Speedometer calibration possible?

[TheSecondChris]

Is it possible to repair or calibrate the speedometer on my 1984 944? It reads about 8mph higher than actual. I've read about the cable replacement that fixes the "bouncy needle" but my needle is pretty stable.

[v2rocket_aka944]

what size tire are you running and is it properly inflated?

mine (85) is a little optimistic too.

the cable can always use some lube, BTW.

[Spring44]

Originally Posted by TheSecondChris

Is it possible to repair or calibrate the speedometer on my 1984 944? It reads about 8mph higher than actual. I've read about the cable replacement that fixes the "bouncy needle" but my needle is pretty stable.

The '84's speedo cable drives off of the front drivers side wheel, not from any replaceable drive gear in the transmission. It goes into the backside of the hollow wheel spindle, through the spindle and is inserted through and E-clipped to a square hole in the center of the grease cap. The other end of the cable goes into the back of the speedo.

Therefore, any recalibration would have to be done inside the speedo itself and I don't know if that is possible or not. You may just have to play with your front tire size and aspect ratio to get a tire diameter that is very close to the stock diameter.

The later 85.5 and up models abandoned this drive method for the speedo.

[TheSecondChris]

Thanks guys, my rims are 15" and tires are stock size too. I was reading how some folks disassemble the gauge and then adjust the position of the needle. If it reads high then it's possible to change the position of the needle so it starts out in a more counter-clockwise position.

Changing the cable and applying lube is a good idea and this would help a bouncy needle for sure, but even a badly lubed cable will rotate at the same rpm as a well lubed and brand new cable.

I'm asking because there may be a better method that I hadn't heard about. I need to work on the speedo to fix the odomter gear so I may do something to the needle at the same time.

Thanks for the feedback.

[matt1415]

I've got the same problem as well in my 924S. Replaced cable as well as the main drive gear in the speedo and it's the same thing. I'm running 195/65/15, if I remember the 944 uses a slightly different size but I think the outer radius works out to be the same

[Jay H]

I had a local speedometer shop repair my speedo in my 924S (one of those 1 man shops in the central city that has been there forever and he had parts in stock on his shelf). He was able to "calibrate" my speedo and according to GPS data, the repaired speedo reads correct right around 60 mph. Anything over that and the speedometer reads higher than actual speed. Once closer to 30 mph, the speedometer is indicating a speed lower than actual.

A new cable helped remove most, but not all, of the speedometer needle bouncing.

[jhowell371]

8 MPH is a good bit of error. There are replacement speedometer gears with differing numbers of teeth. My guess is someone installed the wrong gear somewhere along the line. YMMV

[mikepellegrini]

I repaired the speedometer from my 83 NA myself. I tracked the speed with a GPS to find out what the error was, then pulled the gauge cluster out; I took off the front of the speedo and then realigned the needle. The needle comes right off; you do have to be careful not to damage it.

It took me 3-4 tries before I got it right, again checking it with the GPS. By the end, I could have the gauge cluster out in like 5 minutes.

[TheSecondChris]

Was your gauge reading higher or lower than GPS speed? Did you need to do anything with the pin the needle rests on?

[jjeffries]

Chris, I don’t think you’ll be able to do anything by re-orienting the needle; it’s a fine instrument/mechanism. It’ll need to go to an instrument specialist (North Hollywood Speedometer and Palo Alto Speedometer are two frequently mentioned in this community, but there are others) who’ll be able to make a very fine adjustment to the relationship between the input of the gauge and what it displays. John