Pinion depth and ring gear backlash in an Andial 8:39

[Tom F2]

Can anyone tell me what these marking mean on an Andial R&P for a 930 transmission? In other words, how do I translate them into pinion depth and ring gear backlash?

[Jon B]

R=119,04 is the pinion depth from the ring gear axis to the back of the pinion head.
Measure the pinion head, and subtract that dimension from 119.04mm. It should put you in a typical 930 range somewhere between 78mm to 83mm to the pinion face, depending on the ratio or manufacturer.

R=47,50 is the setting distance from the pinion axis to the back of the ring gear.

I don't see a backlash dimension in your photos.

[Tom F2]

Thank you, Jon. That works. A rough measurement yields a pinion depth of 82.54 mm. (Approximate height of the pinion head is 36.50 mm.) I will have to press off the pinion bearings to get a clean measurement. The dimension of R=47.05 should translate to correct backlash, but how do I get a reading of the back of the ring gear relative to the axis of the pinion? I saw in another one of your posts how this might have been relevant with a split case transmission, but I don't see how it will help here.

I am also surprised that there is no pairing number on these.

There must be some information coded in the 2/1010/24 on the ring gear and the 2/1007/13 on the pinion face, but what? I note that 82.54 mm -0.24 mm=82.30 mm, which is very close to the nominal pinion depth of 82.29 mm for a 930/33, and that 0.13 mm is a reasonable backlash number. However, I would expect to see deviation for pinion depth stamped on the pinion face (here it's stamped on the ring gear, if my guess about /24 is correct) and backlash stamped on the ring gear (stamped here on the pinion face, if my guess about /13 is correct).

That would leave 2/1010 and 2/1007 as a pairing code, only they don't match!

Any thoughts on this?

[Jon B]

Tom, R=119,04 is the setting depth for that pinion, there is no deviation value to add.
The ring gear number is the manufacturer's setting dimension, but there is no practical way for us to measure that dimension ourselves.

The Porsche recommended spec for ring gear backlash was 0.14 to 0.20mm in the 930 Manual (1981), or 0.16 to 0.20mm in the Tech booklets (1978-81).
If there is no obvious backlash number on the ring gear, then you should be fine within those recommendations. You can run a visible pattern to confirm your settings.

Some manufacturers do not pair their gears with matching numbers.

[Tom F2]

Jon, are you saying that I cannot use the VW385 tool to set up the pinion? How do I do it, then?

I had taken it from your first message that I would set the tool to 119.04 minus the depth of the pinion head, or roughly 82.54 mm. Won't this work?

[Matt Monson]

Originally Posted by Tom F2

Jon, are you saying that I cannot use the VW385 tool to set up the pinion? How do I do it, then?

I had taken it from your first message that I would set the tool to 119.04 minus the depth of the pinion head, or roughly 82.54 mm. Won't this work?

You've got it right. No deviation. They are giving you the exact number. On the ones I make we actually give you the head height for doing the math, but Andial didn't.

Its been a few years since I saw one of these Andial units but everything Jon is saying jibes with my memory. No backlash number printed on it. Use standard from the spec books Not matched pairs. Porsche matched pairs for NVH. This is a racecar part. They just care that it runs properly. You will want to print the pattern and maybe tweak it a little bit after the first set up or two.

[Jon B]

Originally Posted by Tom F2

I had taken it from your first message that I would set the tool to 119.04 minus the depth of the pinion head, or roughly 82.54 mm. Won't this work?

Yes, that's what you need to do if measuring the depth with VW385 at the pinion face, with the magnetic disc attached.
If you do not have the magnetic disc (VW385/17), then you'll need to add 5mm to your measurement.

[Tom F2]

Thank you, Matt and Jon. I have the magnetic disc, so it should be straightforward.

[Tom F2]

P.S. Some of the old threads on R&P markings make for interesting reading. It seems that the system of marking the Andial R&P goes back to split-case VW/Porsche days!

[Jon B]

Originally Posted by Tom F2

It seems that the system of marking the Andial R&P goes back to split-case VW/Porsche days!

Those are all standard industry reference points for designing and measuring spiral bevel gears, long before the VW/Porsche days.
You're probably referring to an image I've posted in the past, from a 1960's VW guide...

[Jon B]

Originally Posted by Tom F2

Jon, are you saying that I cannot use the VW385 tool to set up the pinion? How do I do it, then?

Tom, I think you were confusing my comment about the "ring gear number" ("... there is no practical way for us to measure that dimension ourselves.") as a comment about measuring the pinion depth.

[Tom F2]

Originally Posted by Jon B

Tom, I think you were confusing my comment about the "ring gear number" ("... there is no practical way for us to measure that dimension ourselves.") as a comment about measuring the pinion depth.

Right you are, Jon. Thank you for clarifying.