Clunk sounds when shifting into reverse or drive

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sctrl

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So once in a while, I hear a clunk when shifting from P to R to D. Usually happens first time after cold start. And the shift into gear is slow. Not sure where clunck sound coming from. I recently changed motor mounts but it had no effect on this. Did not change tranny mount yet, it seems solid. I recorded a video of tranny and u joint. Also noticed oil drips during shifts. Is that normal?
 

swathdiver

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So once in a while, I hear a clunk when shifting from P to R to D. Usually happens first time after cold start. And the shift into gear is slow. Not sure where clunck sound coming from. I recently changed motor mounts but it had no effect on this. Did not change tranny mount yet, it seems solid. I recorded a video of tranny and u joint. Also noticed oil drips during shifts. Is that normal?
Time for a new tail shaft seal. Not normal! Check your u-joints and rear axle for excessive play.
 

OR VietVet

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I thought I saw play at the u-joint as well but as I looked closer, I could not say for sure but I thought I saw play on the first watch of the video. Yes, seal is bad and should be replaced and while the driveshaft is out for that, it is a perfect time to do a thorough inspection of the shaft. When you slide the shaft yoke out, make sure to inspect the smooth part of the yoke for scrapes or gouges, which is a sign of a tail shaft bushing going bad and the yoke should be replaced at the same time. If one u-joint is bad, do 'em all. Check for pinion bearing play at the rear diff and if you really want to get thorough, remove the diff cover and inspect the fluid and for any gear damage and check for too much slop at the gears.
 
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sctrl

sctrl

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Thanks guys. That’s a lot of work. I’ll replace the seal and check u-joints. But replacing those suckers is out of my league. I don’t even own a vice or a garage. Have to find a good mechanic.
 

OR VietVet

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Don't go cheap on the seal. Genuine GM is my choice. If you don't know how to do the u-joints and have no tools to do it, best to allow a qualified tech do it to protect balance of the shaft. Also, Don't do the seal if you think you are just going to hammer a flat blade screw driver at it to pry it off and then tap in a new seal. That is a GREAT way to damage the new seal. Use a seal driver tool and use a small slide hammer with a curved pick on the end to get the seal out. If you don't have these tools, let the tech do the whole job. Show the tech your video so he can diagnose easier during a before and after road test. He better road test, anyway.
 

swathdiver

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Thanks guys. That’s a lot of work. I’ll replace the seal and check u-joints. But replacing those suckers is out of my league. I don’t even own a vice or a garage. Have to find a good mechanic.
An OTC 4508 makes short work of removing stubborn seals. Solid U-joints are like the Spicer 5-1350X for the rear and 5-795X for the front.

Mine has a different rear seal but to give you an idea, the seal installation tool part numbers are J-8092 (universal handle for lots of tools) and the DT-48210 (seal driver).
 
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