4eat with lsd front diff
 

why don't svx's have limited slip front and rear. also can you get a lsd front diff for an svx.

Re: 4eat with lsd front diff
 

I don't think it would help anything out. When the front diff slips, power is transfered to the rear wheels. And since the rear is LSD and slipping that occurs there is addressed.

Re: 4eat with lsd front diff
 

But the front wheels still slip even when the torque is being sent to the rear wheels. Adding a lsd to me sounds like it would help a lot, especially on those rare dirt road excursions ;)

Re: 4eat with lsd front diff
 

Some of the new tech Subarus don't even have limited slip rear diffs.
I don't know of any compatible parts to make the front LSD on the SVX

The 4.111 and 4.444 conversions easily spin the front before power goes up to 50% rearward.

Lastly, the SVX was designed with Variable Torque Center differential, which sends 65% to the rear where there is a LSD, and up to 50% forward. So, front wheelspin wasn't a problem in those cars :cool:.

Re: 4eat with lsd front diff
 

That is assuming the center differential is healthy.

An open diff on the front end means that traction is lost only if both rear wheels and one front wheel all simultaneously lose traction. It is possible but unlikely. I plan to put blizzaks on my car for the winter. I don't expect to lose traction on three wheels at the same time. The new cars can have open differentials on front and back because it also employs traction control.

Re: 4eat with lsd front diff
 

The SVX was designed with a variable torque center differential, a mechanical planetary gear-set driving 65% of the power to the rear. This diff is always healthy driving power to the rear. The US SVX did not have VTD.

Even with a LSD in the rear, because the LSD is viscous, if the non-US transfer clutches in the VTD are diabled, it is possible to get some rear wheel spin, though I have not experienced it, yet.

As for US transmissions, the 4.111 and 4.444 will get momentary front spin when wheels are not pointed straight, and a good push is applied, as the transmission is normally running about 80/20. The transfer clutch immediately kicks in when rotational differences [spin] are noted, pushing up to 50% rearward, [if the clutches are working properly] which immediately stops the front spin.

At least that is my experience, in our cars, we have both systems :cool:

Re: 4eat with lsd front diff
 

The US market SVX will never spin the rear wheels ahead of the front wheels, it is a mechanical impossibilty for the rear driveshaft speed to be higher than the front pinion gear. Any SVX will easily spin one front wheel, because the front differential is open, and power will go to the wheel with the least tractive effort. Because of the LSD in the rear, they will usually spin as a set. It is not uncommon to see a subaru like this spin three wheels on a slippery surface, or even spin only one front wheel as the overall speed between the front output and the rear output can still be the same because again of the open diff. This would not be likely to occur in the VTD system used in other markets because they have a rear bias.

On dry pavement a properly running SVX will not usually spin any of the tires because there is not enough torque to overcome the tractive effort of 3 wheels much less 4. Even in a turn.

Further, because of the active predictive modeling capability of the TCU, An SVX at more than 50 % throttle in 1st range of D gear is very near full apply pressure at the transfer clutch. In 1 range of gear 1 or 2 range of gear 2 with the manual switch on this is even more aggressive.

A LSD in the front of an SVX would help quite a bit in low traction situations, but on the average road would make no difference IF the transfer clutch is working properly which is a big if because most of them are worn, and the 92s have a problem with holding pressure.

If you had a built motor making 300 plus hp then it would be a more serious issue.

LSDs have fallen out of favor in non performance vehicles because it is easier to use the brakes to achieve the same effect and having A LSD would undermine the effectiveness of electronic stability and traction control in certain circumstances.

Oh, and by the way, no one makes a LSD for the front of the SVX, I looked. If they did, mine would have one in it :D

Re: 4eat with lsd front diff
 

Excellent summary, well said :)
My understanding of the US trans, when selection 1 is made, the transfer clutch locks to 50% rear, which is just what you said.
I don't know how selection 2 works, but likely, just as you said :cool:

Re: 4eat with lsd front diff
 

It doesn't lock, otherwise it would bind. It is just more aggressive with rear apply. Meaning, in position D range 1, at 20% throttle it may be at something like 25% apply, but in manual 1 it might be at 35 %.

I also should mention that in the late 00's they started using the ABS wheel speed sensors for the transfer apply calculation which resulted in a much faster and more accurate operation. I always thought this is how they should have done it in the first place but I wasn't on the engineering team :D

Re: 4eat with lsd front diff
 

i still wish they had lsd all around...:(

Re: 4eat with lsd front diff
 

A LSD in the front would make the steering much harder, especially when parking. Also when going through a sweeping curve, the steering angle would change, with the amount of applied throttle.

Harvey.

Re: 4eat with lsd front diff
 

so much knowledge. god, you guys are awesome.:cool:

Re: 4eat with lsd front diff
 

Subaru really made a great car in the SVX :cool:

Re: 4eat with lsd front diff
 

They tried their best. If we had seen a second generation it would have been an outstanding piece of machinery. As long as it followed the original concept. One of life's greatest cruelties. Or perhaps, just a sound decision from the boys at FHI.