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Old 02-28-2020, 03:56 PM   #1
1976gmc20
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Question Newer IFS front axle system?

Okay, since I am still sort of lost in the last millennium, I am curious to know how the front axles work in the 2000++ model year 4wd pickups:

Do they still have some sort of "central axle disconnect" like the GMT400 4wd IFS had, or do they just forget that altogether and let everything turn all the time ????


My 1989 K1500 4wd didn't work when I got it, and instead of replacing the problematic "donkey dick" actuator, I just unplugged and shimmed it with a short piece of plastic pipe so "the hubs are locked in" all the time. It's been that way now since I bought it about seven years ago. I just shift 2hi/4hi/4lo as necessary.

My concern - besides these actuators failing when you need them the most - is that with the axle on one side (right) disconnected, the left axle will be spinning the spider gears at a dizzy rate because the carrier and driveshaft aren't turning. How can that be good for the differential? You aren't even supposed to run different size tires on a drive axle, and not supposed to spin one wheel at high speeds if you get stuck. And of course if you had the old solid 4wd front axles you really weren't supposed to drive with one hub locked and the other unlocked. The latter is in effect what is happening with the IFS axle disconnect systems.
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Old 02-28-2020, 11:32 PM   #2
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Re: Newer IFS front axle system?

The first few years of GM IFS systems used a thermal actuator which was extremely problematic as you already know. They later switched to a fully electric actuator which is much less problematic. The GMT800 trucks and later were all electric as far as the front diff actuator works. They don't fail like the old ones.

As far as the spider gears turning from one side driving them all the time, again that hasn't been an issue. As long as the fluid in the front diff is at the correct level, the gears are fully lubricated. I've yet to see a front diff in the dealership where I work with 50,000 miles, 100,000 miles or higher where the spider gears were wiped out from normal use with mostly 2wd operation.

I prefer my solid axle in my K5 with the manual locking hubs, but the issues that came from the early IFS systems are no longer there. The trucks are very reliable with normal maintenance. I'm not a fan of pushbutton or rotary knob style electronic t-case shifting, but they haven't been an issue compared to the early years. I recommend anybody that has an electric shift t-case to shift it through the ranges periodically to allow the feedback switch to move with the shift arm to keep it from hanging up. If the feedback switch (that reports the actual shift position to the computer) hangs up or does not move in the correct amount of time the computer will abort the shift and throw it back in the range it came from.

The #1 issue with the rotary knob style shifter for t-cases is moving the knob with the key off. The system will not change ranges with the vehicle shut off and won't respond to the change in position when the key is turned on. What happens is the system will stay in the last range it saw before shutting off and won't respond to any new change to the knob position. The only way to get it to work again is shutting the truck off, moving the knob to where it was before and then turning the truck back on. The tiny little indicator light on the edge of the knob will light up again and follow any new change in position.

Keep this in mind, any IFS truck from any current manufacturer domestic or foreign will work the front axle disconnect in the same concept as the GM system. If I'm not mistaken even the Ram and Jeep solid front axle setups use a similar front axle disconnect to not have to run locking hubs at the wheels and allow a true shift on the fly to 4wd type setup.
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Old 02-29-2020, 12:21 PM   #3
1976gmc20
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Re: Newer IFS front axle system?

I'm not sure but I don't think the Wrangler has any front axle disconnect at all. Some time back I saw YT video about changing the spindles and axle shafts to install lock out hubs. The early XJ's had a right axle disconnect that was apparently a problem so they just eliminated it about 1990 so they made ~10 yrs of them with no provision to isolate the front driveline. I got lucky in that my old XJ has the Selec-Trac so it never had the disconnect but the usual Jeep guy thing is to take it apart and turn it around so it is always engaged. We run ours in "full time" all the time anyway, which the manual says that you can do on/off pavement.

So does the axle disconnect on the new pickups stay engaged if you shut off the key when you are in 4wd? Sometimes I park on a slippery hill and I want all four wheels holding! I knew somebody that had a Honda Ridgeline and that dang thing would default back to 2-hi every time you shut it off

I saw a late model Silverado "work truck" that belonged to the county and it actually still had a manual transfer case lever. I could almost live with that but I suppose it had the electric in-out thing on the front axle.
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Old 02-29-2020, 10:07 PM   #4
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Re: Newer IFS front axle system?

The JK jeep and JL as well as the 2500/3500 Ram trucks all use the same setup.


A thread with a good video on how it works.
https://jlwrangler.com/showthread.ph...sconnect-Works

The center axle disconnects use electricity to engage, so shut the truck off the system relaxes. Honda ridgelines are front wheel drive based with a electric clutch providing power to the rear axle when the 4wd button is pressed.

Yes, even manual shift transfer cases use the electric front axle actuator.

If you have to have the manual control over the front axle engagement, there was a 4x4 posi-lock that replaced the electric actuator with a manual lever using a cable and plunger.

Hate to say it but if one wants full manual control over the 4wd there isn't a new truck out there (or for the last 20 years) that has full manual hubs, manual shift t-case and no electrical nannies in control.
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Old 03-01-2020, 12:46 PM   #5
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Re: Newer IFS front axle system?

Thanks for the correction I had no idea that Jeep had gone back to using that again.

A former neighbor bought a new 4wd F-350 a few years ago, and it did have a solid axle with lock-out hubs. But the TC shift was electric (and of course it was a F**d ! )

I suppose one could just disable the disconnect somehow (like I have done in my old GMT400) so that the two front axles were always locked together. But that would probably be a warranty No-No on a new pickup. I was looking at buying one of the cable controls for my 89 but it just wasn't worth the added expense for a "ranch" pickup. Besides I wanted to get the 4wd working at least temporarily before I spent any more money on it, and once it was working in 4wd then why bother?

The problem (one of them!) that I have with these things is how long do they actually take to engage ??? For instance, let's say you are driving around on paved roads in 2wd and there are random slick spots. You stop at an intersection and there is ice because other people having been sliding and spinning and it hasn't melted there yet. So you need 4wd to get going but you are immediately going to put it back in 2wd as soon as you get back on dry pavement. So you have to sit there while all the gizmos whir and the computer figures it out?
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Old 03-01-2020, 01:19 PM   #6
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Re: Newer IFS front axle system?

Yes if the truck was under warranty it could void that part of the warranty.

As far as how fast the system engages, it happens in only a couple of seconds or less.

Super duty fords do have lockout hubs. They are vacuum actuated automatically but can be locked manually.
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Old 03-01-2020, 02:29 PM   #7
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Re: Newer IFS front axle system?

The actuators for the gmt400’s changed to electric sometime in 1998. My K2500HD is a March ‘98 build and has the electric setup. 200,000 miles and not a single issue. The 4x4 switch in the dash has had bad solder joints for 10 years but I can still get it to work.
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Old 03-01-2020, 03:57 PM   #8
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Re: Newer IFS front axle system?

Quote:
Originally Posted by Zoomad75 View Post
Yes if the truck was under warranty it could void that part of the warranty.

As far as how fast the system engages, it happens in only a couple of seconds or less.

Super duty fords do have lockout hubs. They are vacuum actuated automatically but can be locked manually.
I wonder if you could put it in 4wd and then shut it off and "accidentally" unplug the actuator Probably the computer would have a fit


Years ago our VFD had a ~94 one ton wildland fire engine that the wire got unplugged, probably by driving through sagebrush. With all that weight of water and pump etc in the back we didn't notice it for several days driving around a fire scene in low range, until one evening we tried to drive up a Cat trail. It spun out the rear wheels, and I had to back down the cliff a ways and manage to turn around in a really precarious spot. At the time I had no idea about those stupid actuators, and later another more knowledgeable volunteer checked it out and plugged it back in.

That truck has long been replaced. I actually thought about bidding on it from the county, but it had been used hard - the frame had been cracked and welded and stuff like the lights and wipers didn't work right. Later I got my K1500 from a neighbor after her divorce for $800. It needed a few things I've got it going pretty good now but it just seems like a poor candidate to fix up well enough to make a road trip truck out of it. At my age, sometimes I think would like to buy a new or at least a later model pickup that I wouldn't have to fix up and work on all the time.
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Old 03-01-2020, 08:04 PM   #9
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Re: Newer IFS front axle system?

Quote:
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I wonder if you could put it in 4wd and then shut it off and "accidentally" unplug the actuator Probably the computer would have a fit
Seriously, though … would installing a cable control for the front axle disconnect void the warranty?
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Old 03-02-2020, 11:25 PM   #10
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Re: Newer IFS front axle system?

Quote:
Originally Posted by 1976gmc20 View Post
Seriously, though … would installing a cable control for the front axle disconnect void the warranty?
It would not void the entire warranty of the vehicle. If a failure was to happen to the front differential with the cable control on it I'd say it would be easy to blame and therefore void the warranty on the front diff.
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Old 03-03-2020, 12:35 PM   #11
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Re: Newer IFS front axle system?

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It would not void the entire warranty of the vehicle. If a failure was to happen to the front differential with the cable control on it I'd say it would be easy to blame and therefore void the warranty on the front diff.
Thanks! I guess one should wait a few months or a year at least and make sure the front diff isn't defective. I should have the money at some point in the not too distant future and I am just trying to figure out I would do; I'm not sure I want a new one or not.


So you work for a dealer in Pueblo? A long, long, long, long time I ago I worked for Daniels Chevrolet in the Springs when they were still downtown. I just ferried stuff around and took people home/work and picked them up when their cars were in the shop. Most of the new stuff was kept over on a dirt lot on 8th street, so I got to drive everything brand new.
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Old 03-03-2020, 02:02 PM   #12
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Re: Newer IFS front axle system?

The new tech works my friend. I had a 99 K2500 Suburban and currently have a 2003 2500HD Silverado. Both with push button transfer cases. I haven't had an issue yet. The 4WD engages as soon as you press the button, no wait. If My wheels start slipping just press the button and go.
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Old 03-03-2020, 02:29 PM   #13
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Re: Newer IFS front axle system?

Quote:
Originally Posted by MalibuSSwagon View Post
The new tech works my friend. I had a 99 K2500 Suburban and currently have a 2003 2500HD Silverado. Both with push button transfer cases. I haven't had an issue yet. The 4WD engages as soon as you press the button, no wait. If My wheels start slipping just press the button and go.
Okay.

Our VFD has a 2008 Dodge and it doesn't work like that at all. Stop, turn the knob, wait … oh, shoot - I didn't put it in neutral … try again, maybe better start all over … oh, now the light is ON - what did I do different? Of course, we're not in a hurry to get anywhere or anything like that

So I'm not exactly filled with confidence, though I don't doubt GM could do better than that.
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Old 03-04-2020, 01:54 AM   #14
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Re: Newer IFS front axle system?

I don't work at the dealer in Pueblo. I'm at the dealer west of there the next town over.

I'm no Dodge expert for that matter, but been within GM at the corporate level or dealer level for close to 25 years now. GM's systems only require a shift to neutral when shifting between 4hi and 4lo and vise versa. Shifts from 2hi to Auto4wd or 4hi can be done on the fly all the way to highway speeds.

I totally agree with MalibuSSwagon. The new tech works. It's not to say there can be problems that arise, but my experience is that proper maintenance and use periodically allows the system to function when you need it. The old systems had their issues too. Auto locking hubs were problematic on the squarebody trucks and often pitched in the can for manual locking hubs for reliability. Just like the new stuff, if the old stuff didn't have a traction device in each axle, you could still end up with 1 wheel spinning on each axle even though you are in "4wd".

Honestly, if you are concerned about the 4wd working when you need it, that's the least of your problems. The rest of the trucks, even the base models are so loaded with new technology it might blow your mind. Honestly in the wrong hands it's overwhelming. I see it on a regular basis where the vehicle has more capability in technology that some people can grasp. I'm not saying that as an insult, but as a matter of fact. These are the same people that avoid smartphones for flip phones or no cell phone at all. They may or may not use a computer at home.

Lane keep assist where the truck "sees" you wandering out of your lane and steers the vehicle back within the lines is freaky the first time you feel the steering wheel move without input. Add a haptic motor in the seat to shake the seat cushion on the side you are wandering into so you pay attention and steer back straight. Smart cruise controls that use radar to sense distance to the car in front of you and match speed to maintain a specific following distance and input the brakes to slow down when the car in front of you slows down.

There's so many safety systems now to help avoid an accident and limit the use of airbags and seat belt pretensioners is crazy compared to even 5 years ago.

So if you distrust a tried and true 4wd system that's been in use for close to 25 years you really are not going to like the rest of the really "new" tech these modern trucks have. I'd stick to looking for a low mileage GMT800 truck built between 2001-2007 where you get rock solid engineering in a better frame, better powertrains with the LS engines and better ergonomics in the interior than the GMT400 trucks before them without as much of the added in technology that the later trucks are saturated with.
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Old 03-04-2020, 12:32 PM   #15
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Re: Newer IFS front axle system?

Yeah, I'm sure that lane assist goes nuts when you drive on a winding gravel road I'm just wondering how the phone/utility/construction companies deal with these new trucks when they're taking them off into the brush all the time? Do the "work truck" models have all that too? Our newest VFD truck is a 2010, but it is an F-550 so it's hubs and lever.

One of the first things I had to do on my 91 Suburban ~20 yrs ago was replace the auto-hubs with Warn after they failed me up in the mountains. But that made it rock solid.
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Old 03-05-2020, 12:05 AM   #16
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Re: Newer IFS front axle system?

Base model trucks won't have as much content as LT's, LTZ's or High Country trucks. But they still will have stability and traction control systems. Again, pretty standard stuff now and really is only a function of the ABS system with the added yaw rate sensor and torque angle sensor from the electric power steering.

I have had my share of fleet trucks through from the local electric company, BLM and Forest Service, local city and county, police/sheriff and all of our local prisons. Typically, the durability is down to the fleet driver just as much it is to the truck. Fleet drivers just don't care about the vehicles they are driving. But in general, they hold up just fine.
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Old 03-05-2020, 01:11 PM   #17
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Re: Newer IFS front axle system?

I just wondered … there must be a way to turn all that nanny stuff off or else you couldn't drive off road?
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Old 03-09-2020, 06:28 PM   #18
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Question Re: Newer IFS front axle system?

Found online at "local" (nearest) dealer:

2016 K2500HD "work truck" regular cab, long bed, 6.0 v8 gas, 6 speed A/T, floor shift transfer case, 73K miles

$22K


I really don't want anything that new, but dang I'm getting tired of always needing to work on stuff.
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