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Old 07-02-2008, 03:45 AM
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Default Limited slip vs Locking Differential vs Traction Control

I've decided it's time to consider replacing our current tow vehicle (Excursion V-10) and I've noticed that many of the current midsize SUVs no longer offer a limited slip (or locking) differential. For instance neither the Toyota 4Runner or Ford Explorer offer limited slip or locking differential which is apparently because they think that their traction control systems negates the need for the limited slip or locking differential.

Is a traction control system as effective as a limited slip or locking differential when pulling a boat up a slippery ramp?

BTW, I would really prefer not to go the 4WD route because I've never had any problem pulling heavy boats out with 2WD SUVs but I've always had limited slip or locking differentials before.

Currently our favored option is the 2007/2008 Chevy Avalanche which comes with a locking differential however if we decide to downsize all the way to an Explorer/4Runner sized SUV then the limited slip/traction control question must be answered.

Thanks for any/all opinions.

Doug

PS: We only put about 4000 miles per year on our tow/utility/chore vehicle so the difference in mileage doesn't amount to much gas $$$. However the Chevy Avalanche is EPA rated (15/20) almost same as the V6 Explorer and 4Runner. What's up with that?
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Old 07-02-2008, 04:47 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Have you looked at used G-wagons or Land Cruisers or Discoveries?
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Old 07-02-2008, 04:48 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

its the Chevy motor technology that gives the better highway mileage for the 5.3, the motor and the computer control power output. The motor can switch from a V-8 to a V-4 to increase mileage.
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Old 07-02-2008, 05:03 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Limited slip is a spring loaded clutch arrangement in the differential that sorta locks up both rear wheels. "Lockers" have an arrangement that truly locks both rear wheels together, up to a certain load point.

"Traction control" is a joke. There are wheel speed sensors on each wheel. When the computer detects wheelspin, it either applies braking to the SPINNING wheel, or simply reduces power from the engine.

Nothing beats a true locker for uniform and maximum traction. I've got it in my older Chevy..it'll leave 2 black streaks up the ramp.

Engines. That new series Chevy smallblock is a great motor, but I wouldn't hold my breath on that 4-6-8 cylinder crap. Remember Cadillac from the 1980's? What an embarrassment THAT was for GM.
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Old 07-02-2008, 05:16 AM
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Default RE: Limited slip vs Locking Differential vs Traction Control

Engines. That new series Chevy smallblock is a great motor, but I wouldn't hold my breath on that 4-6-8 cylinder crap. Remember Cadillac from the 1980's? What an embarrassment THAT was for GM.

This is 2008 and you need to study the technology they userather than a 25 year old brush.
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Old 07-02-2008, 05:22 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Quote:
billinstuart - 7/2/2008 8:03 AM

Limited slip is a spring loaded clutch arrangement in the differential that sorta locks up both rear wheels.

"Traction control" is a joke. There are wheel speed sensors on each wheel. When the computer detects wheelspin, it either applies braking to the SPINNING wheel
On a slippery ramp, isn't the end result the same? With an open differential if you apply the brake to one spinning wheel the power (less a bit of friction generated heat) goes to the other wheel.
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Old 07-02-2008, 05:35 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Quote:
billinstuart - 7/2/2008 8:03 AM Limited slip is a spring loaded clutch arrangement in the differential that sorta locks up both rear wheels. "Lockers" have an arrangement that truly locks both rear wheels together, up to a certain load point. "Traction control" is a joke. There are wheel speed sensors on each wheel. When the computer detects wheelspin, it either applies braking to the SPINNING wheel, or simply reduces power from the engine. Nothing beats a true locker for uniform and maximum traction. I've got it in my older Chevy..it'll leave 2 black streaks up the ramp. Engines. That new series Chevy smallblock is a great motor, but I wouldn't hold my breath on that 4-6-8 cylinder crap. Remember Cadillac from the 1980's? What an embarrassment THAT was for GM.
Not sure I'd agree with that. You mention "leaving two black streaks at the ramp", which is impressive (or annoying, depending on your piont of view)I suppose to those standing around you at the ramp...but the entire point is to NOT spin your wheels and simply pull the boat out of the landing. Yes, traciton control does apply the brakes to the spinning wheel, but much like anti locks, it is computer controlled and done in milliseconds--much faster than the old "just put the emergency brake on" trick. It won;t decrease engine power but in extreme vehicle situations..ones which you won't find at low speeds..or at a ramp.

Lockers are notorious for making a lot of noise during in town driving, and the benefits of a "limted slip" type rear end without traction control are quickly lost when you find your vehicle swap ends going around a corner in the rain (a problem that limted slip and locker type differentials exascerbate). And I won't even comment on onyour cylinder shutdown comment; it was correctly addressed.

To the OP,FWIW, I have an '05 2wd V8 4 runner..and I've never even spun a wheel leaving the ramp pulling my 202 Sea Hunt. (about 3500-4000#). But if you are only going to put 4k miles a year on your tow vehicle, I think I'd just dry stack the boat, if you boat local. Whats that..a couple grand a year? You'll pay that in eth first 4-6 months of new vehciel payment.

And how does the Avalanche have the same gas mileage as the 4Runner? The avalanche YOU would probably want to buy won't--the one they test with the lowest rear end gear and smallest motor (which incidently, won't tow as much as the 4Runner) probably does--but it would be close.
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Old 07-02-2008, 05:59 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Quote:
billinstuart - 7/2/2008 8:03 AM

Limited slip is a spring loaded clutch arrangement in the differential that sorta locks up both rear wheels. "Lockers" have an arrangement that truly locks both rear wheels together, up to a certain load point.
Without arguing semantics, there are a number of LSD strategies that will completely couple both "sides" of a differential. Many of the electronic systems (e.g. Jeep Quadra-TracŪ II) do precisely this when needed.

Quote:
"Traction control" is a joke. There are wheel speed sensors on each wheel. When the computer detects wheelspin, it either applies braking to the SPINNING wheel, or simply reduces power from the engine.
Having worked with engine and chassis management systems for almost twenty years, I would have to disagree that such systems are a "joke". Reducing engine output when wheel-spin is detected is highly desirable. What should the system do - increase output? I admit that some earlier systems were sub-optimal, but then most emerging technologies are...

Also, think for a moment about how an "open" differential functions. Axle torque is highest on the side that is spinning the fastest. If a traction control systems keeps the angular velocity of both wheels the same, then what do you think will happen to the distribution of input torque? This is precisely why LSDs are being removed from many "road-oriented" SUVs and other vehicles.

Quote:
Nothing beats a true locker for uniform and maximum traction. I've got it in my older Chevy..it'll leave 2 black streaks up the ramp.
This is only true under specific conditions. Continuously-variable electronically-controlled torque distribution systems can accommodate most any set of conditions.

Quote:
Engines. That new series Chevy smallblock is a great motor, but I wouldn't hold my breath on that 4-6-8 cylinder crap. Remember Cadillac from the 1980's? What an embarrassment THAT was for GM.
Tell that to the owners of GM Vortec 5.3L and Vortec MAX 6.0L V8, and Chrysler Hemi 5.7L V8 (me, for example)...the cylinder deactivation systems used in these engines are effective and unobtrusive.

To the orginal poster - take the candidate vehicles to a ramp and try them for yourself. I think you will be pleasantly surprised how well some of the non-LSD equipped SUVs work under those conditions.

Mike
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Old 07-02-2008, 06:42 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Quote:
billinstuart - 7/2/2008 8:03 AM

Engines. That new series Chevy smallblock is a great motor, but I wouldn't hold my breath on that 4-6-8 cylinder crap. Remember Cadillac from the 1980's? What an embarrassment THAT was for GM.
Bill,
You are speaking about an innovation you know nothing about. I just bought a new Chevy Z71 with the fuel management in it. In cruise the engine drops from 8 cyl to 4 cyl. My first check of mileage gave me 19 MPG and that is a combination city and highway driving...
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Old 07-02-2008, 07:06 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

there is nothing better then a locker on a wet slippery ramp, Gm does offer it on the 2 WD models, Look at the Tahoe or Yukon or Suburban or Yukon XL if you want sport utility or the 1500 HD series trucks with 5.3 2 WD with a G80 code and 3.73 gears. average highway from friends and personal experence all around driving 18 to 19 MPG. Highway trip mileage on interstate at 73 MPH 22 average. I get 17.5 to 18 on average in town and local highway with a custom programed 07 Tahoe 4x4 with 3.73 gears, Highway driving on Interstate around 20 plus at 72 MPH. Does pull a 30
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Old 07-02-2008, 07:14 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

GM's EATON G80.... Nothing else compares!!!!!!!!!!!!!

see here:
YouTube - 20% grade G80
YouTube - Silverado with Locking Differential (G80)

Here is how it works!
YouTube - Eaton Locking Diff. - inside

do other searches of the g80... GM trucks rule!

Here is my fuel mileage with a

2006 silverado crew cab 1500 2wd with 5.3l vortec and 3.23rear. (too high of a rear for most but I drive like 30k a year so it works for me - recommend 3.73 for most )
Highway 20-21mpg
daily driving between Annap-DC-Balt ~18mph
towing over 6000lb boat to the the CBBT on the shore at around 6omph a hair over 10mpg locked in 3rd gear and in tow mode.

2004 suburban 1500 2wd with 5.3l vortec and 3.73rear (wife drives)
highway to SC on vacation loaded with stuff and running ac 18-19mpg
round town driving 16-17mpg (wife driving)
towing over 6000lb boat to NJ via 301 eastern shore (flat) running ac and vacation luggage - a hair over 10mpg

2005 silverado crew cab 4x4 2500HD with 6.0lvortec and 4.10 rear (father drives)
his daily driving is about 12mpg
towing a travel trailer or his judge 27 yields like 8mpg.

Living in Annapolis, I havent missed a day of work either with a 2wd truck. I do take the suburban on snowy days or put blocks in the back of the silverado. 4x4 gets you going but it doesnt stop you... get a bow tie with a g80 and save on fuel and maintenance.
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Old 07-02-2008, 07:26 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Have a front hitch reciver installed buy your self a Warn winch and when you need help on a ramp winch yourself out...


Or buy a 4 whell drive....


Been there done that...


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Old 07-02-2008, 07:27 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

My 2003 Toyota Tacoma Pre Runner 2wd had a locking rear differential.


My 2007 Sierra Classic 2wd has a locking rear differential. I would say you can get it, but you have to look for it, or order it.
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Old 07-02-2008, 07:44 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Quote:
frogbiscuit - 7/2/2008 10:27 AM

My 2003 Toyota Tacoma Pre Runner 2wd had a locking rear differential.


My 2007 Sierra Classic 2wd has a locking rear differential. I would say you can get it, but you have to look for it, or order it.
I think all 2wd gm trucks with the tow package get the g80. To verify, just check the glove box for the code g80 in the build sheet. Also look for the code GT5. That is the 3.73 rear.

BTW, Toyota only offers a LSD, it is not a locking rear. Only GM offers a true locking rear currently.
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Old 07-02-2008, 07:45 AM
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Default RE: Limited slip vs Locking Differential vs Traction Control

Quote:
Onewolf - However the Chevy Avalanche is EPA rated (15/20) almost same as the V6 Explorer and 4Runner. What's up with that?
Its more because the V6 has to work harder than it is becuase of any cylinder shutdown or other smoke and mirrors. 5.4 F150 V8s get about the same as V6 Explorers, I have had both and the 5.4 has no cylinder deactivation.

I also would rather have a LS or locking diff than TC or roll stability control or anything else. I dont want the truck deciding on its own what to do.
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Old 07-02-2008, 07:53 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Onewolf, we are always quick to help posters spend money here, if you are using this for 4000 miles a year you may want
to wait. You will take a beating on the trade either way, why not have more money for fuel and go fishing. In the course of
the next few years the economy of the vehicles should improve and you will have more choices.




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Old 07-02-2008, 08:15 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Quote:
billinstuart - 7/2/2008 8:03 AM ........... "Traction control" is a joke. There are wheel speed sensors on each wheel. When the computer detects wheelspin, it either applies braking to the SPINNING wheel, or simply reduces power from the engine. Nothing beats a true locker for uniform and maximum traction.............
Bill, normally I agree with your posts..... The other guys beat ya up enuf on the V-8 V-4 thing... I had a 98 Caddy STS with their version of traction control. NOTHING, including a AWD Range Rover or anything else I ever drove could pull away from it on ice and snow from a light. It works incredibly well. You need to experience it to believe it.
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Old 07-02-2008, 08:17 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

I have a 2007 Suburban with the 5.3 and the locking diff. It gets between 21 and 22 mpg at 65 mph on the highway and 17 to 19 mpg in the city. Mid 17's is the lowest I have seen. It is about 13 to 14 mpg pulling my 22 foot 4500# boat. I have yet to have the tires slip when pulling out of a wet slimy ramp. You can not tell when it switches betweem 4 and 8 cylinders. You should be able to get some great deals from Chevy now.
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Old 07-02-2008, 08:41 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Quote:
B-Faithful - 7/2/2008 7:44 AM

Quote:
frogbiscuit - 7/2/2008 10:27 AM

My 2003 Toyota Tacoma Pre Runner 2wd had a locking rear differential.


My 2007 Sierra Classic 2wd has a locking rear differential. I would say you can get it, but you have to look for it, or order it.
I think all 2wd gm trucks with the tow package get the g80. To verify, just check the glove box for the code g80 in the build sheet. Also look for the code GT5. That is the 3.73 rear.

BTW, Toyota only offers a LSD, it is not a locking rear. Only GM offers a true locking rear currently.
Not true, our Tacoma TRD/OR DC has 4WD, TRAC, VSC, HSA and it has a LOCKING rear diff. Sorry, but it is true, you can get the locker in the OR package. I think it can be ordered in other configurations as well. I regularly get up to 24MPG with the truck driving under 65 on my (rural) commute and on a recent 2,000 mile tow got 11.9 MPG with corn 10% fuel and 14.1 MPG with gasoline towing at up to 65 MPH and occasionally 75 MPH. Boat being towed was a BW Outrage 190 and we were loaded to the gills.

The Tacoma pulls the boat up slippery ramps just fine in 2WD mode, TRAC activated, on one moss covered ramp we used 4WD, TRAC activated, no wheel spin. The only time I have engaged the locker was in a snow drift. And it is a full locker, the switch is by the LH knee on the subpanel, yes, it is a locker.

The HSA--hill start assist-- by the way is a feature that prevents the truck from rolling backwards when you remove your foot from the brake to go to the gas pedal. It is helpful for my wife more than me.
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Old 07-02-2008, 08:53 AM
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Default Re: Limited slip vs Locking Differential vs Traction Control

Thanks Highndry. I stand corrected. I just read about it. Is it an electric locking rear that you have to engage or is it a mechanical one that auto locks with slip like GM's? Can you get it with 2wd?
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