Hi everyone! Long time member here but really my first post! I am in the process of getting ready my old girl (1970 240z) for a longish rally and thought I should probably change the transmission oil....  Any ideas as to what this mystery piece of metal is that I found when draining my 5spd transmission? 

Aaarh A lurker. Welcome, I think....

 

Those pieces in the photo are from a bearing. Its the cage that holds the balls in position. You can see it in the bearings in the photo.

Im trying to determine the width on the photo. Could narrow down which bearing it is. Not that it makes much difference, if those pieces are floating around in the transmission, won't be long before you do some real damage to the transmission.

Does the transmission make any abnormal noises. Would think you would hear a bearing in there somewhere. I would not drive it anymore with a bearing like that especially a longish rally.

 

 

That is a bearing ball cage, or separator.  Holds the ball bearings separated in the bearing assembly.  Not good, it means that one of your bearings is loose and failing.  Probably one in the adapter plate.

Here's some links and a picture.

http://www.globalspec.com/learnmore/mechanical_components/bearings_bushings/radial_ball_bearings

Thanks for the welcome Eurodat! Definitely a lurker... many tidbits of useful information garnered from this site. The bearing race? is 4.45mm or 11/64s in width. The car isn't going anywhere at the moment, she's up on jack stands with the suspension apart awaiting new springs for the coil overs and getting rust proofed.

She wasn't making any odd noises, never fell out of gear and didn't feel spongy at all. Did have a soft whirring when the clutch was let out in neutral.

I madecsome quick measurements of my old bearings. Looks like Zed Head is right. The cage for the main shaft adapter plate bearing is 4.45mm.

If its not noisy, I would at least fit a bearing kit.

See photo. Its of a 5 speed, but the bearing in question is the same. POS 29.

Thanks for that info. Although I have tackled most jobs on a Z, I have never had the nerve to split open a transmission. Any links that you can recommend for this procedure and any suppliers for the bearing kit? I saw this one on ebay...

http://pages.ebay.com/motors/link/?nav=item.view&id=331763644801&alt=web

 

I just took a guess because I've seen one of those bearings failed.  I bought an abused 5 speed and took it apart.  All kinds of carnage along with the failed bearing.  Some of the balls had fallen out also.

Even though the transmission still works well I think that the shaft is now misaligned because the balls can all move to one side.  This would let the end of the shaft move to the other side.  Close to double the original tolerance, I'd guess, but not quite.  This makes the gear surfaces non-parallel and puts odd loads on them, I would think.

Four speeds are plentiful and relatively inexpensive.  People tend to swap in late model 5 speeds and end up with  leftover 4 speeds.  You might consider just buying a used unit.  Or buy a used unit and rebuild the original.  Although, your 1970 might have the "monkey motion" shifter and unique gear ratios.  So, might be worth a rebuild anyway, for originality.

The car has an L28 and the Trans was in her when I bought it some 23 years ago... probably out of a late 70s 280z.  I may have to try and find one if the shaft is toast. I am just about to drop it out of the car. Would splitting it open tell me anything or should I take it to a shop?

 

Easy to pull the front and back covers off. Whether you do it or not depends on your curiousity. You'll be able to see almost everything inside if you do. Might help with the decision.

Quote

 I am in the process of getting ready my old girl (1970 240z) for a longish rally 

You're prepping for an event and having a debate on whether the transmission can be used?  Pull it and replace it with a known good unit.

Odds are it's a 75-77 4 speed then.  Very common.  I think that you can see those adapter plate bearings from either the front or the back so splitting it would let you see the damaged bearing.  It takes some work to get to it though.  Check the 1976 MT chapter of the Service Manual to see what's involved.

You can tell by the damage though that the cage got ripped off by some gear teeth.  Probably an end came loose, it flapped around a but then got sucked in to some gears.  

Many paths possible.  Tear it down and install new bearings, find a used 4 speed, or take the opportunity to go for a 5 speed (it's a direct swap).

http://www.classiczcars.com/files/category/4-manuals/