I think you may be right. Today I took off the prop shaft and there is absolutely no play in the shaft that comes out of the box when you rotate it by hand.

I then ran the Engine with no prop attached up and down through the gears and it sounds sweet as a nut so I can guarantee that the noise isn't in the output shaft in the box because I would of heard it.

So I then took both caps off each end of the prop shaft and filled them with grease as there was a little play in the prop shaft. Now there is no play in the prop at all

I put it all back together and the noise is still there. So i reckon it is probably the diff.

One thing I did notice between my old diff and this new 4.7 one is there is quite a bit of play in the input shaft on the 4.7 diff and my old one is complete solid when you rotate it by hand.

So I reckon it is the fact that the new one just has more back lash.

Now The reason I think im hearing it more is because I do have solid diff mount collars on the car. They were there when I had the old diff installed and I reckon the reason I can hear the noise now and I couldn't with the old one is because the excessive backlash is now resonating through these solid collars when letting off the throttle.

So next I'm going to remove the collars this week and see if I can still hear the noise.

I'll let you all know

Cheers for the responses everyone

 

Nice process of elimination. That's what I like to see!

Solid bushings transmit a significant amount of noise through metal on metal contact. I recommend doing massive burnouts and then fuggedaboutit!

 

4.77s historically, were sometimes noisier than the OEM 4.10s.

Mine were, but just barely.

 

Sounds just like my 2 transmissions when they blew.

 

So Guys, I have a quick update and sort of a fix.

Right So I eventually gave up and paid a guy who builds gearboxes to come round and help me and we both diagnosed the issue yesterday.

It turns out that basically the diff input bearing had side to side rotational play which at first glance seems like excessive backlash. This however wasn’t the case. It was actually due to the fact the pinion preload was way out for some reason. We coudlnt be sure if it was too tight or too slack so either way we slacked off the nut and reset it back using the correct method to 94ft-lb and now the play and rattle has completely gone away.

However the diff still whines quite loudly. The guy who helped me said that the pinion is most likely now worn caused by driving round with the preload set incorrectly hence the noise.

He basically said all I can do now is either rebuild the diff with new parts or live with the whine and hope it doesn’t get any worse.

So I suppose it’s a Fix but not really a positive one

Cheers for all your replies

 

Hi, the 94 foot pounds is a minimum setting. The load may need to be increased. He is right about the fact that the ring and pinion maybe ruined from being out of spec.

 

Is there anything i should do? Like Should i tighten it up anymore? Or should i just leave it and hope for the best? :S

 

hi, take it up to 110foot pounds but first!!! Did you use a new pinion nut? If not, did you clean the threads and use lock tight blue?

 

Nope i didn't use a new pinion nut or clean the threads or use lock tight blue.

Is it necessary to do all that?

And when tightening the nut is there a process i should follow?

 

So new pinion nut (or at least clean threads), use locktite blue, then are you saying:

Initially tighten to 110 ft/lbs
Loosen, and retighten to 94 ft/lbs

???