It's totally fixable. This is pretty common on the 2005 Mustangs, it's caused by failing stepper motors in the instrument cluster, they control the movement of the gauges. There's a guide on how to fix them here - www.2005-mustang-speedometer-problem.com
You can fix the speedometer in your 1994 Oldsmobile 98 by replacing the speedometer cable. If changing the speedometer cable does not fix your speedometer you will need to replace the entire speedometer.
Assuming a 2005 is still covered by factory warranty (as it should be), take it to the dealer for repair.
Speedometer cables can dry out over time. Remove the cable from the back of the speedometer, and lube the cable with graphite. This should fix the issue.
Need to figure out exactly what's wrong with it first. Maybe it needs to be replaced, or maybe it's just in need of a new speedometer cable.
The speedometer itself will work but you will need to take the instrument cluster apart and transplant the speedometer unit from the 92 cluster into the 87 cluster. The speedo mechanism is the same but the clusters are different.
I have the same problem with my 1994 ford gt mustang 5.0 just got it to.
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A Mustang Cobra;s Speedometer tops out at 160 MPH. But have been known to exceed that.
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To fix a speedometer on a 2005 Kia Sedona, first check the vehicle's fuse related to the instrument cluster, as a blown fuse can cause malfunction. Next, inspect the vehicle speed sensor (VSS) located on the transmission; if it's faulty, it may need replacement. Additionally, ensure that the wiring and connections to the speedometer are secure and free of corrosion. If these steps do not resolve the issue, consider consulting a professional mechanic for further diagnosis.