Ring & Pinion: Usable or trash?

mar2mar · 01-31-2021, 12:48 PM

Hello,

After reading several transmission rebuild post I got the courage to open my spare 911/01 gearbox for inspection.

Unfortunately the pinion gear is pitted on all the teeth. Is it still safe to use this for street use on a stock 2.2S? Is this normal wear or caused by the pinion gear depth not properly set into the ring gear?

Thanks in advance
marlon

r lane · 01-31-2021, 12:56 PM

I cannot get a good picture of the teeth other than the one divot on the pinion head. If the surface has not eroded other than that one place, for a streeter, probably workable. I have a 901 R&P if you decide to replace yours

kevingross · 01-31-2021, 01:05 PM

Pinion is no longer usable. Those aren't pits, they are craters.

Matt Monson · 01-31-2021, 05:49 PM

Ouch. Trash.

mar2mar · 01-31-2021, 09:26 PM

Thank you folks. It is trash indeed

MBEngineering · 02-01-2021, 01:18 AM

HI

Looks like some one did not check/set the pinion deph when they had the box in bits last, from the amount of silicon sealer on the bearing plate, also check the play in the bearings before you remove the pinion bolt and the input-shaft nut.

I take it there was a gasket fitted to the box? and not just sealer

mar2mar · 02-01-2021, 02:24 PM

Mike, are you referring to this bearing-play in the attached video? No gaskets where installed on both side of the intermediate plate, just the maroon colored sealant.

https://youtu.be/osAx4gTTknM

Walt Fricke · 02-01-2021, 03:18 PM

Mike - it is pretty common for rebuilders not to use gaskets. At least for 915s. Honda/Yama bond and the like are common. Or orange Loctite, as with engine cases. Silicone probably not a good choice, though. Those stock paper gaskets are, well, paper thin - hard to see they would affect mesh etc significantly.

kevingross · 02-01-2021, 07:11 PM

Quote:

Originally Posted by Walt Fricke

Mike - it is pretty common for rebuilders not to use gaskets. At least for 915s. Honda/Yama bond and the like are common. Or orange Loctite, as with engine cases. Silicone probably not a good choice, though. Those stock paper gaskets are, well, paper thin - hard to see they would affect mesh etc significantly.

901 gearbox. Gaskets set the pinion depth. They are not optional.

MBEngineering · 02-02-2021, 01:42 AM

HI mar2mar

yes, had a look at the vid' and that amount I find is border line on replacment, also check the in/out, by pulling the speedo drive on the end of the bolt, I usualy check this when I have the pinion depth tool fitted to take a reading of, as the last "builder"/repairer skimped on the gasket set and also did not set the pinion depth with the tool/gaskets, it has pushed the pinion to-far into mesh with the crown wheel and as you have found out, cream-crackered the CWP $$$

Walt Fricke

as you have found out

"Mike - it is pretty common for rebuilders not to use gaskets./ hard to see they would affect mesh etc significantly",

if you look in the Workshop manual/ parts manual/PET, you will find that the gaskets used are of diffrent sizes to adjust the pinion position, before fitting the diff, once the pinion is in the correct position in the box, the crown wheel back lash can be set, this was prob' NOT looked at/checked on this box when it was put together, there is also a basic pinion setting with shims to do before the box is built, the shim calculation is made with the No' etched on the end of the pinion to select what shims should be used/fitted, between the pinion roller bearing and the spacer next to 5th gear

the gaskets for the early 901 Ally case are a slightly diff' shape to the Mag case 911/914 gearbox , so if you are to fit the gaskets, check you have the correct set for the box you are working on,

there should be in a gasket set;

1X end case gasket
3X main case to bearing plate gaskets of diff'sizes, 0.10-0.15-0.2 mm sizes, if you have a Erling set it may have only 3X 0.25 mm gaskets, so you will have to order in from Porsche the gaskets needed to set the pinion depth
?X oil seals

hope this helps with the box repair

one other thing, if you decide to get a S/H box, used or "rebuilt", please check that there are gaskets where there should be and if you have chance to look at the box before spending the $$, check that the diff flanges turn nice and smoothly, both to-gether to turn the box inside, if you have chance also remove the diff side plate to check the pinion before parting with the $$, would be worth getting a "o" ring for the side plate if the seller is not willing to remove the side plate, just to say there is a seal for the trouble?