2003 Ranger FX4. 4.0L V6, auto tranny
Starting back before Christmas, I was noticing what I thought was a hiccup when cruising down the road at a steady speed. It felt as though the ass end of the truck had been hit, or hopped. Sometimes it was mild. Sometimes it was pretty harsh with an audible 'clunk'. It'd only do this when the outdoor temp was below 20F.
I changed the plugs and wires. I cleaned the MAF and IAC. Nothing changed the problem. I went and pulled codes with what Advance Auto has (cheap reader). No codes were found. While talking to the guys, it was mentioned that possibly it's the transmission, and that a fluid and filter change are much needed (I had planned on doing this anyway, I was just hoping for some better weather, ie. Spring time), but this problem is forcing my hand.
Tonight on my way home, I was stopped at a light and felt as though the truck was trying to surge. When I got home (a couple miles away), I played around with it in the driveway a bit. When I shifted from drive or reverse to neutral or park, the idle would drop to 400-500 rpm, and it seemed as though the truck was about to stall out. If I hit the gas, it'd drop back to an idle around 700.
I pulled the IAC and cleaned that tonight, as well as changing the engine oil. After I finished that, I played around with the shifting a bit. This is what I found when I shifted:
1 or 2 --> N/P, no change.
D or R --> N/P, idle dropped.
It almost seems as though the transmission is hanging up and not fully disengaging. Does this sound at all plausible? I know that without changing the fluid and filter, it's hard to pinpoint anything, but is there anything else I should try looking for?
I'm also wondering if both problems are actually just 1 problem, and that the fluid and filter change will take care of it (I hope).
Thoughts? Questions? Comments? Concerns?