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How to determine if you have an LSD?

A

AGrayson84

CEG'er
Joined
Aug 20, 2013
Messages
329
Location
Annapolis, MD
Hi fellas, at least at some point in the relatively recent past my car apparently had a Torsen LSD in it. The person that installed the LSD told me that the car still had the LSD when he sold it to the person that had the car prior to me.

Without popping a CV axle (half-shaft) out of the transmission, I was wondering how you can determine if the car still has an LSD. In a RWD car you can tell by getting on a slippery / loose surface and mash the throttle to see if both wheels spin.

I've noticed on wet asphalt only one wheel seems to spin My front tires aren't great, but they still have a bit of tread on them and when trying to slowly accelerate in the rain I usually get some wheel-spin. Probably because of the low final drive on these cars. But even when I mash the throttle I still only get one wheel to spin. Surely I don't have an LSD in the car anymore, do I??

-Andrew
 
I think if you jack the front of the car up and spin one of the tires with the car in neutral, if you HAVE a LSD both tires will spin the same direction. If you DON'T have an LSD the tires will spin opposite.

Also, if you do have an axle pulled out, if you see a big dowel looking piece going across the opening of the transmission then it has a stock differential. If you don't see a big dowel, and the surface is flat with a small hole in it then you have a LSD.
 
Thanks! Great info! So what is the purpose of an LSD on these FWD cars if only one wheel spins when the tires slip?? Or is the Torsen LSD more like a Quaife, where I've heard it's a "torque-biasing" differential, not a true "LSD"?
 
^ not sure entirely what or how they work but you should be able to do a 2 wheel peel pretty easily. :cool: :D
 
My Torsen will allow a good amount of one-wheel spin before it "locks in".

If I 3-wheel it off a steep driveway and lift one of the front tires, it will rev and spin the unloaded wheel plenty.
 
AGrayson84 said:
So what is the purpose of an LSD on these FWD cars ?
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The purpose is because any stock differential made after mid 1997 were manufactured using BUTTER. The only good replacement parts for a blown out stock diff are the Quaife and Torsen LSD "torque-biasing" setups. Expecially if you have a 3L, you will be sending that much more power to the already weak stock differential. I know of people that finished a 3L swap, left the transmission differential stock, and blew out the diff in a matter of days because it couldn't handle the extra torque of the 3L. Shoot, they barely hold the power off a 2.5L :eek: !
 
Well dang.... that sounds almost useless for any instance other than being stuck in snow or mud, after you have been spinning for a while. Not very affective for racing or 1st gear rolls in N/A cars. Must be totally useless in a turbo/supercharged car. Like stated, it is at least a good replacement for the factory differential. I had '92 SHO with an MTX making about 50 more horsepower than stock, and I just sent my stock diff to have the pin welded and reinstalled it. Worked like a charm. A Quaife would've been nice, but didn't have the money for that years ago. :)
 
You're probably the first person I have ever heard talk bad about a Torsen or Quaife in a Contour. It's pretty much a necesity on this platform. It is very effective for racing, any kind of rolling start, and is the only option for a turbo/SC Contour..... :confused: :shrug:
 
Sorry, definitely not trying to come off as "this sucks" and "that sucks" kind of person! Lol. Was just saying that if one wheel is spinning for 3+ seconds before they both grab then it's not as beneficial as a legitimate LSD. By the time both wheels grab, you already lost the race because of the lack of traction.

I still admire the fact that it's a solid replacement to the grenading factory differential. But as far as the performance aspect of it, I do single wheel-spins in 1st gear rolling starts until I reach second gear and no longer have the power/torque to keep the wheel spinning at that speed. That's not beneficial in the performance aspect, to me. But maybe I no longer have an LSD. I'll check this weekend.
 
I see what you're saying. Honestly, 75% of the time both wheels are working when you need them. When you "3 wheel" you're not doing anything performance wise at the time anyway. It's the best upgrade hands-down even if it isn't a true "LSD".
 
Haha I've actually seen a few small cars "dog leg", as some call it, when do autocross with cones in parking lots. Maybe then you would need both wheels locked up as you accelerate out of the corner, but surely not entering a crazy driveway entrance. :)

Do you know if anyone has had their stock MTX-75 diff's pin welded? It was a great mod for our MTX-IV's in the '89-95 SHOs. I think I paid something like $100 or $150 for it.

Apparently the previous owner of my car grenaded the stock diff at some point, which is why he upgraded to a Torsen. Can't agree with you more on it being the best upgrade for those of us that don't baby their cars.
 
Welding the stock diff doesn't help. The problem is that the spider gears are made of this crumbly sintered metal and the teeth just WIPE.
 
My first Csvt had a quaife when I got it and for 3.5 years didn't know how bad a stock diff actually drove. When I traded the car for the current csvt It took me awhile to get used to driving in the rain. The new car spun like crazy driving the way I did when I had my quaife.

On a side note the pre98 diff is supposed to be a good bit stronger than the post 98 diff. I'm have one going in soon as it's a cheap alternative to a quaife or Torsten though not near as good.
 
They are awesome in the snow as well. Where most FWD cars will crab-walk to one side or the other when you are spinning the wheels on a slick hill, the Torsen makes it pull nice and straight. Just stay on the gas and power on through.
 
How to determine if you have an LSD?

lol @ almost useless. lol again at 3+ seconds before locking up. Complete nonsense. If you have one wheel spinning you have a stock diff, or a broken quaife/torsen.

Easily the best upgrade you can do to the car, imo
 
B3NN3TT said:
They are awesome in the snow as well. Where most FWD cars will crab-walk to one side or the other when you are spinning the wheels on a slick hill, the Torsen makes it pull nice and straight. Just stay on the gas and power on through.
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bingo. completly different car in the snow. i took the coug up to the mountains all winter last winter. friken love it!

and as for your wheel spins, when i still had my open dif i could do burnouts til my tires popped. i would launch the •••• out of it and have both wheel spin. but when it came to rain/snow/ cornering, absolute piece of junk. it would always one tire fire especially rain and trying to accelerate pretty decently into a corner
 
Sure; as long as both tires are getting the same amount of grip, an open diff and an LSD perform exactly the same. If you're just drag racing, there's really no need to spend all the cash; just get a pre-98 diff and go crazy.

It's when you're under cornering load, and the inside wheel starts to lose traction under throttle, that the Torsen really makes itself known. No more lighting up the inside tire when I accelerate out of a corner. If you do any open track or autocross, it's worth every dollar.
 
First off, a Limited Slip Differential is a wheel speed sensitive device, it doesn't start moving drive torque until a difference in wheel speed is "sensed". This scenario is exactly what you don't want on the drive wheels of a front drive car. I once got to autocross a Saab Sonnet with a front LSD and the steering wheel kickback powering out of a corner would have spun me around in the seat were I not belted in. The car was wicked fast, but a 60 second run left me drenched with sweat.

The Torsen and Quaife are torque biasing differentials. As long as there is traction available on both drive wheels, they will smoothly, continuously, and fairly instantly bias torque to the tires up to their grip limit, and beyond if you have enough power available. While the Quaife and Torsen operate in similar fashion, there are some minor mechanical differences. The Torsen T2 has a wet clutch that helps it deal better with split-mu situations where one tire has far more traction than the other, the Quaife does not have this feature and stops biasing torque when one wheel has little to no traction.

I was one of the first people on The Planet to install a Quaife in a zooted-up 1st Gen Taurus SHO and take it road racing, and as B3NN3TT pointed out, compared to an open diff, the improvement in mid-corner and corner-exit traction is simply astounding. In road racing or autocross, it makes these cars go from power-on understeer to power-on oversteer if you have enough juice under the loud pedal.
 
gmorrell said:
it makes these cars go from power-on understeer to power-on oversteer if you have enough juice under the loud pedal.
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can you explain the power-on oversteer bit please.

The only time my car oversteers is when you lift off in a corner ... transfering too much weight forward .... thanks ...G.
 
gorman said:
can you explain the power-on oversteer bit please.

The only time my car oversteers is when you lift off in a corner ... transfering too much weight forward .... thanks ...G.
Click to expand...

I probably could have phrased that better...

It was an odd behavior I noticed after I supercharged the SHO. Because it pushed torque so well to the loaded outside tire, the Quaife made it possible to accelerate rather rapidly at mid-corner, and that could overrun the rear grip, especially if the rear tires were cold. Once the rear tires warmed up, it didn't happen, but it caught me off guard a few times in early laps. The trick was to not lift even as the rear was going away, or as you can imagine, things would get worse.
 
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