Wear of intermediate shaft

[Elferhelfer]

Hello,
I could your help and recommendations about the reuse of an intermediate shaft on a 911 E 2.0L engine. Actually, I’m rebuilding a engine and the engine case is in good shape and I already modified it with an oil bypass and and a proper seat for the intermediate shaft with bearings.

According Porsches booklet “Typen, Masse, Toleranzen“ the shaft should be within 25,000 – 24,980mm.

After measuring I’m a little bit confused and could need your advises and opinions. I checked the intermediate shaft; it looks in good shape, but I measured the bearing No. 1 has 24,966 mm.

I already have two other additional intermediate shaft for comparison and they are also around these diameter…. 24,965 and 24,967mm.

Could I use the shaft and are all the shafts “worn”out. It would be great, if you could give some feedbackand your experience....

[xpensivewino]

As I recall all intermediate shafts are numbered by group. So it could be a zero, or a 1 or a 2 etc. You must use an intermediate shaft that is like for like. So if your original is a 1 you need a 1 as a replacement. When I rebuilt my 2.0L E engine the intermediate shaft area of the magnesium case showed no wear what so ever, after 120k miles, so I did not due the bearing modification. I did however use a different intermediate shaft that was a match by group number and have had no issues with my build after years of driving.

[30westrob]

I would post your question on Pelican engine rebuild forum. A lot of experienced engine builders hang out there. Rob

[Richy]

The size number refers to the gear and not the shaft , ignore 30westrob . I'll measure some shafts tomorrow .

[preS]

Did you calibrate your tool to make sure it’s exact?

With a mutotoyo comes a small piece to do this before you start.

Also are they at room temp?


Richard

[Jon B]

...but I measured the bearing No. 1 has 24,966 mm.

As Richard suggested, check your micrometer with a 25mm standard (Endmaß) before measuring the shaft.
I would not rely on setting the micrometer at 0,000 for a 25mm measurement.

Jon B.
Vista, CA

[Elferhelfer]

Hello together,
Thanks a lot for your feedback and help. I calibrated the tool again and measured, the result is the same. I also measured with an older mechanical one, same result…. So it seems, that all three shafts are around the measured value.




All the intermediate shaft have the gear size “0” and it will be renewed, including the chain sprockets.

[Jon B]

I calibrated the tool again and measured, the result is the same...

Very good!

So then your shafts measure 0,014mm (0.0005") below the suggested factory minimum. Are the measurements consistent?
The recommended intermediate shaft running clearance is 0,030-0,084mm, a range of 0,054mm. So now measure the clearance of your shaft with new bearing shells.

If the running clearance with new bearing shells is within the recommended range, and the shaft measurements are consistent, then you'll be fine.
But if you're striving for ideal tolerances and cost is no concern, then purchase a new intermediate shaft :-)

Jon B.
Vista, CA

[Elferhelfer]

Hey Jon,
thanks a lot for your feedback. Actually I haven't bought the new bearing sheels yet. I will consider your input, a good point. During my checks I became just curious, because I have three used intermediate shafts from differents engines and all seem to be "worn" out....

Shaft 1: 24,966 mm ( 2.0 E )
Shaft 2: 24,965 mm ( 2.2 S )
Shaft 3: 24,967mm ( 3.0????)

[Alaskan911]

Very good!

So then your shafts measure 0,014mm (0.0005") below the suggested factory minimum. Are the measurements consistent?
The recommended intermediate shaft running clearance is 0,030-0,084mm, a range of 0,054mm. So now measure the clearance of your shaft with new bearing shells.

If the running clearance with new bearing shells is within the recommended range, and the shaft measurements are consistent, then you'll be fine.
But if you're striving for ideal tolerances and cost is no concern, then purchase a new intermediate shaft :-)

Jon B.
Vista, CA

For the sake of learning, what is the procedure for measuring the clearance of the shaft with the new bearings?

Josh