Ever since about the time I had my gears and LSD installed in my truck, it has vibrated a lot as speeds increased. At first it didn't vibrate until 85 MPH, bot over time, it's been getting worse, lots worse. Today it started at 75 MPH and by the end of the day it vibrates above 60 MPH.

It's not tires, engine mounts, or anything like that. I have already ruled those things out. It's definitely a drivetrain vibration that goes up as speeds increase.

The truck also makes a squeak, squeak sound in reverse, about everytime the driveshaft goes around.

Since it got real bad today, I had my wife put the truck in drive and reverse while I looked the driveshaft. Everything looked normal. Then I started jerking on things, expecting to find a broken U joint or something. The U joints look fine, no slack that I can see or feel.

Anyway, I get to the driveshaft where it goes into the rear of the transfer case, and it's loose there. I went to the dealership and crawled under a new 2002 F150 like mine, and jerked on its driveshaft, and it wasn't loose at all. My driveshaft has 1/4" of play there, you can tell it's too much.

My question is what is it? Is there a bearing in the back of the transfer case? I saw an output shaft mentioned in an old thread. What does the driveshaft connect to at the rear of the transfer case that could be loose?

I'm a very experienced mechanic, but my work is in cars, mostly imports, so this rear drive stuff is new to me. Any input or help is appreciated.

 

jayntguru,

If you have an extended cab it is probably your drive shaft. Ford makes them with not a large enough diameter for their length. Had the same problem got it replaced and problem went away.

WarEagle

 

Actually I do have an extended cab. I don't understand what you are saying, though? How can the driveshaft itself fail? It's just a steel tube... I don't follow.

 

The drive shaft is turning at a higher RPM. To keep in balance there is a relationship between the length and the diameter, too small a diameter for the length will cause a hamonic vibration. There is a TSB out there somewhere about the problem. Ford knows because after much hell raising they replaced mine with aone with a greater diameter (It looks huge!) for free and I was out of warrenty. Don't tell them about your gear change.

WarEagle

 

I think that's really interesting.

There's a TSB for driveline vibrations related to the tailshaft bushing but it doesn't cover the 4x4.

Part of your problem sounds like it would be with the 4.10 gears. The driveshaft is turning faster than it would have at the same speed before the change so any vibration is accentuated.

Although I have a 4x2, I can move the slip yoke up and down quite a bit at the transmission tailshaft and I do have quite a vibtation coming from below me above 55 MPH. I can't confirm myself that my driveshaft is causing the vibration though. I haven't had the balance checked and I know that my exhaust cause a lot of vibration.

The TSB calls for a 5" diameter driveshaft as part of the solution.

 

Of course, my luck, the local dealer installed the gears for me. I guess that could work out in my favor? I dunno.

I think at this point I'm just over my head. I may take it back to them and just pay their silly fee to see what the deal is. I don't know enough about the driveshaft to know what it is.

Now I DID get more vibration after the gear swap, and I even mentioned it in a post here somewhere. The problem is that it is getting a lot worse. Yesterday alone I drove maybe 200-300 miles and the vibration went from "OK, probably not a problem" to "damn this thing is f*cked up", all in one day. That's why I am worried.

 

I give up. Whatever is wrong is very, very wrong, and getting worse. Top speed in the truck is now 50 MPH. I'm dropping it off at the dealer this evening for diagnosis.

I'll mention the tailshaft TSB, the driveshaft one, the work they did on the rear end recently, and cross my fingers. On a good note, they are going to hear all about the door crack, door rust, and tailgate rust while I'm at it.

I'll post back what the results are here.

 

Well, turns out I'm just an idiot. Took it to the local Ford dealer, who said it was U joints. Told them I had looked and they checked out OK, but they still said U joints. $290 later, after two new u joints, the vibration is gone. Expensive lesson learned, when in doubt, just change the damn joints!

 

Are you serious?

I replaced my U-Joints with heavy duty NAPA parts and my vibration didn't change a bit.

Could it be that they also balanced the driveshaft when they replaced the joints???

Did you get a good look at the driveshaft for balancing marks and rings before you brought it in so you know whether or not they did balance it?

Is the squeak, squeak, squeak gone as well?

 

Yup, it removed the vibration and the squeak, squeak. They are both gone. No more clunking when going between reverse and drive either. I don't think they balanced it, but... wait, just called the dealer, they did not balance it. God that was a steep price for two ujoints and the labor to change them.

They did say my factory joints were full of mud and rust. Doesn't surprise me a bit. Some grease fittings would be nice.

 

I appreciate it

I'm still confused about my truck though because you and I have identical simptoms and U-Joints didn't solve my problem. I think I will finally have a driveshaft shop look at it.

 

you two arent the only ones with a nasty, loud, squeak, squeak in reverse. every time i back into the driveway im sure my whole neighbourhood knows im home. im gonna do exactly what you two did jay, and change up the u joints, c what happens. ill let u guys know what happens.

P.S. - 290$ is too much money for u joints espicially when u convert it to canadian dollars.

 

The squeak is a very good telltale that it is U-joints. Every time I have had them go bad, even though they feel okay, they squeaked.

 

Glad this thread got Popped up for me to read. As you might see; I have a vibration post in this thread as well. My u-Joint looks in good condition but maybe I'm wrong.

Sorry for the poster getting ripped off. Should't take more than $30 in part and 30 minutes of time to replace two u-joints.