Rear differential identification

[Gldwing57]

My 68 Charger has a whine to it when you let off the throttle. I haven't fooled with these old cars since the 80s and just can't remember stuff like I used to. It was an original 383 automatic car and was changed over to a 440 automatic with gear ratio change.
It's a posi unit and I don't think it is set right. I also may have some wheel bearing issues. I don't know what the current gear ratio is but thinking a 3--73 to 3--90.
Anyway what i need to do is identify what is in it because a friend and I are going to work on it next week and don't want to tie up lift to look. Want to go into it with as much info as I can, and getting as much info as I can from the housing #s.
The chunk pulls out from the front so I know it is not a Dana but what I don't know is the size of ring gear and pinion.
While I know I won't be able to tell the ratio. Is there any info I can get from the outside housing or chunk to help me identify before I get into the tear down?
Ant info will be appreciated. Thanks

 

[R413]

Drivers side 7 digit part number down low right behind the yoke. Also a large single digit on drivers side same place as the large fill plug on pass side.
Look for a X, 2, or 9. The Yukon case will have a large Y there. It could also be a late 50’s early 69’s worth dofferent numbers. Get under there and rear what you have,

Originally a 1968 383 would have been a #2 or 2070742

 

[Gldwing57]

Drivers side 7 digit part number down low right behind the yoke. The a large single digit on drivers side same place as the large fill plug on pass side.
Look for a X, 2, or 9. The Yukon case will have a large Y there. Originally a1968 383 would have been a #2 or 2070742

View attachment 1246236 View attachment 1246237 View attachment 1246238

Thank you very much..

 

[33 IMP]

Might be a worn ring and pinion, or just axle bearings. I'd pull the axles, check the bearings. If they are bad, replace them and reassemble, see if the noise goes away.
If the r&p are bad, the case number determines what gear set you need (not ratio)
741-small pinion, 742-large pinion, 489-tapered pinion.
Could also be either a cone style or clutch style sure grip (should be a clutch in a 68).
Come to think of it, the FIRST thing I would do is check the fluid level.

 

[Tony Tee]

It could be the transmission . You need to nail down the source of the noise first.
I had a 727 that whined on deceleration. I hated it. Had to go with a different 727.

 

[Gldwing57]

Might be a worn ring and pinion, or just axle bearings. I'd pull the axles, check the bearings. If they are bad, replace them and reassemble, see if the noise goes away.
If the r&p are bad, the case number determines what gear set you need (not ratio)
741-small pinion, 742-large pinion, 489-tapered pinion.
Could also be either a cone style or clutch style sure grip (should be a clutch in a 68).
Come to think of it, the FIRST thing I would do is check the fluid level.

 

[Gldwing57]

Might be a worn ring and pinion, or just axle bearings. I'd pull the axles, check the bearings. If they are bad, replace them and reassemble, see if the noise goes away.
If the r&p are bad, the case number determines what gear set you need (not ratio)
741-small pinion, 742-large pinion, 489-tapered pinion.
Could also be either a cone style or clutch style sure grip (should be a clutch in a 68).
Come to think of it, the FIRST thing I would do is check the fluid level.

Ok. Thanks will do and let yall know..

 

[Gldwing57]

It could be the transmission . You need to nail down the source of the noise first.
I had a 727 that whined on deceleration. I hated it. Had to go with a different 727.

Tranny just been gone thru. Seems ok but thats a possibility for sure.

 

[Gldwing57]

Drivers side 7 digit part number down low right behind the yoke. Also a large single digit on drivers side same place as the large fill plug on pass side.
Look for a X, 2, or 9. The Yukon case will have a large Y there. It could also be a late 50’s early 69’s worth dofferent numbers. Get under there and rear what you have,

Originally a 1968 383 would have been a #2 or 2070742

View attachment 1246236 View attachment 1246237 View attachment 1246238

 

[Gldwing57]

Looks like early 8 3/4 doesn't it?

 

[R/T Boy 67]

It is pre 65 I think, but it is the same as a 741 carrier. If it has a sure grip then there will be no axle issues.

 

[Gldwing57]

It is pre 65 I think, but it is the same as a 741 carrier. If it has a sure grip then there will be no axle issues.

Seems strong just gotta figure out the whine. Thanks for reply

 

[Gldwing57]

I guess my question is that since this rear end is not out of a 68 charger if I get into it and need parts what do I ask for. Like I said before this seems to be an early differential and I know there were some changes made over the years. So I am at a loss as to what specifically to ask for should I need something for repairs.
Any suggestions or thoughts would be most helpful. Thanks.

 

[Wietse]

From what i see on the internet is that it is the same as a 741 case and parts are interchangable.
You could use DoctorDiff for sourcing any required parts for example, even give them a call and ask about your 657 case.
They will know for sure what you will need and or may use.

Edit: To find out what ratio is in there at the moment you lift the rear wheels off the floor and rotate the wheel 1 full turn, count the amount of rotations the drive shaft does.
At that same time you can find out if you have a sure grip in there by checking both wheels rotation. (Both in same direction is sure grip and if other wheel rotates in other direction it is open diff.)
Also you can check for backlash, if there is excessive/no play between wheel and drive shaft when rotating in both directions, should only be a small "clunck" so to say.

 

[Gldwing57]

From what i see on the internet is that it is the same as a 741 case and parts are interchangable.
Ok thanks.. Im sure its a sure grip but not sure of ratio.
I hope to try what you suggested tomorrow.
thanks again
You could use DoctorDiff for sourcing any required parts for example, even give them a call and ask about your 657 case.
They will know for sure what you will need and or may use.

Edit: To find out what ratio is in there at the moment you lift the rear wheels off the floor and rotate the wheel 1 full turn, count the amount of rotations the drive shaft does.
At that same time you can find out if you have a sure grip in there by checking both wheels rotation. (Both in same direction is sure grip and if other wheel rotates in other direction it is open diff.)
Also you can check for backlash, if there is excessive/no play between wheel and drive shaft when rotating in both directions, should only be a small "clunck" so to say.

 

[joe smith]

It could be the transmission . You need to nail down the source of the noise first.
I had a 727 that whined on deceleration. I hated it. Had to go with a different 727.

Alot of noise can transfer up the driveline.. I have had rear ends going and thought it was the transmission...

 

[Gldwing57]

Alot of noise can transfer up the driveline.. I have had rear ends going and thought it was the transmission...

Hopefully I figure out something this week.
I think it rear end but could be something else..
Ill let yall know..
Its just part of fixing these old rides up.
Thanks for reply..