Speedo showing way too fast

[Blue91Ex]

Hey guys, So this morning I'm driving to school and look down at my speedometer. Now I know what RPMs I run at certain speeds. I was going down a road that is way too rough to 65mph travel, and the speedo read 75mph, RPMs at about 2700 which is normally about 58ish. It did not feel like 75 either because the tires arent balanced all that well and the truck shakes a bit at 75, which it was not doing.

I watched the speedo all the way to school to make sure i wasn't imagining it and everything seems to point to it being off. Also the needle was bouncing around a lot within 5mph at high speeds, which it usually only does under 15 mph.

When I left school to go home today, it was back to normal.

Any ideas what this may have been and how to fix/prevent it?

 

[RangerX]

The speedo cable gets dry and gunked up over time and can cause that. I believe it's supposed to get lubed by the ATF in the Tcase, or trans if you're 2wd.

 

[Blue91Ex]

its 4wd, wouldnt a gunked up cable make the speedometer show as slower? guy at the local repair shop said sometimes teh dash itself gets messed up..

 

[Jason94sport]

Pretty common...I read in another post(can't find it) that the gears in the Xfer case or trans output area had teeth missing from wear & was causing it. I had the problem on a 94 sport, never did fix it, sold it off.

 

[Blue91Ex]

funny, it just decided to fix itself again, prob gunna be like my front pass door speaker, acted up then went away then after months its acting up again lol

 

[sirhk100]

Just had this happen to me for the first time yesterday morning and this morning on my way to work. Lunch and driving home though yesterday it was fine...

I'm with you though, would've expected any issues to cause it to read slower, not faster! LOL

 

[larrydd999]

It's been happening on and off to our '94 Limited for a couple of years now. There's another post on this site that gives - if I remember correctly - the most likely reason as a nylon speedometer gear in the transmission with the less likely reason a cable that needs lube or replacement. Ours happens occasionally at 50+ MPH (shows 60-65) and 'resets' itself when I go below 45. Since it's a commute car and has a tach, I've gotten used to it.