all the way down since I had it on stands working on it, and it's arc is so far off at that point I can't even connect it. I set it up though with the suspension up at ride height, so then when I went to finish the job I couldn't even get the bolt through without actually setting the bed on the frame again and then squeezing under the vehicle and putting the bolt through from there.
That's another reason I wanted to switch to heim ends on those links. At first I didn't and I put that panhard on and used a jack to push the axle through it's travel range and watched the joints. They were twisting so hard at maximum travel I was worried I'd fatigue them and end up snapping one off some day on the road.
I really just put the panhard on there because I was out of ideas of what to do and I thought if that helped stabilize the rear more it couldn't hurt.

I would definitely take the panhard bar out and leave it out. The purpose of the triangulated 4-link is to ensure no side movement of the rear end, so you're just causing yourself problems by adding that bar, and doubling the potential binding by making it so short. As a point of reference, my Jeep has OEM "track bars" which is just their name for a panhard, and they run from the frame rail on one side, extending all the way to the most extreme point on the axle tube to minimize side travel on articulation. They're necessary because the suspension is parallel links, and one is anchored driver's side, the other passenger side to offset the side shift of the axles on the road, to maintain tracking to the extent possible.