I have made a couple posts about this problem in the last few weeks but didn't get any replies, so I have been doing further investigating on my own and seem to have narrowed things down a bit. But, I could still use some input because I'm not familiar with the internal workings of an automatic tranny...

The truck: 2000 F150 XLT Supercab 4x4 5.4L with the 4r70w automatic tranny. Mileage: about 58,000.

The problem: This only occurs when my foot is OFF the gas pedal, in other words only when coasting or breaking... When the rear wheels hit a bump, I hear a slight banging/rattling sound coming from around the tranny/transfer case. If I apply the slightest pressure to the gas pedal (not even enough to accelerate) I don't hear the noise. Also, I don't hear it when the front wheels hit the bump, only as the rear wheels hit the bump. If I put my hand on the 4x4 shifter (lever on the floor, not button on the dash), I can feel movement/vibration in sync with the sound of the noise.
Otherwise, the tranny shifts beautifully. When I come to a stop, I do hear a very slight clang as the transmission downshifts, and I also hear that same clang sometimes if I punch the gas after coasting for a little bit. But this seems somewhat normal to me and I'm not sure if it might be related.

Steps taken: I spent about an hour under my truck last Saturday going over everything looking for something that might be loose. I checked the exhaust heat shields, fuel lines, all linkage, everything I could fine; nothing was loose. I checked the mounting of the spare tire, the u-joints, and the leaf springs. I also replaced the transfer case fluid with Mobil 1 synthetic Mercon and replaced the transmission mount, and reset the PCM a couple times to let the transmission "re-learn" my driving style. The problem still persists.

Because I found nothing out of the ordinary under the truck, and because I only hear the noise when my foot is not on the gas pedal, I have made the assumption that the noise must be coming from inside the transmission or transfer case.

Is there anything inside the transmission that is known to come loose, or anything that could possibly be rattling around? I've heard these trucks have a coast clutch that disengages when coasting. Could this noise have something to do with that? And if so, is there anything I can do to remedy this problem or should I just live with it? The last transmission flush/service was at 30,000 so I'm only 2,000 away from the 60,000 mile service. Could this noise just be a result of almost time for a service?

I'd appreciate anyone's feedback here. I really like this truck but this little noise has been driving me crazy, probably becasue I don't know what it is. Even if I could identify the noise but not be able to fix it, or at least know that it's "normal", I think I'd be happy just knowing what the heck it is. Thanks in advance!

 

I've read where others have stated that the anti-vibration damper that is/was added to some truck frames, will make a similar noise.

 

From what you have discribed I'm thinking U-joints. But since you said you checked them I'll ask you this.

Did you raise both rear wheels off the ground before checking the U-joints for play? The reason I ask is that unless the preasure is relieved from the drive shaft even really bad Joints sometimes look and feel good and tight.

Just a thought.

Doug

 

No, I didn't check them that way. A few weeks ago I had the p/s pump replaced at my dealership. While the truck was there, I had them investigate this problem. To no one's surprise, I was told the familiar "unable to duplicate". However, they did put it up on a lift and claimed to have checked out the under-carriage. So I am assuming that they would have checked the u-joints with the wheels off the ground. I suppose it's a good idea that I dounle-check them as you described. Would the u-joints make a rattling sound like I described when hitting bumps?

Also, while checking the u-joints, I noticed the yoke going into the transfer case moved around a little bit as I pushed up on it and shook it. Is this play normal in the yoke, or should it be solid and not move at all?

 

U joints sound like a good thing to check to me. THats a typical noise from them when they go south.

 

Thanks guys. My next step will be a thorough check of the u-joints (as soon as the snow melts here in PA). I don't hear any clunks or anything when engaging the transmission. How will I know if the u-joints are shot when I crawl under the truck?

Also, as for the "play" where the yoke enters the transfer case... is this normal? I did some searching of the site and from some threads about it but nothing conclusive as to how much play at the yoke is normal. Mine doesn't move much, but if I grab the driveshaft and push on it in any direction, the yoke "deflects" a little bit with the driveshaft. Now if this would be a problem, what causes excessive play? Can excessive play at the yoke be fixed without replacing/rebuilding the transfer case?

 

Ive got a similar sound in my drivetrain on my 01' 4x4 5.4 4r70w scab. This truck has done this since new and I now have only 14,000 miles on my truck. All but maybe a 1,000 or so has been spent towing my bass boat it isnt my DD. The dealer can't find the problem either. I recently had the tranny serviced, the trans shop did duplicate the noise and diagnosed it as a possible loose retaining ring in the clutch pack assembly. I'm not completly sold, and I'm not giving them $3500 to fix it! I'll drive it till it breaks!

 

hammes,
What gear does it do the noise in? If I leave mine in overdrive, that's when I hear it the most. If I turn off the overdrive (go into 3rd gear), I only hear it very slightly if I really slam a bump. It's the same thing when I have the 4x4 engaged. I don't know what that would mean, unless the coast clutch doesn't disengage unless you're in OD.

I am beginning to wonder if this is just how the truck is. I just got my 2000 back in December and I noticed it a couple weeks after. But, I doubt that's when it started doing it. I probably just didn't hear it at first. The truck has 57,000 on it and it very well may have been doing this since new like yours.

 

DTS419,

Mine is during first gear and in a coast to accerlerate condition. Sort of like when you would pull out of a driveway or parking lot slowly and then accelerate to blend with traffic. It is at the acceleration point that it makes a loud "click". It feels like it is from the tranny area and not further back. I have checked, and have had others check the drive shaft/yoke/rear end, and no problems found. My trannsmision tech says that there is a T.S.B., not from Ford but one that is generated from a group of transmision shops that says they are finding that on some 4r70w trannys that the "intermediate clutch assembly retaining ring" were installed incorrectly from the factory. He showed me a diagram and the printed out T.S.B.. The bulletin goes on to say that this "may or may not" result in "catostrophic failure" of the tranny but would continue to make the noise untill repaired. the repair is basically a complete teardown and rebuild, minus the parts normally associated with a worn out tranny. I am not completely sold and I think I will get as many miles out of it as I can. The noise doesnt really bother me as much as the money spent out would. I hope that this helps you out.

I dont here to many bad things about the 4r70w and my tranny tech says that they are very "tough" transmissions. Only time will tell for both of us.