Hoping I can get some ideas on what might be causing some noise in the driveline of my 97 F150 4X4 w/74,000 miles on it. I don't have the trans code but I don't think it's limited slip.

Anyway, when taking off from a stop I am hearing a noise and a clunk that I'm sure is in the drivetrain. The best way I can describe the noise that I'm hearing is it sounds like two plates of bare metal sliding against each other immediately followed by a clunk. As strange as it sounds if I had to picture what's happening it sounds like the connection between the u-joint and the rear diff is loose and when I take off from a stop it twists and clunks when it hits the bolts......does this make sense? I have no idea if that is indeed what is happening or if that could even happen but that's what it sounds like. The bare metal sound and the clunk happen just as the wheels start to turn. I have looked at the driveline, poked and proded by hand an havn't found anything loose or seemingly out of place. However, I'm no expert.....

At a standstill if I hold down the brake and press the gas, the truck torques to the right and then the clunking sound is louder. If I let off the gas, then press on the gas again with the brake on it will clunk again.

I don't know if it might be related or not, but I also get a horrible shudder in the transmission when shifting between 3nd and 4th gear under light acceleration. Usually at about 38-40 mph. Under moderate or hard acceleration there are no problems shifting at all and no shudder.

U-joints? unbalanced driveshaft? Worse?!?

I'm at a loss.

This has been going on for almost a year now and the transmission hasn't fallen apart yet.....I do quite a bit of towing, so i'd like to get this taken care of for my peace of mind.

Any ideas or questions?

 

Oh....if it's not obvious, it's an automatic.

 

Do a search on "yoke".
I have the same problem but fixed it with ford teflon grease applied to the splines on the "yoke". I hope your yoke is still good. There should be no play down there. Ford denies there's a problem.

 

The "yoke" clunk is a common problem, and z97 is correct. I would also check the transmission mount. Have a (trusted) partner sit inside and do the power brake while you watch with a light on the problem area. If its the mount, you'll see the trans lift up and go to the right. If not, you might better be able to listen and determine where its coming from.

 

I think you may have two separate problems. The trans yokes are a definate problem with Ford's. When I bought my '96 I had to take it back several times to the dealer for a similar clunk, eventually they even replaced the yoke. At 74,000 miles I would suspect the u-joints. You may try wiggling the driveshaft to check them, but if they haven't been changed, I would suggest it. They are an inexpensive part and not a bad item to change as a prevenative maintenance. Your tranny shudder sounds like the fluid and filter needs to be changed. Ford recommends you change the fluid and filter every 30,000 miles. Supposably, you also need to blow all the fluid out of the tranny cooler lines and possibly separately flush them.

 

The problem is that the splines are NOT getting lubed by the fluid. They get dry and then wear out and thats where you get the slap at take off.
If it's like mine you will have to remove and lube with teflon grease every year.

 

Interesting information. Sounds like the splines coupled with the u-joints (no pun intended!) are causing the rub-clunk noise.

From reading past posts about lubing the splines, it sounds like something I could surely do myself. Not much to it from what I understand.

What about U-Joints? Could that be a do-it-yourself repair? I'm fairly handy.....would I need any special tools other than a normal persons garage tools?

 

Just mark the driveshaft before you start, then raise the rear....(loosen the drive shaft bolts first), remove the driveshaft at the rear. Put a pan under the yoke for drips.
Slowly pull out the driveshaft and yoke assy......lube the splines male/female with ford teflon grease.......then reassemble.
Torque to I think 90ft/lbs.
If the dia of the yoke looks burned you may have to replace it.
$200/$300.....not cheap.

 

When you say "raise the rear" you mean block the front wheels and jack up the pumpkin or put jack stands under the axle so the wheels can freely rotate right?

Mike