1972 911T Speedometer cable stripped at transmission

[72Concepts]

I recently jumped into the Porsche family with the purchase of a 1972 911T.

The speedometer (and ODO and trip) do not work on the vehicle. I was told that it is a simple fix with a plastic gear and removing the speedometer.

I received, with the purchase of the car, a repair bill from the previous owner. The speedometer cable was replaced, but the mechanic made a note that the "speedometer drive was stripped out at the transmission and should be serviced...". I have a few questions, but here are the vehicle particulars first:

1972 Porsche 911T (2.4 with a 4 speed 915/12 transmission)
The engine is the US Version with MFI (140hp)

There seems to be a change somewhere around '71 or '72 regarding the angle adapter (possibly going to the 915 trans from the 901?).

Here are my questions:
1. If the odo and speedo are both not working, could it still be the gear in the speedometer itself?
2. Does the 1972 911T with 915/12 4 speed trans have an angle adapter and could that be the issue?
3. If "stripped" part is internal to the trans, is it possible to replace without rebuilding?
4. Can this be done without dropping the trans?

My apologies if this is covered in another thread... I am the forum technical equivalent of a blocked punt.

Any help pointing me in the correct direction would be greatly appreciated!

[Dmitry at Pelican Parts]

Hello and welcome to the forum! Let's see some photos of your 72' 911T I'm also attaching a link to help with the speedometer removal procedure. Please feel free to post a Comment just below the tech article with your questions and one of our Porsche techs will get back to you with specifics.

Porsche 911 Speedometer Removal | 911 (1965-89) - 930 Turbo (1975-89) | Pelican Parts DIY Maintenance Article

[timmy2]

Easy testing of cable and speedometer.
Remove cable from transmission, attach a variable speed drill motor to the inner cable square drive. Slowly spin the cable (clockwise?) and watch the speedometer needle for movement.
(Reverse the drill if the needle goes down or doesn't move)

Can't answer about the remaining questions. My speedo is electronic.

[72Concepts]

Thank you Timmy2!

I will do that ASAP.

[Trackrash]

The 915 trans does not have an angle adapter. That ended with the 901 trans in '71.

It is possible to check the cable as mentioned above.

However, IMO, you will have to remove the trans mounting crossmember to gain access to the end of the spedo cable. You will have to somehow, jack?, support the engine/trans in the process.

You may want to pull off the speedo cable from the rear of the speedo. Check to see if the cable can be turned from the speedo end. If so something is broken.

You can just spin, by hand the speedo's "socket" where the cable's square end goes into the speedo. You can use a small screwdriver to do this and you should notice the needle move, if the speedo is OK.

It is true that the old style angle drive of the older 901 transmissions were problematic. You don't have that. I have not heard of problems with the newer style trans speedo drives giving problems, but it could happen.

You will have to remove the nose cone of the trans to access the speedo drive. I'm not sure how this can be done with the trans still in the car.

[timmy2]

Good info Gordon, it's been 12 years since I sold my '73, so I didn't remember what accessing the cable at the trans was like.

[Porboynz]

It is possible for the speedo drive to be bumped when fitting the engine/trans unit such that the drive gear retaining circlip is dislodged and the gear disengages within the gear box. It is a steel drive gear and if you remove the cable from the trans you can see it easily, if it turns by hand you have a problem, if its barely visible or gone completely you have a problem. You should see a round shaft with 2 machined flats that engages with the speedo cable. Otherwise follow earlier instructions for checking the cable and speedometer itself.

[72Concepts]

Thanks to everyone for the response to my question(s). And thanks for taking it easy on a newbie to the forum. I appreciate all the responses!