Posi vs Open: street driven opinions

[Shimmy]

I know the difference between the two, but i keep debating what would be "better" in my situation. My bronco is 98% street driven, sunny day, ice cream shop, family, kinda cruisin. I suppose it may see a gravel road from time to time. An open rear diff would be the most economical, correct? The reason this has come up is because i'll be swapping in 4.56 gears soon. My good friend (jeep guy) bless his heart, mentioned that a posi would add resale value should that time ever come. I have zero plans to sell this bronco, so i dont know how much i should really consider a posi.

Am i missing anything here? i can't think of a situation where i'd need a posi rear?

77, 35's, 3.5" lift, stock 302, stock 3 speed, stock D20

 

[bmc69]

An open dif is certainly easiest the on tires and driveline.

 

[Wild horse 75]

Having owned 2 trucks that had identical drivetrains other than one had posi and the other didn’t. I would never order a truck without a locking diff of some description again. Getting stuck on the side of the road and needing 4wd to get out was a pain in the ass. You don’t need a crazy locker but a simple clutch type posi will go a long ways to making it more fun to drive.

 

[Scoop]

The Ford term is Limited Slip. For what you describe open would be fine. I doubt Limited Slip will add much, if any, to resale value.

 

[gnpenning]

The answer is what is the ROI for you. Will the difference in cost be something you will benefit from? The 2% of time you go off road is it some place that will have a muddy or icy spot that you would need help? If not you don't need one. If there is a good chance and have to pay someone to get you out you might be behind. Anyone that has had a tire on dry pavement and the other on ice would understand.

You know where you want to go and what to expect, let that be your guide.

 

[Broncobowsher]

On the street, nice weather, low power, open diff.
The limited slip in the traditional sense (clutch pack style) was a little better than an open diff, but less than a locker. I remember growing up and driving on ice. A limited slip was great at sending you toward a ditch. Clutch drag is good at letting both tires break loose together. But off-road where you really need it to lock up, slips. It is a bit of the worst of both worlds. The open diff is nice as when you overpower one tire it breaks loose and spins, the other doesn't and acts like a rudder keeping you straight.
There is a nice all around limited slip, the helical gear style limited slip. Torsen makes some, most know the Detroit Tru-trac.

If you want the ultimate in streetability, off-road capability, and resell value, ARB will cost the most but gets you everything.

Limited slip (traditional clutch style) really doesn't add value in the used market anymore. Open is the least expensive. Helical is a really nice limited slip and has value.
Detroit locker (different from a Detroit Tru-trac) isn't a good choice for what you describe. Great off-road performance with some streetability. Clanks, bangs, pops.
Spool is an even worse choice for what you want.
ARB is open, super easy for street use, way more solid than any limited slip. But it is the most expensive. But also the best value added in resell.

 

[Shimmy]

thanks for the insight guys! if i went posi id be trutrac

 

[SteveL]

With your conditions either will get you by. Seeing you're rolling on 35s I would worry about the strength in the rear. The stock open diffs are known for being weak. Over the years of mostly street driving with 33s and 35s Ive broken a handful of stock carriers. Also twisted the splines on a couple axles and snapped one. What type is up to you but I would definitely upgrade the carrier and go with 31 spline axles while you're at it

 

[Eoth]

Lol... Details like that rarely reflect in any significant way into its value. My open rear diff spends the vast majority of time on the street with occasional "wheeling weekends". Life was difficult on the trail until I added an Aussie Locker to the front. No doubt my setup could be improved upon but I am very pleased "as-is"... Street manors are excellent for a high speed tractor.

 

[Quick & Dirty]

The Ford term is Limited Slip. For what you describe open would be fine. I doubt Limited Slip will add much, if any, to resale value.

Limited slip is a generic term. Clutch type for Ford is Traction-Lok, GM is Positraction, Mopar is Sure-Grip, Dana is Trac-Lok or Powr-Lok(better version).
Detroit Truetrac is a great compromise for mostly street. Gear driven torque-bias to limit axle speed difference without the drag and wear of a clutch.

 

[nvrstuk]

I posted a waaaay cool article on 10 or 12 different rear lockers a couple weeks back.

You do NOT want a Detroit locker. TrueTrac is great for the street.

 

[jeffncs]

The original Trac-Lok in the broncos has a weakness in the differential allowing it to crack between the ring gear bolt holes.

With that in mind, opt for a modern 9” carrier not the original one. Just be sure to order the carrier with the correct number of splines (28-spline in stock EB rear axles).

 

[Broncobowsher]

The original Trac-Lok in the broncos has a weakness in the differential allowing it to crack between the ring gear bolt holes.

With that in mind, opt for a modern 9” carrier not the original one. Just be sure to order the carrier with the correct number of splines (28-spline in stock EB rear axles).

Running 35s and 4.56 gears, now is the time to upgrade to 31 spline axles. Many of the diff companies don't even offer a 28 spline option, for good reason.

 

[Quick & Dirty]

The original Trac-Lok in the broncos has a weakness in the differential allowing it to crack between the ring gear bolt holes.

With that in mind, opt for a modern 9” carrier not the original one. Just be sure to order the carrier with the correct number of splines (28-spline in stock EB rear axles).

The combination of countersunk bolt holes and holes for engaging the steels was not a good one. On later ones, the engagement holes are not drilled all the way through, reducing the likelihood of cracking. Excess shimming for increased preload also contributes to cracking the housing. 9" limited slips are hampered by the 3rd pinion bearing not allowing room for a clutch pack on that side.

 

[ba123]

I'm a locker fan, always have been. Lots of people said I'm not gonna like this Detroit locker in my on road for the foreseeable future too pretty Bronco (maybe again someday), but I love it. The traction is stellar and aside from the occasional chirp that gets a head turn from onlookers, some that were already staring at my beauty and some that looked cause of the nice chirp...

What-ev. Drive it like ya stole it and do what makes you happy.

 

[Broncobowsher]

The combination of countersunk bolt holes and holes for engaging the steels was not a good one. On later ones, the engagement holes are not drilled all the way through, reducing the likelihood of cracking. Excess shimming for increased preload also contributes to cracking the housing. 9" limited slips are hampered by the 3rd pinion bearing not allowing room for a clutch pack on that side.

Remember, this is the factory Trac-Loc clutch style limited slip.
Not to be confused with Tru-Trac which is a helical gear style limited slip made by Detroit

 

[Scoop]

Limited slip is a generic term. Clutch type for Ford is Traction-Lok, GM is Positraction, Mopar is Sure-Grip, Dana is Trac-Lok or Powr-Lok(better version).
Detroit Truetrac is a great compromise for mostly street. Gear driven torque-bias to limit axle speed difference without the drag and wear of a clutch.

Never too old to learn something. Thanks!

 

[nvrstuk]

Up north they're not as friendly. lol

If you've ever towed with a Detroit locker or driven on "hard as ice "compact snow covered streets with a Detroit, the desire to have one disappears as you do that 360 at 15 mph on city street or you slide off the trail doing 3 mph because of their both wheels spin at the same speed when going straight design.

For me, I hated it. Ran it for two years and loved it (compared to any other locker at the time) from May till late October. Then on frosty mornings is when the fun started. You can let off the gas and when that sob unlocks you will feel it on ice/snow-not in a good way either! lol

Only other real drawback is when you break a ujoint or an axle in the frt or rear, 9 out of 10 times the Detroit will grenade. It's happened so many times to my wheeling friends that we all recognize the sound.

Pros and cons of everything!!