Traction control vs. Limited slip differential

jeep

#1

Does the traction control systems in newer 4x4s reduce the need for a rear limited slip differential?


#2

The traction control systems use the ABS hardware to brake a wheel that would otherwise spin, allowing the opposing wheel to deliver power.

The LSD does the same thing but mechanically via clutches in the differential. See http://en.wikipedia.org/wiki/Limited_slip_differential

The ABS system could result in excessive brake wear, whereas the LSD could develop problems with the clutches. Both seem to do the same basic job.

Don’t know which is best, but the ABS type is cheaper as it’s just software, and for that reason, it’s also more reliable.


#3

It’s a toss-up Bill. Last year I sold a 1988 Caprice with an LSD rear axle. The unit is very reliable, but GM was very sketchy with the fluid change schedule, which was not included with the owner’s manual.

It actually requires a change of fluid every 12,000-15,000 miles, I recall. I had to wangle this info out of GM. The fluid is standard issue axle fluid with an additive to allow the clutches to work properly.

Since I drove the car mostly on the highway, I went to 20,000 miles, but it still adds up to a lot of money; $40 per oil change minimum. Over 200,000 miles that works out to $400 in fluid changes. The unit itself is very rugged provided you change the fluid.

Antilock brakes cost more when a brake job comes along, but I don’t know the extra amount. Of course ABS is mostly for panic stops, and LSD is a cheap substitute of AWD.

With proper winter tires this car walked through almost any snowstorm. During the worst storm of the Century some years back, I got to work on time, while many of my Jeep-owning friends went back to bed.


#4

despite many quotes of “read the owner’s manual” I find them very uninformative. My manual says to limit speeds to 120mph for breakin the first 600 miles! (actually it says 3/4 of max speed on speedometer, which is 160mph. 3/4 of 160=120)


#5

I think the implication is the ACTUAL top speed, which is probably 100-110 mph for most cars. The 160 mph is mostly there to make you feel good, unless you own a high performance sports car. I once had a Mercury Comet (Maverick twin) with a 200 cu inch 6. The speedo read 120 mph top!

But I agree that manuals are often written by people who don’t really know what is important to maximize vehicle life. My new Toyota has all the info I need, but it is in several places and covers ALL their models, so you need 1/2 hour to summarize which items pertain to your model.


#6

no, because there is no top speed listed. I think the 3/4 part is a leftover from when the speedometer only went to 90mph or so, back when the US gov had mandated that, and they never edited the break-in paragraph.


#7

I do recall when GM tried to be patriotic during the 55 mph speed limit that even Corvewttes had a speedo that only went up to 85 mph!


#8

that wasn’t patriotic, that was the US gov mandating it.


#9

Neither system is going to be perfect and neither will compensate for bad decision making. The newer traction systems are designed to help people like my wife and my mother. And for them, it does. For me, it usually puts me into more danger when it kicks in unexpectedly. I’m not bashing them, but I drive based on past experience before those systems. So it was the driver that made the difference. So the new systems often try to counter-act me and that gets me into trouble. The traction systems will not let you apply power to the front wheels to spin them and pull your front end around. It will activate the brakes and put you into a worse push. If I didn’t use those maneuvers, all would be well. But it’s hard to unlearn driving skills and drive like a dummy.


#10

Good points. At least the traction control can be turned off (At least mine can), and occasionally I have found it useful.


#11

LSD do have a disadvantage similar to some AWD’s in that they require more or less matched tires on the driving axle. Otherwise you may burn out the LSD due to it being in a constant slip state.


#12

Interesting…Subaru for years includes the limited slip rear in their Outbacks. When they started to include traction control…I don’t know if they dropped the feature. I do know for “mudding” they are in compatable. You’ll want to spin both rears to clear treads…so trac control is useless and contradictory for true off road applications.
Our older Subaru with LSD was great till it broke away…then watch out for the rear end.


#13

I don’t like limited slip. If it has problems, the handling and gas mileage will suffer. I know that wasn’t your question but I don’t know your answer. I think the answer could be yes.


#14

Well for the first time since I’ve owned my 4runner traction control really came in handy. Driving to work it started snowing. Cars started to slow down. At one point I was down to 20mph as I was passing one of the 5 accidents in a 10 mile stretch. Then this IDIOT decided he needed to get in front of me so he cuts over (drastically cutting down the safe driving distance between me and him)…and he looses control…I had to swerve a little to NOT hit him…and it was very slippery…The traction control kicked in and I was able to safely manouver around him. Meanwhile he want off the road and tore his rear axle off his pickup. Luckily no one was hurt. If I didn’t have traction control I’m not sure I would have been able to avoid hitting him or loosing control of my vehicle. I have stated in other posts that I didn’t think traction-control was necessary…Well in this case it sure saved me.


#15

Fellow 4 runner owner and I too appeciate the trac and stability control…but as stated earlier, I appeciate that it can be disengaged as well. There are times when it gets in the way…I appreciate also that I have a low range “unlocked” feature that can be used on pavement. Great for pulling waterlogged boats up boat ramps.


#16

Mike for clarity I believe what kicked in was the stability control not traction control. It basically brakes a single rear wheel and cuts your engine power trying to correct the path of vehicle based on directional sensors and steering angle. Its installed standard in current Toyota SUV’s to prevent roll-overs.

Traction control is usually on FWD or RWD vehicles and it applies ABS to a spinning wheel so your vehicle differential sends power to other wheel on axle. It usually only works below 25MPH and intention is to get you moving not correct your path.


#17

Sorry…Our 4 runners have a multimode drive train; 2wd, awd, 4wd lock (high and low range) ; the stability control and trac control are both active in 2wd and awd and deactivated in 4 wd lock for true off road function where trac control is contradictory to deep mud and rock climbing. In awd, it function much like an awd car (Subaru etc) with trac control, good for on road slippery travel and yes, an obvious aid to staying upright when you try to change directions too agressivly. also functions trac control on just the reAR AND stability control when in 2 wd. Can also have low range awd without lock with stability control for down and up hill steep ascents.


#18

PS…they work at ANY speed…we know. We take them out on the frozen lake and wring them out.


#19

PS…the stability control is acticvated only if the “yaw” sensor is activated. W/O it, Trac control is working at ALL speeds utilizing the ABS.