I have a truck 12 bolt that I put a eaton posi in. Check out the weirdness at the very start of the video, it does this in reverse or forward only once then I don't get it until I change direction again and hit it with some throttle. Feels like I don't get it if I ease onto the throttle.

https://photos.app.goo.gl/TqLJ9vQSt4ECUnx7A

When I took the rear apart both the ring and pinion gears were in great shape.

Any thoughts on what this is?

 

I should have mentioned I installed a new tranny. Its a Hughes 4l80E Hughes 25-1bhd

 

Just curious, does it sound as violent as it looks? I had an old school 12 bolt that pinion seal and bearing was trashed, that allowed pinion to move in the housing breaking the teeth off both gears. It made a lot of noise from a stop but was quiet down the road...for a little while LOL! Does that truck have a carrier bearing?

 

It for sure has a thud to it, no carrier bearing, it's a C10 SWB.

I'm wondering if an over filled tranny may have caused the weirdness. Like could it have hit reverse/drive?
OR
if there something wacky with the posi unit which for the life of me I can't figure out what that would be.

The rotational play seen in the video after the initial weirdness does not alarm me and does not seem overly violent at all.

 

Any luck figuring it out? Is that posi unit a clutch plate type or cones? Clutch type has to have the additive. Just a thought, Is U-joint trashed?

 

It's an eaton posi so clutch style with stock spring pressure. I did put additive in as well when I re-filled it. Also the shaft and ujoints are new so no worries there either.

I'm starting to think this is more of a tranny problem. It's hard to see in the vid but it almost looks like the drive shaft is being twisted forward and back when I put it in gear. I'll drain some fluid and see if that helps, there might be too much fluid and while I don't know how that would create this problem I might as well dump some and see what happens.

If that doesn't work out I'll pull the diff cover and take a peek at ring gear and inspect the posi unit.

also I work slow so updates on this are gonna come in over time.

 

LOL, gotcha. Take your time. I'm recovering from surgery so moving pretty slow myself.

 

That does not look to be a differential issue. It recoils for a second hit, my guess is Tranny.

Miles