What's happening to this gear?

Jerome74911S · 07:12 AM

I removed the shift guide fork cover on the bottom of the transmission to see what was happening inside.

I took a look and noticed the gear on the left. A closer picture is below.

What is this gear, and what is happening to it? It's rough. I used Kendall oil. The trans was rebuilt about 15,000 to 20,000 miles ago. Ordinary road use only.

Spumato · Spumato's Garage

Kendall over Swepco? Was this your choice?

Jerome74911S · 04-22-2015, 12:47 PM

Quote:

Originally Posted by Spumato

Kendall over Swepco? Was this your choice?

I've read all the oil debates, and as a result selected Kendall for street use. There is strong support for this here.

Trackrash · Trackrash's Garage

Was there anything on the drain's magnet? I don't think that looks like normal wear. I would guess that something like some synchro or bearing bits got in there.

A little history on the car or trans may help in the diagnosis. Was is making any noises?

Others with more experience hopefully will chime in.

Jerome74911S · 04-22-2015, 01:33 PM

The drain plug had only microscopic 'fur' on it, and not a lot of that. Looked like dark, fine mud, but really only a little. No actual tiny pieces of anything, either.

The only noise I notice all the time I think is the R&P. I had it properly shimmed using the correct Porsche tool, but in the end, there are over 100,000 miles on it and there is some wear.

Jerome74911S · 04-23-2015, 07:03 AM

I'm bumping this post because I really would appreciate some solid advice before I refill the trans with oil.

Can I run this for another season? What does that gear run against? Road use only.

Matt Monson · 04-23-2015, 07:49 AM

You've probably got a bad bearing that is allowing the gear to run crooked and not mesh properly against its mate. You may be hearing the bad bearing and not the ring and pinion. You are taking your chances if you run another season on it.

db_cooper · db_cooper's Garage

If this is your 1974 911..my guess would be at one time in the past the transmission may have had a loose pinion bearing..maybe. Could of been some other transmission fault since 1974 too. Has the transmission been rebuilt? Noises from the gearbox? Could be a loose pinion bearing.

I use Swepco personally...but I doubt the gear wear you see is a lubrication problem..I think it is an old 915 having been rebuilt in its history with a re-used gear that should of been replaced or a loose pinion bearing.

lelix · 04-23-2015, 11:12 AM

IIRC that gear is splined onto the pinion shaft. Can you see if the "raised collar" on the gear is facing the right way? It should be facing the bearing race.

Jerome74911S · 04-23-2015, 12:44 PM

Quote:

Originally Posted by lelix

IIRC that gear is splined onto the pinion shaft. Can you see if the "raised collar" on the gear is facing the right way? It should be facing the bearing race.

Good question. I'll examine my other photos, but if I can't see what I need to see, I'll pull that cover off again. Thanks.

KTL · 04-23-2015, 02:01 PM

Yes that is fixed 4th gear on the pinion shaft and I think the raised section of the gear is properly facing the bearing in the retainer plate. If it was reversed, I think the gear would be really tight up against the bearing on the left.

Does every 4th gear tooth look like that or only that area pictured? Reason I ask is because if it's just that one area, the trans could have munched something in the past and spit it out. 4th gear is typically 1:1 ratio and that means the same teeth are always meshing with each other. So the munched teeth are only contacting the munched teeth on the other gear its paired with. That tooth damage would not be spread to all other teeth in the gear pair, as would be the case on another gear like 3rd for instance (23/29 = 1.260869565....) Just a guess on my part.