If I were to have the open diff of a 1st gen tig welded, about how long would it last? I don't really want to get an old LSD and have it not work well, and I don't want to make the car unreliable either, and I hate open diffs with a passion.

 

Why do you assume that the LSD wouldn't work? I've never had one that didn't.

 

My guess would be that it would last that long on a street car. It's not a good way to go at all man, LSD's offer some slip because when your car rounds a corner, the inside wheels travel slower than the outside wheels, so either A) they slip (in the case of an open diff or a -Limited Slip Differential) or B) they squawk because they're welded (or are a crazy tight LSD) and won't allow the two wheels to travel at different speeds.

Question is, if you're road racing, or taking a long sweeping turn on a highway, how much force will it take for the speed differential of the two wheels combined with the traction of the tires to tear the welds apart?

 

That is a good point. After reading about it I probably should go with an LSD when I get an RX7. I will most likely hurt the cars turning ability with welding the open diff (probably making it more spin happy as well), then there is the issue that Trots brought up with the welds eventually breaking from constant stress. Crits, I originally thought that an old LSD would not be too effective, however I see that you can rebuild them, which is probably the route I will take.

Just for clarification I wanted to know how long a welded rear diff can last. I changed the title from how much abuse can it take, but I figured I wouldn't be abusing it all that much, so that title was irrelevant.

 

Welding a diff isn't always a bad idea, depends on what you want to do with the car and, just as important since everyone neglects this in this argument, your BUDGET.

everyone knocks them, but I've driven LSD/Welded/Open and they all have their place.

As far as it will last.
that depends on your driving style. Expect the other gears in the pumpkin to break before a properly welded diff will.