THSCC Forums

Anybody know what the default split for the center diff on a ’92 Laser is? I tried looking around some of the DSM sites but couldn’t find anything. If anybody has a link or something that goes into excruciating detail, I’d love to see it.

I was playing around in the rain today and under full-throttle from a near standstill (1st gear), I noticed I could spin the inside front tire. I couldn’t feel any of the other tires spinning and while I’m sure some of the power was transferred to the rear, it didn’t feel like enough to cause any rear traction issues.

Everything was happening so fast that it could be I just wasn’t able to feel anything going on the with rear of the car yet. It did amaze me how much power the thing was still putting to the ground even in the wet conditions and it made me curious as to what was going on underneath the car. If I tried anything like that with the Miata, I’d probably still be spinning in the road-- or perhaps the ditch.

Anybody have any thoughts?

Thanks,

Jim

Yeah, the Subarus spin the inside front tire, too. Front LSD would help; if the RS transmission has to be opened up for some reason, pretty sure one will be installed.

I'm assuming that is partially because yours has an lsd in the rear? I know some models did and some didn't but vaguely remember Peter Baio (at least I think it was Peter) telling me that yours did. I don't know how front-biased the Subaru center diff split is but that could have some effect.

Any idea on the split for your car and how much will get sent to each end under extreme conditions? I believe Kristin's BMW has a fixed 37/63 front rear split with no front or rear lsd. I think I remember Kristin telling me that she saw a couple strange circumstances in snow/ice where the car didn't want to move at all. Given the (presumed) setup, I could see that.

At this point, I have no idea if the Laser has an lsd in the rear or not-- I know for sure it doesn't have one in the front. I couldn't seem to find much on the general layout of these cars. Lots of go-fast stuff, though. It's possible the rear isn't working hard enough with a front-biased split to ever spin the rear tires unless there is an extreme difference in front and rear traction.

Jim

The static split is 50/50, and it does have a rear LSD, pretty surprising in that car. AWD Lasers are pretty rare in the first place, and a rear LSD are quite rare. There was a thread on one of the dsm boards once that I participated in that discussion rare DSM combination, on that car was pretty high up there.

Lets open our Mitsubishi Factory Service hymals to Section 21 page 9

"...center differential normally splits power 50/50 ..."

A discussion on the topic can be found here:

http://www.dsmtalk.com/forums/showthread.php?s=38531739b06b730ecfc0552899a27da2&threadid=79314&highlight=Front+Rear+Power+Split

If you have a LSD in the rear its easy to check. There should be 2 stickers on the car. An orange one inside the drivers side door jam (right where the lock latches) and on the rear differential itself. Its white with black writting and says "B16 LSD"

_________________
02 Focus SVT
STF 9

Party on! Thanks guys...

Jim

My Impreza has 50/50 split until one end of the car slips. Then up to 90% of the power is transferred to the end with the most grip. BUT - if you start off turning, and give it enough power, it will spin the Hell out of the inside front tire - like it did Friday night. Still sends enough power to the rear LSD to get it moving pretty quick, though. At least that's what I think Christine meant by, "holy shit."

So how long does a rallyxed/autoxed/generally abused viscous LSD last? And how do you know that it's done?

would it be possible to just change the fluid like you do with brake fluid. I'd think the constant heating and cooling of it would break it down after sometime.

_________________
2006 Civic Si - #24 HS for 2015

2005 GMC Sierra
1991 318is Garage Ornament

Rob - you are absolutely correct - over time, the fluid (really more like goo) in a viscous diff does break down and can no longer lock up the plates and transfer power evenly. It pretty much acts as an open diff after that. You'll find burned out viscous diffs in old Miatas, 240sx's, and plenty of other cars. The viscous diff in my Miata still works!!!

Of all the driveline-related failures in AWD DSMs (I used to have one...), the viscous part of the center diff is decently hearty. Of course there's a known weakness in the transfer case where the transmission fluid leaks out and it may lock up, and you lose control of the car This is a TSB, and Chrysler/Mitsu have to replace it for free.

Every AWD DSM I know of has had the transfer case replaced at least once.

_________________
Tom Freeman
'98 M3/4/5 | '93 Spec3 325i | '12 TSX sport wagon | '03 Tahoe
Team Silver Bullets '91 240SX

What Tom said. The fluid definitely breaks down over time causing the diff to act like an open unit. The 90-93 Miata vlsd's weren't known for their durability and it's usually hard to find one with high miles that still functions properly.

Tom, you sure that thing is still working? How many miles if you don't mind me asking? The Miatas are balanced enough that sometimes it can seem like they are working but it's really just the chassis masking the fact that it has gone open. But it is certainly possible if the car hasn't seen a lot of hard miles.

AFAIK, they aren't serviceable once they fail. While I'm not sure about other cars, I'm pretty sure once the Miata vlsd has gone open, it's not going to be fixed. I believe the units are sealed and even if you could get them open, you can't really get the fluid. Somebody please correct me if I'm wrong...



Dang, another thing Les didn't tell me. Good thing I still owe him money!

Jim

That's a good question. With the Miata, I've heard of them becoming open with less than 20k miles if they are driven hard enough. How much of that was track/auto-x driving, I have no idea. I've also heard of other lasting well into the 100k range but that was mostly (if not all) street driving.

With the rwd Miata, it's usually fairly easy to tell if it's done-- it acts just like an open diff spinning the inside tire under heavy load. As far as the center diff in a Subaru or other awd vehicle, I guess it should act much the same way as a rear one failing on a rwd vehicle. If one end start to slip, power never gets transferred to the other one (duh). That's probably not something you could really tell in daily driving but I would imagine it would show up under heavy driving conditions.

I saw a story on one of the dsm boards (in fact, it was part of the above link that Ryan posted) that somebody bought an awd dsm with the rear driveshaft disconnected. He apparently didn't know it for a long time and didn't find out until he took it in to get serviced one day. How much of that is true, who knows?

Any long timer scoobie drivers, dsm'ers, etc. ever have any experience with this?

Jim

I bought the car in April with 72K, and it only has 76K now. I have done the "spin the rear wheels" trick, and they indeed spin in the same direction. The car was babied from new by an affluent older couple who owned 2 other Miata's and an S2000. That car lead a very easy life before me.

Jim - don't worry - the transfer case on the white car has been replaced, I can almost guarantee it. They all have.

As for the disconnected driveshaft story - that car probably had a welded center diff. If it still had the viscous, it probably burned out in a couple hundred miles. As you've probably read, lots of the drag race DSM crowd has the center diff welded for a constant 50/50 split regardless. Some folks just do it so they can dyno it on a 2WD dyno.

_________________
Tom Freeman
'98 M3/4/5 | '93 Spec3 325i | '12 TSX sport wagon | '03 Tahoe
Team Silver Bullets '91 240SX

I'm not one to argue , but....

I would at least be concerned with it. If you ask the dealer, they can not confirm whether it has been replaced or not, they can only confirm whether the car was brought into the dealership to be inspected. If it wasn't leaking at the time, then they sent it right back out with the faulty part.

It's an easy inspection. If it's leaking, then there will be overspray from the fluid coming out of the bushing onto the driveshaft. Just look at the front of the driveshaft and then look for overspray on the bottom of the car.

I've had my transfer case lockup and it was no fun at all. Luckily, I was only going about 35 when it locked since I had a warning. If you here something similar to spoons being banged together under your car, then slow down.

_________________
In need of car.

Well, I don't know if the transfer case has been replaced or not, but I did check it and change the fluid. It had no leaks and had the full .5 qt of oil it was supposed to have. Pretty impressive for 170K. If it hasn't been replaced, I think it would be safe to say it will be ok regardless, I could be wrong though.

I'd say that the older it gets the more it needs to be checked.

It's so easily checked that I made a habit of checking mine almost every time I jacked the car up.

_________________
In need of car.