Triumph Repair: 76 Spit knocking noise rear end, spider gears, shaft speed

Question
Hi,
  i have a knocking or rapping noise "sounds like drumming a stick inside a hollow box" in the rear end,it seems worse when i turn left but is still noticeable going straight.I have had the car up on a hoist and the u joints seem ok,no noise when wheels are lifted and car in gear running so it is an under load issue and is a rotational noise in gear or coasting out of gear,Any suggestions please.
    Thanks,Barry

Answer
Hi Berry,

First I always tried to note if it was wheel speed noise or drive shaft speed noise and you said it is worse when turning left but does the frequency or speed of the noise change turning left?

Also, switch the rear wheels from side to side and see if the turn noise changed.

If it does not do it on a lift try this. Run it up in gear and listen and then hold one wheel and run the speed up then do it to the other wheel. This exercises the spider gears in the differential.

Howard