atnolan94

Guys,

Just got my 04 5.4 back. I got a new trans at 111k, now at 138k. since before I got my transmission, my truck always hummed and vibrated really hard when I lugged it between 40 and 65ish mph. If I stomp on the pedal and downshift it'll go away. And 65+ mph it never really happens.

I had my trans replaced for other reasons and the sound was still there.

It never concerned me, but someone else drove this truck for a year, and now that I got it back, the humming is still there, but its now accompanied by a big, inconsistent bucking. It almost feels like a miss or skip. Tach stays steady and nothing else alarming is going on. It feels like its near the trans tunnel, I feel it in my feet. But the buck obviously is felt all around the vehicle. I'm thinking the TC is having issues locking up? Anyone have any other input/ideas?

The buck almost feels like a super hard shift in my 7.3. Almost the way it feels when you back into a post or something. It'll do it inconsistently a couple times per second while I "lug" the motor at low rpm at highway speeds.

atnolan94

i should also point out...

The rear end has been rebuilt, driveshaft has been balanced, and the transmission only has 25k on it.

atnolan94

bump...any ideas?

vintageman

Does it do it with the OD turned off? Honestly, it sounds like the classic miss that usually happens around 45mph, have you checked or changed the plugs, COP boots and springs? Any leaks, or have you crawled around underneath to take a look? Do you have a programmer, like the Edge or such that maybe the shift points or torque converter lock points been changed?

atnolan94

No tuner, no leaks. Plugs were done just after 100k. Springs and COP boots I think are original. Would this cause that bump feeling, it happens under load when I'm accelerating from those speeds. If i accelerate half throttle from a stop to 65 it won't do it. Just if I'm already going that speed and lean into it coming over a hill or something like that. Thats when the vibration starts followed by the bumping.

I want to figure this out soon. My trans warranty is out in like 2000 miles.

vintageman

Sounds like the miss issue. A stumble like that feels like a trans issue but has come back as a miss. I would try new COP boots and springs first. I think they run about $6 bucks apiece, change them all, use dielectric grease (the directions on proper use are somewhere on this site) and give the truck a good run to see if it helps.

Tom

atnolan94

If its cheap ill do it. Anyone got a good write up here?

vintageman

Unplug COP electrical plug, remove mounting screw (think its a 7mm), pull COP out, remove the rubber boot and spring. Install new one. As far as the dielectric grease, I think the lower portion of the inside of the boot that comes in contact with the spark plug is where it should be applied. If memory serves, the spring will either already have it on it or need it. Search for "proper application of dielectric grease on COP springs" and you should be able to find it. I would look for the link, but gotta get up early in the morning. Good luck, the whole COP boot and spring change will probably only take about an hour or so. Let us know how it goes or if you find something else fixes the issue.
Tom

atnolan94

Thanks tom!

To everyone else. Are the COPs for 2v and 3v motors? It looks like I can buy sets of 8 online just don't want to order the wrong ones.

Any brand people recommend?

Excuse me, my mechanical skills grew while owning my 7.3. back when I had this 5.4 the first time I didn't know much so I'm starting fresh.

vintageman

You will need the 3v COPS, with the brand, I try my best to go with OEM motorcraft parts whenever possible, especially with the plugs and COPs