Differential questions from a new guy

erwinturner · 08-31-2009, 09:16 PM

I'm new to this and just starting the planning of a Sportsmobile 4x4 ford RB w penthouse.

I am leaning toward ARB front and Limited slip back (is the reverse an option...ARB back Limited front...Possibly a dumb question).
Question is: Is this a recomended setup?

Does the air locker run as an open diff when off?
Is the 4x4 activated seperately from the locker?
Other basic advice is welcomed 'cause I've seen you guys have a lot of differnt types of experiances and opinions.
...I will do a variety of trails including rock, sand and snow and I live in Colorado and have come close to being really stuck a few times on trails and in snow in stock Troopers, Explorers and a hybrid Escape (not to mention my old VW Westy).
Basically, I want to go where I've never been able to before (and be able to come out when (and if)I want.

AndrewST · 09-01-2009, 03:41 AM

Welcome on board.

Regarding the limited in front, from factory it is not available and it is not advisable to have one there; when the hubs are engaged, the front axel will tend to pull the van straight if the limited is to tight. It can be ok for a vehicule used only offroad.

Yes, the air locker is open when not engaged and the locker is independent from the 4x4.

Enjoy the planning phase...

erwinturner · 09-01-2009, 06:55 AM

Thanks, this is the kind of info that can help. Also, specific experiences

Stumpalump · 09-02-2009, 07:53 AM

Limited slip is limited grip. Nothing compairs to a locker. ARB's are great because you can turn them off and have open diffs. That makes turning a lot eaisier. When they are on they are like a full spool and locked solid. You find yourself turning them on only when needed then right back off. A limited slip just adds a little traction on very slick sufaces like a snowy street or wet grass. If you get at all crossed up in the rocks they do nothing. Don't be fooled by what limited slip or posi will do on a regular vehicle with regular tires. Off road they are worthless and the rear is the most important place to have extra traction. Now if the posi is dirt cheap to add and you are on a tight buget then yes just adding the ARB to the front is an option. I don't like that option and because most of you traction off road and in the rocks comes from the rear. Off roaders everywhere will tell you to lock the rear first for that reason. The second reason is that the front axel shafts will be your weak point. With the rear doing almost nothing because of posi then the front will be forced to do more work. You get that 10k rig in the rocks and ask the front to pull you thru and bang goes the axel or front axel u-joint or hub or ring and pinion. Basically it will be better to spread the load to the rear or have your main traction comming from the stronger rear in the first place.

beernutmark · 09-02-2009, 08:37 AM

Quote:

Originally Posted by Stumpalump

A limited slip just adds a little traction on very slick sufaces like a snowy street or wet grass.

What about for those of us in snowy mountain areas. If I am using my van for ski trips also or driving around in the snowy valley will the fully open diff (if I added an ARB) give me grief or is the transfer case diff going to be enough to keep me safe and happy? For the few off road times a locked rear would be helpful would one be sacraficing a lot of control in the snow?

Mark Alston

UJOINT · 09-02-2009, 03:59 PM

Stumpalump summed it up nicely. I agree!

mjeffrey · 09-02-2009, 05:34 PM

Somewhat related, and a question I've always had: is Ford's AdvanceTrac system equivalent to limited slip? It's an electronic system, but does it work the same way? I can't find any definitive answer on the 'net.

jage · 09-02-2009, 06:22 PM

Quote:

Originally Posted by Stumpalump

If you get at all crossed up in the rocks they do nothing.

You need to use the brakes, in theory it will get more traction to the ground... however I'm not a good enough driver to say I've ever used this technique, mainly because the only vehicle I've repeatedly buried was the one with full time lockers front and rear.

Incidentially, I wouldn't want a full time locker in an area where you have to drive in snow and ice. They're terrible becuase you get no lateral traction when both wheels let loose. An ARB on the other hand you leave unlocked unless you get into real trouble where going sideways would be considered progress.

UJOINT · 09-02-2009, 09:30 PM

Quote:

Originally Posted by mjeffrey

Somewhat related, and a question I've always had: is Ford's AdvanceTrac system equivalent to limited slip? It's an electronic system, but does it work the same way? I can't find any definitive answer on the 'net.

I think that system is more for stability control, to prevent rollovers.

carringb · 09-02-2009, 10:16 PM

The traction control on the RSC equipped vans will brake a spinning wheel and effectively direct power to the traction wheel.

Vans without RSC only have engine traction control, and will not stop a spinning wheel. (2007 vans without RSC do have brake controlled traction control)