Speedo guage acting up

[Adam.Buelow]

I have a 1994 XLT coming up on 300,000. I just had the tranny rebuilt and replaced the rotors, brakes and wheel bearings myself. After a long trip from texas to cali and back car ran fine. Driving back in cold texas weather i ntice my speedo guage acting up. It started out being 10 mph slower than what im actually doing but now its managed to be more like 20 mph slower and in the slower range my rpm will fluctute. i can hear and feel the car rev up and down 500rpm or so. Ive searched on here but cant find any issues to narrow the problem down. Do i just need to replace the speedo cable or is it more in-depth that that?? The car dosent have any problems driving and all fluids are excellent. So im confused as to what the problem is and how to fix it.

 

[YBCold]

sometimes the guages just wear out too. mine did. the cable was good. not sure about the RPMS that could be some kind of electrical problem. that needle takes an electrical signal

 

[Adam.Buelow]

where is the speedo cable located? im want to try lubing it up or replacing it first before i go digging into everything to the point of no return.

 

[YBCold]

it is directly behind the speedometer. get the cable grease and see if it helps.