915 transmission 1st gear dog teeth broken fixes?

[Gonbad]

This is first gear on the pinion shaft correct?



Here are the dog teeth on that gear:





I suspect those aren’t supposed to look like that .

Ok I haven’t cleaned the gear up but are the dog teeth separate from the gear and can therefore be removed and replaced?

Hopefully they can so I don’t have to replace the entire gear and therefore the main shaft too!

Not my first transmission rebuild but my first 915 so be gentle.

[30westrob]

Yes, you don’t have to replace the gear. Replaced the synchro hub only. Search and you will find how the hub is removed and installed to the gear.
Check the underside of the first/ second operating sleeve, for damage and wear. Rob

[proporsche]

while you are there replace all synchros and inspect all since all those teeth could have done some damage..

Ivan

[mepstein]

You really want to step back and assess every part. Syncros, sliders, dogs, bearings, ring and pinion. It doesn’t make sense to put out of spec parts back into the box, just to tear it down again in the near future.

[Gonbad]

Reverse and the idlers in the tail section of transmission are toast too.




All the synchro friction bands, bearings and races will be replaced along with the billet bearing plate. Case is likely to get the steel bearing race supports machined in as well.

[proporsche]

i had a feeling there would be something like this...good job..
Ivan

[yelcab1]

There is no such thing as a cheap transmission rebuild.

Disassemble it, clean up all the pieces, and carefully inspect all gears and bearings.

It would not be a surprise if...

1. More than one gear sets need replacement
2. More than one syncro rings need replacement
3. The intermediate housing bearing is spinning in its housing
4. At least one or two bearings are toast, making noise, and showing wear marks.
5. Whatever dog teeth needing replacement, shift sliders also go with that.

[Matt Monson]

You dodged a bullet. Oftentimes when that many teeth are gone the synchro pops off and goes through the whole thing like a grenade. You’ve got your work cut out for you, but it’s all “normal” things as far as a 915 is concerned.

I might have a reverse gear set.

[Dpmulvan]

Who’s doing bearing plates these days?

[Matt Monson]

Originally Posted by Dpmulvan

Who’s doing bearing plates these days?

I’ve never stopped in 2 decades of production.

[Gonbad]

Originally Posted by yelcab1

There is no such thing as a cheap transmission rebuild.

Disassemble it, clean up all the pieces, and carefully inspect all gears and bearings.

It would not be a surprise if...

1. More than one gear sets need replacement
2. More than one synchro rings need replacement
3. The intermediate housing bearing is spinning in its housing
4. At least one or two bearings are toast, making noise, and showing wear marks.
5. Whatever dog teeth needing replacement, shift sliders also go with that.

Only gear set so far is reverse.
All the synchro friction rings will be replaced.
Housing bearings not moving around. Will be doing the one piece billet retainer plate. Maybe go ahead have have the housings machined and reinforced as this will have some horsepower behind it.
1/2 dog teeth definitely and slider. Have yet to determine 3/4 teeth and slider.

[Matt Monson]

How much power? From what source?
The Wevo machined in case inserts are the no holds barred reinforcement, but it still doesn’t do anything for the strength of the gears.

[Gonbad]

Originally Posted by Matt Monson

How much power? From what source?
The Wevo machined in case inserts are the no holds barred reinforcement, but it still doesn’t do anything for the strength of the gears.

My understanding is that WEVO no longer does the steel inserts as they no longer have the inhouse machining available. I will double check that.

I am searching for a M64 3.6L so HP will be 300+.

I was cleaning the bellhousing case today and the pinion race just fell out. So I guess I will be doing this anyways.

[Gonbad]

Boy the parts list is getting long:

1. Reverse gear set $$$$
2. Shift fork 1/2
3. Shift fork 3/4
4. Synchros 1st - 5th
5. Dog teeth 1st & 2nd
6. Sliders 1st/2nd & 5th/Reverse $$$$
7. Needle cage bearing x 5
8. Locknut Pinion
9. Needle cage idler x 2
10. Axial thrust needle bearing
11. Billet bearing retainer
12. Locknut main shaft
13. Bolts release tube x 2
14. CV axle gaskets x 2
15. Main shaft front, center and rear bearings
16. Pinion shaft front, center and rear bearings
17. Gear case bearing circlips x 4
18. Reverse switch boot
19. Billet side plate
20. Gasket and seals Kit
21. Machining Bell Housing case for bearing bore repair

That comes out to $6,200

With new Wavetrac differential it’s $7,900.

Still a few things to check on 3rd and 4th plus I need the carrier bearings for the differential but I can’t do that until after the case is machined and I have correct bearing for the side plate. Apparently it uses a different bearing.

[yelcab1]

Aren't you glad your labor is free?

[john walker's workshop]

Why shift forks and why no 3/4 shift sleeve? Lets see the inside of the 3/4 sleeve, both sides showing the pointed ends of the splines.

[Gonbad]

Originally Posted by yelcab1

Aren't you glad your labor is free?

My labor isn’t free. My wife makes sure the time I spend on the Porsche is more than made up working on what she wants done.

[Gonbad]

Originally Posted by john walker's workshop

Why shift forks and why no 3/4 shift sleeve? Lets see the inside of the 3/4 sleeve, both sides showing the pointed ends of the splines.

I haven’t pulled 3rd and 4th gear off the main shaft. The 3/4 fork though is worn. It is grooved to the point that it has a lip/ridge that you can see and feel. I am hoping the 3/4 sleeve is ok as that is another expensive piece and then add in the associated dog teeth. Ugh!

The damn 5/Rev sleeve new here on Pelican is $1,100. I found another site that has them for $650 from the OEM supplier they say. I was lucky enough to find a good one on eBay for half that price.

The reverse gear set was even worse. I found a good used set in Germany for like a 1/4th of what they were selling for here used.

None of this is a surprise as there is no such thing as a cheap Porsche. This car has over 200k miles on it and the transmission was a known problem when I bought it. This transmission has probably been rebuilt at least once long ago. Although I doubt the bearings have ever been replaced. They role but not well or smoothly. So I figure by the time I’m done I’ll have replaced everything in the transmission other than the gears, shafts, bushings and shift arms. I may end up replacing the bushings or polish them as the needle cage bearings were also done and cracked.

[Gonbad]

Interesting - the cogged bushings are definitely “NLA” and the non-cogged bushings look to be as well. So I guess they will end up in my polisher.

[OsoMoore]

Transmission rebuild work is detailed but totally doable at home. Mine some years back only needed some dog teeth and 1st gear replaced. Shop pushed the teeth off and back on for me for $20.
Cost me $1k in parts about 11 years ago, but I didn't have to replace that much (rebuilt ~60K miles before).

There are very excellent details here to guide you through. Just take lots of pictures and zip-tie stuff together as you take it apart to ensure wear-sides stay matched.