Several months back my 1999 ram 1500 started having erratic shifting when under a load (towing or passing)

Usually happens when towing (tent trailer) and climbing a grade, or if I'm going around 50 mph and I accelerate to pass (while not towing). It feels/sounds like it drops all the way down to first as the engine revs up like mad (5-6k rpm). If I ease into passing it works fine.

When towing uphill I get to about 25-30 mph and it starts to shift down to first and revs up.

When it first happened I did some research and found that a bad TPS could cause that. So I replaced it and it actually worked for about 2 months. Then it started again. First thing I did was replace the TPS, but this time it did not fix anything. I then took it to a tranny shop and they said the transmission looked fine. He dropped the pan, checked the bands and serviced the tranny. He suggested it might be a computer problem.

Since then (like a couple weeks ago) the engine light came on and I'm getting a p304, p305 and p300 (multiple misfires) and I have been idling rough. I changed all the plugs and wires, and though the idling is much smoother, it still throws those codes. I'm not sure if this is related, but it may be.

I've seen elsewhere on the web that people have had this same issue with this truck, and one thread I found said to replace the CKS (crankshaft position sensor). However, I took it to another shop to have them hook it up to the computer and the computer said the CKS and CMS where showing OK, though he noted that their counts were quite a bit off, which he said he didn't think was normal. I couldn't afford him digging deeper to diagnose, so I'm trying to go at it myself (with your help ).

Today I went to my local Kragen (O'reilly now I guess) and picked up a CKS and replaced the old one. Crazy thing started knocking when I start the truck and it threw a P1391 code. I took the new CKS out and re-installed the old one. The knocking is gone, and the P1391 is gone, but the misfire codes are still there.

Could I have just got a bad part? Does it sound like the CKS could even be the original issue?

Thanks in advance for any help!

 

For Crank/Camshaft sensors, go dealer; I had a NAPA crank sensor, and it was causing it to backfire during idle, etc. Ended up popping an OEM sensor in yesterday and it works fine.

Not sure on the issue, just giving my 2 cents on the sensors.

 

Get the BWD part from advance auto parts and you'll be fine as far as the crank sensor goes. Thats what i have...

On another note, i guess it is possible that your truck shifting erratically is being caused from an improporly running engine, Cause its probly weaker.

multiple misfires can be caused by a clogged cat also..

 

Thanks for the responses. It was a BWD. I took it back and got another one, which doesn't knock. So I'm guessing I just got a bad one.

The misfire codes haven't come back yet, but I'm not calling it fixed yet. I'm planning on towing my trailer up into the foothills (close by) to try it out on a grade to see if the original problem was fixed.

Thanks again!