Trying to figure out if the trans. or the rear went on my friend's truck. It's a 97 F-150 2-wheel drive 4.6 V8 w/ 180,xxx on it. He's had a howl coming from somewhere in the driveline for a while now, and it has progressively gotten worse, and now it's to the point that when you have it running w/ your foot on the brake- when you put it in drive all you get is this horrendous sound that sounds to me like gear teeth skipping off of something and it vibrates the whole truck. It doesn't do it in reverse though. I jacked it up so the wheels were free and gave it a spin. Correct me if I'm wrong, put even if it's an open rearend, shouldn't the tires spin in opposite directions when turned?? If so, then something is up, because I can spin the pass. side wheel forwards (like you're driving) and the drivers side wheel doesn't even turn. There is no evidence of leakage. Should I pull the diff. cover and take a look, or just go w/ the trans? I don't see how the rear could make that grinding noise when your foot is on the brake w/ the truck running.

Jay

 

I have a 98 with 170k and it vibrated horribly and made similar sounds you refer to. The way I fixed it was going to these forums, I'm not exactly sure where I found the answer - it's been awhile lol. Anyway it's the rear end, I pulled cover cleaned it out (use a lint free rag) Refill appx. 5.7 pints of SAE 75W-140 GL-5 and most important add a friction modifier. A mechanic a the Ford dealership recommended that I double up on what was recommended by the manual. My vibrations didn't all just go away at once, but they went completely away in time. It worked for me and I thought I needed a new tranny at first. Hope this helps.

 

I would look at your rear diff first as it is cheaper and easier to inspect and repair than the trans. With an open diff, it is normal for one wheel to spin and the other to stay stationary assuming you have the trans in neutral so that the driveshaft can spin. If it is in park and the driveshaft is locked, then the other tire should spin the opposite direction. If it isn't, then you have some serious problems with your diff. Hope this helps!

 

What is really making me think now is the fact that the horrendous grinding noise it lets out when you have it in drive would tell me its the trans. I can see no way for the rear end to make that grinding noise if I have my foot on the brake and am not giving it any gas whatsoever. I just drop it in D and the grinding ensues. The rear cannot grind if the driveshaft isn't being allowed to turn. It almost seems like the trans is trying to engage D, but something internal is not letting it fully engage. Guess I'll be dropping the pan and see what I can see.