New MT driveshaft, too short?

[Tainen]

Hello!

I picked up a Dorman OE replacement driveshaft last week to put in during a m20 motor swap (found a rebuilt m20 locally for $800). I went to go put it in tonight, and I loosen the spline nut enough to attach it to the rear diff, and bam- it de-threads itself, it's about an inch too short.

build date- 3/1987, with dorman driveshaft 936-368, listed here:

https://www.dormanproducts.com/p-83289-936-368.aspx?make=BMW&model=325i&parttype=Drive%2520Shaft

I'm not sure what I'm doing wrong. Does the transmission need to slide back somehow? Is the rear plate thinner on the new shaft? I don't have my stock shaft anymore to compare against, a local e30 kid picked it up for his build.

edit: I did not reinstall the harmonic balancer thingy when I put it back together, but it doesn't seem that thick at all, and reading up here on rev makes it seem useless.

[Tainen]

Found the issue.

The collar lock nut on the driveshaft was BONE DRY, and would not slide rearward at all. Since the item came as a complete unit drop in replacement, I would figure they greased it- but it is not.

After applying grease like the Bentley says, I managed to get it moving a bit, and slide it back towards the rear shaft threads and thread it on.

Mods, you may delete this thread. thank you. (No delete button upon trying to edit the thread)

[agisthos]

No need to delete this thread, as its useful information for someone who may came across the same issue later!