are these oem trac lock ford differentials any good? i ask because i want to upgrade my gears and i would also like to add a posi. the trac locks are half the price of anything else

 

It all depends on what you use your truck for...If you are doing a lot of off roading, go with something more agressive. For everyday use, the OEM works ok if it is set up correctly and with the right amount of additive and you learn how to use your foot on the brake while spinning one tire to make the other one grab.

 

I have an F-250 that's six weeks old. It has the optional Limited Slip axle with 4.10 gears.
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The OEM limited slip is really weak. I found a place off-road where I pulled a rear tire off the ground flexing the suspension. I put the transfer case back in 2WD, left the transmission in Neutral, and attempted to rotate the lifted tire by hand. I found that the clutches in a basically new Traction-Loc could be overcome with relative ease, maybe ~50lb.ft. of torque to reach breakaway.
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An OEM limited slip would probably be OK if you never left the road, maybe if you're looking for better traction in inclement weather or at the boat tramp. Anything off-camber is going to be a letdown because you'll easily reach the breakaway torque of the clutches.
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The main thing I don't really like about the OEM limited slip is that it uses a plate-clutch design to transfer torque. By design, it's clutches are a wearable item. How long the clutches last depends on how wrong the differential fits your driving style: more one-tire-fires results in shorter clutch life and, therefore, even more one-tire-fires! At least the unit is rebuildable.
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In my opinion, if I were adding a limited slip differential, I'd go with something like a Detroit Tru-Trac. It doesn't use clutches, so it won't wear out like the OEM unit. Plus it has a higher torque biasing ratio. The Tru-Trac bias ratio won't diminish as the miles add up. But it doesn't have a way to preload the system. If a tire comes off the ground, it won't even transfer as much torque as the mild Traction Loc.
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If you do some internet searching, you might be able to determine the biasing ratios of these differentials. Don't quote me on this because it's been several years, but the biasing ratios for several popular traction aiding differentials were listed as follows: (most aggressive first)
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Auburn Pro Series --> Auburn High Performance Series --> Detroit Tru-Trac --> Traction Loc --> Open Differential.
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This is with a new differential. The Auburns start out very tight but use clutches (although a little differently). Their biasing ratio goes down with use. The Tru-Trac stays consistent.
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I know this is a super-long reply. But I like to make an informed decision.

 

Or you could go with a clutchless set up like a Powertrax loc right. I had one on another truck and it is rugged but brutal on the other driveline parts.

 

Note that there's a "reason" for the Trac-Loc for being so "loose".

Just like the oil pressure gauge, too many people didn't understand how they worked, and thus complained about the performance -- too much noise/chatter, etc...

Too much friction-modifier, and wavy clutch plates that are assembled with the waves "matched" instead of opposed.

Word around "these parts" is that a competent Ford tech can rebuild them "correctly" and thus result in "proper" function.

-blaine

 

Trac lock needs a little friction on both wheels to lock up. And I agree with Frankenbiker 100%.

 

I'm not sure anyone on this board has suggested the oem LS when doing a gear upgrade

 

He has already that I think

 

Some of the limited slips have a upgrades to make them more or less agressive. I would go with something more long term like the tru trac. My rear axle will factory limited slip will always lock when wet but on dry pavement its a dice roll unless I spin the tires first

 

Certainly not I.

If you are going to add a limited-slip, do NOT use the Ford Traction-Lok. If you already have one, try reducing the amount of friction modifier in the gear lube.

My stock Traction-Lok works OK when I have only 4oz of friction modifier in it, but the book says 8oz. It also chatters a bit, but that's OK.

Last time I got new tires, I topped up to 8oz friction-modifier, I wanted to save my tires

 

The factory LS is junk, anything with clutches will wear out. Get yourself a Detroit TruTrac and you'll be very happy. No clutches to wear out and it works great even with my tuner and 35" tires, breaks both tires loose easy.

 

hey cartmanea, i remember reading on other threads that you got your 4.30's and install kits off of ebay for cheap. did you get them all from one place or just built it all separately?

 

I bought them from a guy on Ebay that had purchased the new gears and install kits and then sold his truck before swapping them, so I got them all from one person.

 

OEM Traction-Locs are ok when properly set up. Most SD's I've owned they were too loose. Only 50 lb/ft on the torque wrench would overwhelm them. The f150's I've owned were mostly good, way tighter than the SD's. And I do get some chatter on the F150's when cornering. But it's nice to see gravel flying from both rear wheels when you hit the throttle.

 

Just some info; Mobile 1 makes two 75w140 synthetic oils. One has "LS" after the name and it has slippery modifiers to control chattering. Don't get it more slippery than necessary or your will start going in the less efficient direction.