Transmission not shifting properly.

I have a 1999 Dodge Ram 1500 4x4 V8 5.9L truck.

I have replaced the transmission fluid and transmission filter 1 year ago with ATF+4.

A few months back, I would notice that the transmission would downshift automatically on a small uphill when I'm on cruise control. I assume that the transmission would downshift to get to the same speed I set my cruise control. I have noticed it everytime I'm on a small uphill.

Last Tuesday, I was driving on an Interstate and set my cruise control at 70MPH and have been driving for about 40 minutes on an uphill and downhill road. Suddenly, the transmission downshifts itself hard but loosing speed. At that point, the transmission is working really hard at 40MPH and I could not gain higher speed unless I'm going downhill. Even on a flat surface, my speed is around 35MPH to 40MPH. After 10 minutes of driving like that, I was able to park my vehicle and check the transmission fluid while the engine is running. The dipstick shows on the ADD line. I did not drive the vehicle for a few days. When I check the vehicle again. Engine not running, the transmission dipstick shows normal. I started the engine and put the transmission on all gears and then back to park. While the engine is running, the transmission dipstick shows ADD. I pour 1 quart of transmission fluid ATF+4 and the transmission dipstick level shows normal now.

I drove the truck and it allowed me to drive around 50MPH to 60MPH tops on a flat surface and gradually loosing power to 35MPH to 40MPH on a flat surface. I was able to drive it home after 10 minutes of driving.

My question here, I would attempt to have my tranny fluid changed and tranny filter changed and band adjusted (NO Tranny Flush or Reverse Flush). Any other suggestions on what I need to check?

According to this thread http://www.automotiveforums.com/vbulletin/showthread.php?t=877083
I will try to swap out relays and see if that makes a difference.

Thanks.

read the transmission dipstick i believe you will read check fluid in neutral not park . put it in neutral and see what it reads also go out under the hood and find the trans relay in the relay box and swap it with the horn relay as it is the same relay in fact the whole row on the right side of the box should be the same relays but don't check the trans level with it in park as the pump is not pumping in park..see if swaping the relays makes it shift better

I did swap the horn relay with trans relay but to no avail. I did check the transmission level while in neutral and needed 1 quart and stayed within that level.

I tried revving the engine while in Neutral but it seems that it lacks power. So, it seems that my engine itself lacks power. When it was working fine, I could rev the engine so high and hear the engine roar. Scan code reveals misfire on cylinder 3. However, I don't feel the engine missing. Spark plugs were replaced 1 week ago and was running great for a while. I went to the parts store and I wanted to get a fuel filter but they said that it does not have one :) I'll try replacing the spark plugs. Next, I'll replace the oil filter and oil again because if I have fuels dumping into the oil pan due to misfire, the oil will get thinned. I'll post my results.

Update, after changing the oil and oil filter, it seems the vehicle is barely able to move 15MPH. I can't do 40MPH anymore. I can definitely hear a lot of air escaping when I rev the engine.

Here's what I'm puzzled, the engine idles great. My plan would be to remove the O2 sensor and try to drive around the block to see the engine will have more power and go past 40MPH. I could get a back pressure gauge but that will take a while. I need it to try to narrow down the problem before I take it to a mechanic.

Either I have a clogged cat. - Possible
Bad intake gasket - not sure because the engine idles ok.
Bad plenum gasket - not sure because the engine idles ok.
Bad head gasket - not sure because when I changed oil, it was not milky.
Broken valve either intake or exhaust - not sure because I don't hear tapping noise.

Did a plug wire go bad from when you changed the plugs?? This could make it
idle fine, but have no power under load. Been there done that.

Jay

Did a plug wire go bad from when you changed the plugs?? This could make it
idle fine, but have no power under load. Been there done that.

Jay

I did not see any sign of broken or chaffed spark plug wires. I'll try to replace the spark plug wires and distributor cap.

Update: I have removed the O2 sensor. Exhaust is coming out of the O2 sensor on top of the Catalytic converter and tried to drive around the block. Still no power.

I'll go ahead and replace the distributor cap and change the spark plug wires that way if that does not work, I'll save the repair shop of trying to change the distributor cap and spark plug wires themselves to try to narrow down the problem. I have already changed the spark plug twice in two weeks just to test it. It has .40 gap for my vehicle.

Update:
I have replaced distributor cap, rotor, spark plug wires. The idle is much better now and I can rev a little bit higher but when I drive I'm not getting much power again. I can go above 20MPH to 30MPH now but still not going much higher.

I don't have other options at this time. I'll probably go ahead and call a reputable repair shop. At least, I can tell them that it just have a recent tuneup. New spark plugs, spark plug wires, distributor cap, distributor rotor.

I'll let you know what is the fix.

I had a similar thing happen on my jeep wrangler and I thought it was bad gas. But I took it to a dealership and it turned out to be the catalytic converter. I guess a piece of it broke off and plugged the exhaust. I wouldn’t have guessed it was that.

My dodge was doing almost the same thing. When i drove it for a while it would begen to shake really bad. I changed the distrubitor cap and plugs and all that and it still didn't help. I took it to a dealership and they told me that it was a broken valve spring. Don't know if that helps and or not

Thanks guys,

Towing $75
Driveability diagnostics $99.
They said that the engine is running Rich (too much gas/less air).
The catalytic converter is plugged. Replaced $375 + labor.
Total Cost $790+

I asked them if they can put some catalytic converter flush. :) They said it will not work :) Of course they want the labor to replace the catalytic converter (one piece).

Darn, I thought that removing the O2 sensor should have restored the power back because that is where the exhaust gases are coming out now. But when I removed the O2 sensor, I still have no power. So, I ruled out the catalytic converter. Is it because the O2 sensor hole is very small and not enough to thoroughly let the exhaust out? Could be. hmm.

I should have used those Top End Cleaner like SeaFoam Motor Flush and just hook it up to the Brake Booster so it will saturate the Plenum to remove the carbon buildup and hoping that it will also then dislodge carbon build up on the catalytic converter once I started my vehicle again.