[JPhil]

Again, I'm posting this rather than than PM in case others are dealing with the same thing....

Got my posi on the bench with Gary's kit in it & setting it up springless. Never done a differential before. I have the .035" shims in, .040" was absolutely siezed. I have two "issues" which may or may not be "problems".

First, I don't know what the "feel" should be for stiffness. With the unit on a yoke in the vice, a bolt tight through a ring gear bolt hole and using a beam torque wrench at 90* from the axis, I read 25-30 lb/ft to turn it. The shop manual calls out minimum 40lb used, 70lb new to turn the axle with a torque wrench on a lug nut, on car. I figure I'm probably in the neighborhood of minimum for used. (Adding 20% for added torque wrench length from my point on the ring gear (which I figure roughly correlates to a lug nut) to the true axis of the unit, I figure a true torque of about 30-36 ftlbs to turn posi unit on yoke.)
Installing the other yoke with a bolt in a u-joint strap hole, I read 12-15 ftlbs to turn it yoke to yoke.
Are these acceptable torque values? Seems awfully light to me.....

Second, as I turn it it pulses--it's 'bumpy.' My actual torque reading goes 25-30-25-30-25-30. It seems to correlate to the teeth of my spider gears rolling over the side gears. This can't be right, can it? It has gotten better as I've been working on it, but does not feel like it will go away on it's own. These are my original used gears, in good condition and I have radiused the gear teeth of spiders & side gears.

Third, a question: Would using shim stock instead of grinding shims be OK? I have some .002" shim stock I could use if needed.

Thanks, John

 

[tracdogg2]

Hi John,
I never use the "break away" torque method for measuring. It's very inaccurate when using new clutches. I set them up by setting the backlash on the spyder gears. This is important area since that is where you get the hammering effect and starts breaking the posi cases. The range for backlash is .001-.005 in the spyder gears. You must preload the side gear to compress the clutches and then check the backlash. Do it for each side. Then assemble the posi unit and recheck.
.002 in my opinion is too thin for making adjustments. These units get hot and it's very common for the therin shims to turn blue from the heat.
Mike

 

[JPhil]

Thanks Mike.
Now for another noob question: How do I "pre-load the side gears to compress the clutches"?
As it sits, I have no backlash whatsoever, the gears are tight to each other. That's why I get the bumpy feeling, right?

 

[tracdogg2]

John,
I'm heading out to the shop right now. I'll do a quick set-up and post some pics for you.
Mike

 

[gtr1999]

John,
The torque spec is for a spring loaded setup and requires up to 70 ft'lbs to break loose one side. The way I do it does not load the clutches like the springs do so there is no constant force on them. That is why they hammer and wear the clutches.

What you're doing following the procedure I use is to cut down the backlash in the gears. When you shim to a point where the gears bind there is no backlash, so decrease shim size .005" and recheck. I like to get them dialed in so I'll grind shims in between the set sizes. Sometimes only a .001 shim will make a difference.

One thing you can do is to swap out the left & right spiders to see if that makes a difference. Sometimes I found the case may be machined differently between sides.

The last one I did I set at .036 and .037. The one before that was .030"

The feel I like is get it where it's knotchy but smooth not binding up. If it spins without any resistance it's too loose. When set there is little endplay in the side gears. If too loose the side gears will move .010"+
If you wanted to go straight line all the time then the backlash is tighter then a street setup. Once I get them where I like them I use a spanner wrench and spin them 25-50 times in each direction to help seat them. Keep the clutches oiled with the additive as well.

It takes a little time to get the hang of it so be patient.

Mike is referring to loading the clutches by compressing them then using an indicator on the 10 tooth pinion gear to check the backlash. The first time I did a tune I also checked the backlash like that and it was very close to the spec. I don't recall exactly what it was but it worked fine.

When a spring setup is done you can not rotate the yokes against each other, but with this setup there is no resistance. It feels like it will not work but it will.

Look on Tom's site and all his are springless as well.

 

[tracdogg2]

[/IMG]

 

[JPhil]

Mike,
Well heck that's pretty simple! I can probably handle that!

Gary,
OK thanks now I have a much better idea of what to feel for.

Both of you, thanks a bunch--I wouldn't even have considered doing this before, but it sure does feel good to do it myself.

John

 

[gtr1999]

I thought I saw this post on the other place as well but couldn't find it when I went to answer you? Was it removed?

 

[mrvette]

When/IF, I get to tearing into the rear again....what is the affect of just removing the springs??

leave everything else alone.....I have looked at them several times over the years and wondering what they are about...why there in first place...

 

[gtr1999]

Removing the springs without the proper shimming is not going to help you.
The springs keep constant force on the clutches causing them to chatter, hammer, and wear. You will get posi action because they slip very little. Correctly shimming the spiders without the springs will keep the force off yet allow the clutches to lock and produce posi. I found stokc units all over the place in tolerence so the springs are also a "band aid" to allow for various tolerences.
I have a copy of a 1979 PHR article on this very subject. I can't post it due to potential copyright infringements. If you find the June 1979 issues of PHR it's in there.

 

[TwinTurbo]

but can you email it?

 

[JPhil]

I thought I saw this post on the other place as well but couldn't find it when I went to answer you? Was it removed?

Wasn't me....

 

[gtr1999]

Hum maybe I'm just losing my mind!

John,TT you could try to email me.