Mechanic says not to use 4a all the time

[oldpaddy]

I'm on my third expy and I've always left them on 4a (4w drive auto). The mechanic says it's bad for the transfer case. What do you guys say?

I use 4a all the time because I live on a long dirt road and it rains a good bit here and we get snow/ice during the winter. I figure it's a good set and forget setting. I've never noticed it come on at highway speeds.

 

[JasonH]

I would think it's the opposite. Generally seals last longer with periodic lubrication. I think circulating the fluids in the transfer case on occasion would be a good thing. The AWD 4A is only going to activate when there's slippage anyway, so it's not like you're engaging the transfer case all the time.

 

[Trainmaster]

Follow your owners' manual. It's clear about these things. I doubt your "mechanic" has read much since high school, and has certainly not read about your transfer case.

 

[oldpaddy]

Follow your owners' manual. It's clear about these things. I doubt your "mechanic" has read much since high school, and has certainly not read about your transfer case.

The guy used to be a tech at a Ford dealership and he's the best mechanic in the shop. I know this because it's my father in-laws shop. Though I can't find anything saying he's right about this.

 

[jkayca]

I'm pretty sure it's mentioned in the manual not to do to leave in 4a or 4wd. Not sure of the mechanics of it.

Found this article which about 4wd drive systems Ford uses: https://www.blueovaltrucks.com/tech-articles/understanding-the-4wd-in-your-ford/

 

[Viper74656]

To quote from the manual, page 169: "This mode (4A) is appropriate for all driving conditions, such as dry road surfaces, wet pavement, snow, or gravel."

4H and 4L are a different story.

 

[Trainmaster]

I'd read the manual and forget what the wisest mechanic in town and people on a Web forum have to say.

Jkayca's link is also very helpful and the information is right from Ford:https://www.blueovaltrucks.com/tech-articles/understanding-the-4wd-in-your-ford/

 

[oldpaddy]

I'd read the manual and forget what the wisest mechanic in town and people on a Web forum have to say.

Jkayca's link is also very helpful and the information is right from Ford:https://www.blueovaltrucks.com/tech-articles/understanding-the-4wd-in-your-ford/

Yeah, I read that earlier and I couldn't find anything saying it's bad.

 

[99WhiteC5Coupe]

The guy used to be a tech at a Ford dealership and he's the best mechanic in the shop. I know this because it's my father in-laws shop. Though I can't find anything saying he's right about this.

Perhaps ask the mechanic WHY it is bad for the transfer case to drive in 4A all the time, and what problems can be caused by using 4A all the time?

 

[mr_dave]

4A definitely leaves the transfer case engaged, meaning more wear on that part and the front driveline, diff, axles, etc. Plus less mileage due to the extra drag. I believe it's just the hubs that auto-engage and disengage. I agree with the mechanic, it's probably not a good idea to leave it engaged 100% of the time since the transfer case wasn't designed for it. That being said, I try to exercise 4A and 4H whenever I can while on dirt roads to keep things lubed. While on dry pavement it's always in 2H.

Edit: My statement above isn't quite accurate, see this conclusion: https://www.expeditionforum.com/thr...-use-4a-all-the-time.48493/page-3#post-446021

 

[tommyddsr]

My 2000 had 4A, 4Hi and 4Low, no 2 wheel drive option period. Never had an issue. They are designed to be able to run in 4A, even the newer ones.

 

[Plati]

400K miles on 3 different Expeditions since 1999
95% of the miles in 4A
Never had an issue

 

[jeff kushner]

I have run my truck since new, in 4A for everything short of climbs....I have 121K and a spring broke for my console hinge, nothing else..............

I prefer to utilize all the features I've paid for..............of course you are free not to.

jeff

 

[chuck s]

Seems like 4A serves no purpose in normal driving and is OK but is it desirable? These are not real AWD vehicles like Subarus.

I don't see any need to engage the front wheels in normal driving and, like Dave, I can feel the drag of the transfer case when switching from 2H to 4A so I've have left it in 2H for the past 14 years (two different Expeditions) engaging 4A periodically in slippery conditions such as rain (and definitely in snow). The drag indicates there's mechanical strain and consequently wear. How much no one seems to know.

For the curious switching the dash display to "off road" shows were the power is being directed. Can also display road angles which is interesting in the mountains although on really steep grades there's no time to look at it.

-- Chuck

 

[Goofy173]

My brother just retired from the Expy plant in KY. He is an engineer. 4A is fine all the time.

 

[Gary Hanna]

I'm on my third expy and I've always left them on 4a (4w drive auto). The mechanic says it's bad for the transfer case. What do you guys say?

I use 4a all the time because I live on a long dirt road and it rains a good bit here and we get snow/ice during the winter. I figure it's a good set and forget setting. I've never noticed it come on at highway speeds.

I have an 2004 left in awd with 170k and no problems

 

[Plati]

.

 

[mr_dave]

Expy is "on demand" meaning that unless power to front is needed, no power to front wheels.

Yes, the front wheels aren't being driven all the time in 4A but the transfer case, forward driveshaft, front differential, and front axles are all continuously engaged. The only thing not engaged all the time in 4A are the wheel hubs.

If you would like to drive all those components all the time it doesn't bother me. However there seems to be some confusion so I just wanted to help clear it up.

Edit: My statement above wasn't correct. It turns out in 4A the entire front drivetrain is engaged and the transfer case applies power to the front as needed.

 

[Plati]

.

 

[mr_dave]

I can feel and hear the front drivetrain engage when I put it in 4A, but now I'm curious as to exactly what's moving at that point. Might have to find a go pro and do some testing.

Edit: OK just did some driveway testing since I was curious. In 2H I can freely turn the front driveshaft coming from the crankcase by hand and it also turns the front diff and axles. I then put it in 4A which engaged the crankcase and it was no longer possible to turn anything by hand. Additionally, there is no mechanism to engage/disengage the front drivetrain once the crankcase is engaged. Therefore, I am 99% certain that my original understanding is correct that the whole front is turning when in 4A, and the only thing that's 'auto' is the wheel hubs.