speedometer problems

[Herman]

Hi,

I have a 2001 sportrac. The speedometer is showing real high speeds. For example, if you are doing 25 it says around 45.. if you are doing 40 it shows 80 or so. The rpms seem OK except when I think it should go into OD it doesn't seem to drop back to the 2500 but stays up around 3000 rpm. Also, when you first pull away it seems to be a little jerky but smoothes right out. There also seems to be a bit of a whistle when moving. I took it to a AutoZone and they tested it with a meter and it passed... no error codes showed up. I had suspected a bad speed sensor up to that point but now am completely confused... Help.

Herman

 

[Herman]

thump and it runs OK

I have been having a problem with the speedometer ever since I disconnected the battery. It was showing 20-40 mhp higher than I was actually moving. No error codes showed up when tested. I was told to drive it a little and things would straighten out.
Today, I drove it about 2 miles and when I put it in park I heard a bit of a grind, that got my attention. I then put it in drive and heard a thump and then put it back in park, this time no grind. I turned off the truck and waited a minute and then started it up and put it in drive and now it is driving OK.
So, whats up with that?
thanks,
Herman