Please help if you can... I bought a used 1997 Dodge Ram recently. It overheated during a trip out of town. Afterwards, I took it to get the transmission fluid changed per a family member's recommendation. The shop did a block test which involved using a vapor? They told me I have a blown head gasket I am FAR from mechanically inclined, but I crawled under the truck after driving it home and noticed some plastic wire/cables in a black plastic sheath were just hanging loose. They are on the driver's side about midway back. One is red and one is black. I know the truck has had transmission work twice. The truck runs really rough in drive only. It seems to idle okay for 205,000 mile truck. Gears seem to shift okay as well, but once it makes it to the final gear around 55mph, it runs very rough, almost like shuddering. I am sure there could be leaking into heads, but why does it seem to only affect the drive gear? I don't see oil in the radiator or milkiness in the oil. It has some white smoke at tailpipe on starting, but goes away after warmed up. Has had issues with water and oil loss. Was wondering if it could be some type of vacuum / pressure sensor loss causing the rough running in drive?

 

Those are vacuum lines down there, that go to the 4x4 switch. Front axle is vacuum operated. The red and black lines should connect to a pair of steel lines right under the trans. Those run to the front of the truck, change back to the plastic fellers, and go to the CAD unit on the front axle. If you don't have 4 wheel drive, they are a non-issue.

Blown head gasket won't always drop coolant into the oil. More often than not, coolant simply leaks into the cylinder, and is burned off. Makes the exhaust smell sweet, and it'll burn your eyes in a major way. Take a whiff, CAREFULLY, see what you smell coming out the tailpipe.

The Shudder in O/D is likely an engine miss. If it feels like the truck is trying to shake itself apart, and gets a LOT worse once it shifts into O/D, yep. That's a miss. Generally related to a blown plenum gasket on the bottom of the intake manifold. You may not notice it in lower gears, but, it is indeed still there. There is a thread that talks about all this stickied at the top of this forum. (end-all, be-all plenum thread.)

Heads in these trucks were pretty crappy right from the factory. The castings were two thin, which made the heads VERY prone to cracking, especially around the valve seats. This also can contribute to a miss... (usually on cylinder 6,8, and 7) Pull codes, and see if the PCM is whining about anything. Be sure and check pending/history codes as well.

If you end up having to pull the heads, don't bother doing anything with them, just replace them. You can get a good pair of NEW, BETTER casting heads, from Odessa, or Clearwater cylinder heads, for under 600 bucks. These have thicker decks, and are much less prone to having issues.

Welcome to DF!

 

If you don't have a bad head or head gasket and can afford it, I recommend a new timing chain and gears, water pump, change the plenum gasket. They don't have to be done together, but it's more cost effective to do them together. I ended up replacing the oil pan gasket also on mine when I did this. It would be a good time to change the thermostat, spark plugs, distributor cap and rotor, plug wires, and upstream O2 sensor. I don't know what you can afford. Our 95 runs awesome after doing this. I re-used the factory steel plate on the plenum with shorter bolts. You need to properly diagnose the problem you're having first though.

I also have a new coil, fan belt, valve cover gaskets, idler and tensioner pulleys, lower radiator hose, coolant temp sensor ( I broke it), and a few other things. Just food for thought if you have this done. I personally like Fel-pro gaskets, Standard Motor Products for ignition and electrical parts or sensors, NGK standard plugs (platinum or iridium plugs don't have a good track record in our engines), NTK O2 sensor. That or use Mopar sensors. I used a Gates water pump, it came with the new steel tube for the heater hose. Almost everything came from Rock Auto, I think there is a link somewhere for a discount code for them. Good luck

 

Thanks for the suggestions, it is much appreciated. I will look into it.