So, welded up a differential i had laying around for my car, mounted it and tested it. As soon as i put second gear i started hearing some whining noise.
This noise got worse as i got more speed. I Assume it's some trouble with the shims ?
I drove the car like this for about a month, and yesterday the differential broke down. Not surprised:p

So, installed the original diff today, and i'm still having these noises, and they are bad.
So, is the problem the shims, or do i need to swap the pinion ?

Have you been swapping the crown wheel and pinions as pairs?

It's much easier to swap complete casings, but no idea if that's doable when welding one up.

how much and what type of oil did you put in the diff?

did you refill the gearbox oil?

Isn't the differential and gearbox separate? I did not refill the gearbox, but the noises are clearly from the diff.
The sound gets higher as i pick up speed, and it's the same in all gears. I'm 100% sure it's not the gearbox.

I used SAE 80W/90 Mineral in the axle. I filled it up to the "inspection" hole on the back of the axle, filled it to the oil started dripping out again.

Is this a 4 or 5 speed?

If its a 4 speed there are shims that need to be there between the gearbox and diff, aswell as the correct gasket. For example if the gasket for the front of the gearbox is used by mistake you will get a similar problem because its much thicker. The gasket and shims must be calculated together.

I did not switch crown and pinions as pairs. If this is the case, then i guess i'm fucked.
It's a 5.speed.