View Full Version : Welded differential... not safe?

03-12-2002, 06:29 AM
Last time I posted asking about welded differentials most of the responses said that it was not safe, and a very rough ride (etc, etc...).

But I keep wondering about it. I don't really understand it.

Can somebody tell me why a welded differential is unsafe and rougher than the regular S13 open diff? Or any different than a limited slip differential (other than the fact that it is always locked)?

This is one area of automechanics that I really don't know much about. I am looking to be educated here. Thanks in advance to anybody who can school me.

The Yak
03-12-2002, 06:44 AM
Witha welded dif, both halfshafts spin at the same speed since the torque is being split evenly between the wheels all the time.

Normally during a turn, the inside wheel tends to spin slower than the outside wheel since it has less of a distance to travel. But with a welded dif, the wheels can only spin at the same speed. The inside wheel can't slow down and let the outside wheel "catch up". This creates stress on the halfshafts, the dif and the wheels themselves. The inside wheel will slip and the halfshafts will eventually break. You can also cause damage to the dif itself.

This is why welded difs are a good idea for drag race vehicles as the only time they need to turn is getting on and off the strip.

03-12-2002, 10:38 AM
The heat from welding the differential weakens the metal. It gets dangerous because it can fail.
Drag racers usually us a locker differential or spool. A locker is a normal differential but is able to lock both axles. A spool I don't think is a differential but a solid piece that turns both axle.
But for street/strip a limited slip is the norm.

03-12-2002, 11:35 AM
You can Road race with a welded differential!!!
I have been doing that for years. The breakaway torque on a normal LSD unit in the datsuin/nissan rear ends is about 35 ft lbs. Almost nothing, when I had the LSD installed in the 510 whenever the inside rear lifted (of a burm) it would spin. That means the LSD was being USELESS. With a locked diff i actually have 2 wheel drive. As far as having one on the street, in normal turns it would be barely noticable, get into a parking lot and you will notice. Yes it will be louder, the erar end will also step out a lot easier and it will be very tricky to drive int he snow, and in overly wet conditions. But, as far as fun factor, you will be able to take on ramps at about 50% faster then you are currently.


03-12-2002, 02:19 PM
i run a welded diff and the only complaints i have are that it eats my tires a lot cuz i do too many donuts, sliding, drifting, burnouts etc. excellent fun factor.
As far as breakage or whatever i have lots of frends that have been running these for years not in nissans but they have no problems.
car will step out a lot easier though but ive gotten used to it.

03-12-2002, 02:25 PM
you can just think of a welded diff as a NSD (NO slip differential) have fun breaking axles with that

03-12-2002, 03:37 PM
Thanks for all the info guys. I feel like I understand a lot better now.

I plan on swapping in a CA or SR just outside of a year or so... With the greater power it sounds like I should be worried about breaking something in my poor 13 year old car. in the mean time, I think I'm going to stay open or maybe do the J30 swap.

06-27-2003, 01:30 AM
can you weld a stick 240sx open dif and create the same sort of posi or locked dif your talking about?

06-27-2003, 07:15 AM
can you weld a stick 240sx open dif and create the same sort of posi or locked dif your talking about?

Did you read any of the post above? That was the whole topic. And what in hell is a 'stick' dif?

06-27-2003, 06:22 PM
hi guys,
ive been driven my car(not a nissan but TOYOTA) with a welded diff over 5 yrs now!!!!!
did street&strip racing,burnouts,donuts etc etc.
only turndown is it EATS up your tires very quick,and parking is a hell of a job--but once you go welded ull never go back!!!!!!!!!!!!!!!!!!!!!!!!!!!!