Rear End Slop

[Fatauto]

My 1966 fastback rear end started making some noise from power on to power off. The video is her with the rear up and me holding the driveshaft. Seems to have a bit of play into the Tremec as well. 427 ci thru a 6 speed with ~525 at the crank. Assuming just order a new third member like yesterday?? Always had a bit of a clunk but significant step change in feel and sound this week. Thanks for the input.

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[paulm1]

my 2021 IRS is no better than that. Doesn't look that bad to me. Are you getting a rear gear whine at highway speed?

 

[Hack]

The noise you mentioned could be rear diff gears. They seem the most likely culprit, I guess. I'm reluctant to agree with you just because I'm not used to hearing about rear gears wearing in such a way. I don't have any experience with a high power setup like you have, though.

I would like to see you pull the axles at a minimum just to look at them prior to throwing parts at it. It's easy and fast to pull them on a 9 inch. How many splines are you running?

 

[Fatauto]

Not sure of the spline count yet, never had it open. Put a new motor in from CREB so had the front end apart but have not been into the back half yet. Also have some slop going into the Tremec. Here is a video of the drive shaft at the output shaft. Hard to hear the rear at highway speed, she is very loud. I thought it was a bad u-joint. That very distinct clunk as the engine goes from putting power down to engine braking. She's a high strung engine so lots of strain on the driveline. Anyone else have that much play in the rear diff?

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