Mechanical vs. Electrical Speedometer/Tranny

[cab83_750]

I have seen a lot of Wanted-to-Buy and Wanted-to-Sell mechanical and electronic speedometers from our sponsor's ad. I know my 83 SC has electronic speedometer. But... my Forrest Gump q's are:

Are mechanical speedo's driven by cables attached to ...where? Attached to the tranny?

Are there mechanical tranny vs. electronic tranny? I have checked the extra mag tranny I have and the only electrical part I could see is the one for the reverse light? Are all 915's electronic?

Help!

[Jack Olsen]

Early trannies used mechanical speedos. I think it was 1974 and earlier, or thereabouts. You can adapt a mechanical to be electronic, but I don't know if the reverse is possible.

[CamB]

It is '75 and earlier for mechanical speedo (and un-galvanised bodies and chrome mirrors). From '76 the speedo went electronic, they galvanised the whole body and the flag mirror appeared.

I would think it would be better to get the mag transmission converted, because running the mechanical transmission would be very difficult. Having said that, you would then need to get ANOTHER SC speedo and get it recalibrated for a 7:31 R&P (assuming that is what the mag tranny has). 7:31 last year was apparently 1974. The 1975 has the first 8:31.

In fact, as years go, '75 kinda sucks (see below, I oughta know). They rust, they don't have short gears. They don't have a decent exhaust (the '74 did).

[ischmitz]

Windsor,

The mechanic 915 speedo drive is at the nose of the tranny right next to the gear selector shaft. It's a threaded piece with a little flat shaft inside. The mechanic speedo cable screws to this thread. The electric pickup on later 915 trannys is at the cover plate for the differential. It's a hall sensor that "listens" to a sectored disk inside the diff housing. I converted my 915 to electronic by using a VDO-supplied transducer. It screws onto the nose of the transmission where the mechanic cable used to go. My 993 speedo is about 1% off the mark (checked with mobile GPS)

Ingo (from Japan)

[IROC]

Originally posted by CamB
It is '75 and earlier for mechanical speedo (and un-galvanised bodies and chrome mirrors). From '76 the speedo went electronic, they galvanised the whole body and the flag mirror appeared.

Actually, the electronic speedos began sometime *during* the '76 model year. I have a '76 and it has a mechanical speedo. My car was mfg. in Dec of 1975.

Mike

[hifeverz]

I converted my 915 to electronic by using a VDO-supplied transducer. It screws onto the nose of the transmission where the mechanic cable used to go.

Ingo:

Where can I get one of these and will it fit on my '74 transaxle? . . . approx. $$ and would you know of a supplier or website??

thanks,
Hz

[ischmitz]

I bought mine in Germany at a shop that is a licensed dealer for Kienzle and VDO. They retrofit logging devices into commercial trucks and stuff.

Unfortunately, I have never been able to locate something similar here in the U.S. All the pulse sender that I found here (used for aftermarket GPS applications) were 6 pulses per rev and you need eight. Maybe a speedo shop such as North Hollywood Speedo can help.

Sorry for not being of more help.

Ingo