I just bought a 1997 12v 4x4 ext cab dually. The truck has 350,000 on it. The trucks problem is that it wont always go into overdeive, while in third it locks/ unlocks. The rpm gauge will bounce around randomly while driving and while idling it will show zero then shoot up. It does all of this on and off. How can i go aboit diagnosing. And fixing this? Please and thank you.
Next question is what should i check and how should i check over the truck for the problems that could potentially happen or could already be happening?

 

I would replace the Crank Position Sensor, that should take care of the tach problem. A rebuild would probably benefit you in the tranny department.

 

On the rebuild should i also put in all new sensors? If i mess with the o/d button on the dash i can get it into overdrive. Is there sny specific reason it will not always go into o/d every time on its own ? I read that it could be the speed sensor? Or could it be my dash switch? Just trying to identify the main reason.

 

I really don't know much about trannys so hopefully someone else will chime in and help you figure it out.

 

have you checked for any bad codes?? Check the following:

-speed sensor
-tranny oil temp sensor
-make sure all plugs are cleans of grease and dirt
-make sure all plugs have the rubber gasket around the pigtail

 

KDP search on here if you're not familiar with it

 

Kdp will be addressed. Did it on my other truck
how do i check for codes on a 97? Do i need a obd1 handheld or is there another way?
thank you. I already cleaned and put di electric grease in all plugs. Problem still persists.

 

My 95 was doing this for a bit replaced all the sensors, what we THINK was causing it was traced all the wiring( thrillsville) and found a bare spot in it near the cross member put a new harnes on and it straighten up. this may not be what is going on but it would be a place to look!

 

yes, you will need a scanner. on the 95's the port is under the hood on the passenger side. i do not know about 97 but i think the port is under the dash.

 

I've never had a scanner on my 12 valve