Incase you didn't already know... Don't ever put a space saver on the rear of a WRX.

Curmudgeon wrote: The difference is the LSD plates are metal on metal rather than paper on metal and are thus more susceptible to galling due to spot overheating. The automatic transmission also has a constant flow of cooled fluid, again something a differential does not have. Some differentials have cooling fins on them to try to keep temps down.

I'm reminded of the massive finned rear housing cover BMW made for competition E30's. I'd imagine if a LSD was going to be subjected to constant heat, a cooler and external pump could be added a la NASCAR.

Knurled wrote:

Opti wrote: I know of a certain local shop that paid for a brand new transmission in a 380K mile camry because they didnt check the "diff fluid". Hint: Camrys diff fluid is seperate from trans fluid.

How old? A lot of Toyota transaxles do have separare differential fills. Right pain in the ass to get to the check/fill port, too, so a lot of people don't know it's there. Have seen a few cars junked because the diff bearings were shot and the car wasn't worth a transmission.

This was only on the Aisin automatics IIRC. The only one I had I didn't have long enough to bother checking, but the general consensus I remember reading was the seal between the two often failed and you really didn't need to worry much about it if the axle seals leaked or whatever, the leaky internal seal would actually keep the level a bit above full.

Catatafish wrote: On a related tangent, if I were to have 215/50/16 tires on 8" wide front wheels, and then the same tires on the 9" wide rear wheels, would that be bad on the diffs on a dsm?

As long as it's the same brand and size tire you'll have the same circumference, so the distance traveled per revolution will be the same.

I read about a company that specialized in building/tuning Evos that ran the same size tire front and rear with the front wheels the optimal width for the tires and the rears either .5 or 1 inch narrower to crown the tread a bit and add a bit of oversteer, IIRC.

As far as I know they didn't have any drivetrain issues directly related to that.

In reply to The_Jed:

Stretching the tire an extra inch will reduce the circumference, I'm not sure if it's enough to matter, but that's why they always give "measuring rim width" on tire spec charts.

In reply to Kenny_McCormic:

Not only that, but the tire width is greatly dependent on rim width.

That's tire width, because tire sizes take into account the whole tire and not the bulge. I remember cheap tires from years ago that were the correct section width, but had maybe 1-2" less actual tread width on them, compared to a decent tire.

Kenny_McCormic wrote: In reply to The_Jed: Stretching the tire an extra inch will reduce the circumference, I'm not sure if it's enough to matter, but that's why they always give "measuring rim width" on tire spec charts.

Yeah, well... you smell funny!

Kenny_McCormic wrote: In reply to The_Jed: Stretching the tire an extra inch will reduce the circumference, I'm not sure if it's enough to matter, but that's why they always give "measuring rim width" on tire spec charts.

circumference is determined by the belts, so although width is affected by wheel width, overall diameter/circumference is not affected by wheel width.

I'm confused. OP, did you cook your rear LSD, or did you cook your multi-plate wet transfer clutch (MPT)? (Or both?)

The MPT is pretty easy to protect. If you're going to be running a tire of the wrong size, you can insert a fuse to relax MPT engagement. On DCCD cars, you may be able to achieve the same thing using the console dial.

If you "cooked" the LSD, what does that really mean? My understanding was that this device achieves its limited slip action using a special fluid. There aren't any friction cones or other mechanical parts related to the limited slip action. If you abuse this sort of LSD, the special fluid will get really hot and thick... but unless it gets so hot and thick that it can melt steel, then the rest of the differential should be OK, right?

Or did you get the LSD fluid so hot that it cooked the MPT? I guess I can see that happening, but it wouldn't make the car unsalable (at least, no more so than a bum head gasket...)

Catatafish wrote: On a related tangent, if I were to have 215/50/16 tires on 8" wide front wheels, and then the same tires on the 9" wide rear wheels, would that be bad on the diffs on a dsm?

I know someone who used to run different wheel width on an AWD Talon years ago for the track and autocross. Lots of miles without any trouble. He ran the 9" rims in the front and the 8" in the back though, that's the better set up for a DSM or Evo. He also ran wider tires than 215's (245's I think).

As far as a tire low on air, that shouldn't make much difference in the circumference of the tire. It changes the shape, but any given point on the tread would travel the same distance per revolution. There would be more drag on that corner, but that is from the tire, not the diff.

Opti wrote:

Kenny_McCormic wrote: In reply to The_Jed: Stretching the tire an extra inch will reduce the circumference, I'm not sure if it's enough to matter, but that's why they always give "measuring rim width" on tire spec charts.

circumference is determined by the belts, so although width is affected by wheel width, overall diameter/circumference is not affected by wheel width.

Good point, forgot there was steel in there, any stretch will be in the sidewall.

In reply to b13990:

A 2002 WRX wagon, if it has a manual transmission, has a purely mechanical drivetrain, there is no "put a fuse in" for those.

I know a guy who did the same thing and his rear LSD diff was toast. As in, it had to be replaced.

I have to say that this thread has been pretty eye-opening. Based on what I now know, Subaru is now off any and all future purchases.

Actually...any 4wd is off the list. Way too much of a hot-house flower for my taste.

NOHOME wrote: I have to say that this thread has been pretty eye-opening. Based on what I now know, Subaru is now off any and all future purchases. Actually...any 4wd is off the list. Way too much of a hot-house flower for my taste.

Careful, that sort of talk will get the mounties knocking on your door to remove your Canadian citizenship.

In reply to NGTD:

Yeah, so that car has an open/mechanical center differential and a rear LSD, right? And the rear LSD would be of the viscous type. So I guess the OP burned up the viscous LSD somehow? I'm wondering what that entails. Generally, if you abuse an OEM limited slip axle, you might lose the limited slip capability, but I don't think the car would be undrivable. The head gasket seems like a much bigger issue to me.

In reply to b13990:

I went back and checked the thread the guy posted way back in 2011. He pooched his centre diff, not rear diff.

Coles Notes - Overheated centre diff caused binding, this lead to snap rings in diff shattering, and the pieces floated around in the diff making a mess.

NOHOME wrote: I have to say that this thread has been pretty eye-opening. Based on what I now know, Subaru is now off any and all future purchases. Actually...any 4wd is off the list. Way too much of a hot-house flower for my taste.

That's too bad. Living in Ontario you are missing out on one of winter's great driving pleasures..........a hot AWD vehicle. I am talking STi/Evo/Audi kind of thing here. The Subaru hate in this forum is getting ridiculous. I am picking up my sixth Subaru this coming week, a 2015 WRX and I can hardly wait. All have been completely trouble free and for the price there is simply nothing else like them.

Feedyurhed wrote:

NOHOME wrote: I have to say that this thread has been pretty eye-opening. Based on what I now know, Subaru is now off any and all future purchases. Actually...any 4wd is off the list. Way too much of a hot-house flower for my taste.

That's too bad. Living in Ontario you are missing out on one of winter's great driving pleasures..........a hot AWD vehicle. I am talking STi/Evo/Audi kind of thing here. The Subaru hate in this forum is getting ridiculous. I am picking up my sixth Subaru this coming week, a 2015 WRX and I can hardly wait. All have been completely trouble free and for the price there is simply nothing else like them.

Yes to all of the above - I have had 2 - 97 Outback and an 02 WRX. After I fixed the deferred maintenance issues from the PO's they were as problem free as anything I have ever owned. I live in Northern Ontario and they were fun cars and I was not easy on them. Used both of them to run on rally roads as part of the volunteer work. Rally-X etc. They never wimpered - just rusted .

The Subaru mechanical AWD actually works all of the time as opposed to most of the electronic systems that only work when slippage is detected. That is why it needs a little more care. I used to look forward to it snowing, not so much any more with the Golf.

Lof8 wrote: Northern cars sound miserable. FL has $1500 hard top miatas rust free :)

Possibly true.

However you also enjoy city block sized sink-holes, hurricanes, gators, etc. You could probably buy a new car every time one rusts out on salt for less cost than the premium you are paying every year for homeowners' insurance. And we don't have to worry about packed Hurricane Escape Routes either.

I just never put a space-saver on the driven axle. I learned it from a former GM tech.

Kenny_McCormic wrote: Never put a different diameter tire on any axle equipped with a limited slip or locking diff. IIRC the Subarus do come with a donut spare, and its safe for the center diff below 45mph.

This.

Subaru doesn't have some VW AWD system, it's mechanical.

G_Body_Man wrote: I just never put a space-saver on the driven axle. I learned it from a former GM tech.

so if you had an AWD, would you replace the spacesaver with a full size wheel and tire ?

In reply to wbjones:

Yup. A Bugeye WRX with rally lights, mud flaps, and a roofrack carrying a jerry can and a full-size spare would be badass.

G_Body_Man - you forgot a skid plate (I skipped the roof rack and Gerry can)

In reply to NGTD:

You're right. Maybe I'll add a 1" lift and Cragar Soft 8s while I'm at it.

G_Body_Man wrote: In reply to NGTD: You're right. Maybe I'll add a 1" lift and Cragar Soft 8s while I'm at it.

Springs and struts from an Outback Sport will get you 1" or Forester struts and springs will get more like 2". I think the combo to use is WRX springs on Forester struts.

I sold mine before I got a chance to lift it. The rust bug got it pretty bad.

Mud flaps made from IKEA cutting boards and light bar made from the arms of an office chair. Unfortunately the IKEA cutting board don't like the cold. I have new ones made from a mudflap from a semi, but now I don't have the car!