My '96 Explorer which has an early "control trac 4x4" system. This had a vacuum disconnect front differential and 2wd mode, then "Auto 4x4" and 4x4 Low. The Explorer guys would "hack" the t-case by providing power to the clutch to give a true "locked" 4x4 high. after 140k miles and 14 years the t-case would sometimes "slip" when in a real offroad situation in 4x4 low but it never failed. I had bigger then stock mud tires on it also.

I'd like to think with decades of improvements in both design and materials that it would hold up even better.

I'll find out with my F-150 since it spends 6 months of the year every day in either Auto 4x4 or 4x4 High mode.

 

I'm curious if the shift-on-the-fly system used on XLs and XLTs would be considered more durable or bulletproof than the TOD system, given that it is apparently more simplistic? Or would this amount to a non-issue in the real world...six of one, and a half-dozen of the other?

 

IDK, the Expedition has used a TOD Transfer Case since it came to market in 1997 and the comparable F-150 had a normal 2-speed t-case. I've personally had more failures with the normal 2-speed case like twice in a new (at the time) 2003 F-150 lariat that lost two shift forks within months around the 15k mile mark.

 

That's a good question. The ESOF transfer cases have been in use since at least '99, and they seem to be susceptible to shift motor problems as they age. I'm not sure about the moving components in the TOD cases for switching to low-range, but the electromagnetic clutch should be more reliable than an electric shift motor.

AWD systems have been using electromagnetic clutches for over a decade now, and they don't often fail. No actual moving components in these...to engage torque the control module applies voltage to an armature which applies magnetic force to the clutch pack.

 

I had a 1996 Explorer as well. Great vehicle, very few issues. I managed to always keep the shiny side up.

These vehicles do not have any sort of viscous coupling or planetary center differential, so the difference in wheel speeds between the axles must be handled by degree of clutch engagement. The clutch method is very common today, because a true center diff adds cost and weight, and then there must be an additional method to actually control slip in the center diff. The center diff *does* allow true permanent 4x4, and is probably more durable in the very long term. Cars like Mercedes, Audi, and a few others use this type of system with various methods to control center diff locking. Land Rover also uses a center diff on their larger vehicles.

For awhile, the viscous coupling unit was the golden child. It could be used in place of a center diff and was pretty light and small and cheap. But the problem was that these systems reacted to slip slower than a clutch and required wheelspin to occur before they could react. They also dragged down fuel economy and could fail after 100k miles.

The clutch is now extremely popular on virtually every AWD vehicle with a transverse engine and obviously popular on many pickups. It can preemptively engage, its reaction time is extremely fast, and it can cleanly decouple for best fuel economy. It is relatively durable...

But, there is a reason no clutch-based 4x4 is offered on heavy duty pickups. It is because the clutches cannot withstand this type of weight, they are not heavy duty enough. They could probably be made so, but they would be large, heavy, and expensive.

 

It works as a all wheel drive system. Think of a toyota land cruiser. That was my experience with 4A in my truck.

 

I have experience with a few VC AWD systems, most noted was the AWD system used on the 96-01 V8 only Explorers which was a full time fully mechanical system that provided 35/65% power in normal driving conditions but would allow up to 50/50% split. I've found that system to be amazing and just a tad tail happy which I like, of course no traction control or RSC stops you from sliding around if you so choose ( I do ). The same type of system but assisted by TC and RSC is in my '06 Chrysler 300 and it does an amazing job of always having traction. So I do prefer the VC type of system as it doesn't allow slippage before the front wheels have pulling power.

You are correct these systems can't handle the heavy duty action that a Super Duty could throw at it, but I have a feeling we're not too far off from it being a possibility.

 

Absolutely would be nice to know that "clutch" info!! When I take delivery of my 2017 f150...I'll make a point to crawl under and look at the ID plate on the transfer case. I'll post back the markings...assuming it is in a place that is visible.


biz

 

I bet the make and model likely won't be stamped on the case. Just Ford internal part numbers. I believe it is a Borg Warner case of some variety...

 

Ram has had problems with their auto Tcase when used in mud or lots of snow. It is the Borg-Warner and I think it is the same unit used in the Ford. The Ram ones also don't seem to lock up until you get moving.

 

The clutch is sealed inside the transfer case, so snow, mud, or water (even submerged) should not be an issue.

 

Maybe from spinning the tires too much?

Haven't heard any issue with t-cases, but Dodge can't keep a transmission alive to save themselves.

Josh

 

This certainly used to be the case, but not anymore. The half-ton RAM trucks are all using licensed ZF transmissions now. ZF is a major transmission (and other automotive components) manufacturer in Germany and supplies many companies...from Rolls-Royce, Audi, Land Rover, BMW, all the way to Hyundai. Every 2009-2017 Ford F-150 with a 6-speed automatic is actually equipped with a licensed ZF 6HP26 transmission. (Ford is moving away from this transmission to the Ford/GM 10-speed in half-ton trucks and produces their own HD transmission, the 6R140 in heavy duty trucks...but new for 2017 is the 6R100 transmission which is a fortified ZF 6HP26 used only in F-250 gas powered trucks).

Meanwhile, RAM HD trucks use one of three transmissions: the G56 manual transmission (built by Mercedes-Benz), the 68RFE automatic, and the Aisin ASC69 automatic. All of these transmissions have generally provided good service.

 

It's probably more about heavy use and heat buildup than it is about contamination. Most clutch-based AWD systems will deactivate when they get too hot, I imagine that's possible in a clutch-based transfer case.

 

I guess, if a user decided to do some mudding while staying in 4-auto mode, the clutch could overheat. It would seem the owner's manual would advise using "4-Hi" for this type of situation which would theoretically avoid slipping the clutch as much, if at all. The clutch must be fairly strong when in "locked" position given that it is used to transmit torque when the transfer case is in 4-low.