It's unlikely that the transmission is the culprit. Auto or manual, btw?

What I would inspect, though, are the U joints on the driveshaft on both ends. Make sure they're good and solid. Surface rust is ok, but orange dust or red dust, etc is a bad thing. You can use some liquid lubricant on them if you like. Can't hurt anything.

EDIT: With the tranny in park (auto) or 1st (standard) and the vehicle on the ground, that driveshaft should be rock solid, I believe. I'll look at this tomorrow on mine and see how mine behaves, but I'm fairly certain that it should be rock solid.

 

yes, I have an auto trans. I will check the driveshaft today and let you know later on what I found out.

 

I know this is an older tread, but if you haven't experienced oil leaks and water leaks yet, you soon will. Mine has 118,000 miles and the first thing that starts leaking on the 99' model is usually the oil pan gasket and valve cover gaskets. The timing chain cover gasket is notorious for leaking too and sometimes can leak internally allowing coolant into the oil. So if you ever replace your water pump, you may as well replace the timing cover gasket, front seal AND the timing chain while your are at it. You will save money on labor in the long run by doing it all at once. Also the rear main oil seal will start leaking. All of these problems I experienced between 110,000 miles and 118,000 miles. Leaks are normal on high mileage vehicles, but with todays engines I would consider old age leaks to occur after 150,000 miles, not before. Other than pesky leaks, these engines will last well over 200,000 IF the cam synchronizer doesn't fail. If you hear birds chirping behind the engine, get the synchronizer replaced. The mileage on when they can fail varies wildly. I haven't replaced mine yet, but I pay close attention if there are any noises under the hood. I replaced the fan belt , idler and tension pulley's because they were making all kinds of noise at any speed. Now everything is nice and quiet under the hood. The last thing I replaced was a bad coil.


If you don't have an automatic transmission, be thankful. I just had it replaced too. This was a well taken care of truck before I got it and had never been on the interstate or driven over 55 mph. I've done spent to much on it to get rid of it.

 

I also forgot to mention my truck was doing the same exact thing when I would first start it up in the mornings. It would run rough like it had a bad plug or dirty fuel injectors, but it would clear up before the "check engine" light would be triggered. When it started running rough continuously, the check engine light finally came on. Come to find out my coil was going bad.

 

Which model year(s) and engine are you refering to? the 4 cylinder engines, 3.0, 4.0 OHV, 4.0 SOHC?

 

The 1998 thru 2000 model years with the 3.0. I see no reason why the 4.0 wouldn't suffer the same problems. Fords and leaks go hand in hand. I haven't owned one yet that didn't leak fluids soon after I bought it. I can't speak for the other Ranger model years, but I've owned different full size Ford trucks.

But one thing I always keep reminding myself of. Spending a few hundred dollars here and there is a lot better than making $600 dollar payments every month on a new truck. I even bought a code scanner because sometimes the problem identified is something I can fix myself and save money. Of course code scanners don't detect leaks and neither does the engine computer.