The 3.73 is a good idea especially if you tow a decent amount. I take it you keep your trucks for about 10 years or so? If you don't tow much the 3.55 should be fine if your looking at the 5.4l/6spd combo. If you can get the truck off the lot and save a bit of coin off of ordering one you could put in a better aftermarket posi and still come out ahead.
Depends what kind of deal you can get on it vs ordering a truck. If the truck has ESOF and don't do much low traction driving you may not really need it. A truetrac or similar aftermarket diff with install would run around $800 or so with parts and labor...
I agree with dkf. I've had limited slip units put into 2 vans over the years--my '86 GMC van (bought used with open diff) got an Auburn limited slip unit waay back about 1990 (not the truetrac) and that got me thru some fire roads where I had no business taking a full size van. I remember that as being a really nice and unobtrusive unit but it's not rebuildable.
My current '02 E150 had an open diff (bought new from dealer stock) and I decided to put an Eaton Positraction in it (this is the actual Posi unit as used in GM cars way back to my old '68 Olds 442). It's always had a bit of chatter when lifting an inside wheel on a wet road and spinning it, but it has gotten me through Michigan winters and some pretty rough roads/trails in the UP of Michigan.
So yeah, an aftermarket unit will cost more than a factory limited slip, but you get the opportunity to put exactly the unit you want in your truck. Have it done at a good shop--I used a local gear shop that does lots of race cars, and they GOTTA put those together well. Van is long out of warranty, and I've never had a problem with the rear end. Just make sure you get the right fluid/additives in the rear end if anyone changes it down the road--my Eaton, for instance, recommends against using synthetic lube.
Better yet just offer the locking diff in other trim levels besides the FX4.
Oh yes, if only........oh well, we can dream, I guess.
I've driven trucks with detroit lockers, and just like you say, the aftermarket units are much better than the factory LS, especially in severe off-road situations. I hate to say it, but the Auburn unit that comes in the Chevy's is a better piece than the Ford LS too . I've been told the Dodge unit isn't as good as the Ford, but that's just here-say. However, in snowy road driving and 95% of the off-roading that most of these trucks will ever see the factory LS is probably sufficient.
A limited slip rear is better than an open diff but not by much. If one wheel is on blacktop and the other is on grass the wheel on grass will still peg leg with the LS. Aftermarket units like the truetrac are much better than the stock LS. You get an open diff up front regardless.
I see comments like yours on this forum, and a few others...and to be honest, I cannot say I agree.
My 2006 FX4 was Supercharged and had 3.73LS out back
I could easily lay down dual black burnouts for 20+ feet no problem...and I never had an issue with a peg leg burnout like you describe.
It took 2,000 miles of constant abuse from me before my Factory LS started showing any age. And I cannot fault it. I don't care what brand/style...you take a 6,000 lb truck & 400+ HP and stuff doesn't hold up so well...especially if the driver is a 'tard like I was.
Before the Supercharger, I had that puppy up on 2 wheels numerous times. The LS did it's job and powered the truck through the nasty stuff.
I think people are having unrealistic ideas of what a LS will accomplish.
They think they are lockers...or somehow a 50k-100,000 mile LS is supposed to be tight and strong after all those miles.
I see comments like yours on this forum, and a few others...and to be honest, I cannot say I agree.
My 2006 FX4 was Supercharged and had 3.73LS out back
I could easily lay down dual black burnouts for 20+ feet no problem...and I never had an issue with a peg leg burnout like you describe.
It took 2,000 miles of constant abuse from me before my Factory LS started showing any age. And I cannot fault it. I don't care what brand/style...you take a 6,000 lb truck & 400+ HP and stuff doesn't hold up so well...especially if the driver is a 'tard like I was.
Before the Supercharger, I had that puppy up on 2 wheels numerous times. The LS did it's job and powered the truck through the nasty stuff.
I think people are having unrealistic ideas of what a LS will accomplish.
They think they are lockers...or somehow a 50k-100,000 mile LS is supposed to be tight and strong after all those miles.
I'm not being unrealistic at all. If you have one wheel on blacktop and one wheel on grass the wheel on the grass will get the vast majority of the power with a stock LS. "Posi" marks on blacktop can be had with the stock LS diff because traction is pretty close to equal between the two wheels. I've had my truck since new and LS performance has always been the same. 38k on the truck now with no friction modifier added to the LS and it still performs the same as new.
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However, in snowy road driving and 95% of the off-roading that most of these trucks will ever see the factory LS is probably sufficient.
I agree. Most people use there trucks strictly for onroad driving and never even venture offroad. The stock LS is decent in snow when theres pavement underneath and equal traction. Helps the ass end not kick out as fast which may surprise drivers that arn't so experienced.
an open diff will power both wheels when there is equal traction. The problem is the traction really is hardly ever equal. LSD will provide torque to both wheels even when there is a lot of traction on one wheel, and very little traction on the other.
If you have one wheel on blacktop and one wheel on grass the wheel on the grass will get the vast majority of the power with a stock LS.
You are basically describing a open diff. Your description is contrary to the entire way a LS operates
Open diff: Power goes to the side with the least resistance. Always. That is why see 1 tire fire all the time. Usually the side of the axle with the least sprung weight. Every blue moon you'll see both sides powered
LS: You have the friction plates in there. Low speed slippage goes by unnoticed. Get some wheel spin though, and the Friction Plates lock up like a clutch & transmission setup...then that power gets split equally to both wheels. Their ability to hold alot of power is determined by the quality of the unit...but the OEM is perfectly suited for the output of the 5.4 motor. Some slippage will occur, but it is actually pretty minimal 99% of the time
Locker: Mechanically locked axles. 50/50 split 100% of the time
are you sure the truck you are talking about has a LS?
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[quote=tylus;7667022]You are basically describing a open diff. Your description is contrary to the entire way a LS operates are you sure the truck you are talking about has a LS?[/
Open diff: Power goes to the side with the least resistance. Always. That is why see 1 tire fire all the time. Usually the side of the axle with the least sprung weight. Every blue moon you'll see both sides powered
LS: You have the friction plates in there. Low speed slippage goes by unnoticed. Get some wheel spin though, and the Friction Plates lock up like a clutch & transmission setup...then that power gets split equally to both wheels. Their ability to hold alot of power is determined by the quality of the unit...but the OEM is perfectly suited for the output of the 5.4 motor. Some slippage will occur, but it is actually pretty minimal 99% of the time
Locker: Mechanically locked axles. 50/50 split 100% of the time
quote]
No I'm talking about a limited slip. You don't know how these stock LS units work. The stock LS have so little preload that if you have one wheel on blacktop and one wheel on grass and hit the skinny pedal good, the wheel on the grass will get the majority of the power. Also yes my truck has LS.
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Get some wheel spin though, and the Friction Plates lock up like a clutch & transmission setup...then that power gets split equally to both wheels.
Wrong. In the stock LS there is no locking of anything. The clutch pack is a bunch of preloaded friction plates sandwiched together in the diff.
The stock limited slip can only handle a set amount of torque before the clutches break free and slip. You make a turn, the clutches slip. You lift a tire off the ground, the clutches slip. You have a tire on wet grass and the other on pavement, the clutches slip.
They are not really speed sensitive, but a torque sensitive differential.
It won't "lock-up" by spinning a free tire more/faster. That'll just slip the clutches more. It biases torque to the best of the clutches ability. Once there is too much difference side to side the unit has done all it can. It limits slip. An open differential would be an un-limited slip. The locker, by it's classic name, is a "No-Slip" or "No-Spin."
if anyone lives where it snows gotta have LS. if like me u dont, im gonna save up and look into that tru-trac concept. especially with 265's on that behave like skiis. my truck belongs in the south, but i do love it still.!!! 89k 99 i asked a similar question in the 97-2004 forum last week
if anyone lives where it snows gotta have LS. if like me u dont, im gonna save up and look into that tru-trac concept. especially with 265's on that behave like skiis. my truck belongs in the south, but i do love it still.!!! 89k 99 i asked a similar question in the 97-2004 forum last week
One thing--if you have highway tread tires and add a limited slip to the rear of your truck, giving the truck some gas on a crowned, ice-covered road will send the rear end of the truck into the curb or ditch. (I had old musclecars with posi's back in the early 70's and they were a riot in Detroit, with bald tires...)
You definitely do NOT want anything called a "locker" in this situation--it will lock your rear wheels very abruptly and hasten your sliding into the ditch. Some good tires and a limited slip unit (I've had the old Auburn limited slip and now have an Eaton Posi in big vans) should get you through most any kind of snow. With 4WD, some decent mud/snow tread tires should get you through even without a posi if you know how to drive in the slippery stuff.
Lockers are best for rock crawling where you have some wheels off the ground.
if anyone lives where it snows gotta have LS. if like me u dont, im gonna save up and look into that tru-trac concept. especially with 265's on that behave like skiis. my truck belongs in the south, but i do love it still.!!! 89k 99 i asked a similar question in the 97-2004 forum last week
I'm trying to build the fund for steeper gears and some truetracs for my truck. I'm figuring with install the front and rear truetracs diffs, 4.30s, bearings/other parts and oil it will run me about $3 grand. My truck should be an offroad animal then. The truetrac is supposed to be OK for the front diff also. I have yet to hear anything bad about the truetrac and the price is right for it. Hopefully the economy gets better so I can at least feel more secure about spending a wad of cash.
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. I've been told the Dodge unit isn't as good as the Ford, but that's just here-say. However, in snowy road driving and 95% of the off-roading that most of these trucks will ever see the factory LS is probably sufficient.
since i will eventually need to replace the clutch packs, wondering how easy and cost effective this is to install myself 
