LSD or Open Differential questions

[Deadly BlaZe]

There is already a similar thread open but I don't wanna hijack it. I'm a bit confused about the whole LSD/open differential thing. For example, my center differential has a viscous coupling and i have the orange warning sticker on my door jamb does that mean i have an lsd rear end or just a center lsd? I guess what i'm asking is, between the center differential and rear differential, can one be an lsd and the other one not? Or are both lsd's?

 

[xveganxcowboyx]

All AWD DSM's have a viscous differential in the center. This is how they divide power between the front and rear. The rear differential divides power between the two rear wheels and can be either open or limited slip. The sticker indicates the type of rear differential. If you want to confirm you can look at the plate on the top rear of your differential and see if it says LSD.

 

[Deadly BlaZe]

Ok so do rear diff's have viscous couplings inside? And also, aren't all 1g's lsd's? And when someone asks if you have an lsd, are they referring to the center differential or the rear.

 

[xveganxcowboyx]

I honestly don't know enough about differential operations to give you a full break down. I can tell you that many 1G's come with open differentials (for instance, early ones could have only ABS or LSD, not both). A viscous LSD obviously uses that design to divide power. My understanding of open differentials is that it's simple gears and just transfers power to the path of least resistance. Again, I'm no expert. I think there is also some difference with the center differential being torque biasing, but some one else will have to go into detail on that.




If a DSMer asks you that question they are probably asking about your rear differential, possibly your front. They would have no reason to ask about the center, because there is only one option. If someone else asks you that question you may just have to explain how the whole AWD system works. Limited in the rear, open in the front, etc... Most cars only have one differential so the question is simpler for them.

 

[Deadly BlaZe]

So then if the center diff has a viscous coupling, the center diff is an lsd?

 

[steve]

So then if the center diff has a viscous coupling, the center diff is an lsd?

Yes stock the center diff has a viscous coupler for limiting slip so you have LSD in the center. In the rear is was an option.

 

[Hideki]

<---I'm in no way an expert on AWD DSM's but common sense tells me that since a FWD LSD's will make both front wheels spin at the same rate, a center LSD would theoretically spin both the front wheels and rear wheels at the same rate. A 50:50 split, but wouldn't that create a car with incredible understeer?

 

[xveganxcowboyx]

The wheels do indeed get equal power in most cases and yes this results in understeer. The differential can distribute power to slipping wheels though.

The stock 50/50 split is a bit annoying.

 

[Deadly BlaZe]

Yes stock the center diff has a viscous coupler for limiting slip so you have LSD in the center. In the rear is was an option.

Ha I'm glad you chimed in, you seem to always answer my questions correctly. So do lsd rear ends have viscous couplings in them or no?

 

[Tri-Edge]

Mine had a plate on the Diff itself that said viscous lsd...so take a peek under the back..
plus

http://en.wikipedia.org/wiki/Limited_slip_differential
I learn a lot from there

 

[steve]

So do lsd rear ends have viscous couplings in them or no?

A rear viscous coupler LSD was an option. I don't think is ever was standard even though many cars came with them. If your came originally with one it should have the orange sticker in the drivers door frame. As has been pointed out the 90 and 91 cars with ABS will not have the rear LSD option from the factory because until the change to the four channel ABS in 92 the options didn't work together.

Steve

 

[eclipsegsx1736]

AFIAK, the 99 is the only year that had the LSD standard, but from what I've seen, most 2gs have the LSD and the % increases with each year. Mine didn't have the orange sticker, but as was said before, the rear diff case itselft has a sticker on it that says Viscous LSD.

 

[xveganxcowboyx]

A rear viscous coupler LSD was an option. I don't think is ever was standard even though many cars came with them. If your came originally with one it should have the orange sticker in the drivers door frame. As has been pointed out the 90 and 91 cars with ABS will not have the rear LSD option from the factory because until the change to the four channel ABS in 92 the options didn't work together.

Steve

Could you elaborate on the ABS/LSD problem. I swapped a LSD rear end into my 91. I've had the abs relay pulled for a long time, but had planned on fixing the wonky sensor at some point. What sorts of problems might result?

 

[steve]

You'll have to ask Mitsubishi since I don't remember the details of what the interaction problem was only that there was one and that the options were exclusive.
I asked when I bought my car and while I'm 100% sure of the issue, after 15+ years, I don't remember anything more than the 3 channel controller for the ABS didn't play well with the rear LSD on the 90 and 91 cars.

Steve

 

[xveganxcowboyx]

Maybe I'll just try and find out. My guess is Mitsu was being paranoid.

Ok, maybe I'll do some searching first...

 

[AndrewD5418]

Ha I'm glad you chimed in, you seem to always answer my questions correctly. So do lsd rear ends have viscous couplings in them or no?

I think they started adding both LSD and ABS on 93+.

Before that, if you chose LSD, you did not get ABS?

 

[steve]

I think they started adding both LSD and ABS on 93+.
Before that, if you chose LSD, you did not get ABS?

Like I said above, it was the 92 model year when it changed, prior to that you could either get ABS or rear LSD but not both.

http://members.shaw.ca/costall/1000Q/answers-makeandmodel.htm#whatarethedifferencesbetweencars
Sean's data agrees with my memory.

Steve

 

[Defiant]

And yes, all the LSD arrangements in DSMs were viscous. There are mechanical aftermarket LSDs available, both erstatz and genuine.