Gearbox # cannot be traced back

[gled49]

The build sheet for Matt Blast's ST,which is documented in the ST thread, states the usual chassis#, engine #, M491 build, color, interior, but gearbox number cannot be traced back. I'm in the process of a rebuild on that transmission and much to my surprise and with Matt's permission, this is what I found. 915/11, 7920011. Transmission With oil pump, 80% LSD, 11:35 production 1st, 16:35 2nd, 20:32 3rd 23:28 4th, 26:26 fifth. The pairing #s etched with eletric pencil are 13, 26, 7 & 13 for the special ratios. The date codes for 3rd, 4th & 5th are 6/70, 7/70 & 8/70. The 2nd fixed gear is to small to write anything but the ratio and part number. In 35 years doing this I'v never seen factory 16:35 2nd or 20:32 3rd.The gears are perfect with very low miles and the LSD has 50 lbs preload measured flange to flange. The oil pump has needle bearing instead of bushings as in all pumps I've seen. Get out your pocket spec books for 72-73 and look at the trans type info on first page of trans section and look at last line of 72; type --, ratios to order, serial # 7920001 to 7920015, special transmission. Pictures of shift cover compare RS to ST. Pressure relief is 8mm ST, 12mm RS. Casting for oil resevior for reverse idler is different. And the speedo casting in center for axel support is smaller. Also no date code on cover. Gordon

[gled49]

I've seen a few Factory 901/911 special ratio gearboxes in 35 years. But this the first 915 Factory special ratio gearbox I've seen. Anyone else? Gordon

[davep]

You have a very interesting box there. As it happens, a 901 box with serial 7399102 has just been found by a Pelican member, and it is one of 10 custom geared boxes.

http://forums.pelicanparts.com/porsc...1-gearbox.html

[Matt Blast]

I had a chance to look at a factory built rally car recently. This particular car was originally a street car that was then sent back to the factory to be converted to a rally car. I am not allowed to get an more specific than that. The transmission is a '73 type 915 with an external cooler in the left front fender ('73 RSR type) and an internal pump. The transmission is type 915/11 and #793 0133 see picture. In the '72-73 spec book there is a "ratios to order" trans that list the trans #793 1001-793 2000. This cars trans number is lower than the numbers listed in the spec book. Any thoughts on that? I don't have any information about the insides of this box unfortunately.

It seems likely that the "ratios to order" transmission might be stamped as type 915/11. Does anyone have any 915/11 type transmission (other than the '73 915/11 that is listed in the spec book as a 4 speed with serial numbers 703 5001-703 9999) ??

Matt

[gled49]

I wanted to bump this to revisit trans number stamping. Gordon

[Harvey Weidman]

I've seen a few Factory 901/911 special ratio gearboxes in 35 years. But this the first 915 Factory special ratio gearbox I've seen. Anyone else? Gordon

Gordon, We ordered and stocked "special" ratios for 915s. I remember we ordered at least 4 gearsets for Darryl Vittone and Frau Baer said some she had never sold before....She also offered to build a trans for the price of the gearsets. I wonder if those special gearboxes had numbering on them? She gave the impresson that they built custom ones frequently..
H