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2008 Tahoe Hybrid AFM rebuild?

Discussion in 'Hybrid General Discussion' started by BG1988, Jul 31, 2020.

  1. BG1988

    BG1988 Full Access Member

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    how much is the typical rebuild for AFM I would like to have mine done
    the VLOM and rods replaced (i hear they can abnormally wear and tear then cause the lifter to fail) mine has the issue with the loose bolts



    I don't mine keeping the AFM i get way better MPG with it as it's an Enhanced version of AFM (I can accelerate in V4 mode) it pays for it self getting 23.5 mpg is better then 18.5 and it's still better then the 12-13MPG you get on your 5.3l in the city


    6.0L LS2 based engine with VVT

    I CAN RUN V8 mode on demand by shifting to M4 no need for a range device
     
  2. wjburken

    wjburken Supporting Member

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    Personally, I would not worry about the rods if you’re not going to mess with the lifters. If the VLOM is acting up due to the loose bolts, the issue will be in the lifters, not the rods. If it was me, I would pull the intake and tighten down the bolts on your VLOM or replace the VLOM and associated gaskets and call it a day. Pulling the intake is a rather easy task. I know you mentioned you are not comfortable doing it so that’s what I would ask the shop to do. Might as well have them swap out the oil pressure sensor if it’s original while they have the intake off.
     
  3. 91RS

    91RS Full Access Member

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    It will depend greatly on if you're doing it yourself, chain shop, independent shop, dealership, whether you use OEM parts or junk Dorman parts, etc. The AFM lifters are not cheap so you're probably looking at a minimum of $1500 in parts for a new VLOM and lifters. Then there's the labor which will have the hybrid tax.
     
  4. swathdiver

    swathdiver Full Access Member

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    1 - VLOM - 12571609
    8 - De-Ac Lifters - 12645725
    8 - Standard Lifter - 12648846
    2- Lifter Guide - 12669184
    2 - Lifter Guide - 12669185

    This is not all inclusive though Brent. You'll still need/want new pushrods, need new head gaskets and cylinder head bolts. These numbers are circa 2017, so they may have been updated.
     
  5. BG1988

    BG1988 Full Access Member

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    it's leaking oil :( little bit.. should i keep it in M4? this will FORCE v8 mode but i lose OVERDRIVE 5th gear (EVT2)
    that means my mpg drops to 18 or so in the city
    never tested the highway
     
  6. wjburken

    wjburken Supporting Member

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    Forcing it to run in V8 mode won’t help if you’re VLOM isn’t keeping your lifters pumped up which is what I think you are worried about.

    In my opinion, your two options are to remove the intake, replace the VLOM gasket and torque down the bolts and move on with life or if you think the lifters may have been damaged, go all the way and replace the lifters and push rods along with the VLOM stuff I mentioned.
     
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  7. swathdiver

    swathdiver Full Access Member

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    This way that Wade describes Brent, it lets you isolate the VLOM as the problem and maybe save some money down the road or at least stretch out your expenditures.
     
  8. BG1988

    BG1988 Full Access Member

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    i have to deal with a Vacuum leak created by the repair shop that messed with the engine they must have damaged a hose as they messed with the PCV the dipshit cleaned it then turned around and charged me 80$ why the freak would i pay to have a 5$ part to get clean when i can put a new one in instead...(did not ask for that work if i would have had the 5$ part then yeah replace it then) i refused to sign the estimate as it had no price on it even if he puts a price or signature (fakes it) i can press charges for forgery
    i thought if it was in V8 mode it's irrelevant as oil pressure was required to activate the AFM.. so if it's off it's not relevant?. that is why you guys use the software shut off?? if i have a manual shut off. why spend the extra money on that item


    i have about 2,000 for repairs for the tahoe (the amount i saved from gas $$$ compared to what i would have spend on my old car) i put it in my repairs fund.
     
  9. wjburken

    wjburken Supporting Member

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    You need to remember what is happening when the engine switches from V8 to V4 and back.

    The VLOM puts oil pressure to the lifter to pressurize or extend the lifter so it engages the pushrod when the cam lifts the lifter. When the VLOM is told to shift to V4, it removes oil pressure to the lifters and and let’s them float while not moving the push rod. The problem with AFM is when the motor goes to shift back to V8 mode. If the pressurization of the lifter is off, the timing of getting the lifter extended by the time the cam lobe comes around is off and can damage the lifter. If your bolts on the VLOM are loose, that means you may have a less than optimal timing on pressurization if the gaskets between the solenoid and the block leak.

    Guys put the AFM disablers in to keep the lifters pressurized all the time and reduce the risk of the timing being off when that switch happens and shelling out a lifter and the cam.
     
  10. BG1988

    BG1988 Full Access Member

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    that is what M4 does as the disabler

    it's only V8 in M4 my running PSI is about idle is at 44PSI

    55-60PSI while driving 1000rpm+.. oil pressure is not an issue... i'll call GM and see if they are willing to own up to the mistake and if some parts need replacement i'll pay for it (but they will have to eat the labor costs )

    of course i will not show my cards first though ;)
     

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