Drive Shaft Wobble

[PeterH]

In trying to track down an odd noise from the offside rear (Spitfire III), I ran the car jacked up and wheels off. There is a significant wobble on the inboard end of the drive shaft, so much so it caused the vertical rear link to move.

 

Initial thought are bent drive shaft, bent diff flange, or some problem with the UJ / yoke.

The drive shaft flange is aligned with the diff flange and bolts are tight.

 

The car was put back on the road last year after major rebuild when all bearings etc were replaced, the noise was probably there from then.

 

Any thought on where to start and how to check.

 

Peter

[Pete Lewis]

if you have run-out  that's making the upright wobble then the shaft is bent , this often happens if  a shaft get refitted to opposite side they get a torsional memory and reversing rotation unwinds and they  can go wonky,   some can start to eminate a crack and they shear nicely

 

may have even had some plonker  jack it up in a previous life   but bent , has to go 

 

Pete

[PeterH]

This could also account for why I didn't notice the noise earlier. The shaft needed to 'unwind'.

It probably mean that I will have to replace both, as the other will also be on the opposite side.

 

Thanks

 

Peter

[Pete Lewis]

Pete,  dont get too carried away with this idea 

 

 

maybe pick one up and keep as a spare ,just in case , Im not saying this is always the case but there is some history with fitting second hand unkown's

and the bend occurs , the wind up clues are from many years in trucks with some much bigger and longer  shafts and this could cause early life failure

luckily many truck or live axle diffs have odd length shafts so you cant get it mixed , but on an old triumph who knows what goes on before us 

 

we used to induction harden shafts and rotation was taken into account as was as was a shear point so any overload would shear the shaft and save the diff.

 situations with ice under one wheel with a lot of wheel spin when  one  grabs a grip  the load through the planets is often destructive.

 

then the trouble is if you locate a nice second hand shaft.  you dont know what side its off unless the backplate or upright are still attached

 

 

Pete