2 piece tailshaft - length issues...

[shelldrake]

Hey guys,

I had a two piece tailshaft made up using a sprinter tailshaft as a base. I required one to suit the t-series diff flange at one end and the ae86 sprinter t-50 at the other. I got the measurements required to modify it by pushing the t-50 end into the box as far as it would go, pulling it out 20mm, then measured the distance from the holes in the bearing carrier to the mounting holes in the floor pan. (This is the distance I had the front piece extended)

I then bolted the centre bearing in at the mounting position and measured the gap between the rear tailshaft flange and the diff flange. (This is the distance I extended the rear section)

I ran with this setup without *(known)problems for about 1000-1500kms, then my diff started getting very noisy upon decelleration. Upon inspection of the diff, I found there was heaps of play now in the pinion, so much so that if shook the diff flange, it would move around in the housing up to 5mm-8mm*(approx) in all directions.

I thought perhaps the 20mm I had allowed the tail to slide into the box was not enough and when bolted in place at the centre bearing mount, I could only push it in about 5 mm. So I assumed I had grossly miscalculated the length somehow previously and shortened the front end a further 15 mm.*(This was f#$king stupid) Now the tail sits out of the box further than flush with the dust/stone guard (tube) housing a bit and the same distance between the diff flange and tail is seen. So, I'm wondering - If the centre bearing was nice and tight and new - Could this be putting excessive pressure at the diff end? Or would you assume the centre bearing could be pushed back and fourth up to 20-30mm without a problem? I suspect I will have to lengthen the front section now...again...

[allencr]

The pinion bearing is a tapered roller & I don't know the center bearing design, but it wouldn't be for thrust, while the trans is most likely just a caged ball.
That pinion bearing can take so much more end thrust compared to the trans mainshaft bearing that there really isn't any comparison at all in my mind, so to me any pinion failure would happen long after a trans failure.