Speedo only works up to 60mph

[Bear911]

Anyone with an idea how to troubleshoot this one? Driving along today, I suddenly realized the speedo wasn't going past 60 mph (96km/h) anymore. Works fine 0-60 though. Odometer also works fine. The car is a 1976 Carrera 3.0.

Thanks

[Bear911]

I should probably add that it is an electronic VDO speedometer. A search shows up plenty on speedo calibration errors or ones don't work at all, but I've never seen one that just goes up to a point and then gets stuck.

Is there a way to give the speedometer an artificial signal to see if the gauge itself is capable of swinging the needle past 60mph? This would help to differentiate between a sender issue and a gauge issue.

This really sucks.

[LUFTMAN]

remove trans side cover clean magnets on ring gear plate (sludge build up on magnets)

[Kidasters]

I have the opposite problem. Speedo is intermittently not reading until past 20 mph. My search says that this is most likely a bad sending unit - so new sending unit is on order......

[Bear911]

Thanks for the replies. Am I correct in assuming getting to the cover plate entails a tranny drop?

[Kidasters]

No - theoretically this can be done without dropping the engine or transmission. I'm betting the hard part is fishing the wires back into the tunnel. What I'll do is tie some strings to the wires on the current sender when I pull it. That way - pull the old sender out - pull the string through. Tie the new sender wires to the string, and pull it back into the tunnel.

[Flat6pac]

Not a tranny drop. Pull the CV off the trans, both sides. Remove the nuts on the side cover, drain the oil by now..
17mm nut on the drive flange, cover side. Remove side cover. Drive flange on the other side, once removed will allow the ring and magnet unit to roll out of the trans.
Replace the rubber O ring on the side cover and you might do the seals for the drive flanges.
Bruce

[Bear911]

Thanks very much for the excellent tips guys. Looks like I have a new weekend project Will report back.

[Bear911]

Just a little feedback on my problem thus far. Turns out the gauge itself is the issue. Managed to troubleshoot it by swapping the speedo out with another electronic vdo. I have sent it in to the local speedo repair shop. Here's to hoping it is sorted out soon (North Hollywood is 10372 miles from me, alas)