Who knows the most about rear axles? HELP!!!!

[UWBadgers27]

In june I did a SAS and a SOA in the rear. I put in a ford 8.8 with 4.10's in the rear. I had a loud vibration/growl coming from the rear end above 40 MPH. It would vibrate when I was about 3000 RPM and I could hear a chatter when I would roll down my window when I was coasting. I thought my driveshaft was to short and the vibration was caused from the teeth, in the slip portion, not having enough contact, so I got the driveshaft lengthened. It also would shudder and shake my truck from a dead start until I got up to about 10 MPH (this might be from the mud tires).

That didn't fix my problem at all so I noticed my pinion angle was off. So I bought some 8 degree shims and put those in along with dropping my AAL out from the rear. Now it vibrated differently. It would vibrate/growl at mid throttle, but it would go away when I would get on it. If I let off the gas it did the same chatter thing but now it had more of a vibration to it.

In October I started noticing a ping noise every time I would reverse into my parking spot. It would ping as soon as I gave it gas when going in reverse. It would do the same when I would pull out.

So now I realized my pinion angle was to perfect. It was right at 0 degrees. I pulled the shims out and put in 6 degree shims for a 2 degree offset to accomidate for axle wrap. Now that changed the occurence of the vibration. Now it vibrates/growls just over 30 MPH or faster when I push the gas pedal in JUST enough to open the throttle. Its pretty loud in the truck but as soon as I would give it just a little more gas it would go away. Now when I coast it vibrates a little more intensley and it still chatters.

Possible things wrong that I've researched

1) U Joint - The U Joint's on the rear driveshaft are only about 2 months old but I ran it with the angle at 0 degrees for awhile so I'm wondering if that wrecked the U Joints. That also can cause that ping noise that I'm hearing resonating through the driveshaft.

2) Excessive Backlash - It also could ping from the pinion hitting the coast side of the teeth and then pinging off the drive portion of the teeth. That would also cause vibration too but I'm unsure because I've never experienced this before.

3) Bad pinion preload - most people say that this isn't it but it seems like the next logical possibility

So anyone got a guess or an answer from previous experience? I'm just tired of guessing wrong and I need to get this fixed. So someone... anyone... Please help!!!!

 

[UWBadgers27]

Anyone?

 

[Rick]

Can you remove your front driveshaft and test it with just front wheel drive? If so that will at least rule out the rear u-joints.

 

[Goofyexponent]

Bad axle bearing? Is it LTD slip or open carrier? It could be a bad set of spider gears or a worn carrier?

How positive are you that the pinion depth is correct and the contact pettern is 100% correct?

I have had U joints that looks good and tight, turn out to be FUBAR-ed when removed.

I would have the rear shaft removed and put new U joints in it as a start. It's the cheapest and easiest fix.

Next I would be looking at pulling the diff cover and pulling the axle shafts to check them for wear as well as the bearings.

Something in your rearend isn't happy.

 

[Goofyexponent]

How are the TCase bearings?

 

[UWBadgers27]

See I've considered all those things. I just wish I could find someone who has experienced any of this. Anyone have an answer as to why the vibration occurrence changed when I adjusted the pinion angle?

Thanks for the replies guys

 

[UWBadgers27]

The TC bearings should be ok. All new fluid and the chain is tight

 

[Goofyexponent]

When the shaft was lengthened, was it balanced?

 

[UWBadgers27]

Yeah it was checked twice because that's what I thought it was but I was wrong

 

[Rick]

Anyone have an answer as to why the vibration occurrence changed when I adjusted the pinion angle?

That makes me think that you have a bad u-joint, but it seems unlikely that you damaged them by driving a short time at 0 deg.

Did you install the u-joints or a shop? Just wondering if a needle fell out while it was being installed. It does happen.

 

[UWBadgers27]

I've replaced the u joints 3 times and all the u joints I've replaced the noise was still there. So what would be the next guess if not the u joints?

 

[Rick]

Next up would be bearing issues. The 8.8" uses a crush sleeve for pinion bearing preload. It's only supposed to be used once. Do you know if the yoke had been removed and replaced at any time without replacing the crush sleeve?

A ping is usually u-joint related, but too much lash could make the noise as well.

 

[UWBadgers27]

Ok so since I have the ping noise it's most likely my back lash then. I'll try to check it tomorrow. How bad can it wreck things if my backlash is off?