intermediate shaft gear--more trouble more cost

[TR]

911 Intermediate shaft gear replacement.

like Wayne says in his book, rebuilding a 911 motor is more like restoring it, so if you are going to do it do it right. i agree thats why i want to replace all the internal sprocket's gears, chains and bearings.


So what is the dilemma? The intermediate shaft is good but I want to renew the Aluminium gear. Why the F*#&%"* can't I. There always seems to be some reason with these cars, that you need to engage some wizard, hobbit, warlocks, shaman or witchdoctor to iron out some gremlin that Porsche engineered into the car.

Just wondering. Does anyone know why intermediate shaft gears are sold separately when all the literature says you should replace the whole shaft with gears and chains sprockets all in one go.

I can understand the shafts being adjusted in situ when the motors were built but surly Porsche didn't make a different aluminium gear for every motor they built.

Or maybe they did if you look at the ridiculous price for the complete shaft.

I would like to know has anyone replaced JUST the aluminium gear and chain sprockets what has been the result.

Thanks

[Henry Schmidt]

Welcome to the board.
First, like every part in every engine there is a spec for a worn out part.
The intermediate shaft rarely should excessive wear.
The bearings will show wear but the bearing surface on the shaft will rarely wear. They are always true unless subjected to a catastrophic failure.
Now for the gear. Look at the aluminum gear and if you notice material movement the gear is likely trash. If the gear appears to be in good condition, set the bearings and crank in the case half mounted in the stand, install the intermediate shaft and check back lash. If the back lash is good .004-.007", run the gear. More backlash will not hurt but can sometimes lead to a slight knocking noise at idle. The sprockets can be purchased separately and should be replaces if you can lift the chain 1/8 " off the gear when placed in 180 degree contact with the gear. Always replace the chains if you are uncertain of their history.
Good luck

[TR]

Thanks I won't buy a new gear until I fully examine the aluminium gear but I will buy two new chain sprockets for the shaft.

[Eagledriver]

There are 2 sizes of aluminum gears. They are labeled "1" and "0". When I rebuilt my engine only 1 of the sizes was available. I think the other one is NLA. I don't remember which size was still available. There are markings on the crancase and crankshaft gears to determine which size you need. I reality your old gear will probably be so worn out that you will need to replace it and even the wrong size will be better than what you have. As long as you have some backlash with the new gear you are OK.

-Andy