3.91 sure grip

[67yelodart]

Hello All,
This is a general question,since the 8 3/4 i am refering to is not in an A-body.
I installed a 8 3/4 ,3.23 clutch type sure grip,742 case, from a A-100 van into my truck.It was/is a good third member but i wanted lower gears so i changed it out with a 489,3.91 clutch type sure grip,and new yukon axles with the green bearings installed.
turning on to the street from my driveway,i noticed that the rear end acts like it has a locker or spool or welded spiders in it.
the 742 with 3.23's did not act that way.does that mean something is wrong with the 489 case,or does it mean that the clutches in the 742 diff.are worn out?
thanks
Clark

 

[mullinax95]

The 489 shouldn't make any noise if it has clutch type sure grip. Might need to remove the case and check it out to make sure it really has a clutch type installed or if there is a problem. Sounds like your 742 is working correctly... did both wheels spin when you nail it?

 

[RedFish]

The clutch type would act up and sometimes just a dose of friction modifier would cure it. Worth a try.

 

[demon seed]

Yup, make sure you put in a small bottle of the slippery stuff with the standard rear hypoid oil.

Terry

 

[67yelodart]

thanks for the replies.
i havent nailed it yet,didnt want to hurt anything if its not already hurt.
i used royal purple 75w-140 synthentic,,,could it be too thick,,,maybe try 80w-90?

 

[demon seed]

thanks for the replies.
i havent nailed it yet,didnt want to hurt anything if its not already hurt.
i used royal purple 75w-140 synthentic,,,could it be too thick,,,maybe try 80w-90?

80-90 non-synthetic is all I ever use in A bodies and B bodies