Who actually has a welded diff half of these posts that are about welded diffs are only filled with negatives from people who haven’t actually had one. Who actually has a welded diff? Do u daily drive it? What bothers u the most? Any regrets?

 

I don't and never had have one so I cannot directly answer your question but I can comment on why it's not for everyone despite it being an extremely cheap way of getting both wheels to turn at the same time:

With a welded diff both wheels are ALWAYS turning at the same time no matter what. An open diff is extremely common and cheap to manufacture and while not good for high performance does provide an important function in that whenever the vehicle does anything other than travel in a straight line it allows smooth driveline operation and differentiation of the speed of the inside wheel versus the outside wheel.

In addition to providing a smooth and predictable driving experience it also prevents uneven wear on the tires and also doesn't transmit extra stress through the driveline.

With an open differential that has been welded you get a very crude 100% full time lockup of both wheels on acceleration, deceleration and through turns but as a consequence you also have:

--a tendency to skip your rear tires through turns since there isn't even a partial lock percentage but 100% lock which means both wheels are forced to travel at the same speeds.
--added shock/wear through the driveline
--full lock at all speeds and all conditions is not very good for rainy weather driving and can be far less predictable for some

A welded diff is a fairly common modification to have done for a budget track car or drift car. And most LSDs do tend to be the 2-way type that lock on acceleration and deceleration and also skip a little in turns but those are still not as severe and hard on the driveline as a welded diff.

FYI, there are LSDs such as Torsens or some types of OS Gikens (and various FWD application LSDs) that are 1.5-way locking which means they only lock on acceleration but not on deceleration. Used more in 100% street as well as road racing applications. These drive the closest to a stock open diff with the least amount of added tire wear, least amount of added driveline stresses and the most predictable (for most) handling and turning behavior *except* when you want to get on them and apply power on acceleration and through turns.

Additionally, Torsen T-1/T-2 LSDs, Quaife ATB LSDs and Wavetrac LSDs (all considered "1.5-way") are of the type that is always varying the application of torque between both wheels rather than providing a high percentage of lock or full lock the way 2-way clutch-type LSDs do.

And again, since it's a widely practiced modification on the cheap mostly for track cars, a welded diff is providing 100% lock ALL the time in all possible conditions which even in racing is not usually totally ideal. But it is inexpensive compared to buying any model of limited slip differential and getting it set up in a diff either as an upgrade from a factory open diff or upgrade from an unsuitable (for whatever the performance application will be) factory limited slip diff.

...

Those are the technical pros and cons.

As for the personal experiences of SC owners with welded diffs and how they feel/felt about them and how tolerable they felt they are this is where I'll step aside.

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How a common differential works:



How a traditional clutch-type limited slip differential works:



How a Torsen Type-1 gear-based limited slip differential works:


How a TRE gear-based limited slip differential works (similar to a Torsen Type-2, Quaife ATB, Eaton TrueTrac, Wavetrac and others):


Generally how to weld an open differential (you want the welds to be strong):


A couple of videos talking about what it's like to drive on the street with a welded differential:

 

ill take these things into consideration, the thing is im scared that i will end up buying a lsd that i think will both work in the manual transmission and auto because i want to be able to drift. If i want until i got manual its gonna take long and alot of money for that manual and a lsd

 

I've had a welded diff, and now own a Kaaz LSD. Obviously, the LSD is a much nicer unit and makes everything from burnouts, to track days, to driving to work easy as pie. However, welded diffs aren't the worst thing in the world. Will it spin the tires, yes. Will it do terrific donuts and burnouts, yes. Will it be annoying, yes (but not awful IMO). Will you eventually blow up the differential and perhaps toast a wheel bearing or two, yes.

If drifting and hoonery is your only goal, weld the diff, have fun, do a manual swap, and put a nice diff in when you have the chance. Just don't be too sad if/when you toast a diff. It's all a sacrifice and it takes some prioritizing to decide what's worth it to you.

 

^^ Very sound advice from Rudy! Key takeaway is what pros and cons an quirks you can live with as you prioritize over buying an LSD and getting it installed with the gear ratio you want.

On that note, 2jzali, are you planing to do a full Supra MKIV 6-speed M/T 220mm rear diff swap including the whole MKIV TT 6-speed rear subframe in order to work with a rare and expensive V160 transmission? Because if you are not going to do all of that very expensive endeavor then you will be buying an LSD for the much more common 200mm rear diff that came in ALL SC300's, SC400's, Toyota Soarer Z30's, Supra MKIV NA and TT Automatics, GS300's, GS400's and Toyota Aristos.

All of those cars (with the sole exception of original Supra MKIV TT 6-speeds that came with larger 220mm rear diffs) use the exact same open differentials, exact same factory Torsen LSDs and the exact same size and shape aftermarket LSDs in the 200mm size. Meaning... it doesn't matter if your car is automatic or manual when you install an LSD into the SC300/400 differential.

Driftmotion sells a full kit to rebuild any of the 200mm diffs that our cars use with the exception of specific thickness side shims that can only be ordered from Toyota based on measurements that your driveline shop will take once they are tasked with installing the LSD for you (and that is an important step for any diff installer to get right even if it is determined that no extra shims will be needed).

Other than that you just pick the aftermarket LSD you want (find yourself a factory 200mm Torsen LSD to install) and you're good to go. Just be sure you are good with the final drive gearing your SC's diff already has or if you want one with different gearing before you get started.

Some aftermarket LSD manufacturers require you to swap in specific NA axles when putting in one of their units but that really only applies to installs for Supra TT Automatic diffs with stock LSDs.

Rudy, when you did your Kaaz LSD install into your SC diff you required nothing but the seal and bearing rebuild kit, right?

 

Kahn,

I pulled the diff and dropped it off along with the Kaaz unit to a local gear and axle shop that said they would handle the work. They did preventatively replace the seals, however, they said the bearings (and all of the internals) looked like they day Toyota installed them so the originals were left in place. These cars are built so well, it makes me giddy!

Overall, the LSD is a big upgrade from a welded diff in many ways. However, a welded diff is damn near free and you can't argue with that.