Yes, the rear oil seal is replaceable:
* 32136-H5000 OIL SEAL-REAR EXTENSION

But what about the bushing? Nissan doesn't list one. The Factory service manual says:Quote:

That rear bush is removable, you just tap it off with a soft mallet, then put the new one on, I usually use a large socket & hit that to drive the bush home. Check to see the back half of the housing isn't cracked. I can still remember Woody blowing this part of the gearbox off at speed. He was chasing leaks from the back seal for a while, maybe thats the problem. Good spray of some degreaser & a clean up should show up any cracks.

It's somewhat better further in but the yoke is almost bottomed out already on account of my car being 3.5" lower than standard....

not worn on the splines?
if you feed the shaft in a little does it take up the play???

Hey thanks for the reply! I don't think it's the seal or dust cover though... when you grab the dive shaft yoke you can wiggle it and there is obvious slop. Not a ton, but enough I think to cause vibration.

That’s what the B210 series and B310 series manuals say alright! Had this tranny novice perplexed too. Thought I had your same problem once, but after I broke the transmission apart, I found the Rear extension bushing to be in good shape and it turned out to be the Rear Extension Dust cover and oil seal assy that was loose.

SKL Rear Extension Dust Cover and Seal Assy P/N 11619 for FS5W60A

I made a note to check this when I opened up four other Datsun 60 series 4 and 5 speeds- all had acceptable bushings. I was worried because I have had not seen entire transmission rear extension cases for offered up for sale. And after all this is said, you may indeed have a bad bushing, this is just my experience. If it is your bushing, a specialty transmission shop should be able to adapt one for you.

Is there any cure for a sloppy rear bush at the rear of a FS5W60A 5 speed? (Where the Driveshaft goes in) The manual is unclear and says if it's worn to replace the whole rear case with a new one! Maybe in the '70s, but that doesn't seam likely these days! any help?