![]() |
|
|
|
Registered
Join Date: Sep 2007
Location: Boston, MA
Posts: 1,469
|
915 Rebuild - Help Me Assess Gear Wear
I'm hoping to finally complete a project that actually started 20 years ago. I naively opened up my 915 back then after I found some chunks of metal on the drain plug.
What I found was so discouraging (in the days before Rennlist, Pelican, and online tutorials with photos) that I wasn't sure what to do. The chunks of metal turned out to be a piece of the pinion gear, and also the shattered bearing cage from the pinion shaft bearing in the intermediate case. Those bearing rollers weren't bearing much of anything anymore. The intermediate case bearing bores were out of round, and the bell housing bearing races were loose. I was also missing a ball from the pinion shaft bearing in the bell housing. I gradually started to accumulate new and used replacement parts, mostly from Gary Fairbanks. Someone on Rennlist (the old email list version) told me about a machine shop in Maine that fixed his bearing bores, so I shipped the cases off to them. Took a year to get the parts back. Hopefully this was done right, they used brass inserts rather than the steel used by CMS now. ![]() ![]() I pretty much have all the parts, but after all these years I hope I'm a bit wiser, and I realized that my plan to reuse second and third gears was a mistake because of wear on the pinion shaft gears where they are separated by a thrust washer. Here is the surface of 2nd gear where the thrust washer goes. No longer shiny and smooth: ![]() Same with the mating surface on 3rd gear: ![]() And the thrust washer is also chewed up: ![]() So I'm pretty sure these gears and the washer need to be replaced - agree? Now I'm also worried about first gear. I just noticed that the gear surface up against the syncro hub looks worn, even though the hub itself doesn't have a mark on it. And the needle bearing in there is distorted, so I need to replace that too: ![]() In summary, looks like I need to replace 1st, 2nd, and 3rd. Anyone disagree? And if I replace first, that means a new main shaft too, correct? What a mess. Looks like I'll be spending more money than I expected on this. Good sources of these parts used would be appreciated...... Thanks, Mark
__________________
1979 911SC Targa Last edited by Mark Salvetti; 08-22-2017 at 07:44 PM.. |
||
![]() |
|
Member 911 Anonymous
|
A close up of dogteeth, synchro bands, sliders top and below the gear and all gear teeth walls for unusual wear or pot markings would help us
As for the housing race/s if they do not slip out , they are good to go Consider getting a one piece bracket from CMS Edit, reading from a very small phone screen Yeah those gears on the sides are torn up
__________________
'85 Carrera Targa Factory Marble Grey/Black * Turbo Tail * 930 Steering Wheel* Sport Seats * 17" Fuchs (r) * 3.4 * 964 Cams * 915 * LSD * Factory SS * Turbo Tie Rods * Bilsteins * Euro Pre-Muff * SW Chip on 4K DME * NGK * Sienes GSK * Targa Body Brace PCA/POC Last edited by DRACO A5OG; 08-22-2017 at 08:03 PM.. |
||
![]() |
|
Registered
Join Date: Sep 2007
Location: Boston, MA
Posts: 1,469
|
Thanks Draco. I have the one-piece bracket from Guard. I didn't post the other pieces you mentioned because I already have them new.
New syncros for every gear, new Porsche dog teeth for 1st, 2nd, and 3rd. New sliders. Figured I'd take this one step at a time. I'm pretty comfortable with the condition of the other bits and pieces. Mark
__________________
1979 911SC Targa |
||
![]() |
|
Member 911 Anonymous
|
Yeah, I read you post carefully
Geez, I would not put those back in You may need a donor gear box for matching sets and shaft/s????
__________________
'85 Carrera Targa Factory Marble Grey/Black * Turbo Tail * 930 Steering Wheel* Sport Seats * 17" Fuchs (r) * 3.4 * 964 Cams * 915 * LSD * Factory SS * Turbo Tie Rods * Bilsteins * Euro Pre-Muff * SW Chip on 4K DME * NGK * Sienes GSK * Targa Body Brace PCA/POC |
||
![]() |
|
Registered
Join Date: Sep 2007
Location: Boston, MA
Posts: 1,469
|
That might make sense now, but long ago I bought a used R&P from Gary Fairbanks (and yeah, I'm familiar with the setup challenge there). So I think it may be cheaper at this point to just get the used parts I need. I think used 1, 2, and 3 are going to be around $1000.
Mark
__________________
1979 911SC Targa |
||
![]() |
|
Member 911 Anonymous
|
Yes, you waited this long just be patient you will find the parts you need and we are here to guide you on assembly.
![]() Break a Leg Brother!
__________________
'85 Carrera Targa Factory Marble Grey/Black * Turbo Tail * 930 Steering Wheel* Sport Seats * 17" Fuchs (r) * 3.4 * 964 Cams * 915 * LSD * Factory SS * Turbo Tie Rods * Bilsteins * Euro Pre-Muff * SW Chip on 4K DME * NGK * Sienes GSK * Targa Body Brace PCA/POC |
||
![]() |
|
![]() |
gearhead
Join Date: Nov 2007
Location: Loverland, CO
Posts: 23,555
|
I will be impressed if you can pull together 1-2-3 for under $1000. Also take a really good look at the condition on your 5/R slider. Those can get pretty hammered.
__________________
1974 914 Bumble Bee 2009 Outback XT 2008 Cayman S shop test Mule 1996 WRX V-limited 450/1000 |
||
![]() |
|
Registered
|
For what it's worth... these are a good deal: For Sale: Guard Transmission short gears for 915
__________________
1981 911SC restomod "Minerva" 2004 Boxster S 2021 Cayman GTS 4.0 manual "Olive" 2014 Cayenne GTS V8 (wife's lover) The slope is not slippery; in fact it is entirely frictionless. |
||
![]() |
|
Registered
Join Date: Sep 2007
Location: Boston, MA
Posts: 1,469
|
Thanks all. Those Guard gears are beautiful, but not in the budget/overkill for me, I'm afraid.
Matt, I was also thinking $1000 might be low, that's based on an eBay seller. But I have had a well-established member offer me 2-3 for $150 each, and 1st/main shaft for $250, so I'll probably go that route. It's hard to believe that despite all the damage, I had run a few autox events and two track events, and it still shifted. I was probably lucky it didn't blow up. Mark
__________________
1979 911SC Targa |
||
![]() |
|
gearhead
Join Date: Nov 2007
Location: Loverland, CO
Posts: 23,555
|
You owe those members beer and pizza. Those are brother pricing. Check the mainshaft for run out. Nothing worse than tightening everything up and then it won't turn.
The GT gears are super short. Not for a street built.
__________________
1974 914 Bumble Bee 2009 Outback XT 2008 Cayman S shop test Mule 1996 WRX V-limited 450/1000 |
||
![]() |
|
Registered
Join Date: Sep 2007
Location: Boston, MA
Posts: 1,469
|
Thanks again, Matt.
Yes, I will definitely check the main shaft for runout - I had already checked my original one and it was within spec. Mark
__________________
1979 911SC Targa |
||
![]() |
|
#147 of 2096
Join Date: Jul 2002
Location: Puerto Rico
Posts: 1,701
|
Why don't you search for another gearbox?
__________________
#147 of 2096 |
||
![]() |
|
Registered
Join Date: Oct 2005
Location: Northern California
Posts: 3,750
|
If you need an alternative source for stock gears, including a first, some of the dismantlers may have them. Apparently some of the parts are getting hard to find. I usually start with Partsheaven since I live nearby... going there tomorrow to inspect and likely pick up a Carrera main shaft/stock first gear and an 18:32 second.
Does anyone know off hand the runout spec? The GT gears I have for sale are not stock. They are still available. Good luck Mr. Salvetti, hopefully you'll get it back together with minimal hassle and cost.
__________________
Mike PCA Golden Gate Region Porsche Racing Club #4 BMWCCA NASA |
||
![]() |
|
Registered
Join Date: Sep 2007
Location: Boston, MA
Posts: 1,469
|
I've thought about that. It would have to be cheap, meaning a rebuild likely needed. I already have most of the parts for that (bearings, sliders, syncros, dog teeth), but once I replace these three gears, I don't think I'll need any more parts from a donor.
The one place a donor would really help is if the ring and pinion were in good shape, it would save me the setup issues. But that would mean having to use the donor cases as well, which will likely need the bearing bores repaired, and I've already done that to my case. Another gearbox was probably the best option when I started this mess, but at this point I think I might as well stick with what I have. Mark
__________________
1979 911SC Targa Last edited by Mark Salvetti; 08-24-2017 at 05:16 AM.. |
||
![]() |
|
Registered
Join Date: Sep 2007
Location: Boston, MA
Posts: 1,469
|
It is 0.1 mm measured at the pilot bearing surface.
![]()
__________________
1979 911SC Targa |
||
![]() |
|