diff 8.75

[cudamadd]

Hi   could any one help me with these  questions ?  With out takeing the diff out at this stage , and pulling it a part.  Car is a  cuda 340 auto .  Question 1 would this car have come from the factory with a L.S.D ?   Question 2 if it is the factory diff ARE they a clutch type OR a Cone type ?   The only thing i know about the diff is 489 case .  The diff is in a bad sad way at this time. Any input would be great . just wanting to do some home work before i have it rebuild here in Aus . IF THEY CAN DO IT  or  i can ship a centre from the U.S.A    P.S i was told it was a L.S.D  but it doesnot spin both wheels it is in that bad of shape . plenty diff centres on ebay just not sure which way to go. Thank you again have a great day cheers.

[Chryco Psycho]

#1 - Maybe the LSD is usually an option on any car with any gear ratio , not a given .
#2 -  until 69 the factory used Clutch type which is the better design , 70 up used cone type , generally a 489 carrier will have the cone unless it has been rebuilt .
 You could order the True Trac unit & have it installed in Aus , this is probably the best option .
 You say it is bad shape , are the gears howling? Usually the gear set can be reused as long as they are reset properly

[cudamadd]

No the gears are not howling at all. The diff is very clean , and all uni joints very tight . The problem i have is when i am turning right at a very slow speed it will jump or hop and rock the back of the car a little . The axles turns true , Not much movement side to side . I think i will have it checked out and if it is no good i could order a True Trac unit and that will be that . I COULD always use the old centre as a door stop.  I would like to post pictures of the car as soon as i work how to post them . Any way Chryco psycho thank you again 

[PlumCraZRT]

No the gears are not howling at all. The diff is very clean , and all uni joints very tight . The problem i have is when i am turning right at a very slow speed it will jump or hop and rock the back of the car a little . The axles turns true , Not much movement side to side . I think i will have it checked out and if it is no good i could order a True Trac unit and that will be that . I COULD always use the old centre as a door stop.  I would like to post pictures of the car as soon as i work how to post them . Any way Chryco psycho thank you again 

If you have a LSD and you replaced the fluid with standard gear oil, but didn't add a friction modifier, the rear end could hop around like you describe if the clutches are still good.

Try adding a bottle of the friction modifier and seeing if it works any better.

EDIT:  It's worth noting, the friction modifier won't hurt if it's an open diff, but it should help if it's a limited-slip.  It's sort of a no-loss gamble.

[Rich G]

That sounds like his problem. Clutches are sticking. Like PlumCRAZRt said put some clutch additive in and go to a parking lot and drive some figure 8s with it to see if they free up.