Haven't got under there yet to look but what size diff is in an 05 1/2 t supercrew? Doesn't look like an 8.8 housing.

Thanks

 

Prob a 9.75 then... Post the axle code on your door sticker or see if the metal tab is still bolted to your diff cover.

 

H9 is the axle code.

 

Looks like a 9.75. with the 3 L 55 would guess it is supposed to be a lsd but it is definitely an open diff.

 

Might have some sticking clutches... or worn.

I’d suggest a diff service and don’t forget the friction modifier. Find you a field or open space and do some figure eights and see if you can get things moving again.

 

3 --
L55 means Limited Slip 3.55. All information found via a Google Search
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Your axle code is
3 V 951 R
L55 9.75 5B16

Which translates to
V=Van Dyke, Model 951, Revision R
Limited Slip 3.55, 9.75" ring gear, Manufactured 2005-02-16

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Date codes are as such, for example: 5B16:
First digit is year
Second digit is month (A = Jan, B = Feb, C = March, ect)
Third and Fourth is day of month

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This is my axle code:
3 V 907 C
L55 9.75 5K25

Which translates to:
V = Van Dyke Model 907 Revision C
Limited Slip 3.55, 9.75 ring gear, Manufactured 2005-11-25

 

FWIW, the door sticker gives you ratio and whether or not it's a posi, but does not determine which housing you have. Obviously a moot point here since you have the axle tag.

 

I've seldom seen a factory locker whose clutches still exist much after 150k miles. Wrong fluid at any time can accelerate the unlocking.