vibration revisted

[reborn55]

Hate to beat a dead horse---working on driveline vibration--occurs above 60 mph and it is cyclical in nature. Have raised the trans so engine is just about 0-1 degrees down--raised it a little over and inch at the trans mount. rear end is still about 2-3 degrees down--I know it should be up and before I change the perches(am still trying to find a other rear end so I don't have to do it twice) are these angles great enough to cause the cyclical vibration I am feeling. Up to around 63 mph it is smooth as can be but as I increase speed over that you can start feeling the vibration. Maybe I should have driveshaft balanced next instead of perches. any help will be appreciate. thanks

[tomslik]

i think i would (check the driveshaft balance) and while you're at it, have 'em see how straight it is.
possible it's just a tight ujoint but that'll show up at the driveshaft shop...


or you could have somebody pull you 65 mph without the shaft in...

[wayne petty]

how much play do you have in the transmission out put shaft bushing to drive shaft yoke??

it should be minimal.... if there is too much.. you will get vibration..


its as easy as making sure there is no tension on the yoke.. from the transmission being in park and the wheels wedged ..  just grab the front yoke.. push up and pull down.. does it move any... if so.. output shaft bushings and a new rear seal...


there have been internal transmission rear case bushings that have failed... and caused similar problems..

[Charlie Chops 1940]

Ken,

You should be able to buy a tapered shim to tip your rear housing up 4 degrees. Speedway has them in 2 and 4 degree increments. They call it an angle shim.

Charlie

[chimp koose]

Charlie chops ,I was going to suggest the same.....shim it.Tomslic, great Idea,eliminates the driveshaft as the cause or not. Wayne,good idea I have also seen too short of a driveshaft with yoke hanging out too far ,do the bushing in with resultant vibration. All of these are driveshaft related. I replaced  an axle out of a friends 62 Tbird that  was machined so far off center from the forging that the bearing size would only have cleaned up on the last machining pass......and no vibration. probably because it would spin at 1/3 driveshaft speed.

[PeterR]

Hate to beat a dead horse---working on driveline vibration--occurs above 60 mph and it is cyclical in nature. ......

I have found driveshaft vibration due to misalignment is worst when drive load is applied and almost disappears when there is no load.

If you run up to the speed the vibration occurs, then slowly feather the gas pedal up and down so the engine passes from drive, to engine braking then back to drive again, then the severity of vibration due to misalignment will be barely noticeable as you float through the zero load spot.

If it persists through the test, then I would be looking at a balance problem.

[reborn55]

Got a call from driveshaft shop today--They said one end of the shaft  cocked to one side--whatever.  needed to be taken apart --put back together straight and rebalanced.  We shall see if I am any closer to Nirvana

[reborn55]

Installed driveshaft and a whole lot better--runs down the road like it should--can cruise at 70 with no problems and have located a 67 Camaro rear end with 2:73 gears for next to nothing.  thanks for all the help and enlightenment