So here's another silly question - why bother grinding down the lip on the diff case at all?

Here are some more photos of the details of the Gary Fairbanks R & P tool as requested by other Pelicans:

http://forums.pelicanparts.com/uploa...1179075656.jpg
http://forums.pelicanparts.com/uploa...1179075722.jpg
http://forums.pelicanparts.com/uploa...1179075743.jpg

Earlier photos were posted on 2/10/07, this thread.

P258 and Fairbanks tool
 

I was googling on P258 and came up with this excellent old thread!

Here are a couple of tidbits about these two tools. (I now have one of each). The Fairbanks tool uses the late 901 differential carrier as its base. Thus the tool is sized to work with the pressure case version '69 and later of the 901 transmission that has larger carrier bearings than the earlier aluminum case 901 tranny. The good news is that the tool will fit in an early tranny if the faces on the carrier are machined down. You still have to use the larger inner part of the tapered roller bearings, though.

http://forums.pelicanparts.com/uploa...1203212589.gif

The genuine P258 tool uses the small bearings from the early 901 carrier and the P258b spacers to adapt it to the later 901 gearbox.

There was a genuine vw385 that sold last week on ebay for $1800! It was the only one I have ever seen for sale on ebay and apparently included all of the necessary adapters.

http://cgi.ebay.com/ebaymotors/VW-385-UNIVERSAL-PINION-DEPTH-MANDREL-PORSCHE-AUDI-NEW_W0QQitemZ200196758647QQihZ010QQcategoryZ43989Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem

I would like to get my hands on a set of the p258b bushings. ;)

SV

I posted some details of the pinion depth tool my friend made in this thread:
XPerts: Ring an pinion patterning

differential thread
 

Thanks for the links.

It seems to me that the hard part with the home made depth gauge is determining the reference depth for the gauge adjustment.

SV

Explain, perhaps I can help.
-Chris

setting P258 tool
 

The P258 tool includes a mandrel, P258c (shown in the previous picture) that has a known depth, and the tool has a machined face with a known depth, and then when P258c used, the dial gauge is zero'ed at the correct nominal depth of the pinion face. Thus when reading the pinion depth, the offset from nominal is directly read on the dial gauge. Gary 's tool has a similar setup. The one pictured has a brass cap of known depth that is placed over the dial gauge pin and the gauge is zeroed. This is also referenced to a machined face on the differential housing. The P385 has a micrometer for setting this dimension and zeroing the gauge.

If you are making a tool, and it does not have this reference, which is a machined face on the tool with a precisely known dimension, then how is the dial gauge zeroed?

SV

If one is constructing such a tool, I don't see that there is a way to get a reference reading for the dial indicator without determining some reference surface. On the Fairbanks tool in the photos above, the reference surface was measured by Gary and stamped into the diff carrier. But I measured the surface anyway just to get the confidence that the stamped number represented what I thought it was. Here is a photo of my test setup.

http://forums.pelicanparts.com/uploa...1203296931.jpg

Of course, having the measuring tools on hand made this pretty straight forward. First, I determined the diameter of the shaft, divided by 2 to get the radius, and subtracted the radius from the height of the reference surface above the Jo blocks.

Any well equipped machine shop should be able to provide the measurements. My math got within a few hundredths of a mm from the stamped number.

P258 tool reference
 

Exactly.

So to make a tool like this it is of primary importance to machine a reference face so that the tool can be calibrated for measurement. It is a little more complicated than just mounting a dial gauge into an old differential carrier.

SV