Cone Suregrip rebuild question

[CopperheadDart]

I read the rebuild in the how-to section, and just tore into a cone suregrip that was one-legging when I removed it from my car.
I expected to see the cones bottoming out in the case like the how-to thread, but this wasn't the case. I put some clay between and rough measured .036" clearance. There's no indication it's bottoming.
The back side of the cone and side gear have strange wear, which is weird considering these pieces are moving in unison locked together by the axle splines.

So are my springs just worn causing the slippage, and is there a fix for that?

 

[Sterling]

I think you want about .060 clearance , from what I remember. I always add 727 clutch drum springs inside the factory springs to increase tension. I have one that looks like that apart now, so I cleaned up the parts so they were smooth, and going to reassemble and try it.

 

[AJ/FormS]

That strange chatter-wear is normal.
As the cones wear they drop down into the cavity, and the spring-preload eases and eventually the cones are no longer pushed into the cavity.
While .036 is enough, if you already have it apart, the .060 mentioned by Sterling is better.
However, as the cones drop down, they take the side-gears with them, and the spiders are moving into the cases and away from eachother. Eventually the spiders are driving the sidegears by their tips only. This is bad news because all the power of your engine is going thru those two tiny spiders and at any one time only a few teeth on each spider are transmitting power.
Follow the power; Pinion to ringear to case to cross to spiders to sidegears to axles.
So you gotta restore the spider to sidegear contact.
I do this by two ways whichever works best.
First tho; I grind off the unworn parts of all the gears, so that they are not high-spots. Then
I install new Ford side-gear washers between the cones and the sidegears. This pushes the sidegears towards the spiders. Next, If I have enough room, I double up on the spider washers, which push the spiders towards eachother which increases the tooth contact. When I think I'm done, I assemble everything minus the springs and make sure the spiders and sidegears all rotate freely, and are not baggy. Those side gear washers that I get from Ford come in a package of various thicknesses, so it might take several tries to get it just right.
After that is done, the springs will now have more tension on them, so the next step is to set the turning torque. I lube everything up with the same lube I am gonna use, with the correct percentage of whale-oil in it. Then assemble it, but case bolts only finger tight.
Now, I made myself a couple of tools from old broken axles with splines that fit my sidegears. Each is about 7 or 8 inches long. I put one in my bench-vise, and clamp her hard. Then I put the assembled case on that axle. The other stump has a pinion nut welded on the end, and I slide that in the top. After all the splines are engaged, I tighten the case bolts. Then I measure the turning torque( NOT the break-away torque) with a torquewrench.
Here is what I like to see.
For a streeter with 245 tires. 90 to 100 ftlbs. Too much more than 100, and she will spin the inside tire around every sandy corner.
For a streeter with 295s and 350/400hp, I like 120ftlbs It will still occasionally spin the inside wheel, acting a lil like a spool, but most of the time you will get differential action. And when you gas it, both tires will spin, and you can do nice full-lock power-slides . And of course 120# is more than you need for just straightline action with street tires.
I got these numbers by trial and error in my own cars.
Adjustment is by spring-pressure; more springs, different springs, shims, or by swapping thinner side-gear washers between the cones and sidegears.
If this is your first time, with an A-body, I would try 100ftlbs +/- 10#, no less than 90#.
RnR is only 1.5 hrs, less on a hoist.

 

[RustyRatRod]

I have a heavy hand with machining the cones. I normally remove about .100". I do that because, first, it won't hurt a thing, and secondly, I want to do it ONCE. Then of course, you need to re shim the spring pack. On yours though, it does sound like your primary issue is weak springs.

Do keep in mind though, this is not a bonafide repair in any service manual, as these Auburn style units are technically not rebuildable. They were really a light duty unit to begin with, so do keep in mind those limitations and you'll probably be fine.

 

[my68barracuda]

I have a heavy hand with machining the cones. I normally remove about .100". I do that because, first, it won't hurt a thing, and secondly, I want to do it ONCE. Then of course, you need to re shim the spring pack. On yours though, it does sound like your primary issue is weak springs.

Do keep in mind though, this is not a bonafide repair in any service manual, as these Auburn style units are technically not rebuildable. They were really a light duty unit to begin with, so do keep in mind those limitations and you'll probably be fine.

Dr Diff has a shim kit on his web page for cone sure grips that have been trimmed.
And, is it possible that a previous owner trimmed the cones, and that is why you see the clearance, but not shim it properly and that is why it is not working correctly.

 

[RustyRatRod]

Dr Diff has a shim kit on his web page for cone sure grips that have been trimmed.

I've always just gotten a box from Summit, but I'll check his out. Thanks.

 

[Bewy]

Give both the cones & housing a light skim to clean the surface. Whatever distance has been lost to wear/machining results in reduced spring tension, by that amount. So the springs should be shimmed by that amount to restore the correct tension to the assy.
I would use a high quality synthetic oil like Redline LSD oil to reduce wear & increase the effectiveness of the LSD itself. I use RL in my cone diff, for over 20 yrs now.

 

[CopperheadDart]

That strange chatter-wear is normal.
As the cones wear they drop down into the cavity, and the spring-preload eases and eventually the cones are no longer pushed into the cavity.
While .036 is enough, if you already have it apart, the .060 mentioned by Sterling is better.
However, as the cones drop down, they take the side-gears with them, and the spiders are moving into the cases and away from eachother. Eventually the spiders are driving the sidegears by their tips only. This is bad news because all the power of your engine is going thru those two tiny spiders and at any one time only a few teeth on each spider are transmitting power.
Follow the power; Pinion to ringear to case to cross to spiders to sidegears to axles.
So you gotta restore the spider to sidegear contact.
I do this by two ways whichever works best.
First tho; I grind off the unworn parts of all the gears, so that they are not high-spots. Then
I install new Ford side-gear washers between the cones and the sidegears. This pushes the sidegears towards the spiders. Next, If I have enough room, I double up on the spider washers, which push the spiders towards eachother which increases the tooth contact. When I think I'm done, I assemble everything minus the springs and make sure the spiders and sidegears all rotate freely, and are not baggy. Those side gear washers that I get from Ford come in a package of various thicknesses, so it might take several tries to get it just right.
After that is done, the springs will now have more tension on them, so the next step is to set the turning torque. I lube everything up with the same lube I am gonna use, with the correct percentage of whale-oil in it. Then assemble it, but case bolts only finger tight.
Now, I made myself a couple of tools from old broken axles with splines that fit my sidegears. Each is about 7 or 8 inches long. I put one in my bench-vise, and clamp her hard. Then I put the assembled case on that axle. The other stump has a pinion nut welded on the end, and I slide that in the top. After all the splines are engaged, I tighten the case bolts. Then I measure the turning torque( NOT the break-away torque) with a torquewrench.
Here is what I like to see.
For a streeter with 245 tires. 90 to 100 ftlbs. Too much more than 100, and she will spin the inside tire around every sandy corner.
For a streeter with 295s and 350/400hp, I like 120ftlbs It will still occasionally spin the inside wheel, acting a lil like a spool, but most of the time you will get differential action. And when you gas it, both tires will spin, and you can do nice full-lock power-slides . And of course 120# is more than you need for just straightline action with street tires.
I got these numbers by trial and error in my own cars.
Adjustment is by spring-pressure; more springs, different springs, shims, or by swapping thinner side-gear washers between the cones and sidegears.
If this is your first time, with an A-body, I would try 100ftlbs +/- 10#, no less than 90#.
RnR is only 1.5 hrs, less on a hoist.

Thanks for the excellent description, that makes a lot of sense. I have the Dr.Diff shim kit, and while it only has one thickness shim, I'll assemble and check the turning torque.

I have a heavy hand with machining the cones. I normally remove about .100". I do that because, first, it won't hurt a thing, and secondly, I want to do it ONCE. Then of course, you need to re shim the spring pack. On yours though, it does sound like your primary issue is weak springs.

Do keep in mind though, this is not a bonafide repair in any service manual, as these Auburn style units are technically not rebuildable. They were really a light duty unit to begin with, so do keep in mind those limitations and you'll probably be fine.

Thanks, RRR, I will take some off while it's all apart. I'd like to only do this once!

I think you want about .060 clearance , from what I remember. I always add 727 clutch drum springs inside the factory springs to increase tension. I have one that looks like that apart now, so I cleaned up the parts so they were smooth, and going to reassemble and try it.

I happen to have some of those clutch drum springs laying around. They're a bit shorter than the suregrip springs but they should be contacting by the time the unit is bolted back together under tension.

 

[Bewy]

If you want the LSD to work as designed, you want the springs set to the same tension as the factory set them, not some other spring that might have too much or too little tension.

 

[Dave999]

shim both sides between side gear and cone untill the cross shaft JUST sits in its well in the case. do boith sides on an axle in a vice and then zip it up
should be bob-on stock setting provided its never overheated and needs new spring pack. and the spider gears will run true on the side gears again.

never had an issue cuased by NOT cleaning up the chatter mess on the backs of cone and gear...
once shimmed no more chatter and forward motion again on wet grass sand gravel etc.

BorgWarner in Australia produced these as well for 6.5 to 8.8 inch Borgwarner/BTR/spicer diffs and shimmed as necessary. some came new with shim some did not.

Dave