I consider the blue an essential diagnostic and set up tool. I don't rebuild gearboxes anymore, but the first thing I used to do on the front end of the tear down is blue print the ring and pinion. I want to know how it was running prior and if the pattern is good I want to return it to that on the back end when the box is done.

Porsche ran them in and matched them, but not enough for it to matter if you have brand new parts. But put 50 or 75k on the parts and now they have bedded in and matched to each other. You want it to keep running quietly, you want to take it back to that same setting.

On the rebuild, if you haven't changed anything, step one is recheck it, and if the pattern was good to start with, you're good. But let's say you are adding an LSD? Then you go through the whole process according to the book. When it is done, then you print it again. If the print is way off, I am not going to leave it like that. I am going to assess what is wrong and attempt to fix it with minor changes to shimming. this is from a Corvette forum, but gives a good idea of how to read a print.
http://corvettepartsonline.net/siteb...01-760x721.jpg

Cool thread with nice pictures. Appreciated.

I am rebuilding my ZF 911SC LSD right now so appreciate the listing of part numbers. I am going to refresh it it with factory internals and put it up for sale in the classifieds in the next week.

Moving to a Guard diff since my application is racing.

Thanks for the thread and contributions by the community.

Hi Peter! Glad you're back and feeling better!

No worries on the LSD. It gave me the opportunity to tear it apart and rebuild it, so now I understand how it works and have it set up in spec. I look at it as a great experience. Thanks for stopping in!


Thanks for the input Matt, and the pictures. I've ordered some Permatex Prussian Blue from Amazon. I'll post pictures when I get the gear printed.


You are most welcome Mr. Mahler! Though it is I that should thank the community for getting me through this, I'm really happy if it can help the next guy as well. BTW, nice forum name. As a washed up composer I enjoy the reference, though now I'm decomposing and fixing my Porsche instead. Happier this way... SmileWavy

The yellow paste in Matt's Corvette illustration is General Motors Gear Marking Compound.
I've been using it, and three or four other marking solutions, since the late 70s.

http://forums.pelicanparts.com/uploa...1516827295.jpg

Using the tools to duplicate the manufacturer's specs is far more accurate than running patterns, and I've been doing both for four decades, at many levels including CART IndyCar.
There are reasons that manufacturers create expensive tools and instruments to do this, instead of just providing a $20 tube of paste and an instruction sheet.
You cannot accurately duplicate the loads and spreads involved when running patterns by hand. It will only get you reasonably close, if the tools and instruments are not available.
There are also different methods of running patterns for Hypoid, Palloid or Cyclo-Palloid gears, Klingelnberg, Gleason or Oerlikon gears, etc...

Like many other things, it is not as simple as whatever various random people might post on the internet.

Absolutely. And it is this exact reason why I don't sell retail to the DIY guy and turned down Wayne when he asked if PP could become a dealer.I internally call my dealers authorized installers. I want my dealers to be using the tools and the paste is an extra tool, not a replacement tool. I've seen so many threads where people use the paste to install a performance differential with no way to check things or measure anything.

And on that note, I've located a nice example of the VW tool Ken posted on the previous page. I'll get it professionally machined and give it a go, adjust if needed, print the ring gear, use the washer tool, and see where the backlash is then. I'm going to get this gearbox set up no matter what!

As Ken suggested, you can probably create a replica of the Porsche P258 tool by machining down an early Volkswagen VW289d tool.
It would require a few precise machining operations to the VW tool, and to the VW setting block.
If you don't have access to the VW385 tool and can find a VW289d, this will probably work for you.

P258 was the original pinion tool for the 901 transmission, and was used into the 915 series with additional sleeves and a new setting block.
http://forums.pelicanparts.com/uploa...1516834771.jpg

Here are the P258 and VW289d tools together, for comparison...
http://forums.pelicanparts.com/uploa...1516834806.jpg

The original setting blocks for the Porsche and the VW tools...
http://forums.pelicanparts.com/uploa...1516834840.jpg

Thanks Jon. Man would I love to tour your garage. It seems you have one of everything! Below is a pic the VW tool that is on its way to me, I should have it in about a week to 10 days.

Machining the spigots seems straightforward: get my machine shop to center it properly in their lathe, and machine down the spigots to 50mm diameter, same as the carrier bearing ID. The machining should be such that the bearings can be set the correct distance apart which Ken said was about 120mm.

Machining the block is a bit more scary. Again, I'll get a professional shop to do this for me, but it is getting the right measurements to give them I will need help with. Since you have the actual tools and blocks, can you offer any advice here? Essentially, how deep to machine into the block to have 66.30mm be the zero point, if I'm understanding this correctly.


http://forums.pelicanparts.com/uploa...1516872913.jpg

Yes, that is the correct VW tool. It looks very nice.
It will be a shame to chop it up :-(

The measuring distance to the setting block will be stamped on the plaque as Istmaß mit Einstellmeister. It will be about 58.70mm.
Since you're trying to achieve a measurement of 66.30mm, you would deepen the setting block by the difference, about 7.6mm.
Instead of machining the setting block as Ken did, you can put gauge blocks on it instead, to achieve the same 7.6mm difference, or create a precision 7.6mm spacer.

That's it for me tonight, Evan, gotta go...

Well, I prefer to look on the bright side. This tool was just sitting in a guy's garage unloved and collecting dust, I'm giving it a brand new life checking pinion depth in Porsche gearboxes! The guy I bought it from had two actually, and a whole bunch of other old VW tools that were his Dad's. (Anyone interested, PM me and I'll put you in touch.)


Excellent, thank you!

There is a way to DIY the pinion depth tool. You will need an open diff, or yours disassembled to do it. Go to this tread for more details.
http://forums.pelicanparts.com/porsche-911-technical-forum/337213-xperts-ring-pinion-patterning.html
http://forums.pelicanparts.com/uploa...1516899433.jpg

Here's a 70s BMW illustration for Gleason and Klingelnberg ring gear patterns.
Porsche never recommended doing this, but some manufacturers reasoned that the special tools involved might not be available to many repair shops.

http://forums.pelicanparts.com/uploa...1516910334.jpg

http://forums.pelicanparts.com/uploa...1516910364.jpg

Still following this thread.

Mr. Evan9eleven: Mahler's 9th is my favorite piece of music. But it is not for everyone. I also like many other Mahler compositions especially the 2nd and 3rd symphonies.

I am rebuilding what appears to be the same diff you have. I have some questions about your LSD rebuild:

What spec did you use for the stack height and margin? The 5.20 mm spec seems to apply to the later Carerra diffs, and I wonder if it also applies to the range of SC LSDs.

My LSD has four plates and one friction disc per side. Is that what yours had?

It seems that you used two friction discs per side in your rebuild. Is that correct? And what was the stack order you used? Did you build it for 80% or 40%?

Good luck with the ring and pinion set up. I did this once on a 968 box with tools I fabbed up. Very time consuming but rewarding. If I recall correctly, the biggest pain was not having a press. After I was done I took it to a shop and they double checked my work.

Even though I now have a press, I am having a shop do my next R&P set up... buying a Guard LSD this month.

Thanks again for such an interesting and informative thread.

915 Rebuild
 

Jon B's suggestion of using gauge blocks to change the Vw 289d setting depth sounds good.
Another way to get there would be to use a VW 385/17 magnetic plate on the pinion face. The plate is 5mm thick which would reduce the effective R from 66.30mm to 61.30mm. The difference between 61.30mm and the VW 289d setting block's 58.70mm is only 2.6mm which means the dial indicator could reach both points. A magnetic plate costs about $100 though so it would probably be cheaper to modify the block.

I spent some time with Mahler's work while studying composition, though Stravinsky is my favorite when it comes to 20th century classical, or modern composition. On the other hand I love blues and rock and roll, so I'm an electic mix. What does that get me? I brew beer for a living and fix a Porsche to keep my sanity. But I digress...


Yes, I had 4 plain plates (including the 1.4mm thin lamina, as its called) and 1 friction disc per side.

Below are my measurements at dissassembly. Basically, the diff tested at a breakaway torque of 26 lb-ft, which is below spec for this unit (an '81.) The clutches and steels were well worn, expected after 165K miles. The one side was more worn then the other. I followed Paul Guard's link for disassembling and measuring everything and discussed the results with Matt. He assured me that going to a 4-clutch setup (80%) wouldn't have any downsides for a street hotrod like mine, so I ordered new parts and rebuilt it. It was actually very easy to tear down and rebuild, follow Paul's guide and its cake. Great to have a press, all your parts ready, and don't forget the locking tabs for the diff ring bolts and a bottle of LSD gear oil. It took me one evening to tear it down and clean it and another evening to rebuild it.

I reused the thrust washers, 1.4mm lamina discs, and Belleville washers (cup springs.) I purchased 4 new 2mm steels and 4 new 2mm clutches and installed them alternating. This is what everyone refers to as 80%, though again, I've been advised that this will work for my needs. From the outside the order is: Thrust washer; Belleville washer; 1.4mm lamina, 2mm friction disc; 2mm steel; 2mm friction disc; 2mm steel. Same on the other side in opposite order. Breakaway torque after rebuild is 47 lb-ft, about in the middle of spec for this arrangement.

My numbers after teardown (old parts):
Body depth: 100.6mm
-Cover depth: 8.5mm
= 92.1mm

Belleville washer material thickness: 2.45mm both sides

Pressure ring assembly: 68.21mm

Plates and discs, ring gear side:
1.35mm
1.86mm
1.95mm
1.95mm (friction disc)
1.96mm
=9.07mm

Plates and discs, speedo side:
2.0mm
1.97mm (friction disc)
1.99mm
2.0mm
1.39mm
=9.35mm

So, the whole stack including the belleville washers was: 91.53mm vs. a body depth under the lid of 92.1mm.

Hope this helps!

http://forums.pelicanparts.com/uploa...1517003709.jpg

Thanks for the suggestion Ken. I'm also very interested in hearing what others have to say on this.

Thanks for those details. My existing stack is a bit diffferent-- I don't think it is what was shipped by PAG.

If anyone has interest I will post what I found in my unit.

I called a few dismantlers-- it appears these LSDS are hen's teeth. Hopefully that will help when I go to sell mine.

The world is small... yesterday I met the gentleman how owns/owned the diff from Paul Guard's rebuild thread. Very nice gentleman. Small world indeed.

Rite of Spring and Firebird are two other pieces I like-- main stream Stravinksy pieces. Stravinsky and Mahler were connected-- at minimum through Alma Mahler. She was one of those "center of the star" folks. Even connected to modernest architecture.

By the way, I think you are all set on teh ITB/EFI part of your project but just in case...

I think the new cat's pajamas in ITB's are the shaftless butterfly rigs. The US co-developer for Porsche applications is my engine builder. I cannot use them (not legal for my racing class) but if I were interested in ITBs and power with EFI, I'd consider that new family of ITB products. We have quite a few guys already running them and they make quite a bit more power than everything that has been previously available.

Oh, I've seen them, and they are beautiful to be sure. But just the throttle bodies were close to the price of Al's complete basic kit. At this point the ITBs and EFI are going on a stock Euro-spec 3.0 motor, so the fancy throttles are way overkill for my needs-- not to mention out of budget.

I guess its time for a teaser on the upcoming ITB portion of this thread, the X-Faktory santa was very good to me. Just as soon as the gearbox is done I'll start on the engine.

http://forums.pelicanparts.com/uploa...1517173922.jpg

http://forums.pelicanparts.com/uploa...1517173922.jpg

What are your plans for filtering intake air?