Setting Pinon Depth on 901 gearbox, Transmission Fixing Options

[porsche735]

I have a transmission in pieces with the gaskets removed. According to the Haynes manual, you pretty much have to have the intermediate plate shims to measure them and put the same measurement back (with new shims). This sets the pinion depth. According to them, you should not mess with this as you have to go to a Porsche mechanic for them to use a special tool to get this set right. There must be a way to do this at home (open up the differential cover and use a feeler gauge or something). Does anyone know what the "special" tool looks like? Is there a way to do it at home, what is the measurement?

Thanks,
Chris
1973 914 2.0L BP

[Brad Roberts]

This is one of the rare times I feel you actually need the setup tools to do this properly.

What did you change that make you feel like the pinion depth changed ?? Did you install a diff ?? or replace the bearings ??

B

[porsche735]

Hey Brad! No, the previous owner of this transmission kind of kludged some things together, so I don't trust the stack of gasket/shims. i would prefer to take a measurement. how critical is it? What if you just use the "middle" gasket/shim if it is unknown?

Chris

p.s. Coming to our rain fest at Thunderhill this Friday-Sunday?

[Brad Roberts]

It is very critical. Bad things happen when the pinion depth is not correct.

I have a guy in south bay that sets up our boxes for 150$ He is fast.

I cant imagine that yours would be wrong.. even if the previous owner kludged together the gear sets... most people dont dive into the pinion depth settings when taking a box apart.

Look online for "gear tracking" there is a way to check and see if the R+P are meshing correctly. I do this with white lithium grease, but cant exactly explain what I'm looking for. I just know when I see it. I have read some very good write-ups about this.

B

[Zeke]

I have seen mechanics use machinist's layout blueing on the gears to see where they mesh. Can't be on the edge of either gear. Can't be too tight or too much back lash. Sounds like a job for "THE SPECIAL TOOL"

[Dave_Darling]

Kap'n Krusty over on the 914 Rennlist said that the "special tool" was used to set up backlash (I think it was?) and then either another special tool or the bluing was used to check/mess with the tooth engagement.

I have heard rumors that Bruce Anderson knows a technique to deal with this stuff in a 901 gearbox without the special tool. And that he talks about it in his transmission rebuild class. I think we have one or two people around who have taken that, maybe? Someone who has taken the class tell me if I'm off base here...

--DD

[Alfred]

This is from my vocational school days. (You have to brush the gear teeth with some "Prussian blue" paste to see this pattern.

Alfred

(IMG:http://persweb.direct.ca/aschwenk/scan3.jpg)

[porsche735]

Great info, thanks. Any idea where to get some "Prussian Blue"? Maybe this should be added to the CD set.

Chris

[ChrisFoley]

Prussian Blue is also known as Dykem, and is available in red as well. Sources include MSC Industrial Supply and J & L Industrial Supply.

[TimT]

Prussian blue is a just an ink, Brad mentioned using white lithium grease. All you need to see is the path where the gears mesh. I just put a quaife in my 911 box, and I used the white grease method to check the pattern.

A little tube of prussian blue costs about 5 bucks,and will last a lifetime, but it has very limited uses.
white grease is cheaper, and has lots of uses.