70 Z28 12 bolt 4:10 Eaton posi springs question????

[70 RPO 28]

Does anyone know which size springs came from factory in the posi on a 70 Z28 12-bolt 4:10?
Green-200 lb
yellow-400 lb
Mine has the 200. Wandering if anyone has the yellow, and what their thoughts are on street driving with them?
Chirps/pops frequently even with the good friction modifier?
Thanks, Jim

 

[Hogdaddy]

I put an Eaton posi w/ yellow springs in my 86 Chevy truck professionally installed with new 3:73 gears.
Although not a Camaro, it does just fine on the street nonetheless.

 

[COPO]

My 70 Z28 with 3.73.

 

[70 RPO 28]

Thanks guys. My ring/pinion backlash seems fine at .009(was .008 original), but I'm concerned about the amount of end play on the axles, which is about 1/16" (.062). Thinking it should be no more than half that, and am feeling the occasional "shift" or " jerk" (can't think of a better way to explain it) when cornering or driving over a rough surface like gravel, which is what led me to opening the differential.
Even though the backlash is good, I'm wondering if all the axle end play is telling me to replace/rebuild the carrier and spring packs, or if it just needs shimmed more to tighten it up? The posi itself, which both wheels up, appears to be working ok and can get it too slip some when turning the wheels by hand and changing direction. I'm guessing 50-75 lbs of pressure, but hard to tell for certain just doing by hand.
What do you all think?

 

[2ndGenCrazy]

Thanks guys. My ring/pinion backlash seems fine at .009(was .008 original), but I'm concerned about the amount of end play on the axles, which is about 1/16" (.062). Thinking it should be no more than half that, and am feeling the occasional "shift" or " jerk" (can't think of a better way to explain it) when cornering or driving over a rough surface like gravel, which is what led me to opening the differential.
Even though the backlash is good, I'm wondering if all the axle end play is telling me to replace/rebuild the carrier and spring packs, or if it just needs shimmed more to tighten it up? The posi itself, which both wheels up, appears to be working ok and can get it too slip some when turning the wheels by hand and changing direction. I'm guessing 50-75 lbs of pressure, but hard to tell for certain just doing by hand.
What do you all think?


View attachment 212911

When assembled, what is the clearance between the end of the axle and the center pin? .009" should be fine.

 

[70 RPO 28]

1/16” (.065) on both sides between axle button and center pin.
.009 is the ring/pinion backlash

 

[2ndGenCrazy]

1/16” (.065) on both sides between axle button and center pin.
.009 is the ring/pinion backlash

Yes, two different things.
That gap on the axle is common.
"C" clip eliminator will remove all worries.

 

[Mitch_Z]

Just some info (1970 Camaro supplement), check your cross pin for wear or get thicker c-clips.

 

[70 RPO 28]

I’d love to just install thicker C-clips, but I can’t find the size of them anywhere online or in the manuals? ID, OD, or standard thickness.
There’s a company in Tempe,AZ that sells them, but I’m not sure which size to order.
Small= 1.375 OD / .740 ID
Large= 1.530 OD / .800 ID
Does anyone know the right size and standard thickness for C-clips on 70- 12 bolt 30 spline axles?

 

[Mitch_Z]

Overhaul manual says they come in 4 sizes, does seem like these parts are getting harder to find, call a GMC dealer to see if they can help.