Ok, I have a 1989 with a 351w and C6. The truck drive fine except when I get above 60 MPH or so. Even after that, it drives just fine UNTIL I take my foot completely off the gas. After that, I feel/hear a significant vibration somewhere in the drivetrain until the truck slows to around 60 mph, then it's fine. Now for the weird part, as soon as I give it the normal cruizing amount of gas, the vibration stops. I could be going 90 mph (theoretically) without a problem just as long as my foot's on the gas at a normal level (not smashing it). BUT, if I just feather-touch the gas, it vibrates again. If I'm going at around the 60mph mark, and it isn't vibrating yet, giving it a little gas will make it start until I give it normal gas, then it stops again. So, No gas makes it vibrate, little gas makes it vibrate, normal gas bakes it stop, and anything below 60mph makes the vibration stop. Have I lost you yet? It started quite a while ago and was barely noticeable at that time, but over the months I have noticed it more and more. Any thoughts? Thanks.

 

I'd be almost positive in saying that this is a u-joint problem.

 

[updated:LAST EDITED ON 04-Dec-02 AT 07:27 PM (EST)]JBronco beat me to another one...U-joints, without a doubt.

 

that's what I thought, but don't you check those by trying to move the driveshaft by hand and if it moves, then you have bad u-joints? If so, I tried that but there wasn't any play in the driveshaft....

 

In my experience you cant allways see the movement by hand. Sometimes you can see a little rust coming from under the caps in the ujoint. Have fun changing that double yoke U.

Keith

 

Please tell me that this will be a straight forward repair...I just finished replacing both from spindles because the old ones had stripped threads (That was a fun discovery) all because I had just wanted to replace my rotors. Not that I don't enjoy working on my truck, but I'd like a repair to go through flawlessly if it's possible. Any help would be greatly appreciated.

 

You cannot check these u-joints while they are on the truck. They are actually cv joints in the shaft, not u-joints like in a regular car. Take the driveshaft off and rotate the joints around in their range of motion. Chances are one will not be loose, but bound. When you move it around, you will feel it bind up. That will definitely give you the vibration. Of course, there is a chance that it could be in the front. You could always take the rear driveshaft off and drive the truck to see.

 

Ok then, thanks for all the help guys. I'll check it out this weekend and will be back because I'm bound to run into another problem....but that's what makes it fun, right?!

Thanks

 

....but that's what makes it fun, right?!


RIGHT!!!!
O.K. I had the same vibration as well as one of my friends. We found mine was that the rear yoke was loose. His was the U-Joint. Check the yoke at the rear end for any play. Good lugk with it.

Chris

 

[updated:LAST EDITED ON 10-Dec-02 AT 02:40 AM (EST)]Ditto to the post regarding the CV joint at the front of the rear shaft. I knew mine was bad but could not tell by trying to move the shaft. When the shop put the new CV joint together the machinist was concerned that he could not get the shaft to lay out in a straight line on his bench. I put the shaft back in knowing full well that once installed, the shaft would straighten out as needed. The spring and centering ball in these joints when new, make it almost impossible to lay the shaft out straight by hand due to the tension of the spring. If when you drop the rear shaft, the CV joint flops around easily, thats most likely the culprit.

 

>You cannot check these u-joints while they are on the truck.
> They are actually cv joints in the shaft, not u-joints like
>in a regular car. Take the driveshaft off and rotate the
>joints around in their range of motion. Chances are one
>will not be loose, but bound. When you move it around, you
>will feel it bind up. That will definitely give you the
>vibration. Of course, there is a chance that it could be in
>the front. You could always take the rear driveshaft off
>and drive the truck to see.
Actually they are u-joints, two of them, 1330 series spicers if they are the originals. they are quite easy to pull apart, it really only requires a few sockets and a 5" vise. other places to check are the slip shaft at the axle end. most likely the problem resultsfrom a worn centering pin in the Dual Carden CV (normally due to lack of lube because most folks don't know about the hidden nipple until they fail - nice of ford to mention it huh)

 

I could be wrong about them being cv joints, but the shop told me that they were cv joints and they look like cv joints. However, I DO know that you can't feel them being bound up or loose while they are on the truck. It was not until we pulled the driveshaft, and then it was very obvious that they were bad.

 

...so is this something I can do myself? I have never taken the driveshafts off, but I suppose it can't be TOO hard. I HATE taking my truck to a shop unless it's just something far beyond my knowledge (such and the tranny). Any helpful hints or "whatch-it" warnings would be great. Thanks for all the help.

Eric

 

I replaced the the u-joints on my 1989 about 8 years ago and am getting ready to do it again. This time I am just going to remove it and take it to a shop that can also balance it or at least check the balance on it. I didn't have any problems replacing them before, but the double cardan or whatever it is called did give me a major headache. I dropped a couple of pins and ended up paying someone $10. bucks to finish it for me. I am no expert on this but you should be able to do it an a couple of hours with a few common tools like a vice and a socket the size of the joint that you can hit with a hammer and knock out. You could rent a press from an auto parts store though.

Sorry for being long winded.

Good luck and let us know how it went.

 

These joints and the cardan joint seem to be more difficult than those on a regular rear wheel drive car. I used to do those with a hammer, punch, and a couple of 2X4's. Sometimes I would drop one of the pins, it was annoying but you could put it back in. However, for the Bronco I had the driveshaft rebuilt and balanced at a driveline shop. It rode a million times better than before.