915 – P259 tool measurement request… (With pics)

[Rich Rosenberg]

I saw your post from 2009 asking if anyone knew the dimension of the arm to measure the lash in a 901 gearbox. Did you ever get a reply? I am in need of that length now and haven't found a source as of yet.
Thanks
914 racer

[violin959]

tools 11, 12, and 13 are available under different numbers along with the sleeve.

[violin959]

I have P259 for sale but only as part of the VW385 R&P setup I will be listing.

[Walt Fricke]

My understanding is that the radial distance involved is to the outside of the ring gear.

This looks sort of like how the 930 did it.







The pinion shaft splined end is eversomuch harder than the old vice grip.

[Jon B]

Walt,

The pinion shaft must be assembled & torqued for accurate backlash readings. When measuring pinion depth, you'll see substantial movement rearward when the pinion nut is undone. Likewise, the housing sidecover must be completely fastened down.

[T77911S]

Originally Posted by sc_rufctr

Update:

"We haven't rebuilt one of those in more than 10 years" (it's probably being used as a door stop in the toilet)

did you ask where the toilet was

[Peter Zimmermann]

Originally Posted by werkstatt

walt,

the pinion shaft must be assembled & torqued for accurate backlash readings. When measuring pinion depth, you'll see substantial movement rearward when the pinion nut is undone. Likewise, the housing side cover must be completely fastened down.

+1.

[Peter Zimmermann]

Bringing this measurement into the G50 & G50/50 world... The tool to use is definitely the VW 521/4 with sleeve #9145. Measurement "a" is done, on a G50, from the flat side of the 521 to the tip of the adjustable insert in holder extension VW 388 (inscribed with "Made in Germany", no number, in below picture). The red insert is used to set the distance of 80mm.

For a G50/50 (Turbo), the white insert, tool #9196, is needed, and distance "a" must be 92mm. Of course, the measuring shaft of the dial indicator must be at 90 degrees to either the white or red gauge extension when measuring backlash.

[sc_rufctr]

Thanks Pete

[b930]

Originally Posted by Jon B

Grady,

The 101mm dimension is for early 930 transmissions, from the "Turbo Carrera" manual, page 39-17. Yes, that would be added to 15.95 for your "b" dimension in green. The ball on the extension tip is 10mm, so subtract 5mm for the actual measuring distance.

The original 915 manual shows the 901 backlash tool P259 being used, but I question how accurate that can be. The 915 ring gear is larger than a 901 ring gear. The P259 bracket was designed for use on Nadella flanges, and doesn't register on any CV flange. If using the 901 bracket on a 915, it should at least be modified for a different indicating point. The manual recommends doing this to the 905 tool for a 925, but doesn't to the 901 tool.

Hi, dragging up an old post. I have just rebuilt by 930/36 in my 88 930. I'm fitting a wavetrack. The pinion shaft is using the same factory spacer in front of the bearing plate so pinion is in the right place. Pinion shaft bearing is good, no play.

Before pulling bearings and spacers off the old diff, I'm trying to baseline the lash, the ring gear says it should be 0.16mm. It ran beautifully quiet with no problem.

Now in the 930 workshop manual, as stated above, they show tool 521/4, with gauge holder 388. If I work out where that would put the measurement in radius its about 112mm, very close to the OD of the ring gear. If I measure my factory set up here I get .25mm lash (Diff drive flange locked off and pinion shaft locked at the reverse gear). Way too high.

However, based on the comment above that the set up in the workshop manual is only for earlier turbo's, I did a bit of experimentation to see at what radius I get the required .16mm lash. That radius turns out to be precisely 76mm, very close to what the tool 215 (915 trans) radius. I am wondering if anyone can confirm the radius to measure a late model 930/36 lash if what is in stated in the workshop manual is incorrect. Thanks.

[Geary]

I can't provide the answer for you (I'm sure someone will soon), but a couple comments to add to this great thread:

While "new" spec is 0.16mm, this dimension will grow over time as your R&P set wears. Resetting and older R&P set to 0.16 might not yield the quietest operation. Adding a tiny chamfer to edges of ring gear and pinion teeth with a dremel might be wise if insisting on setting an older R&P set back to 0.16.

Avoid shops that say they set backlash "by feel". My own experience is that while diff bearing preload can probably be set by feel, it can't be relied upon to yield an accurate backlash.

[sc_rufctr]

WOW... 8 Years just like that!

[b930]

Originally Posted by Geary

I can't provide the answer for you (I'm sure someone will soon), but a couple comments to add to this great thread:

While "new" spec is 0.16mm, this dimension will grow over time as your R&P set wears. Resetting and older R&P set to 0.16 might not yield the quietest operation. Adding a tiny chamfer to edges of ring gear and pinion teeth with a dremel might be wise if insisting on setting an older R&P set back to 0.16.

Avoid shops that say they set backlash "by feel". My own experience is that while diff bearing preload can probably be set by feel, it can't be relied upon to yield an accurate backlash.

Thanks so much for your response. I think I will aim at maintaining the current backlash so all I need is a fixed reference point in terms of radius of measurement and set the new LSD equipped ring gear back to that.

[b930]

Originally Posted by sc_rufctr

WOW... 8 Years just like that!

This forum is fantastic!

[Matt Monson]

Originally Posted by b930

Thanks so much for your response. I think I will aim at maintaining the current backlash so all I need is a fixed reference point in terms of radius of measurement and set the new LSD equipped ring gear back to that.

This is where printing it becomes essential, before and after. See how it runs now and make sure it runs the same after. If the pattern is terrible now, you can't use the current settings as your after goal because it has moved too much and needs to be reset.

[Trackrash]

Originally Posted by Matt Monson

This is where printing it becomes essential, before and after. See how it runs now and make sure it runs the same after. If the pattern is terrible now, you can't use the current settings as your after goal because it has moved too much and needs to be reset.

"Printing"? Is that what you call it when you use blueing to see the contact pattern?

I have not heard of allowing wear on the R&P to justify more backlash. Is that true?

Thanks for your feedback.

[Geary]

0.25mm is a bit high to reset to. Since the range for a new R&P is actually 0.12-0.18mm, I'd shoot for the high side of that, and check the new pattern against what you have now.

[evan9eleven]

Hi everyone,

Can one of you tell me if this method of "painting" the R&P is an absolute necessary step in setting up backlash on a diff, and what the "paint" is?

Thanks

[LM3929]

The "painting" material is Prussion blue.

Lorne M.

[mikedsilva]

Thanks for a great thread.
The sensor (p259b)that goes into the end of the dial gauge pointer.. is it merely a right angled pointer? So when in use, does it touch against the side ribs of the cover?
In this photo it appears to be in two parts, but in the porsche manual, the photo only shows a single part...

Also, what keeps the P259 centralised with the output flange? I have the 259 arm, but it is a 'sloppy' fit...At this point, I have simply wrapped the shaft of the bolt with masking tape to remove the clearance and my hope is that this is enough to centralise the p259 with the bolt when it is tightened against the diff (using the washer to lock)

Thanks, Mike.

Originally Posted by Grady Clay

Here are all the tools necessary for measuring backlash.