differential 101 - spider gears loose on cross pin - confirm this please

have a clunk in the rear axle on the alavanche. it has become worse over time, and of course the junkyard rear axle(h2 hummer 14 bolt, electric locking differential) is just out of the 6 month warranty that came with it.

i read all kinds of crap online about driveshaft slip yokes, greasing splines, etc... so i tried that for the heck of it, but this is a real clunk coming right from the diff, i laid on the ground next to the truck while my wife moved it and it was easy to isolate. it happens when accelerating(clunk) then again braking, over and over.

so i pulled the diff cover. when i push one of the tires back and forth i can see the spider gears moving on the cross pin. enough to squirt out gear oil every time. i have not tried to check the clearance yet but it is more than 1/16", which seems to me a ton, but i have never actually done any axle assembly where this was an issue.

i'm assuming this slack between the spider gears and pin is bad, and it looked almost as if the gears on the pin were close to binding on the gears that go to the axle shafts when i moved it back and forth, as if the peaks of the gears could hit each other instead of meshing smoothly.

am i correct in figuring this is not right and at the least i need new spider gears and cross pin? fluid looks pretty dirty for being under 3k miles old, and i have a pinion leak so i'm wondering if the thing was run dry or really low prior to me getting it causing this wear. the bearings feel good, i get no play in the carrier, the pinion to ring gear pattern looks nice and even, and other than the clunk i have no issues with the axle.

Aren't the spider gears under essentially -0- torque while going straight?

well, they're under no rotation as they're just locking the side gears to the carrier to spin the axles. but they have load applied to them via the cross shaft. so i think if there's slop in there, it would cause noise as they are loaded one way under acceleration and loaded the other way under braking.

i pulled the shaft and got the gears out, there is enough wear on the pin where the gears ride to cause a ridge. the gears show some signs of getting worn on. when i slide the gear on to where it would ride on the shaft, it's got quite a bit of slop, like i can move the shaft enough to deflect it 1/8"+ on the other end. i put it back together as i can't get parts tonight and it was in the way, and i need it to get to work tomorrow. now i'm debating between new spider gears and cross shaft kit($168) or a powertrax lock right, as the "electric locking diff" is essentially an open differential with some electromagnet stuff that i haven't even hooked up, and that is $450. the latter sounds like the best option right now all other items in the case looking good, but if i spend that kind of cash and the thing still clunks i'll be sick.

for peace of mind i even pulled the shocks and ran them through their range to make sure one was not binding making a suspension travel clunk pretend to be inside the diff.

I have the Powertrax locker in my truck and There are compromises to taking that approach. For one your tires are going to wear faster. The Powertrax unit does have a relief mechanism to allow different tire speeds for turning but it requires a substantial friction at the tires to do it which makes for wear.

Second, and you will read about this in the user manual but not I the marketing stuff. There is a little bit of turn in that will occur when you accelerate or decelerate with engine load. You get used to it after a while but it's always there and can be annoying.

If I were to do it again I'd go with an air or electric locking diff. Being a Chrysler unit makes my choices pretty limited and therefore costly, but if I had a 14 bolt I would have ditched the Powertrax already.

Unless you are trail riding where 2 in the air happens often I'd even go LSD over a locker.....

Too much one wheel peeling. Get those spiders whirling, and they start to melt themselves and the pin. I might have had personal experience with this when I was a rowdy youngster.

As long as the pin hole isn't worn in the case, you can buy the kit of pin, spiders and side gears. I don't think they are even that horribly priced right from the general, but its very possible I am lying to you.

If you replace the diff, get a Detroit locker if you don't go selectable. There is a big difference between the operation of them and a "lunchbox locker" like a powertrax.

Also since you have a 14 bolt.. Add this to your bookmarks: http://www.pirate4x4.com/tech/billavista/14b_bible/

ok cool no powertrax, glad someone had experience. sounds like new spiders/pin are in order, and wire up the e-locker to a switch for when it is needed.

I'll jump on the no lockright bandwagon. I had one in my jeep. Its nice for a primarily trail vehicle, but they lack road manners for a street vehicle.

Yep. They're awesome in the front axle(unless you are using 4wd in snow ALL the time, still not bad though), but miserable in the rear.

When engaged they essentially lock the left to the right, basically a spool under power.

Detroit's on the other hand have a ratcheting mechanism on each side, when torque is applied it will allow either wheel to spin FASTER than the ring(meaning the outside wheel in a turn under moderate power). You're essentially using only the inside wheel to go forward under normal conditions.

Now apply enough power to break traction on the inside wheel, then it will be using both sides to go forward, chirping the inside tire to match the speed of the outside.

I had Detroit's F/R in my 1 ton TJ.

So i just got out from under the truck. The "fits all 9.5 carriers 81-up kit summit sold me, for $168.95, that specifically has 2006 in the package paperwork, doesn't have the right spider gears. Mine are convex with a thin stainless shim where they contact the carrier. New ones were flat with giant washer, also flat. No work. On top of that they had just as much slop on the cross pin that the existing ones have. Put it back together, again, and am leaving stuff alone. When whatever is clunking blows up, i will have successfully diagnosed the problem and can fix it then.

How worn did the cross pin look? From autopsying dead diffs, the gears don't wear nearly as much as the pins do, which kinda makes sense since the pin is fixed and only gets loaded in one small area per end.

My favorite was the pin worn almost all the way through on the end that didn't break. The gears were still a close tolerance to the unworn section of pin.

(well, gear. One was on top of the transmission, the other was AWOL)

The pin has enough wear that i can catch fingernail on it. Not much but visible, was angry enough that i did not measure before putting back in. On another note, no clunk today before or after. I have read the driveline clunk TSB as it relates to greasing the slip yoke to transfer case output splines and did that, maybe the grease worked its way into them all and "fixed" it. Who knows at this point, ive had the diff guts out twice in 3 days. And i got my 3500hd ready to put a flatbed on yesterday, started it, and while warming up oil pressure dropped to 0 and it started knocking. So between the phantom clunking avalanche, knocking 3500hd, knocking 9-7x, impala with cracked heads, and chevelle in middle of cancer surgery, i have too much going on to wrap my head around

Wait do you have a full floating 14 bolt?

If so its not a 9.5 ring gear... That is an AAM axle not GM. Same as front in RAM 3/4 and 1 ton trucks, except they use a 9.25 ring gear.

Take a pic of the diff cover.

No i have a 9.5 semi float 14 bolt from an h2 hummer. I know the difference, have a 3.73 locking full floater behind the garage. I should have kept the original rear and cut off the brackets and welded them to that one. I was going for bolt in though, and the h2 rear is as bolt in as you can get for more strength than the 10 bolt. That one ate itself so hard only the housing would have been salvaged.

patgizz wrote: No i have a 9.5 semi float 14 bolt from an h2 hummer. I know the difference, have a 3.73 locking full floater behind the garage. I should have kept the original rear and cut off the brackets and welded them to that one. I was going for bolt in though, and the h2 rear is as bolt in as you can get for more strength than the 10 bolt. That one ate itself so hard only the housing would have been salvaged.

Doh, didn't put 2+2 together that it was an H2 rear end, just read 14 bolt and assumed it was a real 14 bolt. The post about a 3500HD also threw me off.

FWIW I've had great luck with Chase at East Coast Gear Supply. Super nice dude, knows his stuff. He even sent me some ring gear bolts for free once.

the HD has a dana 80 in it not gonna break that one if i try.

i'll check them out. at this point i might try to just source a new pin and do it as time permits.

http://eastcoastgearsupply.com/i-19221811-gm-9-25-9-5-open-spider-gears.html

It sounds like you could get used cross pin and spider gears from any GM 9.25 front diff(from IFS 3/4 and 1 ton) or 03-06(at least, possibly newer) Dodge 3/4 or 1 ton 9.25 solid front axles. You should be able to find a good used set pretty easily.