Some questions on 8v92 to a Allison 545

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by gkmissingca, Apr 24, 2017.

  1. gkmissingca

    gkmissingca Light Load Member

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    I have found a deal I think I can't pass up to break into hauling RV's. In a round about way it's an 89 flat nose with 125k on the chassis, 3k miles on the trans, and the engine is also relatively new on a rebuild. I don't want to give away too much info as I don't have the title yet. I realize not everyone might be jumping on this but never the less I want it and for the price, he's practically giving it away.

    Moving on: I have a car background, and currently only service heavy equipment, and nothing this old. The drivetrain is the 8v92->Allison 545 (I think, it's a 4 speed auto)->4.56 gears. I plan on running a gooseneck 53' so my trailer loaded should be under 20k. With that said:

    An online calculator says if I change my axle gear to 2.91 (rockwell) I can actually make it to 77 mph at 1800 rpm on 11R22.5's. I understand 65 mph is probably a more realistic speed. I'm aware that mpg isn't going to be close to modern trucks. But i'm making up for it in the price of the rig.

    Now.....will the 2.91 gear destroy my acceleration and climbing? I realize this whole setup is kind of unconventional but the price is too good to pass up.

    Another question: can this engine be detuned on the fly like some modern engines for mpg? Would an aux trans/splitter be an option?

    Thankyou in advance.
     
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  3. BoxCarKidd

    BoxCarKidd Road Train Member

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    From an 8V 92 guy: Walk away for what you want to do.
     
  4. gkmissingca

    gkmissingca Light Load Member

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    walk away from that rig for the RV hauling?
     
  5. BoxCarKidd

    BoxCarKidd Road Train Member

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    I do not know about the RV hauling. Like everything else I suppose. You have to have the want to, someone that treats you fairing and work to do.
    The 8V92 uses a good bit of fuel loaded or empty. It is heavy for what I thank you are doing. It's getting hard to find people that know how to work on them. While greatly improved over older models they still tend to leave some oil behind and can get you ran off the the RV business. They like some RPM's and if you get it out of it's operating range it will hurt both of you.
     
  6. Ridgeline

    Ridgeline Road Train Member

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    Yeah, walk away, it won't work for you.

    This is a business and being a business, you need something more than an antique to make money with. First breakdown and you will figure that it will take more time to get back on the road IF you find someone to work on it, a lot of shops will not touch it.

    Edit, no it can't be tuned on the fly, it is a mechanic engine which means no ECM.
     
  7. Roberts450

    Roberts450 Road Train Member

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    Not only is it mechanical its a two stroke.
     
  8. slickWillie1980

    slickWillie1980 Medium Load Member

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    Ridge there is a plenty old iron still turnin and earnin lol
     
  9. OLDSKOOLERnWV

    OLDSKOOLERnWV Captain Redbeard

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    IMG_8044.PNG This is my 8V92TA rated at 430hp. They are a 2 stroke engine, do not like long periods of ideling. Small water jackets so watching the Temp gauge is a must! Can be a real powerhouse actually, but tuning is critical to keep them running good. But many will tell you they are junk, then again many drove wore out untuned engines. My big concern would be the transmission.
     
    slickWillie1980 Thanks this.
  10. gkmissingca

    gkmissingca Light Load Member

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    Ok thankyou. I'm looking at another rig with the same engine but a HT740. The extra gear would be nice. Thanks for the note on the temp guage.
     
  11. Yourawahoo

    Yourawahoo Light Load Member

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    That 8V92T makes a great boat anchor. They come with 90 injectors stock. All you can do to cut it back is put in some 75 injectors. Never seen one painted red like our friend here.
     
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