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

  1. #11
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    Quote Originally Posted by Larry View Post
    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
    Last edited by FellowTraveler; 04-29-2012 at 10:41 AM.
    1999 GMC K2500 BURBAN, NAVISTAR enhanced 6.5 td aftercooled, dual alt's, PSC p/s pump w/HD cooler, redundant FSD's, HEATH program, turbine/downpipe wrapped, 4" SS exhaust, real time OBD2 data logging w/device controller, EVANS waterless coolant @ zero (0) psi & 135 gpm pump, 4L80e w/kevlar and premium steel w/cryo treated input/output shafts running @ 100 deg. F & 140 deg F towing, all synthetic fluids, AMSOIL bypass system, MileMarker hydro, dual fuel tanks, and on and on, questions PM me.

  2. #12
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    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……
    1978 Chevrolet K10, Vortec 8.1L, NV4500, NP205
    2011 Phoenix Camper
    1992 Toyota 4Runner
    1989 Chevrolet Suburban, V2500, 5.7L, NV4500
    2001 Chevrolet 2500HD 4x4, 8.1L, ZF S6-650 6-speed manual trans. Owned since new

  3. #13
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    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.
    Last edited by FellowTraveler; 04-30-2012 at 11:10 AM.
    1999 GMC K2500 BURBAN, NAVISTAR enhanced 6.5 td aftercooled, dual alt's, PSC p/s pump w/HD cooler, redundant FSD's, HEATH program, turbine/downpipe wrapped, 4" SS exhaust, real time OBD2 data logging w/device controller, EVANS waterless coolant @ zero (0) psi & 135 gpm pump, 4L80e w/kevlar and premium steel w/cryo treated input/output shafts running @ 100 deg. F & 140 deg F towing, all synthetic fluids, AMSOIL bypass system, MileMarker hydro, dual fuel tanks, and on and on, questions PM me.

  4. #14
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    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.
    -
    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.
    -
    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.
    -
    Last thing, someone mentioned sled pulls with locked GM front diff so here ya go.
    http://www.youtube.com/watch?v=Qra0b...feature=relmfu
    http://www.youtube.com/watch?feature...ZN3mooidQ&NR=1

  5. #15
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    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.
    Last edited by Buliwyf; 04-28-2012 at 08:42 PM.
    '08 Ford F250 XL
    Half of a '94 Jeep YJ
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  6. #16
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    Quote Originally Posted by Balzer View Post
    Last thing, someone mentioned sled pulls with locked GM front diff so here ya go.
    http://www.youtube.com/watch?v=Qra0b...feature=relmfu
    http://www.youtube.com/watch?feature...ZN3mooidQ&NR=1
    Ah, oh….looks like I’ll have to eat my shoe now. Locked IFS rigs pulling a sled work pretty well by these videos. Huh
    1978 Chevrolet K10, Vortec 8.1L, NV4500, NP205
    2011 Phoenix Camper
    1992 Toyota 4Runner
    1989 Chevrolet Suburban, V2500, 5.7L, NV4500
    2001 Chevrolet 2500HD 4x4, 8.1L, ZF S6-650 6-speed manual trans. Owned since new

  7. #17
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    No dont eat your shoe, I was just pointing out that it does happen. I definatly wasnt trying to step on any toes.

  8. #18
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    This discussion is happening on many forums...

    http://coloradok5.com/forums/showthr...ifs+solid+axle

    Seems to me big lifts, massive amounts of flex are not too "expedition" like. But hey, I'm a noob to the portal. I would think 3/4 ton IFS with moderat lift and good tires would make for a nice ride on rough roads...Guess it depends on your needs. We can't all have 4 linked dana 60s

  9. #19
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    Well, looks like I will be a ginny pig here. I have had numerous trucks, wheelers, etc for the past 40 years of driving from custom axles to HD tow rigs with beam axles. My JK is set up pretty decent as a do it all kinda truck- tote kids, wheel most anything, or DD. However, I just sold my '11 F250 diesel- awesome rig, but found an '00 2500 4x4 Suburban w/ 35k miles and barn doors. Plan is to add a 2" front lift via torsion key replacement, fit some 285/75-17 A/Ts on H2 wheels, use as a DD, and tow rig for the JJ, M101, and a single car trailer. Also explore the simple gravel forest roads, etc. May add a Detroit rear, ARB front bumper, and a winch. Also considering an Aluminess with rope in lieu of cable to keep front weight down. I have read as much as possible, and think/hope the comfort will improve and the minor build will aide in keeping it all together and reliable. Time will tell... But my logic is the 'burb for the mundane and JKU for the fun, and not build any more trucks.
    Any thoughts, input, advice appreciated, and I promise to report back here on a regular basis. First point being a 500 mile ride home without issue, 16.7 mpg and a sweet ride!!
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  10. #20
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    ive beat on my dmax pretty hard number of times towing my 15K lbs 5th wheel and getting it buried in sand but havent had any issues with that front axle. when the bros s15 gmc jimmy was still IFS, we bombed the crap out of it. that was the 1 thing on the front of that truck that never gave us any issues


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