Bad Vibes man

Bad Vibes
Working on refining my van:

I have been doing a bunch of diognosis on the bad vibs in my Van

#1 the drive shaft is too long (maybe).

#2 the rear end pinion angle changes too much, (spring wrap)Looks to be moving about 7* or so.The pinion picks up so much it pushes the drive shaft right into the trans and then pushes the trans forward when I apply enought torque.

#3 I also notice, with normal driving I get a vibration building up as the engine RPM increases and then it goes away right when the trans changes gear, same for all gear shifts and any road speed .

Have a look at it here.
https://s119.photobucket.com/albums/o122/m1dadio/?action=view&current=drivelineanglechangeduetospringwrap.mp4
#2 will need a set of trackion bars like panelmanrd recomends However I am going to use Track rods which when used on leaf spring suspention act like the 3rd and 4rth links of a four link setup.
This is what they look like.I will build a simular set up.


This might also fix problem #1 I will show vidio when I get it done in about 2 monthstime.
I will get all I need for that from this family busines.
http://www.welderseries.com/hardcopy/weldercat.pdf

http://www.welderseries.com/blog/onl...egory/catalog/



Problem #3 I have encountered before, this is either crankshaft, flywheel, torque converter and/or trans input shaft imballance. Usually a Going bad torque converter although it can simply be the fact that the flex plate or torque converter has thrown a ballance wieght. First clue is, This is actually a replaced or posibly overhauled trans from some nickle and dime trans shop. I like to refer to it as a rattle can overhaul.often one can try just repositioning the torque on the flexplace by rotating it to the other bolt holes.
A simple test is in park or nutral I get the vib coming on around 2200 to 2500 RPM same as on the road.

We will see how that turns out.

M1D [img][/img]

I have run into #3 myself. And am thinking along the same lines. I noticed it more when I adjusted the shift points up a bit with the TV cable.

if you get it in park or nuetral, it cant be spring wrap and not likely to be driveshaft length either. what motor? is it internal or external balance and do you have the right balancer and flexplate?

jrinaman wrote:if you get it in park or nuetral, it cant be spring wrap and not likely to be driveshaft length either. what motor? is it internal or external balance and do you have the right balancer and flexplate?

M1
If your interested in shipping me your drive shaft,i will dynamically balance it for you at no cost to yourself except shipping,if you take it somewhere else, balance it to an ISO G GRADE OF G 2.5 WHICH IS A VERY FINE LEVEL OF BALANCE for this application.

Id 1st- take the driveshaft @ the trans & see if that spring wrap(likely) has worn the tailshaft bushing?? See if tailshaft Yoke- will move around? doesnt need to be much as this alone will cause a vibration. If all's ok= maybe internal to tranny-as u say its in gear or not. What about rear springs & mounts? weak springs ? Rubber mounts worn,loose? just what ive experienced. Remember - traction bars are nice yet most are not using??

I fixed that poor vidio link.

You have to watch the change in pinion angle to drive shaft angle to see the spring wrap. the correct angle is about 3*, under normal load the pinion lines up straight with the drive shaft and thats where I begine to feel the vibration. AS can be seen, when I am hard on the gas other bad s#!^ also hapens including the pinnion angle going to about 4* opposite angle.
The spring wrap is because the 1st gen van has only 2" leaf springs. It was a commun problem back then, thats why the future vehicles went wider and thicker.
I will make vidio and show the difference after the track bars are installed.

I am talking more then one vibration issue. It takes a bit of effective diognosis to filter out multiple vibrations because the can "harmonic" at different speeds and feel to be in different locations when they do that. So one really hasto pay attension to detail and gather all the facts before changing anything. I also have one very out rotor on the right rear and the tires need reballancing too. Once I have the list made up I will go at it.

Thanks for the offer Roll-in , I might take up the offer later I don't really trust the shop out here

Here is one problem: you can see the yoke bind and push the trans forward on this vidio
https://s119.photobucket.com/albums/o122/m1dadio/?action=view&current=yokepushingtrans.mp4
Yoke has very small twist and clear internal wear to the drive side.
I can also see shinny marks indicating the splines on the outside of the yoke, It has clearly undergone strain deformation enough to change its shape on the outside machined surface.

When I twist the drive shaft the opposite way of rotation to load the drive sides, it slides in and comes to a definite stop with a clunk 3/4" short of full insertion. Then relieving the hand torque it will release on go the rest the way,

I don't think the drive shaft is too long, a new yoke and some torque bars should fix this part of the problems.


The detail view shows the curve of the twisted splines in yellow. The Galling on the drive side in the red elipticle and the purple pointers show polished high spots where binding occures.

Its a good thing I cought this before I broke other stuff.
M1D

Wow... good detective work, and great pics / description M1D

Awesome write-Up Michel!!!

been slowly picking away at my van.
I have installed a new yoke and added braces to the trans mount. I realized that the trans mount hanging down 10" at 90* from the chasis lends to too much flexing no mater how you look at it. Most trans cross members are level with the frame of the vehicle so they can't flex forward and aft.

I added some braces to control that.





getting ready

to install the track bars



m1d

Nice!

I don't have the track bars on yet but allready its much improved. with the trans held more rigid there is alot less movement, I can feel the acceleration is more responsive and it all sounds different too.(on the inside that is)

here is the before and after trans mount vidio.

before

https://s119.photobucket.com/albums/o122/m1dadio/?action=view¤t=yokepushingtrans.mp4

after

https://s119.photobucket.com/albums/o122/m1dadio/?action=view¤t=newtransmount.mp4


m1d

Wow that certainly made a world of difference. Well done m1.

M1D,
Are you running the trans am rearend you said that you have?

Yes I have a 1979 trans am same as camaro or whatever, 1970 to 1981 10 bolt posi with 3:42 gear

M1D

What did you have to do to fix the off center issue with it?

Finally got around to instally the track bars.
rilled some holes


Made some nut plates



Bolted on the brackets I had welded to some angle iron.



Installed the bars







I will get some vodio action when the wether improves.

M1D

Looks great Mike ! What size tubing is that and how did you figure out what length you wanted to aim for?

The tubes are 1" X .219 wall X 48"

Fpr street use these track bars cannot be set up like when they get used on the track.



I had to draw it out from real time measurments off the van.

This is like a four link system. The two ends of the bar are two points and the other points are the forward leaf spring eye (#3) and the other point is the center of the axle at the top leaf spring. Unlike a drag race setup, this street setup must keep the pinnion angle the same as the axle moves up and down its suspention travel, no twisting of the axle housing can be permited other wise it will just break welds and parts.
If you were just doing strait line driving on a flat surface you could set it up to drive the axle down and lift the front of the vehicle but that won't work on a street machine that turns cornners and leans and twists.

Here is the before the track bars vidio

https://s119.photobucket.com/albums/o122/m1dadio/?action=view&current=drivelineanglechangeduetospringwrap.mp4

here is after the track bars
https://s119.photobucket.com/albums/o122/m1dadio/?action=view&current=Videoproject2012-04-01.mp4


M1D

That's a pretty big improvement from before. Something I will have to watch for as well. Thanks for the videos. And that looks like it's going to work well to.

Took the axles out of the rear end to machine them straight. They were both causing some bad vibes, seems they both had a woble, one .008" and the other .015".



I machined them straight and added larger 1/2" 20 thread in studs just to get rid of those wimpy 7/16 studs.







I had to tap the axle stud holes and the stads went in torqes to 110 ft/lbs with lock washers and loke tight thread locker.



M1D