Half shafts
#11
Thread Starter
Nice video. You can easily hear that rattling/grinding sound as the revs drop to their lowest amplitude/frequency.
Just my opinion, but I think that is just excessive backlash in the rear diff itself. Excessive backlash noise tends to manifest itself most when the load on the gears one way or another (accel or decel) is at its lowest. I also don't think it is a problem to be concerned about. For example, when going from a dual mass flywheel in a Toyota Supra to a single mass flywheel, you will get a lot of noise (at idle in neutral) very similar to that in your video. Now maybe this backlash is excessive or it is just the right amount needed to account for thermal expansion at high torque/power levels.
Remember the SR-71 was designed to leak fuel on the runway so it would stay together at Mach 3+ after significant thermal expansion took effect.
Anyway, this is just conjecture on my part so take it with as many grains of salt as you dare.
Just my opinion, but I think that is just excessive backlash in the rear diff itself. Excessive backlash noise tends to manifest itself most when the load on the gears one way or another (accel or decel) is at its lowest. I also don't think it is a problem to be concerned about. For example, when going from a dual mass flywheel in a Toyota Supra to a single mass flywheel, you will get a lot of noise (at idle in neutral) very similar to that in your video. Now maybe this backlash is excessive or it is just the right amount needed to account for thermal expansion at high torque/power levels.
Remember the SR-71 was designed to leak fuel on the runway so it would stay together at Mach 3+ after significant thermal expansion took effect.
Anyway, this is just conjecture on my part so take it with as many grains of salt as you dare.
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
#12
Registered User
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!
Solid bushings transmit a significant amount of noise through metal on metal contact. I recommend doing massive burnouts and then fuggedaboutit!
#13
Community Organizer
4.77s historically, were sometimes noisier than the OEM 4.10s.
Mine were, but just barely.
Mine were, but just barely.
#15
Thread Starter
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
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
#17
Thread Starter
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
#18
#19
Thread Starter
Is it necessary to do all that?
And when tightening the nut is there a process i should follow?
#20
Initially tighten to 110 ft/lbs
Loosen, and retighten to 94 ft/lbs
???