I am new to this forum so I apologize in advance if this post is in the wrong place.

I have '00 F150 Lariat 4x4 4.6L V8 Automatic..not sure of the Transmission type. On my way home from work yesterday the truck started behaving as though the transmission was slipping. I was on the freeway driving approx 60-65 mph and the vehicle began to shudder as I was going up a gentle incline. I stepped down on the gas to down shift thinking maybe it was just the grade but, when the transmission downshifted the shuddering became significantly worse and it felt like a serious lack of power as the truck did not accelerate (leading me to the "slipping clutch" comparison).

As soon as I could, I got off the freeway. I immediately checked the transmission fluid (idle, in neutral) and it was fine. My wife was with me so I had her rev the engine a couple of times just to see if I could hear if the engine was sounding funny, maybe missing spark or something but I couldn't detect anything by ear.

I am not a mechanic but I don't want to get ripped off by a mechanic either and I am looking for reasonable explanations as to what the problem might be. I am hoping I won't have to replace the whole transmission. Please help.

Thanks!

 

Check the spark plugs and the coils sounds like a misfire and will get worse if you let it go.

 

Adding to original post.

Truck has 115,000 miles on it. I did not get a check engine light and did not notice if the OD light was blinking.

I just had a service and tune up done on the truck about 1,000 miles ago. I know they replaced the spark plugs but don't know if they replaced the coil. Will have to call and ask.

I haven't driven the truck since I got it home. Going to fire it up this weekend and see if the problem persists.

 

I had a '94 that did the same thing. It's possible one of the coils is going bad. Usually under load or at higher speed they'll seem to be working erratically. You might not get a code for it, unless the problem starts happening more often. You might get a "pending " code for a misfire.

On my truck, the torque converter was bad. Slipped during acceleration, especially when cold, and slipped and shifted hard with no smooth transition between gears. Tapping the brake pedal while the shuddering was happening would cause the converter to lock up. The brake tap won't affect the coil though.

Check for any trouble codes for the engine. If nothing shows up, have the drive train checked for a code. Not every parts place can do the drive train, but they might get lucky on the engine.

Dave

 

Hi Dave,
I was in stop and go traffic commuting home when this happened. I had to brake a lot, what would the symptoms of the torque converter locking up be? I am assuming that would pretty much bring me to a stop?

Thanks for the recommendation.

 

Nathan

The converter is suppose to lock as power/speed increase. When it's going bad, it won't lock up, and slipping in gear, hard shifts, and shuddering can happen. Tapping the brake, if the converter is faulty, can sometimes make it lock up, and the shuddering stops.

I don't want to mislead you on an attempted repair, but you seemed fairly convinced that the transmission felt like it was slipping, That's a big symptom of the converter. Just shuddering/erratic engine performance leans more towards a coil problem. Your truck is about the right age to have the COPS instead of 2 larger coil packs/plug wires. The packs tend to be pretty reliable, whereas the COPS can fail just about anytime.

You should be able to get a code read if the CEL was flashing.

Dave

 

********UPDATE*******

I drove the truck all weekend and was not able to reproduce the issue. I got a hold of a code reader and checked my cpu and there were no codes stored. Not happy about this but until I can identify the problem or reproduce it...what do I do.

Thanks everyone for your help! I really appreciate all the input!