Help me diagnose this gearbox drain plug debris

[Noah]

1970 911T, stock 5-speed gearbox, open diff. Street miles only. Was apart only 3K miles ago in the hands of a well-known specialist who freshened up a couple of synchros but otherwise declared it in great shape. It's original to my car and while TMU almost certainly doesn't have more than 100K on it.

After the rebuild, I noticed it now had a slight on-throttle whine in 5th gear. This was pretty minor so I ignored it, but the throttle was like an on-off switch for the noise. Touch the gas and it came on, let off and it went silent. It recently started getting louder, and then became audible in 4th, and then got even louder. Meanwhile it developed a faint ticking sound while pulling away in first gear.

I finally got around to draining the gear oil today and filtered it through a fine screen. Nothing came out on the screen. But the magnetic drain plug had some bits on it, along with a fair amount of gray paste that must be ferrous since it accumulated on the drain plug. Pics below, including of the sludge spread out on a paper towel (looking for metal bits). I'm not a gearbox guy but the metal bits on the drain plug don't actually look that horrendous. Small in number and tiny. But the whine doesn't lie so I assume I'll be doing a teardown.

Curious to hear any suggestions on what's going on here. I'm hoping it's not ring and pinion. Maybe the mainshaft or pinion shaft ball bearings?

[Jon B]

Was apart only 3K miles ago in the hands of a well-known specialist who freshened up a couple of synchros but otherwise declared it in great shape... After the rebuild, I noticed it now had a slight on-throttle whine in 5th gear. This was pretty minor so I ignored it, but the throttle was like an on-off switch for the noise. Touch the gas and it came on, let off and it went silent. It recently started getting louder, and then became audible in 4th, and then got even louder. Meanwhile it developed a faint ticking sound while pulling away in first gear.

Noah, have you brought this to the attention of the "well-known specialist" who did the work? Have you had him drive the car, and hear the noise himself? If you did, then what did he say... and if you haven't, then why not?
Did the transmission make any similar noises, even to a lesser degree, prior to the work being done?

Some metallic fuzz on the drain plug is normal, but the small steel shavings are not, and they're not a good sign. Unless he neglected to clean the plug 3K miles ago and it's the remains of an old issue, then it's possible that parts are making contact where contact normally shouldn't occur.

You say "...so I assume I'll be doing a teardown"- why will YOU be doing it? If the builder "declared it in great shape" 3K miles ago, then any damaged parts could be his responsibility, but he'd have to agree that something's wrong and take it apart himself. You could ask to be shown what the problem was when he has it apart, but you shouldn't take it apart yourself.

Jon B.
Vista, CA

[Jon B]

I was assuming that the work was done by someone local to you, but maybe you shipped the transmission to a rebuilder.
Even if the rebuilder isn't local, you should still explain the situation to him and hopefully work out a plan to remedy this, whether you send it back or have him cooperate with an alternative builder.

Jon B.
Vista, CA

[gled49]

I haven’t freshened up a gearbox in 20 years, except my race boxes that I know. 50 year old transmissions need careful complete overhauls including ring and pinion setup. G

[Noah]

I was assuming that the work was done by someone local to you, but maybe you shipped the transmission to a rebuilder.

It's complicated. He's now retired (this was three years ago) and I no longer live on the east coast. And it wasn't a full-on rebuild, it was a $1,200 inspection and freshening up. Could be that he missed something or set up something wrong, could also be that something wore out fast. Who knows, maybe no way of knowing. It's not a huge amount of money in the grand scheme of things and I'm not gonna make a federal case out of it.

[72targa]

That's an incredible amount of used oil goo for 3,000 miles...

[Richy]

To answer your original question , I think they may be pieces from one of the intermediate bearing races . Were they replaced ?

[HughH]

I dont know what the shavings may have come from and I note that the also work was done by someone who has now retired and was not a full rebuild.

However IF it was my gearbox I would not be using it any more until I found someone close who I trusted to take it apart, inspect it and (probably) repair it.
With any metal shavings on an oil plug I would be fearing the worst (but hoping for the best) and making sure I found out what had caused it before any more potential damage was done to internals.

If there is an emerging issue with it one thing that I would be certain of is that IF left it is likely to get a lot more expensive. If not (at least to me) it is worth the peace of mind to find out for sure.

Some years ago the pinion on my 915 box was being chewed up - all I heard was a faint whine at steady revs on freeways where there was not much else mechanical noise and there was NO debris in the oil at all.

I had the gearbox pulled apart as I knew the slight mechanical whine was not "right" despite no other symptoms and this, below, was the result when we had it apart


The gearbox had not been abused in any way and it has only street miles on it (and about 100,000 miles since the last full rebuild) but it seems that it could not take the torque of the 2.7E engine (all 2.7 RS bits but I kept the E cams) over a 40 year time frame. However if we had left it I have no doubt that it would have become much worse at some stage.
It now has a very beefy 8:35 R&P in it which makes the stock parts look puny and delicate and which I expect to last much longer than me