A few questions of longtime Chevy/GMC IFS 4wd owners.

FellowTraveler

Explorer
There is a rash of comments about chevy/gmc ifs front differentials being weak and even blowing apart when used for anything other than on road. There are many ifs diffs that are used in various models of chevy/gmc my questions are for owners of 3/4-1 ton units K2500/3500, however, other lighter duty truck owners should chime in too. These questions revolve around owner failures not some I've read stories, seen on another site, heard or whatever.

Describe your truck, tires, gears and power-train, pictures would be nice.

Any problems w/front ifs differential blowing up when you are off road, or?

If so, what were the circumstances encountered when the front ifs diff blew apart?

If you converted to a solid axle setup was the decision based on your knowledge or someone else telling you your front ifs differential is weak, or?

My K2500 IFS 4wd front differential has an ARB air locker and I've never had issues with anything breaking under all conditions.

I suspect the blown chevy/gmc ifs 4wd differential stories are more myth than fact!
 
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Dont own and will never own a chevy ifs but I do know they are weak. I plow snow in the winter and I own a blizzard 810 weighs right around #1000 and most blizzard dealers refuse to install one on a chevy. I have seen more ifs trucks broke in the winter plowing because their just not hevy duty enough. jmo
 

DoWorkSon

New member
I have a 2007 H3. The non-alpha front ends are notoriously weak, which is why I went with 255/86/16's instead of the 315's most guys put on... This way I will be able to justify my complaints when it explodes.
 

Larry

Bigassgas Explorer
While I have not suffered or seen the failure of an IFS front diff, by the sure design of the GM IFS case where it is made up of two cast aluminum pieces with a carrier sandwiched in between flat out looks feeble by design. I imagine there was a reason GM changed the front IFS 9.25 differential in the 2011 HD trucks to a new full cast iron 9.25HD case instead of the two piece aluminum design.

In all reality even as cheesy as the aluminum front differentials are on the GM IFS rigs, I have not seen a front differential actually fail. Then again, I know of nobody other than you (FellowTraveler) that is willing to run an ARB locker in one either but even at that the driver has a lot to do with the breakage of anything, even the beloved Dana 60 SFA. If the driver is ginger on the loud pedal and wisely uses the front ABS locker switch when terrain actually calls for it then it would probably live just fine. I would be more concerned about tie rods than the front differential.

About 13 years ago when I was right out of college I worked on the Chevrolet Technical Assistance hotline in Detroit that supports dealers with technical issues, I had the pleasure of working in the truck driveline, suspension and steering group. I think I heard of just about every failure type on the older GMT400 IFS trucks and front diffs were not one of them but that was well before the big power diesels and 8.1L’s appeared in 2001 in the new GMT800 HD trucks that used the same aluminum 9.25 front diff as the older trucks. When I was on the hotline upper control arms ripping off the frame on GMT400 2500 and 3500 series trucks, tie rods breaking, broken torsion bars, and broken torsion bar supports were pretty common. Granted, these type failures were usually on GSA trucks, plow trucks, ranch trucks, lineman trucks and railroad service trucks. Basically, IFS was not working well for the severe duty customer which is one reason I feel the Stupid Duty got so popular. GM lost their edge when they chose to cater to the people that should be driving cars or S10’s instead of remaining true to durability in the severe service sector. GM’s choice to use IFS on an HD truck has pretty much isolated them to the personal use retail type customer. My personal feeling is IFS has no place on any truck with a GVW higher than 10,000 lbs. IFS works great on a small Tacoma or 1500 series Silverado/Sierra, Ram, F-150, Titan, etc.

That said, is IFS a bad thing for the average Joe weekend backcountry adventurer that likes to get out and go ride some trails and see what the back country looks like? Absolutely not, IFS works fine. Just be conservative with the tire size and drive wisely but I sure wouldn’t bet money on a GM IFS truck at the redneck renegade tractor pull with a front locker.
 

herm

Adventurer
i own one. an 09 1/2 ton gmc pickup. I have been on some roads/trails that people have told me i was crazy to drive and have yet to have any issues. I think it is a case, similar to the G80 locking rear diff. people do not understand their use or limitations, and expect everything to last like a D60 or a rockwell. It is amazing the abuse i have seen people put trucks through, then blame the manufacture for the problems that arise.

"as slow as possible, as fast as necessary" words to live by.
 

Larry

Bigassgas Explorer
Here is an interesting string on chevy/gm ifs survival it even touches on the red sled test posted herein this forum.

http://www.gmfullsize.com/forum/showthread.php?t=160152

Interesting article indeed. An article written by a company that their entire existence is hinged on IFS suspension systems. Written with bias and some stretching of reality and missing true engineering data.

BTW….Reallift is a cool deal for those running lifted IFS trucks. Their pieces tuck the torsion bars up out of the way nicely. If I ever lift my ’01 Silverado HD I will definitely incorporate their parts as I hate the torsion bars hanging so low. On the other hand, if I were to buy a new truck I would forgo my GM discount and just buy a RAM Power Wagon made of real drivetrain components straight out of the shoot and call it a day.

IFS is one of those deals like the age old argument of diesel vs. gas, manuals vs. automatics, EFI vs. carburetors, blah, blah, blah. Everybody has their preference and reasons for it. It all comes down to whatever floats your boat and fits your needs. No need to justify or defend what you want to run in your own rig.

BTW….your sig. Navstar is spelled NAVISTAR….which is where I work. I know of nothing where we were involved with GM or GEP (AM General) on enhancing anything on the 6.5L diesel engine platform. Maybe your “Navstar” is different than the way I am read into it.
 

Ponyracer

Adventurer
Basically, IFS was not working well for the severe duty customer which is one reason I feel the Stupid Duty got so popular. GM lost their edge when they chose to cater to the people that should be driving cars or S10’s instead of remaining true to durability in the severe service sector. GM’s choice to use IFS on an HD truck has pretty much isolated them to the personal use retail type customer. My personal feeling is IFS has no place on any truck with a GVW higher than 10,000 lbs. IFS works great on a small Tacoma or 1500 series Silverado/Sierra, Ram, F-150, Titan, etc.

I have never understood why GM took themselves out of the big truck market. It seems to me they could easily market 2 different front suspension designs, say IFS for 1/2 and some 3/4's then a SFA for 3500/4500/5500. Yes it would cost them $$$ but I'd bet they get it back in HD sales market. It's a shame as thier interiors are beautiful.
 

herm

Adventurer
agree, though where i work, the chevy's last longer because all of the ford 6.0 and 6.4L engines are junk. I have 130k on my 2009, and it has had 3 turbos, 2 oil pumps, fuel pump, emissions assy, countless injectors...... we have some fords with less miles that have had to have complete engines and transmissions replaced. I believe it is about the whole package when it comes to the HD market. We have been replacing with the new ford design engine. jury is still out on those. there are around 100 ford 250/350's and maybe 20 chevy's in our camp.
 

Larry

Bigassgas Explorer
For what it is worth, a few years ago I picked up a well beaten down 100K mile work truck package 2005 Silverado 2500 HD standard cab 6.0L, 4L80E, rubber floor mat, with the good ole manual shift transfercase. It had absolutely no options other than cruse and A/C, which is all that matters anyway right? Stripper trucks is how I like them anyway!

The ’05 Silvy was only a few years old at the time but snagged it for 5K from a fleet than ran duties around the Navajo Nation servicing natural gas wells where it completely fell apart. Being a GM type of guy I figured I would easily patch it back together and set it up for the sole purpose of backcountry adventures. I had lofty plans for it including a FWC, ARB bumper, lockers, etc. Well, after many months of replacing engine mounts, the exhaust y-pipe, most all front suspension parts, fixing interior rattles, welding body cracks ( rear cab mounts totally broken off), replacing broken bumper, broken ECM brackets, replacing both front leaky axle seals and axle shafts (broken boots stuffed with tumbleweeds) and tons of other parts that just shouldn’t have broken on a newish truck I quickly realized that I don’t have any faith in later model GM trucks to serve the duties that I want to do as an amateur outdoor adventure type of guy. I knew for the type of stuff I like to do the IFS would need major money tossed at it to make it durable or replace it with a coil boinger Dodge front axle or older Ford SFA system or just sell the whole damn truck and finish off my old truck to serve the same purpose. So, I sold it and used the profit to stuff an overdrive NV4500 overdrive transmission into my 34 year old GM truck that I had already owned for 17 years and had already upgraded to a late model 8.1L fuel injected big block a few years prior. The ’05 Silverado sale proceeds also helped finance the new Phoenix popup camper for the ’78. At that point the old ’78 truck became the main outdoor adventure rig and I feel I have a better truck in this old ’78 than if I would have stuck to the ’05 IFS Silvy HD. The funny thing is my ’78 only has a D44 front axle but I feel more confident in a D44 than a late model GM IFS HD truck.

Below is the late model GM rig that had I had grandiose plans for that quickly died every time I pulled it into the shop to fix the next problem that popped up. It was the best vehicle I’ve ever bought, fixed and sold while making a profit. Sold it for double what I paid. Glad it is gone and the ’78 is happy too because it got a new leash on life and gets to go on long distance outdoor adventure trips now! The '05 Silvy did look pretty cool after it was put back together but I just didn’t have faith in it for what I wanted to do with it and places to go. I would have driven the Silvy to Alaska once it was done with it but wouldn’t have wanted to maintain it along the way.

5305412692_f42ac356c7_z.jpg


5305410474_3051c02d47_z.jpg
 

FellowTraveler

Explorer
BTW….your sig. Navstar is spelled NAVISTAR….which is where I work. I know of nothing where we were involved with GM or GEP (AM General) on enhancing anything on the 6.5L diesel engine platform. Maybe your “Navstar” is different than the way I am read into it.

Hello Larry, yes, you are right in my sig NAVISTAR is spelled NAVSTAR my bad. Anyway, in May 1999 GM started installing enhanced 6.5 td blocks identified w/NAVISTAR logo in the lifter valley and this is the block installed in my 1999 K2500 Suburban, this block has no connection whatsoever to AM General as it's cast before their enhanced blocks appeared I'm thinking AM Generals appeared in 2004 after they lost big $$$$ replacing all the bad blocks they sold to H1 owners. The bearing caps are a little thicker, the casting when compared to other GM 6.5 td blocks is much more beefier in it's build. With the introduction of the 6.6 duramax it appears 6.5 td castings w/NAVISTAR logo went into 2002. I've heard some rumors that IH made some enhanced casting too for GM but I have never seen any.

I believe you'd be hard pressed to find stories of these NAVISTAR casting 6.5 td blocks failing like the pre MAY 1999 blocks did.

When this one goes south I'll install a P400 engine, however, this 6.5 td runs perfect in every way.
GMC 6.5 TD NAVISTAR ENHANCED BLOCK 001.JPG
 
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Larry

Bigassgas Explorer
That is definitely interesting FellowTraveler. I’ll have to ask around and see if any International old-timers can tell the story with that engine. Maybe someday I can dig up some cool stuff to send ya.

AM General created a new company called General Engine Products that purchased the 6.5L tooling and manufacturing rights from GM. GEP was born Jan 1, 2000, which is 1 year after my old division of GM was sold off to an independent manufacturer as well then 5 years later got picked up by Navistar. Anyway, we used the 6.5L in several thousand Post Office and Frito-Lay trucks from 1999 to 2005. I remember all of the 6.5L engines after early 2001 where engine manufacturered by GEP, not engines built of GM’s leftovers. Along the way I got to know our supplier, GEP very well and even became close friends with one of the product support engineers. Like I say, I’ll see if I can dig up details of whatever the involvement was on this engine through one of these channels.

Sorry for the engine detour…..Now back to regular scheduled programing on the topic of IFS…… :sombrero:
 

FellowTraveler

Explorer
More info on this enhanced 6.5 td always welcome, it's history is shaded indeed, thanks.

Let's not beat the IFS horse to death, if I find the need for an SAS conversion it would be a FORD high-pinion differential.
 
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Balzer

Adventurer
I have owned a lot of GM IFS trucks but all have been 1/2t or heavy half (6 lug labeled as a 2500) So I have no experiance with one locked up because there is no locker option for the 1/2t front diff.
That said I have abused the hell out of some of them and never broke the diff itsself. I have gone through axle half shafts/CV shafts a lot though. I also have many friends that have had them and abused them, but have never seen the actual diff break. Yes its 2 part alum, but its thick alum.
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I will admit I am a GM fan. I might be a little bit biased, but I do not love the IFS, And I do not love the lowrider stance the way they come from the factory.
However I have seen the new dodge IFS trucks that sit practically on the ground, same goes for the new fords.
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SO dont single out GM they are not the only ones. It goes along with a lot of things simular to jeep D35 rear axles some people will say if you sneeze at the they break other guys lock them and run 35's and never break.
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Last thing, someone mentioned sled pulls with locked GM front diff so here ya go.
http://www.youtube.com/watch?v=Qra0bbra3OI&feature=relmfu
http://www.youtube.com/watch?feature=endscreen&v=aZZN3mooidQ&NR=1
 

Buliwyf

Viking with a Hammer
I blew up a 2500HD backing a trailer up a steep gravel service road to a cell tower. Steering angle, rolling bouncy washed out road conditions, loose marble-like gravel. The perfect storm. One wheel slip, and SNAP, explosive drive shaft at the joint.

That truck ate tie rod ends as well. Same truck killed three power steering pumps and a flexplate/flywheel/blower resistor/ ignition switch/ seat foam/ door hinge. Standard 150k mile GM stuff. Pumps were likely defective rebuilds, I hope.

Run what you want to. If it isn't broke, don't fix it. But IMO, GM's IFS is setup to win Car and Driver reviews and to attract like minded truck buyers. It's not really intended for folks that value flex, durability, lockers, manual hubs, and lift adaptability.
 
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