915 Trans Internal Inspection

[Jcslocum]

My daughter is building a 3.4 (from 3.2) engine for her 76 backdate project. Dual Plug a little bit of porting, 20/21 cams, JE Pistons set to 9.8:1. The 915 that sits in front of this new build needed a clean up, inspection and reseal. I pulled it apart this morning to check the gears, dog teeth and syncro bands and have taken the pics below. The trans looks to have been opened previously as it has SS nuts and washers holding the various parts on. It could well have been rebuilt, the PO didn't know.

I would like a 2nd thru 100th opinion on condition. I'm no expert but have built a few trans of these type (901 and Alfa which uses very similar parts) and I'm pretty sure everything looks good except 1st gear.

I would appreciate any input you wish to offer.



1st gear (small) looks to have some wear.



1st Gear (large) shows a pitting line to me.



1st gear dog teeth



Syncro ban with a shiny spot but that wear area does NOT have a step that can be felt with the edge of screwdriver when dragged across



2nd gear dogs



3rd gear dogs



4th gear dogs

[lelix]

Is it a '76 box?
1st, 3rd and 4th dog teeth look a little tired. 2nd gear dog teeth look better than the rest, which might have been replaced last time it was opened. What do the shifting sleeves look like? Is the correct 1-2 shifting sleeve installed for your transmission year?
Definitely go further in and inspect the pinion bearing race(install 1pc retainer plate?), intermediate case races, shifting sleeves etc.
I guess it depends on how far you want to go into it. You will be running more power through the gearbox so it would be a good idea to go through it for a peace of mind while you have it apart.
I would START by putting new synchros, sliders and possibly dog teeth(depending on their condition and measured height of the new synchros). It's kind of a chain reaction.New synchros with worn sleeves and dog teeth is counter productive.
Just my $0.02

[yelcab1]

1st gear is tired, you know that comes with the shaft, right?

Your synchros look very shiny, candidates for replacement. The rest, I would suggest pulling them apart, clean off the oil, then repost the pictures.

[Jcslocum]

Update:

This from a 1976 911S Trans version 915/44

I have been able to pull the gear sets out of the trans and have a few pictures.

The races for the input and pinion shaft are not loose in the housing, or at least the do not move at all by hand and there appears to be no repairs made to the housing that I can see.

The bearings on the input and pinion shafts look good but the races do not. They are very smooth but completely grey in color where the rollers have been running. The rollers are a nice shiny chrome look to them. Are these bearings bad because of the color of the races?? See pics below.

I have yet to pull the diff out yet. That might happen tonight or on my conf call tomoorow morning :-)

[john walker's workshop]

You still need to disassemble the shafts for a proper look at the condition of the shift sleeves. they rub on the syncros and material wears off. Can't see that when they're installed. I see some polished syncros and blunted dog teeth.