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I've got a '91 F150 (4.9L) - with the E4OD transmission. Appx 180k miles on the ticker...
On a drive today to a jobsite - I noticed that the speedometer was WAY up at 80-85MPH - when my road speed according to GPS was actually in the 65-70MPH range. I also seemed "bouncy".
As far as I could tell - I didn't notice that the odometer was running any faster (but who knows - it may have been)...
Opinions on whether this would be in the transmission... Mechanical Speed sensor, (or the gear on it - which I haven't been able to find on RockAuto), Cable, or in the speedometer itself...
Do you have a tachometer and did it seem like its revving higher than normal?
What you didnt mention is if this truck is new to you or if youve owned it for a bit....That would lend a broader bit of info...
When I buy a vehicle the first thing I check is the difference between the speedo and the dash by GPS so I know my limits on the road as we have a 6mph over the limit allowance...If I went by my speedo I would be 11mph over the limit with no valid excuse and I cant afford to lose my CDL...Its my golden ticket for sidework....LOL...
My hunch says its gonna be the cluster thats going bad.........
Do you have a tachometer and did it seem like its revving higher than normal?
No tach on my model.
What you didnt mention is if this truck is new to you or if youve owned it for a bit....That would lend a broader bit of info...
I've had it for about 10 years, now. I bought it (literally - for a song) after it had been sitting in a field for 10 years, and it had about 84K miles from the original owner. Had to replace both fuel tanks & sending units (rusted), brake booster, calipers & rear pistons, etc, etc. plus regular maintenance items. I had the E4OD rebuilt last winter by a local shop. And now - looks like I may need to replace the ABS module under the truck. Or just leave it. lol...
When I buy a vehicle the first thing I check is the difference between the speedo and the dash by GPS so I know my limits on the road as we have a 6mph over the limit allowance...If I went by my speedo I would be 11mph over the limit with no valid excuse and I cant afford to lose my CDL...Its my golden ticket for sidework....LOL...
My hunch says its gonna be the cluster thats going bad.........
It isn't too hard to pull the speedo cable and inspect the gear. The speedometer is all mechanical, so the only components to look at would be the speedo cable, its gear, the drive gear on the trans output shaft, and the speedometer itself.
I got the rough country speedometer calibrator that you just plug in put the tire size and you should be good. When I put in my size of 34 the speed was still off. It only give you .25 increment sizes to choose from so ive gone down .25 all the way down to 32 and its a 1 mpg off from GPS at 60. Im just wondering if anyone else has had this problem and if so how did they fine tune it more or is there anytbing else I can do. Might just leave it since its 1 mph but going a on a trip with high speeds this coming week so I'll get to see if its more off the faster I go
Speedometer Showing higher speed
