901/13 question

[G50911]

hey all. i have 1 901/13 (serial: 7195609) transaxle im thinking of rebuilding. i picked it up years back to use on a build i started. my question is, are all 901 5 speeds doglegs? if not, how can i tell if my box is or not? also it's going in a 67 911 normale with a stock 2.0. it's got a 4spd in it now but i always wanted to stick a 5 spd in it for better freeway driving. i heard thru the inter webs that this 901/13 has the same final drive ratio as the 4spd i have now. is this true?

[Jon B]

... i heard thru the inter webs that this 901/13 has the same final drive ratio as the 4spd i have now. is this true?

The final drive ratio was the same as a 67 4-speed, but the 5th gear is taller than the 4-speed 4th gear.
And yes, all 5-speeds through 71 have dogleg 1st gears.

Just be aware that 67 axles wont bolt up to the 901/13 axle flanges.

Jon B.
Vista, CA

[davep]

Yes, all 901, 902, 911 & 914 are dogleg.
Yes, the 4 speed generally has a similar top gear as a 5 speed, it is just the gap between the gear ratios is smaller for the 5 speed. Theoretically this means it is easier to find just the right gear in more situations. Freeway driving is not one of them.

[Jon B]

Yes, the 4 speed generally has a similar top gear as a 5 speed, it is just the gap between the gear ratios is smaller for the 5 speed.

Dave, I think the 67 4-speeds had 28/24 "X" top gears... no?

Jon B.

[John Straub]

Dave, I think the 67 4-speeds had 28/24 "X" top gears... no?

Jon B.

That's correct. It's shorter.

John

[Jon B]

The final drive ratio was the same as a 67 4-speed, but the 5th gear is taller than the 4-speed 4th gear.

Here are the numbers:

902/0 ..... 67 4-speed ..... Final drive 7/31 ..... Gears 11/34, 19/32, 24/27, 28/24 (A-H-Q-X)
901/13 ... 69 5-speed ..... Final drive 7/31 ..... Gears 11/34, 18/34, 22/29, 25/26, 29/23 (A-F-M-S-Z)

If you have a 68 4-speed in your 67 911, it could have either a 28/24 "X" or a 29/23 "Z" top gear.

Jon B.
Vista, CA

[G50911]

thanks all for confirming the dog leg. not a huge fan of it but it would be nice to have closer ratios and the over-drive.

Just be aware that 67 axles wont bolt up to the 901/13 axle flanges.

i didn’t know this? is it a difference in the spline count or coarseness? or length of the axles?

[beh911]

..........

[davep]

You are correct, in general. However, except for the 1967 911S the five speed trans also had an X top gear, the S got the Z gear. The AFMSX transmission gearset was THE ubiquitous 5 speed set for the early cars.
Then in 1969 both the 4 speed and 5 speed got a Z top gear. So, in general both the 4 and 5 speed had the same top gear in the same year excepting the more powerful 911S. There are always exceptions.
The change from an X to the Z was probably due to increasing emissions regulations. For 1970 the 914/6 got the ZA gear, and the 914/4 was saddled with a ZD gear; the 914/4 is lower powered and lower rev range than a six so the fifth gear is nearly useless unless going downhill. Climbing a hill you need to drop into third. But if you want a really low revving freeway ride, then try a ZD in your five speed 901.

[Jim Breazeale]

thanks all for confirming the dog leg. not a huge fan of it but it would be nice to have closer ratios and the over-drive.


i didn’t know this? is it a difference in the spline count or coarseness? or length of the axles?

Troy

You've got a Mag Case 901. You can use 914 axle flanges in that trans. The 912 flanges only have 4 bolts and 2 roll pins. You can modify your axle flanges to accept the roll pins or just go with 4 bolts. In either case, you will be fine, unless you are planning on 300 plus HP. Knowing you, that may be the case.

Jim