Transmission shaft play (damage?)

[sato]

Good day all.

Similar to what @chaoskaze experienced with his transmission after clutch replacement (Similar thread), I started experiencing a certain vibration nearing the 3000rpm range. This vibration was felt even more while decelerating and especially in 5th gear.

When I replaced the clutch components, I decided on new Exedy flywheel, ARP flywheel bolts, Exedy Stg1 kit (including input shaft bearing and obviously replacing the infamous clutch release bearing with the updated part.

I'll be posting pictures of the old components (here), replaced after approximately 100k miles of use (they didn't look pretty), car approximately ~155k miles on car. At time of clutch replacement, there was a little bit of trouble with the throwout bearing (surprised it lasted so long).

In the meantime, here is a video of the teardown and primary issue, as stated by the mechanic.

Shaft Play Video


Not discarding anything as a root cause or contributor at this point in time, my initial question would be what can create such shaft play?

PS This is a completely OEM daily driver with the exception of tires.

[Ultramaroon]

That play is normal. Radial alignment is maintained by the pilot bearing in the crankshaft. The input shaft actually needs some play to account for manufacturing imperfection.


edit: I used the wrong term to describe the type of alignment in question.

[sato]

NOTE: Added pictures and video regarding previous clutch replacement in 1st post (for reference only).

Originally Posted by Ultramaroon

That play is normal. Axial alignment is maintained by the pilot bearing in the crankshaft. The input shaft actually needs some play to account for tolerance stack.

Thanks for replying. I was recently mentioned exactly that.

I do ask though, is there such a thing as too much play (like the mechanic was stating)? Is there a specification for such play in the repair manual (perhaps)?

[Ultramaroon]

Yes, there can be too much play but the manual does not specify an inspection. That joint is a slip fit for good reason. With each reversal of torque applied to the input shaft, the bearing slides until it comes to rest against the opposite retaining clip. It is also swimming in oil as it does so.

By design, the input and output shafts are driven apart by the mid shaft whenever forward torque is applied. Under engine braking, the axial forces are reversed.

I wonder much more about what that bearing does to the case when it slams back and forth under wheel hop. That's why I swapped my original transmission for a salvaged one. I'm still twelve years old on the inside and I like it that way.

[Ultramaroon]

Now that I've watched your video clip a few times, I think I've had it wrong. I couldn't believe that the trans front cover - the quill - was the thing reacting to the input shaft bearing. Now I see that it must!

This means that the axial hammering from wheel hop causes the ONE clip in between the case and cover to slam back and forth. Hmmm... o.0