Sp19

Put a Quaife QDF26E Torsen type LSD in the IS350 about 8 weeks ago. I have been using Torsen type LSD's in my race and street cars for 20 years so I understand their strengths and limitations quite well. After a couple of weekends in the Tahoe snow and rain and a track weekend I can say it is working as expected. There is no impact to the traction control, etc. It is completely transparent to the cars systems. An LSD should be unnoticeable until you push the car hard.

So the pros:
1. Greatly reduced wheel spin especially when starting out into a turn. You still can't stomp on it except with race tires! Driving in 3" snow on summer tires went better than I expected. I was passing 4 wheel drive cars!
2. If you drive hard you will get noticeably less rear tire wear, slightly better gas mileage, lower drivetrain temps.
3. Dramatic reduction in low speed push. There was such a reduction in push that I though there was a low rear tire for the first couple of turns. The drive on the outside wheel really overcomes the front end push, as it should. Driving down the twisty CA coast highway was a real pleasure with the LSD.

The cons:
1. Yes the inside rear tire will spin if it is off the ground. The time a tire is off the ground is so short that it doesn't have much impact. In all the years of racing cars with at least 3 different LSD types I have never found a measurable difference between them except in the case of heavy high horsepower cars like GT1's which tend towards axle tramp under most conditions. Yes you can feel the difference between LSD's but the lap times won't show it unless there is something really wrong with the car, or the driver.
2. If you are not used to a limited slip and you stomp on the gas you will probably not be ready for the rear of the car abruptly breaking loose as it VIOLENT tries to go sideways! In other words if you don't anticipate the cars tendency to spin when both rear tires brake loose you will probably not catch it in time to prevent a spin. This can happen even if you are going perfectly straight. With an LSD you have to be even more careful with the throttle if you have the power to easily break the rear end loose, not less!
3. There is a tendency for axle / wheel tramp depending on several factors such as tires / air pressure, road surface - smooth or wet or dry. The Conti's will sometimes tramp but the compliant race tires would not. I suspect that the typically high level of anti-squat and "soft" differential mounting has a lot to do with this. Which also explains why Lexus has not put an LSD in the IS until recently. In any case the level of tramp is reasonably low. It is like a fast skipping not a violent judder. Dropping the tire pressures to a more normal 38lb, no tramp. I replaced the existing 18" wheels with 17" wheels and with wider and "taller" sidewall tires which are more compliant, have not noticed any more tramp. This will help with the too stiff front tires jumping around on anything other than smooth pavement as well. It would be interesting to find out what the suspension differences are on the new LSD equipped IS350's.
4. My cost was $2250 to install.
a. $1050 for the LSD including shipping
b. $250 for the Pumpkin from a wrecking yard
c. $200 for axle seals
d. $120 to get it installed into the Pumpkin
e. $630 to install Pumpkin in the car including conventional 85W90 diff oil (Toyota dealer)

After 1500 miles I switched to Synthetic LSD compatible 75W90 diff oil. You may benefit by adding friction enhancers and at the next track event I will try some. Quaife used to make their own but I am not sure if they still do. I had the backlash set to 0.002" to 0.0025". LSD's like to run tight. If the ring and pinion runout is more than 0.0008" I would not use the diff. Mine had about 0.0003". You should not have to re-shim the pinion so it can stay in unless the contact patch on the teeth is really offset. Again I would not use the diff if the contact area is small or offset.

So is the LSD worth it? For me it definitely is, but most drivers will either not notice it at all or dislike the rear end kicking out on occasion especially in the rain. The "soft" Torsen type is the most benign of the LSD's available and will give you 85-90% of the performance of a racing LSD without all the headaches a typical clutch pack has. I have driven 250k hard street miles with a Quaife without any maintenance required. You may need to change your 18" or 19" wheels or maybe just the tires if you are getting more than just slight wheel tramp. Changing to stiffer shocks will not fix this and only makes it worse! Lower tire pressure will always help but running to low is not a fix.

I now have an extra Pumpkin. Anybody interested in buying it with the Quaife installed?

circuitt

iTrader: (3)

Nice read, thanks !

Gville350

iTrader: (10)

So much for being the first on here to have installed one into a 350. Lol! Very useful info and informative.

So you now selling that read end with the Quaife LSD in it?