8 3/4 sure grip slipping and noise

[Koronetti70]

Hi,

I have a '70 Coronet with original 8 3/4 sure grip and 2.94 ratio.

It didn't want to do a burnout so I loosened up the rear brakes and the first burnout was perfect. Stood on the brake and let the tires smoke for couple seconds, then let off the brake and it made two 100ft long lines on the street. Ofc I had to try it again. I could hear a funny sound and when I took off I saw it only spun the passenger side tire. I tried to loosen up the drivers side brake more and tried again. Now the noise was even worse and it definitely came from the rear end. One wheel peel again.

Is the LSD gone or is there something I can do to it rather than full rebuild? And is it safe to keep driving it like this? Wouldn't want to end the driving season yet.

 

[beanhead]

Rebuild time. Or buy a new complete 3rd member.

 

[Thrashingcows]

Does it make these noises when driving straight, or only when you make turns? Most likely it will need a rebuild or replacement depending on what type of sure grip you have, clutch or cone?

You can rebuild the cone style units, I've done it, by having the cones machined down a bit then having a stainless steel shim machined up in the approx thickness that was removed in the machining and putting the shim on the top of the cone so that the spider gears mesh properly and are within spec. The clutch style are easy since you just swap in new steels and clutch discs.

 

[WileERobby]

I'd open it up , just in case , to see if you've done anything destructive.

 

[33 IMP]

I'd bet you smoked (burned up) a cone style sure grip. It will only get worse. Contrary to what some will tell you, they CAN be rebuilt/renewed. Just a bit of machine work, and some shims.
There is a good tutorial on the A-body site.

 

[R/T Boy 67]

Dr Diff has shims and instructions for the cone suregrips.

 

[RJRENTON]

Hi,

I have a '70 Coronet with original 8 3/4 sure grip and 2.94 ratio.

It didn't want to do a burnout so I loosened up the rear brakes and the first burnout was perfect. Stood on the brake and let the tires smoke for couple seconds, then let off the brake and it made two 100ft long lines on the street. Ofc I had to try it again. I could hear a funny sound and when I took off I saw it only spun the passenger side tire. I tried to loosen up the drivers side brake more and tried again. Now the noise was even worse and it definitely came from the rear end. One wheel peel again.

Is the LSD gone or is there something I can do to it rather than full rebuild? And is it safe to keep driving it like this? Wouldn't want to end the driving season yet.

WHY DID/DO you want to do "burn-outs".....it proves nothing....except to keep the tire industry in Business......leavng two 100 foot patches......for what purpose....???
It quite likely that the Sure-grip unit in your '70 Coronet has a #489 case 8-3/4" and has the cone clutch sure-grip unit. These are sort of fixable by machining the faces of the clutch units ~ 0.060" from opposing clutch faces, to allow the tapered cones to re-contact the carrier. The only issue is the differential gears move further apart allowing higher contact forces on the available gear tooth area which could cause tooth breakage under shock loading......ie, burn outs..........just my opinion of course.....others will have their own opinions......
BOB RENTON

 

[Curiousyellow71]

 

[70bigblockdodge]

My kid's, center section from this weekend at the Nats. Almost made it home with it until the broken shaft piece decided to jump up and get involved again.

 

[dadsbee]

View attachment 1509762
My kid's, center section from this weekend at the Nats. Almost made it home with it until the broken shaft piece decided to jump up and get involved again.

Was gonna say lift the *** end and turn them axles... may have broken one..

 

[RemCharger]

View attachment 1509762
My kid's, center section from this weekend at the Nats. Almost made it home with it until the broken shaft piece decided to jump up and get involved again.

Just crunched one up last time at the track.
Slapping a new one

in now

 

[Lefty71]

WHY DID/DO you want to do "burn-outs".....it proves

Its an addiction really. He needs to purchase a spool, and get down to the local drag strip for proper therapy.

**Note** there's no cure per say, but the therapy helps temporarily.

 

[Fran Blacker]

Get a line lock for front brakes.
Get your cone sure-grip repaired. Burn-out fun for some but paying for parts isn't the fun part.

 

[70bigblockdodge]

Was gonna say lift the *** end and turn them axles... may have broken one..

Switch cars out in the trailer to make it home. He put another center in it today. All good. Now he needs to put together a better one than some patched up junk.

 

[Koronetti70]

Does it make these noises when driving straight, or only when you make turns? Most likely it will need a rebuild or replacement depending on what type of sure grip you have, clutch or cone?

You can rebuild the cone style units, I've done it, by having the cones machined down a bit then having a stainless steel shim machined up in the approx thickness that was removed in the machining and putting the shim on the top of the cone so that the spider gears mesh properly and are within spec. The clutch style are easy since you just swap in new steels and clutch discs.

It doesn't make the noise driving straight or turning. Heard it only when doing the burnout.

 

[Koronetti70]

Was gonna say lift the *** end and turn them axles... may have broken one..

Had it up after the second try. Didn't make any sound and both of the wheels turned in to the same direction.

 

[RJRENTON]

Get a line lock for front brakes.
Get your cone sure-grip repaired. Burn-out fun for some but paying for parts isn't the fun part.

Instead of burning out tires and then buying new tires and burning them out also, just send me the tire dollars you would have spent and I'll invest it ... is investing an addiction..??....or not wasting money the same??......
BOB RENTON

 

[33 IMP]

Instead of burning out tires and then buying new tires and burning them out also, just send me the tire dollars you would have spent and I'll invest it ... is investing an addiction..??....or not wasting money the same??......
BOB RENTON

Cmon Bob, boys just wanna have fun. Fun costs money, how much fun do you want?!?
Part of it is showing off, part of it is being like a racer.
I can't remember the last real burnout I did on the street. Five to ten burnouts every trip to the track.....

 

[RJRENTON]

Cmon Bob, boys just wanna have fun. Fun costs money, how much fun do you want?!?
Part of it is showing off, part of it is being like a racer.
I can't remember the last real burnout I did on the street. Five to ten burnouts every trip to the track.....

To me, doing burn outs is totally mindless......perhaps tearing up $20.00 bills and flushing them down the toilet and wstching them swirl around the bowl could be considered "fun?" to some......dollars up in tire smoke....but to each his/their own volition......what ever floats your boat.......
BOB RENTON

 

[RemCharger]

...but to each his/their own volition......what ever floats your boat.......
BOB RENTON

You're kinda in your own dinghy on that one.
Nothing wrong with that, of course.