AWD/Ft4WD Conversion to 2WD/Pt4WD... DONE

Discussion in 'Tech Info' started by GM-MAN, Feb 27, 2012.

Car Parts
  1. GM-MAN

    GM-MAN TYF Newbie

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    DENALI 2.0 / 2WD

    Real long read, may want to print out and take to your bathroom break....lol

    Part 1 = Hysterisis
    Part 2 = Out with the old
    Part 3 = Convert me & save me [non-religious]
    Part 4 = In with the new
    Part 5 = Loose your IFS grip


    Part 1 THE VICTIMS………

    99-2006 [GMT800 series],
    Yukon Denali, with the BW 4481/**/ Series “All the time” AWD -
    Sierra Denali/C3, with the NVG149/BW’s? with “Part time” AWD
    Yukon+[XL]. Tahoe, Suburban? With the BW44**/82-84/** with Full time 4WD

    Who all suffer from popular front drive train growls, hums, squeaks, vibrations, poor gas mileage or premature wear, or frequently use HD highway towing.

    Everyday use, when on road driving, keeps a lot of mechanical parts rotating, sling mud like a corrupt politician.!!!!!!!!!!!!!

    In my case, I have had the dreaded light acceleration growl for about 3-5000 miles. Split the diff, found bad side carrier bearings, but still had some concerning noises and was not sure if it was TransCase related, so thought a good time to pop it all out to inspect. Since I travel long distance and sometimes tow heavy loads with not much if any 4WD needs, be a good time to convert.


    THE GOALS………..

    ** Find a suitable replacement Transfer Case [TC], that allows the vehicle to be switched back to, 2 wheel drive, while still retaining the option for 4WD type capabilities.
    ** Find a unit that is close in specs and size, that would not require a lot of modifications
    ** Complete R&R for the average DIY’er
    ** Make a cost effective/selective replacement and while making the vehicle have factory restorability.
    ** Efficient installation possible as 1 man R&R



    Looks to be, four potential options…

    1/ Manually shifted transfer case with front drive shaft removed
    2/ “ “ “ “ “ front CV shafts removed
    3/ “ “ “ “ “ front IFS right axle swap to 12v actuator
    4/ Electrically shifted TC with 12v controlled IFS axle actuator


    THE CONCERNS……..

    ** The effects of the Active Brake/Traction Control [ABC] and Engine Torque
    ** Management [ETM] my abbreviations for laypersons, not the industries.
    ** The controllment / adjustability and securement of the shifting mechanism.
    ** The loss of automatic rear to front power distribution/ biasing, currently
    achieved by AWD


    THE GUINEA PIGS……

    To understand what you need, you have to know what your have!

    For the sake of this writing, I will be describing, my 2005 YD, with the BW 4481, which has the all mechanical, “open differential”, planetary type TC.
    In normal driving, the power output is approx -70% rear/ 30+% front.
    AWD is achieved by a always active, power redistributing [biasing] from F-R/R-F by the open diff in the TC, meaning when the TC senses rear wheel slip, [activates ABC], the differential in the case, automatically sends more power to the front wheels, via the front output shaft on the TC.

    The other aspect of AWD is the ability of the power to be distributed, from the spinning wheel with less traction, to the other side. This is achieved by Active Brake/Traction Control, in which the computer senses thru the WSS [wheel speed sensor] the difference in speed.

    The third aspect of AWD is Engine Torque Management , in which, the computer senses, wheel spin, it reduces torque to not over heat the brakes that are controlling traction.

    Since my setup, has NO electrical control/measuring on the TC, just the ABC/ETM, the best suitable option to convert was a similar, “mechanical” TC.

    With that said………
    I will be going with option 1 to start and working on 2, 3 and 4


    Step 1, was to find a TC that was close on it’s specification.
    Most of the TC’s had Hollander ‘Interchangeability” as far as mounting goes. The 4481 mates to the 4L65E trans, which is similar in specs to it’s little sister the 4L60E, having a 27 spline output shaft.

    The BW4481, has a front case mating surface to rear output shaft case measurement of 19.5”. [sorry to you metric heads]
    It also has a 32 spline output shaft, with a female front output.
    The difference between the front case face and the front shaft output seal face was 3.5” [ in parallelism]

    The NVG series has a longer front case half, which in turn makes the front face to front output face, 1” further rearward. However, the front mating to rear seal remained the same 19.5”. It also has the 27 in/32 out and female front shafts.

    It’s closest sister part in platform, would be the New Process / NVG 246. Since the 246 has 2WD and a Auto 4WD option, I looked at that unit as a potential replacement. Unfortunately, the ‘Auto’ 4wd feature is controlled by a clutch pack that is electronically controlled by the monitoring of other speed sensors on the front and rear output shaft of the TC. The 2002 an up also have a star shaped shift mounting fork, which made a quick resolve, more complicated.

    Since mechanically it would be a ‘bolt in’, I couldn’t justify the installing / wiring / re-flashing a TC control module [TCCM] etc, for this hack.

    Next up was the NVG 261 / 263 series which both have a 2WD/PT- 4WD feature
    The 263 sparked, immediate interest as it is a heavy duty unit and uses a electrically controlled encoder [actuator] motor to shift. Unfortunately again, because of it’s heavy duty status, it was only available to the 4L80E and Allison.

    Moving on to the 261.…..

    The 261 was available in three different models, but are only available in manually floor shifted trucks.

    ** 261 LD, which mates behind the 4L60E in 1500 series trucks
    ** 261HD, “ “ “ “ 4L80/Ally1000 in the 1500/2500 trucks
    ** 261XHD “ “ “ “ Ally 1000+? 6 Spd Auto

    And the ’Wiener” is………….

    The 261 LD a direct bolt in for the 2WD side with some mods needed for shifting, with the potential with heavier duty custom build enhancements

    My parts choice vehicle is a 2004 Silverado ExCab1500 Z71 with 84K mi. ©
    [Still not sure how there is a Z71 with a floor shift T/C]

    My local yard salvage yard, has one of the best websites with Hollander parts interchange listings I have seen. A little different from Car-Part, but same idea, except they actually show pictures of vehicles and one of those pics is of the RPO tag in the glove box

    By having viewing access to this tag, I was able to see exactly what options the vehicle had, without a lot of running around or asking questions.

    NOW…..
    Knowing what my YD has [did I mention that earlier?] I knew I was going to need a GT4 axle ratio [373]. My YD also had option JL4, [ABC]

    Moving on to the different TC case length issue. I knew I would be 1” further away from the pinion yoke. Most drive shafts are measured by “weld to weld” of the main tube. My YD being 25”. A little research found that there were some in the platform that were 26”…..yea, me!!.

    However, the next obstacle was the JL4/ABC.. Coincidentally the 04 1500 had the 26” Drv Shft but was not JL4, so it was worth a looksi…Same pinion yoke…. Same u-joints….. Same T/C slip yoke… Once my factory shaft was out, the only difference is the tube thickness. [yep the highly accurate, ping test…lol] So, worth a shot, eh?. I would have to equate this to the ABC/ETM were there is added torque being applied that is transferred sending power back rearward when applied, required a stronger gauge tube. Strangely the 4WD with High/Low and Auto does not require the heavier tube wall.

    Anyhoo……….

    A little custom shift braketry….and some effort on the ease of installation side, in the form of a floor jack mod, some Weaties diluted in coffee and wha-laa… about three hours and I’m singin a Willie Nelson tune with MotorHead vocals.


    Now preliminarily, I choose to go the front shaft delete, with CV ½’s shafts still in for the time being while Beta Test-beatin. I due plan on removing the shafts and eventually will be looking at either rebuilding my front diff with a electrically actuated right housing shaft and gears or maybe just swapping a complete assembly.

    But if anyone chooses to go this minimally invasive physical effort to have the need for 4WD, it would take about less than 5-15 mins to drive up on ramps, shift into 4x/2x and pop the front shaft or axles back in, or push a button

    BE FORWARNED…………

    2WD is 2WD, but this conversion it will only allow part time 4WD, meaning 50/50 split only >>OFF ROAD> SNOW> SAND or situations were traction can be lost..
    This is not intended for ON ROAD USE and will harm or break drive train components.
    ©
     
    Last edited: Feb 27, 2012
  2. GM-MAN

    GM-MAN TYF Newbie

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    Part 2

    The 4481 Removal

    Part 2



    Decide on which option you want to utilize, if you choose to remove your CV shafts, loosen axle shaft nuts, before raising vehicle

    If no access to automotive lift, support vehicle safely, I found 20-24”from running boards to ground, to be sufficient

    ** Drain T/C

    ** Mark your front and rear drive shafts. Even if you plan to replace your U-joints, drive shafts are balanced from GM “with” the yokes, so make a mark on the tube and the yoke on one side. When replacing shafts, take note of where the weight is on the removed shaft and try to install the replacement shaft with weight in the general area to eliminate potential vibration issues….. then remove

    ** Loosen the boot clamp, from the TC side of the front shaft, slide shaft out of TC.

    ** Support TC with small blocks of wood to eliminate case/bolt stress when loosening bolts or use trans jack/ floor jack to hold TC when loosening bolts.

    If your on a lift your good to go, if on floor, take precautions.. Slide back TC about ½” and let any residual tranny fluid out.

    Here’s where it gets a little tricky, you need to slide it back, about 2”, tilt it strait down and it will slide strait out, BUT, you need to undo the TC and transmission vent hoses and speed sensor on the top of the TC, try to reach up first before unbolting, if not, you need to slide the TC down a little so you can have more room.

    In my pics you see I made a custom floor jack - TC mount. As neat as it is, this job can be done by hand If……
    ..
    YOU CAN BENCH PRESS 80LBS AND HOLD IT UP FOR 20-30 SECS with your hands about 10” apart, while singing Supercalifrangelisticexpealdocious…….lol

    Seriously, if you are going to attempt a floor removal, what I would suggest, is to get a ¾” sheet of plywood about as wide as your torso, from chin to belt long. Lay with you head under the tranny and feet towards the rear axle, as it slides down, let it slide onto the plywood………. CAUTION AT YOUR OWN RISK… I will not be responsible for injury from little people with big attitudes…. I’m 6’1” /240 and still would take proper precautions.

    Roll the TC to the side to the floor and slide out from under the vehicle. ©

    ---------- Post added at 10:25 AM ---------- Previous post was at 10:24 AM ----------



    PART 3

    Custom Shift Linkage


    The original 261 shift brackets, mount and are activated from the top

    The factory bolt on arm is reversible and could potentially work, but would not allow 4WD HI

    Using 1 ½”W x 1/8-3/16” steel flat stock x 6” long [exact specs pending], make new shift bracket with activation now from the bottom.

    Make a pivot point the secures to the TC bolts

    Measure and drill needed rod positions

    Remove for TC installation


    Floor Jack Adapter

    Luckily, being a metal smith [tape measures and machinist quality equipment, not allowed] has it’s benefits

    Having a bunch of steel laying around, a set of torches, mig welder, drill press and another Waaa-La!!!!!!

    Had to perform some modifications on the fly, but defiantly gave some piece of mind . Designed it so I could pump the jack with my leg, while guiding the
    TC into place.

    Not a absolute necessity as I had to drop the TC back out [heads up later] and found, by hand wasn’t that bad.

    Interestingly enough, with a small modification to the BW 4481, It also work for that unit for it’s removal.

    ---------- Post added at 10:26 AM ---------- Previous post was at 10:25 AM ----------


    NVG 261 LD Install

    Part 4


    Pretty strait forward…..

    ** Clean mating surfaces and inside back of transmission opening

    ** Clean threads on TC for locktite

    ** Get your small wood blocks ready, so when TC is up, it holds in position as to not damage threads, gaskets, case etc.

    ** As TC is going up, remember to re- connect VSS and vent hoses
    The 261 came with it’s own short hose. There is a plastic 90° vent on the top
    that faces forward, the factory vent goes up to the top over the trans.
    The trans also has one that runs down near the TC.

    ** CAUTION
    I left the gasket off, till everything was lined up. Little did I know the gasket
    ONLY GOES ON ONE WAY, and ripped it

    Who’d a thunk that 6 holes in a circle are not exactly spaced, not noticeable by eye, 5 are 3 3/16” apart one is 3 3/8”… so practice and mark before installing.

    ** Retighten case bolts, add rear drive shaft, leave front shaft off [unless changing out front IFS diff. [see part 5]

    ** I used the yoke from my old front shaft in the TC front output, to keep everything clean.

    ** Install your custom linkage and recheck gear positioning

    ** All the way rearward is 4WD HI
    ** The next position forward is 2WD
    ** Forward of that is Neutral
    ** All the way forward is 4WD LOW

    ** NOTICE

    The current position of the TC in relation to the cross member, it would be more difficult to get the linkage to achieve 4WD LOW. Since I don’t off road or see the need to get that ultra low gearing, I didn’t include that position in my design. Not to say it can’t be done, I was just trying to keep things simple.

    NOTICE

    ** The factory uses Dextron III for it TC lube

    ** There has been many instances where excessive heat has caused the fluid to overheat and foam or vaporize and be lost out the
    TC vent. Many complaint that fluid is low, burnt or near empty. [or potential rear case failure from pump rub]

    ** The recommendation is to use 5w-30 motor oil / synthetic
    Not sure if the new Dextron VI, addresses that issue.

    ---------- Post added at 10:28 AM ---------- Previous post was at 10:26 AM ----------


    Front IFS Differential/Axle options

    Part 5

    The perfect scenario, would be to the electrically controlled TC and front IFS axle like the 1500 series, but retain the 2WD and torque split biasing full time 4WD, but that seems to be a large undertaking and cost.

    The next reasonable outcome would be the manually shifted TC and the electrically shifted front IFS. This would allow a quick under reach to switch 2WD/PT 4WD and push a button for the front IFS, for 4WD, which also allows the front drive shaft to remain in place.

    Getting a little more effort, will be the manually shifted TC and the removal of the CV ½ shafts. [using dummy spindle shaft ends thru the hubs or pull the outer boots and slide the CV shaft out of the cup/would require sealing for reinsertion]. This would allow the most efficient 2WD usage with no rotation or front drive axle and also keep the front drive shaft in place. It would require the ½ shafts to be reinstalled when 4WD is needed.

    The last option is currently how I am running for the beta-beatin. I left the CV shafts in, which allows the differential to continue to rotate at drive speeds. It leaves the front drive shaft off and can quickly be reinstalled for Pt 4WD.

    Not sure of the long term wear or safety effects of the differential spinning with no drive shaft, but my IFS axle is failed anyway and will need repair or replacements, but have not noticed any binding etc.©

    Opinions?
     

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    Last edited: Feb 27, 2012
  3. GM-MAN

    GM-MAN TYF Newbie

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    Not sure what happend here, may need admin help?
    Tried to post 5 replies with pics in each part
     

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  4. GM-MAN

    GM-MAN TYF Newbie

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    Going in
     

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  5. GM-MAN

    GM-MAN TYF Newbie

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    Completed........
    200+ miles Road Tested
    No CEL's... No Drivability complaints
    No ETM, ABS, Traction Control Involvment

    Quick report on MPG is +2/3
    Avg's on strait hwy was 19+ @ 60MPH
     

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  6. GM-MAN

    GM-MAN TYF Newbie

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    Ok'doky
    For the first 30+ miles, I left the front shaft off and CV axles in
    Since there was still a rotating mass, I could still hear noises

    I then popped one CV shaft out, and noises changed, so I know there is front 'spider' gear isses

    Next up was to remove both 1/2 shafts [and leave the CV spindle cups in to keep hub bearings in place] and just have a 'be'danglin front Diff
    This elimnated any type of involvment or drag from the front drivetrain

    Just picked up a Z71 front axle with actuator, so will be working on that changeout and report.

    Questions/concerns welcome
    btw... the victim
    Rikster
     

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  7. Friggy

    Friggy TYF Newbie

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    nice work! This is why I want 2wd/selectable, rather than the other.
     
  8. carluvar

    carluvar TYF Newbie

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    I'm getting rid of all my 4wd stuff and will be looking for a 2wd trans and driveshaft. My truck is dropped 3/5 and I only used 4wd a few times a year any ways. doesn't look like any pickup driveshafts will work I think I need a custom one made, any ideas? Thanks!
     
  9. adriver

    adriver Full Access Member

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    Yes, make a new thread. This thread is 7 years old, and up to 22K people may have gotten an email about a post that is not even really relevant. Local driveshaft shop, even summit sells all sorts of sizes.

    https://www.google.com/search?sourc........0....1..gws-wiz.....0..0i131.FThdR37Tlnk
     

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