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Old 10-19-2012, 05:44 PM
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Rear end hum

Hey guys I just installed and 8.8 in my buddies 65, and I had to change the pinion bearings. I reused the same pinion shim so I didn't change the gear pattern at all. I'm getting a hum in cruise that goes away on acceleration. my buddy says its the axle bearings. He said that if the pinion bearings are bad, then the carrier and axle bearings are probably bad too. Any thoughts?

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Old 10-19-2012, 06:14 PM
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I wouldn't blame the axle bearings right away, especially if you just changed the pinion bearing. I'm not saying it isn't the axle bearings but, did you torque the bearing? Using the same shims is OK if you use a back lash gauge. Shims will crush and change your tolerances, after market bearings can be out just a bit from OEM. So many variables, always use a gauge.

Hope this helps
Ray
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Old 10-19-2012, 06:37 PM
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Depends on how bad those pinion bearings were and how long they were run. It is entirely possible metal from the pinion bearings have damaged the axle bearings. That is why when I replaced pinion bearings I also replaced axle bearings at the same time. Generally though noise from an axle bearing will not change or go away with throttle manipulation.

Vince
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Old 10-19-2012, 06:49 PM
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Bad axle bearings will be easy to spot because the axles will be worn or pitted. The axle bearings in the 8.8 run directly on the axles, so the axle is the inner race for the bearing. Any wear from the bearings will be easy to spot on the axles.

The question that needs to be asked is how did you set the bearing preload on the new pinion bearings? Did you use a new crush spacer? Did you crush it correctly? How did you measure the bearing preload? This is most likely where your problem is.
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Old 10-20-2012, 10:03 AM
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Quote:
Originally Posted by big gear head View Post
Bad axle bearings will be easy to spot because the axles will be worn or pitted. The axle bearings in the 8.8 run directly on the axles, so the axle is the inner race for the bearing. Any wear from the bearings will be easy to spot on the axles.

The question that needs to be asked is how did you set the bearing preload on the new pinion bearings? Did you use a new crush spacer? Did you crush it correctly? How did you measure the bearing preload? This is most likely where your problem is.
Like this? My son's Crown Vic, it cr@pped out 400 miles from home, destroyed the seal and spewed all the lube. You could grab the brake rotor and rack it up and down 1/4".

Russ
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Old 10-20-2012, 11:34 AM
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Yea, that's an extreme case, but a good example.
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Old 10-22-2012, 05:31 PM
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well fellas it turned out to be a loose pinion flange. I didnt set the proper pinion bearing preload. I need to get a hold of an inch pound torque wrench so that wont happen again. I tightened it up, until all the slop was gone, and took it for a spin. All the noise went away. Now I just gotta keep an eye on it to make sure that it doesnt happen again. If it does, theres a different problem.

As for the axles, the old 4 bolt axles were smooth, so i determined that the bearings are fine. i replaced them with a passenger side aerostar axle and driver ranger axle that were smooth too. The swap was worth while.
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Old 10-22-2012, 07:46 PM
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I always use red Locktite on the pinion nut. I've had a few that backed off on me and cost me some profits.
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