my first second gen 12v, need help with some problems please
 

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.:pca1::c:

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 :c:

Kdp will be addressed. Did it on my other truck :tu:
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 :humm: