Good morning, the digital speedometer spontaneously quit working on my 1990 Cadillac Brougham. The fuel gauge still works and everything is illuminated, but the speedo, trip, and odometer are not. The speed reads 0 all the time and the meters are not counting up anymore. I removed the speed sensor from the 4L60/700R-4 and the gears seems fine. I hooked up an ohmmeter while spinning the gear by hand and it does change resistance. IIRC, I have 5V on the one terminal and ground on the other. I pulled the cluster out and took it apart. I cleaned off a bit of green corrosion on some important looking stuff and I don't see anything else obvious. I just don't know what else to do and can't find anything on the internet on how to fix this. I guess I'm not completely sure it'* not a wiring problem, or even a sender problem. Can anyone give me some tips on how to fix this and what else I can check? I just don't know how this digital magic happens. Thanks in advance! The car is in excellent condition BTW and has been garage kept a lot of the time.

Soldier the grounds and any cold soldier joints on the cluster.
They can look fine and be bad. Does it work if you bang on the dash?

I didn't see anything obvious, and no, it didn't come on when banging the dash or wiggling the connector. I put the cluster back in and put my drill on the sender and got all kinds of readings depending on drill speed. I don't understand it. I put it back in the trans, jack up the rear, put it in drive and go all different speeds and it reads 0 all the time. I pull it back out, take the gear off, put my drill on it and get 10, 35, 55, 75, whatever. The gears both look good. I can watch the gear in the trans turn when I rotate the driveshaft by hand. The gear can't freewheel, at least, I can't rotate it with my finger. I just ordered a new sender. This makes no sense, but I don't know what else it could be at this point.

That'* weird. Keep us updated after trying the new one.

I put the new sender in and it does the same thing - reads 0 all the time. If I pull it out and spin it with the drill I get readings. I am dumbfounded. While writing this, I started thinking if it'* possible for the gear in the trans to slide out of place on the shaft... Hmmm that must be it.

I think you're on the right track.

I'd do this:

1. Mark the sender where it engages with the gear in the transmission

2. Put it together

3. Turn the driveshaft a quarter turn

4. Pull the sender

5. Is it in the same position as when you put it in?

So right after my last post, I removed the sender, took the gear off, and held it in the trans on my finger, roughly where it would go, and it barely made contact with the gear in the trans. I bet it wasn't making contact at all once bolted in place. I jacked up the rear, put it in neutral, and rotated the driveshaft while prying the gear back into position so it would be at 12 o'clock; right over the sender gear. I'm not sure how that plastic gear is supposed to stay located on the shaft, but it'* a tight enough fit that I imagine it will stay in place for a long time. Thanks for the help guys, and I hope this might help someone else diagnose an inoperable speedometer in a 700R4/4L60.

Thanks for letting us know how it turned out!

Well, I work about 60 miles away. I made it to work, around the job site all day, and about 10 miles into the drive home before the speedo quit again. I'm sure that gear in the trans slid up the shaft. I'm not sure how it is supposed to stay located on that shaft, but since I really don't feel like taking the driveshaft off and removing the tail shaft housing, I think I will try to make something work. I only have a little hole to work thru, so maybe some JB weld if I can't come up with something else... It is nice to drive the car and keep the miles off of it! LOL

LOL the miles are still there . . . lurking!