Tow vehicle axle question.

S

seabeagle

New member
In about a month or so we'll be ordering a Ford F150 extended cab long box 4X4 powered by the 3.5 Ecoboost. The only thing I'm not sure about is getting the 3.73 limited slip or the 3.73 electronic locking. I can't find much official Ford info on how the e-loc works in it. I've read a few posts elsewhere that mention that the e-loc will only work in certain conditions and certain speeds.

As for my driving habits, I don't go off road much, tow regularly, 4 months of the year have snow, and the rest is scattered with rain.

What would you choose?
 
personally I would go with the limited slip. That truck should easily handle towing your boat. I have a long bed ford (F-350) and love being able to slide sheets of plywood, drywall etc into the back and being able to close the gate. The only drawback is crowded parking lots.
 
The e loc completely locks the differential. This allows no slip--and is used in low speed, like pulling the boat out of the water on a steep ramp, where you would tend to spin the wheels in mud, or sand, or on ice.

With the 4 x 4 you will have good traction. With a limited slip, you can use it at higher speeds, more as you encounter in snow. The only reason I can see for a full lock up rear is if you have some ramps which are very bad--like lots of sand. I would go with the limited slip in your case.
 
Having used selectable locking (ARB) and limited slip differentials here is my take.

A limited slip can cause stability issues on slick surfaces especially when turning a tightish corner. The inside drive wheel wants to turn the same speed as the outside one. This is good when you want straight line traction but in a tight corner you lose grip on the inside tire prematurely. This puts all the traction stresses on the outside tire.
Case in point. Our pickup came with an open differential. When taking off from stoplights in wet conditions much of the time a tire would spin. After installing a TrueTrac limited slip now both tires may spin leaving little lateral traction. You can drive that truck sideways all day long now, fun for Pops, not so much for Mama.
It was a shock for me to realize you are better off with an open differential the vast majority of the time. It also reduces the unnecessary driveline stresses a limited slip adds.

The selectable locker is the best option. It is invisible most of the time but there on the rare occasion it's needed.
 
The limited slip would be available any time and would try to work when going around corners as mentioned when not desired. It seems the E-locker only works when in four wheel drive and available with the off-road package. You can change out the transfer case control module with the Raptors to make the E-locker function in two wheel drive.

One more advantage of a good locker over a limited slip. Pick one wheel off the ground and a locker will still pull the other wheel on that axle. Most limited slips have trouble here. When crawling down a slick incline if one wheel loses traction or leaves the ground the other wheel will "free wheel" and you lose compression braking and the vehicle accelerates downhill just like you popped the transmission in neutral! With a good locker the one wheel will still try to hold the vehicle in control.

The advantage of being able to turn the locker on and off as needed is useful. In a front axle both wheels pull and in really slippery conditions make it difficult to turn to avoid an object. (like a tree) Momentarily switch off the locker, the vehicle turns and lock in again for maximum pulling ahead. In the rear axle locked sometimes the tail will kickout side ways. Unlock momentarily to straighten up and lock in again for maximum pull. This is usually experienced at slow speeds on very slick and cambered surfaces.

I have had both and myself, if ordering new would swing for the E-locker. I would even pay for one in the front axle but they probably would't do it. Wouldn't hurt to ask. The most capable four wheel drive vehicles have lockers in both axles for control both uphill and down. My 96 F150 came with factory limited slip in both axles, manual locking hubs, manual transmission and manual transfer case. Two wheel drive low was often used for backing trailers and in 1st/low would idle anywhere. It was a great crawler with minimum wheel slippage.

If you ever find yourself on a steep slick ramp with the back wheels in the water when launching/recovery? Engage four wheel drive before exiting the vehicle. This will have four wheels hold the vehicle instead of just the back two in the water. Might save the truck from a swim.

As long as you understand how the system works they are great. To the unwise they can break parts.
 
Chester":twkh3tl8 said:
A limited slip can cause stability issues on slick surfaces especially when turning a tightish corner.

The selectable locker is the best option. It is invisible most of the time but there on the rare occasion it's needed.
Click to expand...

I couldn't agree more. In fact, up here in the cold north I have a detroit locker (non selectable) in my 78 f250 4x4 and it is nearly impossible to drive in slick conditions in only 2 wheel drive as all it does with its 500 hp is go sideways. In four wheel drive, it is far tamer without any handling issues. If course with all this power, you can even get it to do it in 2 wheel drive on dry pavement all day long, but that is another story......LOL....

Our play car, a 2009 mustang GT has a limited slip from ford, and it basically does exactly the same thing in slick conditions as my pickup. It is terrifying to drive sometimes with the traction control off.

If you drive in the ice and snow often, I wouldn't recommend a limited slip at all. All they do is make handling the vehicle a chore. The selectable locker is by far the best choice as it is invisible with no handling concerns. There is nothing better than that setup.
 
Limited slip can also shorten tire life, especially during the dry season when making turns on pavement.

One of the best tow rigs we had in the past, was a 1994 FJ80 Toyota LandCruiser. It was set up with electric actuated lockers. Worked well when needed, but never any issues with handling or abnormal tire wear during normal driving.
 
A light brake application can sorta work like a poor man's limited slip.
The brakes have to be applied to the driven wheels only, it won't work on front wheel drive rigs with the parking brake on the rear axle.
On a vehicle with-in two wheel drive apply the parking brake lightly. With a four wheel drive apply just a bit of brake with the pedal and maybe a bit of parking brake too or just set a light parking brake as in two wheel drive applications.
Be careful, a heavy hand (foot) could damage the driveline.
 
I would go with the limited slip. Don't really know how e- lock works but electronic lock sounds to me like another source of problems. I had a F-250 2x4 - limited slip for 28 years. Hauled lots of wood out of the bush and carried a set of chains. Limited Slip will lock the axle momentarily when the drive wheel slips, so both wheels will grab. With a 4x4 you don't need anything else, esecially not for your type of driving!
I'm very interested in the Eco boost myself, sounds like a good Truck.
Hope this helps and good luck.
Peter.
 
Back
Top