FirebirdStud

iTrader: (5)

I am trying to finally get rid of a vibration that is driving me nuts. I have a dana 60 that has about 7500 miles on it now. I installed a Tick Perf viper mainshaft conversion tranny in my car the same time I did the dana with Strange's seamless chromemoly driveshaft. Ever since I did this, I have had a vibration I cant seem to kick.

I have had the driveshaft high speed and low speed balanced, so that shouldn't be the problem. over time, it seemed to get better, until recently. I was developing a clunking, and upon inspection, the rear ujoint had play. I changed that out, and now the vibration is back worse then ever! from 75 on up it starts to vibrate, and gets progressively worse as I increase the speed.

I just balanced the tires, and I have run the car with the rear on jackstands, and the vibration is still there.

I think the worn ujoint may have masked the vibration, and installing a new one made everything tight again and the vibration is back with a vengence.

I have fought with this for some time now, but since I never go over 75 I have pretty much lived with it. But now I want to take it to the track, so the vibration has to take a hike because it just isn't right.

I have talked to Tick, and they said the tranny shouldn't make a vibration. I agree with them, but I did install this at the same time.

I have been playing with the angles of the driveshaft, and here is what I got:

Tranny angle is at 88.5 degrees
front of the driveshaft is at 91
rear of driveshaft is at 91
rear end pinion is at 89.5
All of these angles dont matter until you compare them:

I have shimmed up the tranny to get the tranny at 88.5, and when compared to the front of the driveshaft, this is a difference of 2.5 degrees. I have read that you should shoot for no more then 2 degrees, but I have already shimmed up the tranny as far as I could (the rubber mount on the top of the T56 is almost touching the tunnel now)
the rear of the tranny is only 1.5 degrees off from the rear, so I think that is ok.
The pinion has -1 degree built in difference from the tranny.

I think this is all pretty good, isn't it? If not, what should be changed?

This vibration is deffinately a speed-related issue, and not a motor RPM issue, as it comes on at 75. It doesn't show up hardly at all until that point.

AS a side note, this is the second time I have had to replace the rear ujoint. the front ujoint is still the original from strange engineering. Should I chage that one out too? It doesn't seem loose though.

I do have polly motor mounts and trans mount, but I have had a rubber tranny mount too recently and it still vibrated.

Im at a loss here. Like I said, this has been present since I installed the damn thing, and I dont know what else to do...

Thanks for your help and insight...
Cody

Bob@BruteSpeed

iTrader: (16)

We have tried different ways of setting up the pinion angle, and BMR's seems to work well. A negative 2 degrees has always worked well for street use and track use for us. Since you have gone through two rears u joints since you did the rear and trans, it seems to me the pinion angle is where you are off at. Bob

Set the pinion angle using the following method:

Load the rear axle by either setting the car on the ground or letting the car rest on jack stands positioned under the rear axle.

Place the angle finder on the driveshaft and record the angle. The driveshaft angle is negative if it slopes downward towards the rear of the car. The driveshaft angle is positive if it slopes upward towards the rear of the car.

Now place the angle finder on the rear end torque arm mounting plate and record the angle. The rear end angle is negative if it slopes downward towards the front of the car. The rear end angle is positive if it slopes upward towards the front of the car.

Add the two measurements. This is your pinion angle. (Example: -2 rear end angle plus -1 driveshaft angle = -3 degrees)

FirebirdStud

iTrader: (5)

Well, my problem with that way of measuring angles is that it doesn't take into account the transmission angle. I thought that the pinion angle has to be down 2 degrees negative relative to the transmission output shaft, not to the driveshaft. Am I wrong?

c5z28

iTrader: (11)

I put a poly mount on my transmission and it vibrated a lot. Put a stocker in there and it stopped it. Just a possibility I thought I would throw out there.

FirebirdStud

iTrader: (5)

Thanks for posting!

I have had the rubber one in too, and all it does is absorb the vibrations a little. With a finely tuned car, the polly trans mount shouldn't be a problem. I need to find the source of the vibrations, and not just cover them up with the weak mount. I want to get this thing running good so I can go to the track and see what she can do!

sheikss

iTrader: (11)

I have the same problem.

FirstYrLS1Z

iTrader: (4)

pinion angle is relative to the driveshaft,-2 degrees will put the driveshaft/pinion in the shape of a very wide open V.
2 degrees downward from a straight line/centerlines.
I've never data as far as angle relationship between trans output shaft and driveshaft.

Bob@BruteSpeed

iTrader: (16)

That is true, it does not take into account the transmission angle, but you should try it once to see if it gets rid of the vibration. Bob

FirebirdStud

iTrader: (5)

first: I LOVE your sig. That is pretty funny.

Second, what are you running for drivetrain? I have tick perf viper converstion tranny, strange seamless chromemoly driveshaft, strange dana 60 rear. Tires are irrelevant because they have been shown to be fine (bolted up stock set, same crap)

Interested in your setup though!

FirebirdStud

iTrader: (5)

by shimming the tranny up, I have the transmission and the pinion at the same certerline angle. the driveshaft is now 3 degrees down from the tranny and 3 degrees up from the rear.

I was given a GM technical manual by a co-worker ( I work at a Dealership) and it said to minimize vibrations, the driveshaft needs to have the same working angles on both sides. So I thought I would give it a shot... Ill see what happens when I get to drive it!

FirebirdStud

iTrader: (5)

I have tired from -4 degrees to +2 degrees relative to the driveshaft, doesn't seem to be doing much. So that is why I equalized the angles, we shall see what happens when I can drive it.

stock01ws6

I have the same problem. I have a Spohn Extream driveshaft with a moser 9. I have been under the car 2 days total of 18 hours adjusting pinion angle and centering the rear with no luck. I have all on car Spohn susp. The only thing now is to get a longer driveline do to the fact that I noticed that when I changed the yoke to the viper that it was shorter. So it looks like the driveshaft is not going into the the bushing in the trans deep enough, casuing the front yoke to vibrate.

FirebirdStud

iTrader: (5)

Sorry I haven't posted back the results... Ive been in China for over 3 weeks.

But, Im back and the car is a new beast. No longer am I limited to 80mph in the car... I can go as fast as I want with very little vibration!

Setting my pinion angle to be the same angle, but in the opposite direction of the tranny did the trick! So, everyone with this vibration at 70+ here is your solution!!