Hi all, I finally got my 98 on the road, the brakes are (at long last) fully functioning so I went out for a drive...first of all the smoothness and power of these things is just great. The only downside is that my speedometer is on the fritz.
It works right (sometimes) up to about 25 MPH, and it usually sticks, so I'll go faster and it still says 25, then I go slower and it still sticks. The weirdest thing is how it'll jump up to incredibly high readings by itself. I was going about 25-30 MPH the other day and it jumped up to 100 all of a sudden. If my speedo is going to say 100MPH I'd at least like to be going that fast! Also, it'll jump to 15 MPH while I'm parking it (at like 3MPH) and stay at 15 while the car is parked and off.
There is also the possibility that my gas gauge is messed up, too. It reads on full even when I turn the car off all the way.
If anybody knows a fix for speedometers/instrument panels I'd appreciate it. I've tried searching around for similar cases but haven't found anything like my problem.

All the best,
Mack

 

First thing to check is that the cable is indexed properly into the special grease cap on the LF wheel. If you've been messing with brakes, entirely possible it wasn't put back in correctly. Did you notice the square drive tower in the LH grease cap when you were messing with those brakes? Cable has to index properly in it for speedometer to work right. If it was working right before you did the brakes I can about guarantee this is what has happened.

Next is to make sure the cable itself is not binding or sticking. Pull it out from the wheel end and make sure the inner cable and outer casing are not bent or kinked. Clean it with some WD40 or similar solvent, then use a little graphite or speedometer cable lube on it when you put it back in.

Possible after 45 years the speedometer head itself needs cleaned and lubricated. It's not terribly difficult to pull out unless it's a factory A/C car, then all the ductwork has to come out. Once that's out the way, reach up behind the dash and remove three nuts that hold the instrument bezel to the dash- one at each end and one toward the middle- and pull it toward you. After the bezel is out the way, disconnect the cable at speedometer end, unplug the two round wiring plugs and the speedometer head can come out for repair.

On the gas gage, this design should drop to E with switch off. Check the ground at the tank, and the wire to sender- it's on the front of the tank, right behind the rear axle. Olds actually had a special service tool to check gas gages but for your case, simply disconnect the sender wire and turn the ignition switch ON. Gage should go to full. Then ground the wire and gage should go to E. If it works during the test, the trouble is in the tank sender unit, but those can be rebuilt.

 

Thanks a lot for the help, that seems to be all I needed to hear. I'll get out and work on the speedo this week. My gas gauge was working earlier, it's possible I tweaked a wire or something while fiddling around under the dash board installing the brake booster.
I hope the speedo just needs the cable to be readjusted/graphited, because my car does have factory AC and when I checked the shop book for removing the instrument panel is when I decided it would be a major PITA and I'd ask around first and hopefully find an easier way out. I'm glad I did!

Thanks again