grrrmonster

Just did a track prep on my 997.1 GT3. Was terrified to discover loose bolts holding the driveshaft flanges to the differential. More horror when it was discovered that the bolts, when tightened, only engaged the thread by one turn.

My dealer had replaced the axles last season. A year prior to that the dealer had replaced the diff with a Gard diff.

My tech says the 85mm bolts were too short- not able to properly engage and fully screw in to secure the driveaxle flange to the diff. He took 100mm bolts and cut down to 93mm to fully engage the threads.

Brought this to the attention of the dealer who had done the work on the axles and diff. They said 85mm are the proper bolts (had installed new ones). Attached is the Porsche part diagram calling for 85mm bolts (see item #10).

Something is wrong. Either Porsche's documentation is wrong, or the wrong axle was installed. Would appreciate insights and technical information to shed light on this.

Obviously has this come apart it would have been catastrophic. I'm losing faith in who to trust to work on this car.

Spyerx

check the axle part numbers. i'm guessing they're the wrong part.

I torque and paint mark these things on all my cars.

grrrmonster

Suspicious of axles. The short bolts freak me out

Spyerx

Hold on I'm confused. Those flange axles to the differential, there is ONE part number for all years for that. They're the same. That #10, there is 1 part number.

I thought you were referring to the drive axles. Those do have different part numbers .1 to .2 cars. However the bolt is the same on all, 49mm. (axle to the drive flange).

Something is weird.

coryf

The GT diff uses the motorsport flanges. The street flanges are longer and hollow in the end. This hollow center section fits over an extended threaded part inside the stock diff. The stock bolt engages the threads inside the end of the stock flange so the bolt works even though it barely extended out past the edge of the flange. The GT diff (or any factory cup diff) does not have the extended threaded section and uses the shorter motorsport axle flange. (I believe this is the same flange as on a 996 gt3 street and 996 turbo)

We ran into this same problem on a 997.1 turbo that had a GT diff installed by another shop. The flange bolt wouldn't engage and the flange would shift out of the seal in corners and leak gear oil.

Its hard to explain, a picture of the two flanges side by side would show the issue. The issue is part number 5 on the diagram is different than on the GT diff and is causing the problem.

Charles@dundonmotorsports

on a street car using a guard LSD those bolts (10) need to be longer.
My guess is that they replaced your axles and found those bolts not OEM so they replaced them, which was not the correct thing to do, but that shop probably did not know that the LSD was not aftermarket.

Get longer bolts and reinstall.


IF you are talking about the actual axle bolts, the ones with the t55 torx head on them, then that is another problem