901 gearbox question

[CHILI]

What is the meaning of "airport" gear box? Saw it in an ad. Don't know anything about 901's. I think some have first where 2nd is on a 915??

Man, I feel stupid.

[oldE]

A close ratio gearbox with top gear (5th) being about the same overall ratio as 4th in a normal 5 speed.
Les

[jluetjen]

An "Airport" gear box has gear selections optimised for "Airport" circuits which tend to be fast with a lot of higher speed corners. I think that these were also used for Le Mans. If you look through the spec book you'll also see that they have the following other special 'boxes listed:

Standard Street 901:
11:34 / 18:34 / 22:29 / 25:26 / 29:23

" Hill Climbs" The shortest combinations of gear ratios. Most likely also good for rally use. 5th gear in the "Hill Climb" 'box is the same as 4th gear in the "Airport" 'box.
12:34 / 17:34 / 20:31 / 22:29 / 23:28

"Airport"
12:34 / 18:34 / 21:31 / 23:28 / 25:26

"Fast Circuits" which have longer gears then the Airport box
15:36 / 20:32 / 23:28 / 26:26 / 28:23

"Nurburgring" where the gears are even more closely grouped since about 12 and a half of the 14 mile Nurburgring is all 2nd and 3rd gear stuff.
14:37 / 20:32 / 22:29 / 25:27 / 27:25

[304065]

[Grady Clay]

Chad,

Good qustion.

The earliest notation for “airport ratios” is a Type 741/5 transmission for “CoupeGS/GT, Coupe Abarth GT, Standard gear ratios for U.S.A and airport races.” The 901/52 transmission had gears AAFJOS “for airport races.” Interestingly when you ordered this transmission it came with a 904 input shaft and a separate F 2nd gear to fit. This was also true for the later 901/77 and 911/82. While a 915 could be ordered with special gear ratios, the “airport gears” designation wasn’t used.

Best,
Grady

[RallyJon]

A chart to help visualize just how short those gears are:

[CHILI]

Man, you guys came through! I saw the post slipping away last night, then woke-up to see this. You guys rock! Thanks for the info. This is a good post for the "search" button.