8 3/4 rearend question

[vetteman91]

Questions- I put car in air today and turned left wheel forward with trans in neutral. Right wheel turned backwards(opposite direction). I was trying to determine if this was a sure grip(posi) or not. Is this an open rearend? And Can I buy a posi 3rd member and use existing housing? Are axle shafts the same for posi and non posi?

 

[Moparmatt72]

Sounds like open to me but some posi's are torque sensitive, if you and another person on both wheels try to turn them what happens? More then likely its open. Yes you can buy just a positive unit and everything will bolt right back up. Just look out to shims and make sure they stay with the side they came off. I think 8 3/4 use shims like the dana does.

 

[vetteman91]

Ok Thanks. I kinda figured it was but was unsure if everything else would work.

 

[Meep-Meep]

Yeah, it's open or a seriously worn out sure grip. Axles are the same and yes, you can just swap in a different 3rd member.

 

[tallhair]

And you may have to buy a combo u joint if the one you change to is the small or large and yours is the other

 

[bigblock]

There is only one shim in the 8 3/4. It is between the pinion and the rear bearing.But no matter you can put any locker in it without disturbing the pinion set up.

 

[dvw]

Questions- I put car in air today and turned left wheel forward with trans in neutral. Right wheel turned backwards(opposite direction). I was trying to determine if this was a sure grip(posi) or not. Is this an open rearend? And Can I buy a posi 3rd member and use existing housing? Are axle shafts the same for posi and non posi?

It is definitely a non Sure Grip. To install a sure grip.Pull the axles out about 12". Remove the drive shaft and carrier. Measure existing back lash. Mark the caps right and left. Remove the locks, caps, adjusters, case, and ring gear (left hand bolts). Transfer ring gear to the Sure Grip unit. Make sure to deburr the carrier where the ring gear sets. Heating the ring gear in the oven will help. Torque ring gear bots. Start the cap bolts in the caps and start the adjusters. Snug the bolts, not torqued yet. Move the adjusters until the right side has a little clearance to the bearing cup. Tighten the left adjuster until the back lash reads zero. Now tighten the right adjuster until you are at your original recorded back lash. Torque the caps, install the adjuster locks. Reinstall the carrier,drive shaft, and axles. Adjust the axle end play with the right axle bearing adjuster 0-.005". Push in on the left axle. Now push in on the right axle and record the movement, this is your axle endplay. The threaded adjuster on the right axle bearing will tighten to reduce play, loosen to increase it. Fill the housing with lube and go do burnouts.
Doug

 

[wedge69]

It is definitely a non Sure Grip. To install a sure grip.Pull the axles out about 12". Remove the drive shaft and carrier. Measure existing back lash. Mark the caps right and left. Remove the locks, caps, adjusters, case, and ring gear (left hand bolts). Transfer ring gear to the Sure Grip unit. Make sure to deburr the carrier where the ring gear sets. Heating the ring gear in the oven will help. Torque ring gear bots. Start the cap bolts in the caps and start the adjusters. Snug the bolts, not torqued yet. Move the adjusters until the right side has a little clearance to the bearing cup. Tighten the left adjuster until the back lash reads zero. Now tighten the right adjuster until you are at your original recorded back lash. Torque the caps, install the adjuster locks. Reinstall the carrier,drive shaft, and axles. Adjust the axle end play with the right axle bearing adjuster 0-.005". Push in on the left axle. Now push in on the right axle and record the movement, this is your axle endplay. The threaded adjuster on the right axle bearing will tighten to reduce play, loosen to increase it. Fill the housing with lube and go do burnouts.
Doug

All good info here . BUT put new Axle seals in while you have it apart !

 

[440ronnie67]

my wheels also rotate in opposite direction, but always leaves two rubber marks on the road:headbang:

 

[Cranky]

my wheels also rotate in opposite direction, but always leaves two rubber marks on the road:headbang:

Is the rear end stock? It's possible your car has the right balance that it'll make the open rear act like a limited slip unit. How does it act when you turn a corner while nailing it? One wheel peel?

 

[440ronnie67]

bone stock, 2:94 ish no one wheel peal around corners. Ill double check..lol

 

[Cranky]

Never seen a non limited slip rear lock up around a corner. Ever have the rear opened up? I'm thinking that you have a unit that's worn but not quite enough to give up the ghost just yet....?

 

[vetteman91]

I just bought the car a few weeks ago and have never driven it. Figured if it was an open rearend I would add a posi 3rd member to my list of parts to find. Won't get to drive for several months as it is coming apart for paint and body work. Am I understanding from one of the posts above that if I buy a posi 3rd member I don't have to switch pinion? Isn't the pinion m/atched to my ring gear? Weren't a lot of these 3:23 gears from Mopar ? What if I find a 3:55 or 3:91 gear? Pinion would have to be changed then wouldn't it? What are gear ratio suggestions on these cars for street use and an occasional trip down the strip for fun?

 

[5.7 hemi]

Swapping a one wheeler peeler to a sure grip is no problem. Check your backlash first, swap the ring gear over to the sure grip, recheck backlash, add fluid with the sure grip additive, and burn both tires. This is the down and dirty order of things to do, but you get the idea.

 

[wedge69]

From what I am getting from this you have Never done a gear or rear swap ? If I am rite you should get a book and read up on it First OR have it doen by someone that know how to do it rite. This is best as it can cost you money if its done wrong !
We do rears at the shop ALOT and have seen them set up wrong and burnt to crap !
Better safe tahn sorry !

 

[62 Dart Convertible]

I just bought the car a few weeks ago and have never driven it. Figured if it was an open rearend I would add a posi 3rd member to my list of parts to find. Won't get to drive for several months as it is coming apart for paint and body work. Am I understanding from one of the posts above that if I buy a posi 3rd member I don't have to switch pinion? Isn't the pinion m/atched to my ring gear? Weren't a lot of these 3:23 gears from Mopar ? What if I find a 3:55 or 3:91 gear? Pinion would have to be changed then wouldn't it? What are gear ratio suggestions on these cars for street use and an occasional trip down the strip for fun?

Yes the pinion is matched to the ring gear. Dougs instructions are for keeping your original ring and pinion and just swapping an open carrier for a sure-grip carrier. As wedge69 says, it needs to be done right. If you aren't comfortable doing it, I would pop out the axles and remove driveshaft, remove pumpkin and hand it to expert for fitting S-G and set up, then you reinstall. Even more so if you are changing ring and pinion too. Gear ratio choice is all about compromise - between cruising RPMs and stop-light launch neck snapping ability. It all depends on what you want the car to do well. Never on the highway and want to win drag races? 3.91 or more for sure. Drive to your holiday house 100 miles up the freeway often? Then 2.94 or less. Want to do both? 3.55 seems the common compromise...