901 trans: how to tell a 4-speed from 5-speed?

[UrelferDK]

Need some advice from the transmission gurus on the board: on a 901 transmission, how can I- from visual inspection only- tell if it is a 4 speed or 5 speed?

- Pictures only, I can't just shift through it.
- Trans type is not helping. I have a 901/02 transmission which I thought is 5 speed. until I found out today that my 901/02 is 4 speed. always learning...
- I have been told the interior is different, and a 4- can't be turned into a 5 speed.

So how can they be told apart from looking at them?

thanks in advance!

[Jon B]

I have been told the interior is different, and a 4- can't be turned into a 5 speed.

There's no difference in the housings between a 4-speed and 5-speed, and they can easily be converted either way.
There are no visible clues from the outside except for the stampings on the bottom, which give you some information from when they were new.

The only way to tell for sure, out of the car, is to remove the front cover or to shift it on the stand (or bench or floor, whatever).
You could remove the oval shift guide and look inside the transmission, but I don't think you'll have a clear view of the lower gears to tell for certain.

Jon B.
Vista, CA

[gled49]

Removing the shift cover will revile this if its a 4 speed. G

[UrelferDK]

thank you! will remove the shift cover to check.

[71gold]

I believe the serial number (if available ) has a digit that identifies 4 or 5 speed.

[Jim Breazeale]

thank you! will remove the shift cover to check.

You are about to open a can of worms! Just shift the transmission, manually with the shift selector, using the coupler as a handle. It is very easy to tell a 4 spd trans from a 5 spd trans by shifting into the dogleg. You either have 1st gear or you don't. A 901/02 is a 5 spd trans. What makes you think it is a 4 spd? Did the, ill informed person (I'm trying to be nice), that told you you can't make a 4 spd into a 5spd tell you that? I have never heard of anybody turning a 5 spd into a 4 spd, but I guess anything is possible.



Regards

Jim

[Jon B]

To test shift the transmission, out of the car:

Facing the front of the transmission, in neutral, turn the shaft counter-clockwise until it stops.
Pulling on the shaft will select 1st Gear on a 5-speed, or be blocked on a 4-speed. Pushing on the shaft will select Reverse in either case.

It helps to use a shift coupler as a handle, as Jim suggested. Don't use pliers.

Jon B.

[UrelferDK]

Thanks for the advice, much appreciated

- as suggested, I will try to shift using the coupler as handle and shifting into the dogleg to figure out if my spare transmission is 4- or 5-speed

- 901/02 = 5 speed was my understanding as well. Until I got my rebuilt 901/02 back yesterday which is now a 4-speed- no doubt. Transmission case is from a June 1967 911 normal. I assume someone preferred 4-speed over 5-speed and converted it at some point.

- 4-speed to 5-speed conversion can be done, and my trans rebuilder doesn't know or doesn't want to risk me asking him to make my 901/02 a 5-speed. Good to know...

[NeunElf]

The little specification brooklet:

• 911/912 Technical Specification Booklet (65-68)
• 911 Technical Specification Booklet (69-71)
• 911 Technical Specification Booklet (72-73)

has listings that will show you how many gears a transmission originally had. It also has some of the transmission serial number ranges.

From the 65-68 booklet:

901/0 5-speed
901/02 5-speed
901/03 5-speed
901/10 4-speed
901/50 5-speed
901/51 5-speed
901/52 5-speed
901/53 5-speed
901/54 5-speed
901/75 5-speed
901/76 5-speed
901/77 5-speed
901/78 5-speed
901/79 5-speed
901/80 5-speed
901/81 5-speed
901/82 5-speed
901/83 5-speed
901/84 5-speed
902/0 4-speed
902/1 5-speed
902/01 4-speed
902/02 5-speed
902/50 5-speed
902/60 5-speed
905/00 4-speed
905/01 4-speed

Of course, if a transmission's been converted from 4 to 5 speeds or vice-versa this doesn't apply.

[UrelferDK]

shifted through my spare 901/03 trans using the coupler as suggested- 5 gears. Thanks again for the help!!!