Driveline vibration

[KMcCullah]

The F100 has a driveline vibration that starts at about 95 and by 115 it's vibrating so hard the tach looks like a bobble head doll. Lol well maybe not that bad. But damn near. Our yoke angle up and down is around 3 degrees. But our side to side is off by about 2 1/4 from the trans to the rear end. It's a long story how we ended up this way.  But we're pretty sure this is the source of our vibration.

So, dad and I are thinking about is adding a double cardan/CV joint to the tranny end of our driveline. Have any of you guys ever drag raced a 1350 CV joint?

[67xr7cat]

If it was the driveshaft I'd expect it to start vibrating at a lower speed. U joints don't care much if angle is up and down or side to side. I was always told as long as the angles are within reason and the same front and back.

I'd start by getting the balance checked. I'd try some other tires too. Good luck with it.

[BattlestarGalactic]

The offset sounds more like the issue.  It needs to be equal, like the up/down is.  If not, it's going to whip.

[Leny Mason]

Make sure it is clocked right, so the U joint's are in line, it is odd that it starts at that speed like a tire falling apart maybe. Leny Mason

[machoneman]

Spare the rod (driveshaft?) and spoil the child? 

I'd take it off and have a shop run-up the shaft to your critical speed 1st.

Long story....Uncle Bill's shop had a Dodge delivery van that all of a sudden had a bad shake at highway speeds. Dealer could not figure it out. Factory rep. came to see the vehicle, had the shaft off to a local shop and spun it up. A really tiny dent gave it away: the recent oil change at a quickie shop dented the shaft by not setting a 4-arm lift correctly. A new shaft fixed it. Bill btw hammered the shop with the Dodge reps. letter and they did pay for the shaft!

[Royce]

Oh I bet that 2 1/4 offset from center line is the culprit.. I been there too... U Joints do like to deal with 2 angles at once..In the end I bit the bullet and did what was necessary to get the pinion and the tail shaft lined up