8-3/4 rear with 489 case ....sure grip?....decoding the casting numbers?

[71charger500]

My rear end is not in the car, so I can't do the "spin the wheel" trick I keep reading about, to tell if it is a sure grip. It is a 3.23 gear tag on it, but no other letter or number on that tag. Other than the 2881489 number, t has several other numbers/letters on it as well. I would like to know what they mean just out of curiosity, even if they don't mean anything significant.
One number is "324"....another is a single number "3". Also there are the letters "AAPW" and what appears to be the letter "A" inside a circle. Like I said, just trying to learn as much as I can, even if it doesn't mean anything important. Thanks

 

[Cranky]

Should be some numbers on the edge of the ring gear...part number, date and ratio. I'll see if I can dig up some pics showing what a Sure Grip looks like or you can take a pic and post it up and someone can tell you what you have. Another way to find out the ratio is to count the teeth on the pinion and ring and divide it out. Kinda hard to count the pinion teeth on one that's together but it's not impossible.

 

[69chargerboy]

Should be some numbers on the edge of the ring gear...part number, date and ratio. I'll see if I can dig up some pics showing what a Sure Grip looks like or you can take a pic and post it up and someone can tell you what you have. Another way to find out the ratio is to count the teeth on the pinion and ring and divide it out. Kinda hard to count the pinion teeth on one that's together but it's not impossible.

I hope this can help. I just had my 489 rebuilt and had Posi Added.

 

[Meep-Meep]

You will have to pull the 3rd member to see. The casting numbers do not separate SG from open; they are just casting numbers for the case. Like Cranky said, there will be a clear 3.23 or 3.55 number stamped on the edge of the crown wheel.

 

[Cranky]

The pic in post #3 shows a factory clutch plate style Sure Grip (Power Lock) and this one is a cone clutch type, a Borg Warner unit.

 

[Mr Belvedere 30144]

When you say the rear end is not in the car do you mean the chunk or the entire axle? If you have the axle out of the car you can just do the turn the wheel trick just as in the car, easier even. You ca also count the turns on the yoke and get the ratio. Just put the axle on blocks and turn the tire or hub and see if the other side turns as well.

 

[Cranky]

When you say the rear end is not in the car do you mean the chunk or the entire axle? If you have the axle out of the car you can just do the turn the wheel trick just as in the car, easier even. You ca also count the turns on the yoke and get the ratio. Just put the axle on blocks and turn the tire or hub and see if the other side turns as well.

I've been fooled by this method before....twice. One was rusted up so bad that it acted like a Sure Grip was in it and the other was worn out bad bad enough that it slipped like an open diff. The rusted one pissed me off because it was in a junk yard and I wasted my time pulling it. The worn out one was rebuildable and was a pleasant surprise because I was about to swap it out with a SG and found it had one already. But if both wheels turn together when the yoke is turned, chances are it's a SG and you can count the gear ratio.

 

[Mr Belvedere 30144]

Yep that can happen but usually in a car that has been running down the road this method works. It has for me so far anyway.

 

[Rick62]

8.75 Open

If it looks like this it's open. Or, if it's still mounted in a housing turn the yoke. If the axles turn in opposite directions it's open.

 

[Cranky]

71Charger hasn't been back since the 5th.....maybe someone else can benefit from the information here.....

 

[b_body_hopeful]

Great read, thanks to all.

 

[challenger6pak]

Old thread just helped a customer. I'm glad this site saves pics instead of deleting them at the end of the year.