[LJM97Z]

Thanks, I had the driveshaft checked, it was out, so they balanced it, I also re-adjusted the pinion angle for -2, the trans mount is good also, none of this changed the way the car reacts from before, I also installed non-adjustable upper arms from UMI, I then installed lower "adjustables" to currect the pinion agle & side too side tracking, still does the same thing, It really feels like a slightly bent driveshaft to me, but they showed me it on the machine as it was spinning with the dial indicator, The rear joint should be fine as it is new, its a combination joint, its sitting in the saddle good & snug from the looks of it.

I do know that the 9" sites off to one side on the pinion then the factory rear, could this cause a problem at a side angle? It still looks like the driveshaft is going fairly straight back in the tunnel.

[Blown496]

I fought a buzzing vibration like that on a Chevelle with narrowed 9". Turned out the big tires and wheels needed load balanced on a Hunter machine.

[LJM97Z]

Originally Posted by Blown496

I fought a buzzing vibration like that on a Chevelle with narrowed 9". Turned out the big tires and wheels needed load balanced on a Hunter machine.

I run 2 sets of tires/rims with the same problem, so i'm thinking i need to rule that out. But who knows. Is this type of balancing done on like dyno machines??

275/60/15 Coopers & 26x11.5 MT ET Street bias ply.

[prostreet6t9]

Originally Posted by LJM97Z

Thanks, I had the driveshaft checked, it was out, so they balanced it, I also re-adjusted the pinion angle for -2, the trans mount is good also, none of this changed the way the car reacts from before, I also installed non-adjustable upper arms from UMI, I then installed lower "adjustables" to currect the pinion agle & side too side tracking, still does the same thing, It really feels like a slightly bent driveshaft to me, but they showed me it on the machine as it was spinning with the dial indicator, The rear joint should be fine as it is new, its a combination joint, its sitting in the saddle good & snug from the looks of it.

I do know that the 9" sites off to one side on the pinion then the factory rear, could this cause a problem at a side angle? It still looks like the driveshaft is going fairly straight back in the tunnel.

Where on the driveline did they show you it was straight? On the ends? or? Do they have a balancer to fine tune it?

[timothale]

Spicer, U joints have a web site that has charts on how to compute the actual working angle, using the horizontal and verticle off sets. up and down and side to side. Normally the trans output-crank shaft is down and the pinion angle should be UP, both angles paralled at load position. If your suspension components have a large difference in length the pinion angle will change a corresponding larger arc swing. The 2003 Ford GT, modern version of the old GT40, has the rear half shafts running at an angle. It looks strange when I was used to looking at a Jag or Corvette rear suspension. We had links a few months ago when someone else was having drive shaft problems

[timothale]

I searched spicer drive line installation guide. http://www2.dana.com/pdf/J3311-1-DSSP.pdf The trig to calculate working angles is a couple pages and complicated. the above link is 19 pages n good info .

[Blown496]

Originally Posted by LJM97Z

I run 2 sets of tires/rims with the same problem, so i'm thinking i need to rule that out. But who knows. Is this type of balancing done on like dyno machines??

275/60/15 Coopers & 26x11.5 MT ET Street bias ply.

I could not get it to vibrate off the ground. Finally stumbles into a tire store that does a lot of big drag tire stuff and he tole me I needed an experienced operator to force balance them. Here is a link for locating the nearest shop.
Hunter GSP9700 Wheel vibration Control System solves wheel vibration and tire pull problems that balancers and aligners can't fix

[LJM97Z]

Originally Posted by Blown496

I could not get it to vibrate off the ground. Finally stumbles into a tire store that does a lot of big drag tire stuff and he tole me I needed an experienced operator to force balance them. Here is a link for locating the nearest shop.
Hunter GSP9700 Wheel vibration Control System solves wheel vibration and tire pull problems that balancers and aligners can't fix

I too put mine on stands, the drivetrain was very smooth, Now i do have one of the rims taking over 9 onces of weight, could this cause a problem even though it balanced out?

What exactly is force balance?

[timothale]

I have an old BEAR brand Balancer. It does both static balance and dynamic balance. static balance is like balancing a bicycle tire. It is free to turn by it's self and the heavy spot goes to the bottom. You wrap some wire around spokes on the light side until it doesn't turn. from any position on the clock That is how I balance the wire wheels on my 22 T antique racer. Dynamid balance is spin balancing. If you tie a lug nut on a 16 in piece of string and and slowly start spinning it horizontal, the string will NOT be horizontal at slow speeds. when you get it up to speed it will spin with the string horizontal. When the heavy spot on a tire is not centered but on either the inside or outside of the tire, at speed it will try to move that spot towards the center line giving you a wobble force. I don't remember what the factory spec was on wheel weights but I try to keep them under 6 oz. More than that and the tire will go on one of the farm trailers. or equipment for field use

[Blown496]

Look up that Hunter equipment or use the locator page and call one of them. They are very popular in the tire world. The machine uses a roller to simulate the tire on the ground under load. One of my tires had to be rotated to balance the heavy spots. I replaced the tires, yoke, all the bearings, new housing, new drums, new drive shaft and jacked the pinion angle up and down 1/2 degree at a time from 3 up to 3 down and the vib was always the same. I did runouts on wheels and axles and drive shaft and all was okay. I spent a lot of time and money before this $24 fix. I would guess that one of the Weld wheels is heavy on one side and the 29x18 wide Mickey radials don't help.

[prostreet6t9]

Originally Posted by LJM97Z

Thanks, I had the driveshaft checked, it was out, so they balanced it, I also re-adjusted the pinion angle for -2, the trans mount is good also, none of this changed the way the car reacts from before, I also installed non-adjustable upper arms from UMI, I then installed lower "adjustables" to currect the pinion agle & side too side tracking, still does the same thing, It really feels like a slightly bent driveshaft to me, but they showed me it on the machine as it was spinning with the dial indicator, The rear joint should be fine as it is new, its a combination joint, its sitting in the saddle good & snug from the looks of it.

I do know that the 9" sites off to one side on the pinion then the factory rear, could this cause a problem at a side angle? It still looks like the driveshaft is going fairly straight back in the tunnel.

Was the shaft straight all the way down the shaft? Did they Balance the shaft on a machine?

[LJM97Z]

Originally Posted by prostreet6t9

Was the shaft straight all the way down the shaft? Did they Balance the shaft on a machine?

Yes it was balanced on a machine.

[Blown496]

Have you talked to Brydon Papenburg? I assume that is who you bought the 9" from. GM is usually 1/2" offset. He can tell you how he built it.

[Blown496]

I will also add that the pinion angle should be opposite the engine angle. If engine is 3 degrees down pinion should be 3 degrees up. Parallel and opposite is the key.

[prostreet6t9]

Originally Posted by LJM97Z

Yes it was balanced on a machine.

And the tube was straight all the day down the tube?