915 – P259 tool measurement request… (With pics)

sc_rufctr · 05:54 PM

Hi all

I’m in the process of making a copy of the Porsche tool - P259.

This tool is used to measure the "BackLash" of the Ring and Pinion gear of the 915 gearbox.

I have already made a clamp for locking the Pinion Shaft.
I used a cheap socket that I slotted down one side and the welded it to a piece of steel…
An M6 bolt is used to lock it onto the big nut at the end of the Pinion Shaft. (zero play)
It’s a bit ugly but it’s very similar to the P Tool shown in the pictures.
I have also sourced an appropriate washer and bolt for locking the axle flange to the differential.

I’ve searched here and found a thread that states the 930 Turbo gearbox is measured at 92mm.
In that same thread it also states the Carerra is measured at 80mm.
However I also found in a different thread a measurement of 83mm for the Carerra.

~ 3mm doesn't sound like much but it would affect the final backlash measurement.

I'm assuming this measurement would be the same for all 915 gearbox made after 1977… (Probably the same for all 915s)

My car is a 1978 911 SC.

What I would like is to know for sure is the measurement shown in the picture bellow between the two red lines.
(The distance between the Gauge holder and the centre of the flange fixing bolt hole)

Thanks in advance…

sc_rufctr · 04-26-2009, 06:38 AM

Up for views...

David E. Clark · 04-26-2009, 08:27 AM

I'm no help with the measurements but here's a slightly different picture from the 1965 Factory parts manual. Please let us know what you find out and show us your finished product.

sc_rufctr · 04-26-2009, 03:28 PM

Thanks for your input... I edited the picture to get a better view of the tool.

If I can't get the actual measurement, I may make mine adjustable...

Doesn't anybody have this tool sitting in the draw of their tool box?

PLEASE.... Measure the distance from the centre of the flange hole to the centre of the mount for the dial gauge... (bottom item in photo)

sc_rufctr · 12:33 AM

Update:

I asked an independent Porsche specialist if I could see their tool this morning... "We don't have one and never measure it directly... we do it by feel"

The local Porsche dealership mechanic almost laughed at me when I asked if they would have this tool on hand...

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

David E. Clark · 04-27-2009, 01:16 AM

Peter,

When I was drafting the MFI compilation threads I looked at all the old MFI threads, found posts by people who seemed to know what they were talking about, and sent personal messages to each asking for input. I got some great feedback. You might look up some old transmission rebuild threads and see if any of those people have this tool lying around and could measure it for you.

sc_rufctr · 04-27-2009, 02:34 AM

David

Thanks but I have sent some PMs to various people on here who post in the 915 transmission threads asking for help but I didn't want to pester them.
Maybe this tool is rare considering what I was told this morning by the independent Porsche specialist (see earlier post)

I did stop into a transmission only workshop asking for advice and the mechanic there was very helpful.
He said the the R&P backlash on almost all cars is measured at the edge of the "Ring Gear"...
Only some 60s model Fiats, Alpha Romero's and Ferrari's are measured at the "middle" of the crown teeth.

Meanwhile I think I'll be making an adjustable version of the tool so that I can move the dial gauge if needed.

My tool will have a range of adjustment of 75 to 95mm. I'll post some pics when finished.

Peter Zimmermann · 04-27-2009, 08:01 AM

Peter: pm sent...

1980 911 sc · 04-27-2009, 11:45 AM

Its funny but we are in the same boat as him. I am trying to put a LSD in my 915 and me and a buddy are thinkin of making one ourselves. If you find out this info please spread the word....

Peter Zimmermann · 04-27-2009, 02:01 PM

Quote:

Originally Posted by sc_rufctr

David

Thanks but I have sent some PMs to various people on here who post in the 915 transmission threads asking for help but I didn't want to pester them.
Maybe this tool is rare considering what I was told this morning by the independent Porsche specialist (see earlier post)

I did stop into a transmission only workshop asking for advice and the mechanic there was very helpful.
He said the the R&P backlash on almost all cars is measured at the edge of the "Ring Gear"...
Only some 60s model Fiats, Alpha Romero's and Ferrari's are measured at the "middle" of the crown teeth.

Obviously, Porsche transmission backlash is measured with the pinion head and ring gear fully engaged. Care must be taken to not damage any of the components by being sure that backlash clearance of some amount is present during tightening.

Meanwhile I think I'll be making an adjustable version of the tool so that I can move the dial gauge if needed.

My tool will have a range of adjustment of 75 to 95mm. I'll post some pics when finished.

Quote:

Originally Posted by 1980 911 sc

Its funny but we are in the same boat as him. I am trying to put a LSD in my 915 and me and a buddy are thinkin of making one ourselves. If you find out this info please spread the word....

Remember - Diff bearing pre-load first, pinion depth second, backlash last.

sc_rufctr · 03:24 PM

Quote:

Originally Posted by Peter Zimmermann

Peter: pm sent...

Thanks heaps for the PM and info. That's exactly what I needed to finish the tool...

I'll post some pics here when it's done...

Seriously... When are you going to write that book about re building 915s?

It needs doing. You may not sell many copies but it would be on the "have to have" list for me.

ed mayo · 04-27-2009, 09:00 PM

Peter, I'll try to remember to measure that for you tomorrow.

sc_rufctr · 04-27-2009, 11:37 PM

Quote:

Originally Posted by ed mayo

Peter, I'll try to remember to measure that for you tomorrow.

Thanks Ed... That would be great. I need to ask a stupid question...Do you actually own this tool?

I was thinking it was the "Moby Dick" of the Porsche tool world.

Please take a picture if you can and post it here. I'm curious to see a good picture of one. Is it cadmium plated, painted or blued?

Jim Williams · 04-28-2009, 04:25 AM

I know this doesn't directly address your question, but here is a photo from a previous thread on measuring backlash. The "tool" was configured from common stuff found in the shop. It might give some ideas on different ways to do the measurement or to make up a tool. Typically the measurement is done after other adjustments, and the CV flange is out of the transmission.

http://forums.pelicanparts.com/uploads7/IMG_1873+Copy1145228336.jpg

The photo is in this thread:

915 R&P Whine - How do you get rid of (fix) this??

sc_rufctr · 04-28-2009, 04:55 AM

Thanks Jim... I've seen these before but I do appreciate the input.
Both of those threads are great and provide some excellent ideas.

Thanks again

Peter Zimmermann · 04-28-2009, 07:27 AM

Quote:

Originally Posted by sc_rufctr

Seriously... When are you going to write that book about re building 915s?

It needs doing. You may not sell many copies but it would be on the "have to have" list for me.

I've actually been thinking about your suggestion. I've got to collect all of the photos that I've taken, and see what I've got. Photographing the special tools wouldn't be difficult, I already have a few pictures of most of the tools. My publisher is working on another project at this time, but I think that I'll send him an e-mail to see if a book is possible, or if he thinks that I would be better off doing a handbook type publication at Kinko's.

I've heard that China has printer/publisher services available, but I'm struggling with not wanting to be a hypocrite (working with the Chinese at the same time that I complain about everything from their crappy wood products, to paint with lead in it, etc., etc.). Maybe I'll talk to the local Kinko's manager and see how much something like that would cost.

David E. Clark · 04-28-2009, 08:17 AM

Quote:

Originally Posted by sc_rufctr

... Seriously... When are you going to write that book about re building 915s?

It needs doing. You may not sell many copies but it would be on the "have to have" list for me.

Add me to the list too. I'll even pay upfront!

Grady Clay · 05:02 AM

EDIT
I reached in a drawer and pulled out the wrong bracket.
The correct bracket / holder P-259 has dimension of 76.5 mm.
This is used with the washer part of P-357 (45x35x2 mm).
I posted a better explanation on page 2 of this thread.
Best, Grady /EDIT

The dimension you want measures 70.60 mm on the actual P357 tool in my hand.

I measured the center-line distance by measuring the inside distance between
the two shafts. I then measured the diameter of each shaft. I added the
distance between shafts to half of the diameter of each shaft. Measurement
accuracy should be about ±0.04 mm.

Critical to measuring the backlash accurately is the thin P357 washer (shown in
your 1st image above). This goes between the axle flange and the differential
housing. When you tighten the bolt through the center of the axle flange and
P357, this removes any axial clearance between the flange and differential
housing. This clamps the P357 tool and flange directly to the differential
housing. Without this, you will have the additional clearances of the
differential ‘spider’ gears added to the R&P backlash. I posted the washer
dimensions in some previous thread.

The Factory backlash measurement is etched on the side of the ring gear. This
measurement was performed with the pinion tooth with the single mark
positioned between the two teeth on the ring gear also etch marked.

I like to make many measurements completely around the ring gear several
times. I simply loosen the pinion nut clamp P259 or P259a and rotate the pinion
one flat on the nut.

This measurement (and even pinion position) is slightly subject to the torque load
while running. I like to simulate this with a pry bar and weight prying the pinion
5-R gear (or 1-R on a 901/911) away from the differential. Most will move only
about 0.005 mm but can have a noticeable affect on the backlash measurement.

When replacing a casting, bearings or the differential, it is best to measure all the
positions, pre-loads and backlash first so you have numbers to set to. This is
particularly important if you are transferring a R&P from one transmission to
another.

NEVER, EVER risk tightening the side cover without ring-to-pinion backlash
clearance. Serious damage can result. If in doubt, set the ring gear farther
away from the pinion and move it in with small steps.

Best,
Grady

Peter Zimmermann · 04-28-2009, 11:41 AM

This is where the whole issue gets murky. The flat P 357 has a different original purpose, but can be used to calibrate backlash on Sporto transmissions, but even for that it requires that a new hole be drilled at a distance (center to center) of 10mm further away from the axle than the original hole. That means, using Grady's measurement, that the total distance for Sporto use becomes 80.6mm.

The P 259, with the bend, was made to use on 911s, and has a measurement different, and roughly in between, the P 357 or the P 357 modified for Sporto use.

sc_rufctr · 03:29 PM

Grady

Thanks a bunch for posting the pics and measuring the tool.
Also... Thanks for the information posted with the pics.

Peter Z

This all makes sense now. I can see how that formula you sent me via a PM for calculating the measurements of the P259 tool works.
I bet you feel a bit smug now (in a good way) considering you made your own without the benefit if seeing the real one. Well done...

Looking at this tool it's very basic but like all special tools only has one or two purposes so it doesn't need to be "SNAPON" pretty.

I'm hoping "ed mayo" chimes in with the measurements of P259 as he has access to the tool.