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Discussion Starter #1
I’ve been chasing some driveline noise for a while at speeds over 60. I’ve fixed the pinion angle, new bearings, newer driveshaft and u joints. I put a stethoscope on the trans tail shaft with the car run in gear with the wheels off the ground and heard some noise. A little bit of a pulsating, grinding sound but not horrible sounding. I decided to drop my driveshaft to check the measurements to see if maybe there wasn’t enough inserted into the trans. Have a M20 trans 2.25” in the trans and 1.25” outside of the trans. Does that depth sound right?

Didn’t hear any noise from the diff with the scope either.
 

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1.25" showing sounds a bit much, but I don't know if it's too much. When I had Denny's Driveshaft make my high performance shaft they wanted the yoke pushed in until it bottoms, then pulled out 3/4", then measure center-to-center on the u-joint cups for correct length.
I know if you get it out too far, the driveshaft can go into a "jump rope" kind of harmonic rotation forcing the yoke to wobble and it tears out the yoke bushing in the trans tail housing and eats a groove in the yoke tube....I had that happen with a BorgWarner Super T-10 trans
 

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Is that measurement with the weight on the differential? you want to measure it with the suspension loaded. Also I would be looking into the tailshaft bushing if you think its making noise. There is a bushing that supports the yoke in the tail housing.
 

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Is that measurement with the weight on the differential? you want to measure it with the suspension loaded. Also I would be looking into the tailshaft bushing if you think its making noise. There is a bushing that supports the yoke in the tail housing.
It is with the cars full weight on the suspension.
 
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