I was leaving my buddies house amd went to grab 2nd I heard a bang and some grinding and there I sat I ran home and grabed another truck and trailer and was on my way to see the damage
I pulled the cover and found that I granaded the power lock diff and now I'm down to one cummins powered truck on the road the bad part about it is the truck has only been on the road since I put the getrag in it about a month ago

 

wow you must have REALLY grabbed it!!! hmm 4.10 or 3.54

 

he has 3:54

 

I bet the clutches were long past shot. When the clutches in the Powr-Lok design get worn, the side gears move away from the spider gears. Eventually only the tips of the gear teeth are engaged - and then you are one firm shift away from breaking the rear.

Good news is that a new set of diff gears and clutches will fix you up. Should cost around $250 and take you a couple hours in the driveway.

Anybody who has unexplained slack in the driveline really needs to take the cover off the diff and have a look inside. The open diffs eat cross pins (especially if you spin the tire a lot) and the LSD's need the clutches replaced about every 100 - 150k.

Here's what it looks like just before it breaks - mine had about 1/4 turn of slack.

 

Great, something else to be paranoid over .

So you measure that 1/4" at the pinion yoke right? How much it rotates freely inside the pumpkin.

 

The open diffs eat cross pins (especially if you spin the tire a lot)

They sure do. Been there done that X2.

 

I have an auto, I reckon they're in those as well? I have a lot of slack in my drive line. Been wondering whats going on and planning on taking off the cover, just haven't. I just have an open diff. So what exactly is it that I need to replace and how? If ya don't mind explaining. Thanks!

 

Not 1/4" - it was a quarter turn! 1/4" would be fine, no problem there. Do it with the cover off to make sure it's not excessive R&P wear - although you will normally hear a R&P howling before it gets that bad.

 

The cross pin is the shaft the spider gears ride on. You need a new cross shaft and new spider gears.

The basic procedure for repairing either type of diff goes like this:

Lift and support truck as needed for adequate working space behind the diff and chock a wheel. Removing the spare tire helps here. Pull the axles and the diff cover. Mark the bearing caps for proper position and orientation and remove them. The diff will probably not fall out, it will require some prying if the bearings are good. Keep the races with the bearings if you are not replacing the bearings. R&R the bad parts in the diff. Put the diff back in, this will likely require a mallet and some beating. Torque the bearing cap bolts to 90 ft-lbs, reinstall the cover and axles, fill with oil, and enjoy. Couple hours tops.

 

Oh yea , now I see it...

 

Could wear in these gears give a nasty, nasty clunk when on the throttle hard in 4x4?

 

It'd do it in 2wd as well.

 

Going through the same thing with mine. Noticed the excessive slack/clunk when dropping in drive or reverse but was too lazy to check it out..........until it let go on the way home the other night. Fond the kit with everything you need down to the additive on Ebay for $200.00 plus $10 freight. Speaking of which I guess I should order that now.

 

What are some signs that a rear end is on its way?

 

where would you order the parts to fix this.