Changed G80, now howling

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RoadRashRon

New member
Feb 15, 2012
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I few friends and I changed my G80 out to a different G80 that locks up better last night. Also changed the pinion seal that was leaking.

The seal is still leaking, although the seal surface on the balancer sleave has some groves in it so thats not surprising. We didnt have a way to check the inch lbs before taking the pinion nut off but counted threads and put it back on to the same spot or pretty close with a 1/2" impact(250 ftlbs).

The diff went in well and we thought the backlash felt right but while decelerating from 35 or under it howls. Doesnt seem to do it over 35 and stops when decelerating and put in neutral.

Could 250ftlbs not be enough to retighten the pinion nut?

Due to the howl stopping in neutral Im assuming the pinion is moving and changing the backlash under deceleration load and once the load is removed(neutral) it stops.

Ideas? Thanks
 
Chevy1925

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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take it to a shop that knows how to setup a differential. you can not "feel" for the correct back lash and ill bet you guys didnt check for the correct tooth pattern on the gears after you were done. there is no correct torque for the pinion once you back that nut off as the crush sleeve inside is only usable once, retorquing the nut back down has the potential to crush the sleeve more and changing everything. Sometime you can get away with marking the nut and putting it back on to its exact spot but not always. stop driving it immediatly and get it in somewhere or you will quickly trash that rear end
 
D-MAX Mafia

D-MAX Mafia

Hood down, smoke up!
Nov 4, 2009
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x3! Diffs are one thing I wont touch! That stuff is moving way to fast and there is a lot of power and strain going through there to just guess at it.
 
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Bryce418

Still slow
Oct 5, 2009
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If I'm reusing ring and pinion I measure backlash and set it back where it was.

Now setting up the whole deal is a whole different story.
 
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RoadRashRon

New member
Feb 15, 2012
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Bryce418, what do you do to measure backlash? Dial indicator? Unfortunatly I have nothing to go on because it wasnt measured prior to removal. I think it should be around .008, correct me if I'm wrong please.
 
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Bryce418

Still slow
Oct 5, 2009
611
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.006-.007" is pretty much what it should be. If you don't know what it should be you could try checking the pattern.
 
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Bryce418

Still slow
Oct 5, 2009
611
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madmatt said:
it also depends on if you're using new or resusing old bearings. i always set them a little tighter if using new. I set them by feel if I'm reusing all the old bearings.
Click to expand...

As long as the bearings aren't wasted there is very little change from bearings, most of the wear is on the gear set.
 
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Sledheadxp800r

That was only my tow tune
Dec 13, 2010
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Backlash should be set to the same spec whether your using new or old bearings. It's the bearing preload that is set different. 4 holes for old bearings 6 holes for new bearings.

When changing a pinion seal the best way to do it is to measure rotating torque before with the axles removed. Then when reassembling its recommended to tighten the pinion nut until you achieve 5 in/lbs more rotating torque.

Also 250 ft/lbs is nowhere near what it takes to crush the cruch sleeve on an aam 11.5. They start crushing somewhere in the 7-800 ft/lbs range
 
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Bryce418

Still slow
Oct 5, 2009
611
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0
If you set up a diff where it was and there were no issues or bad bearings, you benefit from putting the gears back in the same pattern they wore into.


As far as bearings, my two cents if the bearings are worn enough to need adjustment, they need to be replaced. Tolerance on new bearings these days are awful close, starting out where you were is usually really close.
 
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