Gear Combinations??

[euro911sc]

I got an XL program from a fellow PCan that had a list of all the 901 gear sets in it.

Problem is, I have a 915 Anyone have a list of all the OEM 915 gear combinations possible? That is, a gear set includes the number of teeth for each input gear and output gear and the identity code for the set... that's what I need.

Thanks!

-Michael

[KTL]

Originally posted by euro911sc
Anyone have a list of all the OEM 915 gear combinations possible? That is, a gear set includes the number of teeth for each input gear and output gear and the identity code for the set... that's what I need.

There's a lot of gear sets out there. It's going to depend on what type of gearing you're trying to achieve. Short track, change one gear, more top speed, etc.

Here's a good topic that talks about gear selection


Re-gear tansmission - 915?

And some more background info and gear choices

http://www.pelicanparts.com/techarticles/mult_tranny_ratios/gears915.xls

http://www.carquip.com/parts/911/trans/gears/915gears/index.asp

http://www.carquip.com/parts/gchart/index.asp

[euro911sc]

Thanks for the links One had what I was looking for.

Actually, I'm putting the whole list in to a gear selection program so you can simply pick a set and see what the graphs look like. I have what looks like a complete listing of 901 sets, though I would not know if it were complete or not for sure. I was trying to get the same for a 915.

Best regards,

Michael

[Grady Clay]

Michael,

Post your lists of 901 and 915 gears and let’s see if we can complete them with part numbers, etc.

Best,
Grady

[Bill Verburg]

here is a complete list of 915 gears as of 1973

[Grady Clay]

Bill,

Great list.

I would reference it much later than ’73 because it has 923 (1976) and other.

My only question is the 925 R&P. Will that fit a 915 case and differential?

The R&P P/Ns also need to address the mechanical vs. electronic speedometer.

There are also differences in input shaft/1st gear to accommodate the nose-piece oil pump.


Many racers grind off 1st gear and install (welding) a 2nd gear. I have even seen 915 gearboxes with 1-2 & 3-4 being close ratio racing ratios. Has anyone built 5th as a starting 1st? Has anyone converted to 3-4 & 3-4? The latter requires a new shift fork or sliding sleeve.

While the resolution is limited by the printing, my long time friend Paul Bingham has diagrams in Bruce Anderson’s book (2nd Ed. pp. 238-240).

Since we are designing an ‘original’ Porsche transmission (never provided by Porsche AG) we need to look at the engineering principals.

Best is to have a 4-speed around 1:1 as 3rd or 4th. Having the ratio for 4th at 26:26 and 5th for top speed seems appropriate. Having 26:26 as 3rd , This allows the 2-3 being appropriate for the lower speed turns. @nd second should be ideal for the slowest speed turn.

Many of these issue are addressed with racing G50 & G64 transmissions. The point is to address these issues for our 915s (and 901s) using the later technology..

Best,
Grady

[Bill Verburg]

Originally posted by Grady Clay
Bill,
I would reference it much later than ’73 because it has 923 (1976) and other.
Best,
Grady

Could be from some time in the mid '70s, It's old.