99 Chevy Express Van Speedo Going Crazy

[Rag64top]

Greetings!

 

I am a new member in need of some help on my 99 Chevy Express van with a 350 engine.

 

The problems I am having, is that the speedo has gone crazy in my truck!

I recently resolved a connection problem at the battery, where there was tons of green stuff causing

a bad connection, and no start.

After fixing that, and maybe it had nothing to do with it, now my speedo is going nuts!

As soon as I take off, and go anywhere from 10-15 MPH, the speedo reads 40-60 MPH, and causes the truck

to shift into 4th gear while I'm only going 10-15MPH!

Now I have to shift the truck manually, or it is about useless.

Is there a bad speed sensor somewhere? If so , where is it located?

As you can probably tell, I'm no mechanic..

Thanks in advance for any help you may be able to provide!'

Peace

Rags

[ChevyTech007]

If this happened immediately after the battery, I would disconnect both cables and put a jumper wire between the cables for an hour. This will power down all modules. It is a long shot but it might work. If it does not, I would have it scanned for codes.

[Rag64top]

If this happened immediately after the battery, I would disconnect both cables and put a jumper wire between the cables for an hour. This will power down all modules. It is a long shot but it might work. If it does not, I would have it scanned for codes.

 

Thanks, I will give that a try.