It didn't take long to screw up my rear diff.
I welded up the spider gears on my H150 this past summer and then supercharged the motor. After our 2 weeks of snow here in Seattle I finally got a chance to get the car out of the garage and go for a spin. Drove it out to my test strip were I test and tune the motor (county road). Rev the motor, drop the clutch, hit the NOS and smoked it off the line (now mind you, I've done this many times before). When I started to slow down, I heard a noise in the rear but it wasn't all that loud. Drove it home doing 15 mph. Jacked the car up and spun the rear wheels. The right wheel turned the driveshaft when I spun it. The left wheel was slipping when I spun it. Left wheel shaft is not broken otherwise I'd be able pull it out so it is still connected to the gears but not connected to the right wheel or driveshaft. Not sure if it's just my weld on the spider gears that broke or what?
I won't be able to pull the thing apart until Monday.

why would you be able to pull the axle out if its broken?

they always break at the end of the splines as thats the weakest point in the axle, then the axle just cruises around inside the diff smashing the parts of the centre that it comes in contact with

the axles arent like alot of older bigger car axles that are undersized the whole way and break on the outside of the wheel bearing, causing the wheel to fall off

but yes its either a broken axle or the welds in the centre werent up to the job and have broken

Hummm.....
Well the left axle is not smashing around in there and it seems pretty tight with tension when I spin it. It's just not connected to the other wheel or the driveshaft. Very little noise when I was driving down the road. There was no noise when I spin it on the jacks.
I must have broke the weld.

mmm lack of noise is interesting

coz for it to loose drive to one wheel and not break the axle means that its broken the welds on one side and then smashed all the teeth off that spider gear so that it can spin freely....but that would surely be making some noises

Unless the inital noise I had grounded the teeth clean. At that point I would have been at full throttle and the car is pretty loud.

I guess I won't know until monday.
I hope it's just the welds. I only tack welded each point of contact on the spider gears. I've seen pictures where someone filled it in completely. I hope I still have a chance to do that.

if the axles still intack and the gears havnt caught any of the loose bits of metal then i dont see why you wouldnt be able to weld it back up again

really do need to put more than just a couple of tacks if you want the diff to stay locked

You should put this thing on a dyno once you've got your rear axle woes sorted. I'd love to know how much power it makes.

Going to pull the diff apart tomorrow but got a lead on a new diff. There is a lady here in Seattle that I have know for years that deals with vintage Datsuns. Pre 1200 stuff. Never had a need for any parts from her but she's got some rear diff's out of some 411's.
I believe these are H165's, I think.
We'll see tomorrow what my H150 looks like.

I think the 411 came with H190 diff. Should be plenty strong.

Sounds like a little ball tearer.

+2 for dyno