Speedo not reading correctly

[devans]

My 02 ram has been sitting for a few months while I get settled into my new surroundings and the last time it was driven I was told that the speedometer went right to 90 mph as soon as it started moving and didn't read correctly while it was moving.
I'm thinking it uses a wheel sensor or something like that and there is surface rust on it causing the problem. Can anyone confirm? I'm still no where near my truck to check it right away but I'm hoping to go get it soon and want to try to fix it before I drive it on the highway. The only other option is making sure I have a GPS with me so I know how fast I'm going.
Thanks.
Don.

 

[MADDOG]

I had a similar problem on my 1999 1500 4x4. It could be the speed sensors but that wasn't the problem with my truck. It was the connector to the ABS box. If it's not secure, wet, dirty or corroded it can cause the speedometer to behave exactly like that.

 

[devans]

Thanks Maddog for the reply. I've been talking with my dad, the truck is at his place and he's been using it. Turns out he somehow left the truck ignition on but thought he shut it off and killed the battery some time back. He charged the battery but he did it again the other day and it must have damaged the battery. He put a new one in it today and everything is fine.
Maybe me writing this will help someone else if they find this on a search.
Thanks again.