Possibly Need a speed sensor for a 915 trans, and a little help!

[lsc ss]

I am installing an Autometer speedo in the car I am working on, it has a 915 trans that came out of a 1987 911 Turbo, Does anyone knnow if the stock style pickup will work with the autometer speedo? Autometer does not seem to know.
When I look in the hole in the trans where the sensor goes it looks like a blind hole, is it supposed to look like that or am I supposed to see something in there ??
If it will work anyone have one for sale ?

Thanx in advance !!

[James Brown]

The blind hole holds the sender that picks up the signal from a wheel inside the transmission fitted with 8 magnets. It counts them and the spedo translates that to mph/kph. Not sure how a Autometer speedometer works (most likely it has a cable). At least that will match the Chevy power plant you have in the car!!!! Might want to look into GPS based speedometers.

[lsc ss]

Autometer speedo is electric, I found a place out west that makes a pickup wheel that bolts on the axle and uses a magnetic sender but if I can use a stock one it would save alot of time and money !!

[James Brown]

Our host sells them, they should be all the same as long as you can adjust them.

[lsc ss]

Adjustment is not a problem, the speedometer is internally calibrated. Just want to make sure I get the right one that will fit in this trans, I see a couple different styles for different years.

[James Brown]

Well what year is the trans.??? what is the serial number??? It's just a signal. Does Autometer has a way to calibrate the unit based on wheel diameter? Im sure they do.

[Walt Fricke]

All the electric speedometer 915 transmissions (starting in '76, I believe) use the same speedo sensor.

The 930s came with a 930 transmission. Not the same, stronger. But same impulse senders: from '76 through '84 915 and 930 trannies, part # 911 606 209 00. '85 and '86 were same, but 01 on the end, not 00.

Don't ask me what was different, though.

FYI, these sensors are simply a reed switch. The 8 magnets on a plate inside the transmission and bolted to the right side of the differential open and close that switch, which is separated from the tranny innards by a pretty thin part of the housing casting. The switch, when closed, grounds the wire which comes from the speedometer. When open, no current flowing through that wire. You can duplicate this by manually grounding and ungrounding the sensor wire from the speedo.

So you can attach the 12V and ground on your Autometer, and put a wire with an open end on the sender terminal. Tap that wire's end of and on and of and on to the ground and see if the speedo needle moves.

That is the factory procedure for testing a speedo! Does serve to tell you if it is the speedo or the sensor which is failing.

Were I you, though, I'd just contact Autometer. They can tell you if it works the way the VDOs Porsche used do. They have really great customer service and promptly answer technical questions. I sent in m 15 year old tach to see if it was the cause of a problem I had. They tested it, said it was good, and sent it back on their dime with no cost to me.

Walt

Walt

[lsc ss]

James, The only number i can find on the trans is stamped near the drain plug: 77H00680 . (Was told it is a 1987 model trans.) The autometer speedo gets calibrated using a marked mile, push a button on the speedo, drive exactly 2 miles, push button again, calibration done.

Walt I don't have a problem with it not working, I am trying to install one where there is nothing, the car was built by someone to be a race car and all the speedo stuff was removed so I am starting from scratch. I see that there are a couple of sensors for different years, not worried about it matching the speedo, just want to make sure it will fit in this trans.

[scarceller]

The 915 trans in the 84-89 carrera cars generates about 6,500 pulses per mile. I have a nice document with these details, I created the doc when working on my project to record speed in MPH via my laptop. It was part of my WBO2 setup project.

I have this doc, PM me if you want it.

The doc also shows the basic schematic circuit to condition the pulses from the stock speed sensor into very clean 5vdc square wave.

[Wil Ferch]

You mean the 915 trans on the 84-86 Carreras.... no?....because the 87-89 Carrera''s used
G50 trans.

[scarceller]

Yea I stated this wrong. The 87-89 G50 and the 84-86 915 work the same for the speed sensor. No matter the trans the speed sensor and speedo are the same.

Thanks for correction on the years and trans types.

[lsc ss]

So anyone should pretty much work on the trans, here is what Autometer says about senders for their speedometers:

"The speedometer is designed to operate with an electrical speed sender. The speed sender signal range must be between 500 and 400,000
pulses/mile (310 and 248,500 pulses/km).Any speed sender or electronic module that meets the following two conditions can be used:
1. Pulse rate generated is proportional to vehicle speed.
2. Output voltage within the ranges listed below:
• 4 to 16V (Hall effect sender, 3-wire)
• 4 to 120V peak to peak into a 10K ohm load (Sine wave generator, 2-wire)
• 5V Square wave (TTL)"