Two 901 questions

[Jim Sims]

I'm now involved with rebuilding my first 901 transmission. A couple of questions have come up.

The first is with the synchronizer brake bands; all nine brake bands originally in the transmission are longer in arc length than what I thought was the correct replacement brake band (911-302-316-08). They are about the the same arc length as an early 915 1st or 2nd gear brake band (915-302-316-01) but have a lesser (tighter) radius. See the below image of the profile tracings. The transmission housing has the characters "HA 24 10 Z" stamped on it. I believe the transmission to be from a 2.0 liter 914. Can anyone explain the brake band difference and provide the correct part number for these longer, tighter radius brake bands?

Second question: The bronze (brass?) speedometer gear projecting from the special shaft bolt has significant play (both lateral wobble about the roll pin axis and some rotational play about the gear axis) at the end where it is secured to the bolt with a roll pin. This doesn't appear normal but the speedometer was working okay before the transmission was removed from the car. Is this "play" normal and if not, is there a repair that can be done other than replacing the speedometer drive gear.

Many thanks for any help you can provide. Jim Sims

[Grady Clay]

Jim,

This is going to tax my memory but here goes. Sometime in ’72-’73 maybe later Porsche had a retrofit kit for the type 911 that used the shorter bands and longer stops. Apparently the idea was to more evenly spread the band & stop forces on the inside of the syncro. You can fit the later (short band & long stop) parts to any transmission.

Along in there Porsche was trying all sorts of things to improve the syncro function. This is where the grooves on the inside of the syncro ring first appeared. There were even titanium bands.

To answer your first question I’ll look in the early parts manuals and find the part number. I can then check the price list to see if they are available from PCNA. I’ll bet they supercede to the later parts. I’ll bet some shops (JWW?) have 100# of good used.

Q2 is probably “How worn is too worn?” question. The speedometer drive gear was somewhat floppy when new. I would drive the pin out and inspect the machined surfaces. I notice the 914 guys all remove the speedometer angle drive assembly so this gear centers in the nose piece first. They then reinstall the angle assembly.


Your S/N is probably HA24102. That is a type 914/12 from 1973.

Best,
Grady

[Jim Sims]

Thanks Grady!

[Grady Clay]

Jim,

Unfortunately I gave away almost all of my technical books 20+ years ago but I still have a few rags.

Where I show prices, it is from the 12/05 PCNA price list and is probably an indication they still might have some.

The later (by 11/72) three pieces are:
911.302.315.00 energizer $4.70
911.302.316.00 break band $1.32
911.302.317.01 stop $11.74

The early (revision VI 6/67) three pieces are:
901.302.315.02 energizer $2.18
901.302.316.02 break band NL
901.302.317.02 stop SS to 911.302.317.01

My paper 914 parts manual (revision 1-74) shows the same 911 parts.
The paper ’69 911 parts manual (rev. 11-72) shows the later 911 parts but I know it came with the 901 parts.
These 911 parts were used in the 915 3-5 gears until the late ‘70s? or more.

The 911 brake bands are short and the 901 long.
The 911 stops & energizers are long and the 901 short.

On any early 901, 914 or 911 I would use the type 911 parts. From experience they work better. The only exception might be a very early 901 for show.

Best,
Grady

[Jim Sims]

Grady, Thank you very much. This is of great assistance to me and the young man (it's his transmission) I'm rebuilding this 901 with.

To summarize it appears there are two basic options:

1) Reuse the original, shorter energizer and stop blocks and reuse the longer original brake bands since the are NLA; there was some polishing of the original brake bands at the centers but they didn't look too worn. This is the way we put the synchro assemblies back together for the time being.

2) Replace the energizer and stop blocks with the later, longer versions and use the nine new shorter brake bands we ordered (911.302.316.08). Adding up the cost of the new blocks: four- 911.301.315.00 mapping to Pelican 930-302-325-00-M260 at 13.00 each are $52.00 and the one special 1st gear single band energizer block with the "inward hook" which I believe is Pelican 930-302-318-02-M260 at $28.50 each.

(Grady do you have the "911" part number for special 1st gear, single band energizer block?)

Five 911.302.317.01 stop blocks which map to Pelican 911-302-317-01-M260 at $9.25 each are $46.25.

Total block update cost is $126.75. We may look for these new style blocks as used parts as they seem to only suffer a little wear.

Thanks again! Cheers, Jim

[Grady Clay]

Jim,

The first gear hook energizer is 901.302.318.02 and has never changed from ’65 911 to ’76 914. Of course there were obviously .01 and .00 versions but they were prior to 6/67 and might never have made it into production. In the early applications it shows the long band (901.302.316.02) and short stop (901.302.317.02). In the later applications the same 901 hook energizer is used with the short band (911.302.316.00) and long stop (911.302.317.01).

The 911 parts are in 3-5 of every 915. There should be lots of good used parts for almost free.


Jim, as an experiment take the parts list into a PCNA Dealer and have the parts person enter the numbers in the system. It would be interesting to see if there is any availability. What price?

Best,
Grady

[Jim Sims]

Thanks again Grady. I pulled a set of the later energizer and stop blocks (911.302.315.00 and 911.302.317.01) from a 915 3rd gear synchronizer assembly (out of an SC transmission) we also have apart for rebuilding. I trial fitted them to the 901 synchronizers with the later, shorter brake bands (which we already have) and they appear to work as you stated. There is a subtle but critical difference in the later energizer blocks (911.302.315.00) that allow them to function correctly with shorter brake bands - the outward projecting tab (the feature that resides in the gap of the synchro rings) has a taper to it. Since we have a new set of the later, shorter brake bands we are going to see if we can round up a set of the later energizer and stop blocks. Cheers, Jim