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1991 GMC, Dually, bodywork and 6.2 diesel questions!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MR4WD, Mar 28, 2004.

  1. MR4WD

    MR4WD 1/2 ton status

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    I'm posting this in multiple forums looking for lots of feedback, so bare with me.

    I'm looking at getting a 91 crew cab GMC. Last year for that style (V3500) It's pretty much the truck I've wanted since before I could drive, but it's single wheel. If I do purchase it, I WILL convert it to a dually, which shouldn't be a problem. The only thing I'm having difficulty with is finding aftermarket dually rims greater than 6" in width? I'd like to run 35's (the truck presently has 5 new 35x12.5x16's or whatever that works out to in metric terms) so I'd need to buy two more tires and 16x8" dually rims.

    I realise that I could convert 6 or 7 16x6 steel rims to 8" fairly easily, but I'd like to run aluminum rims mostly for aesthetic reasons. I've sifted though a few websites, but manufacturers seem to concentrate solely on 16x6" wheel sizes? The other side of this is would a 35x12.5 run on a 6" wide wheel? I would guess no, but I've never seen or done this.

    I can get outrageous deals on alcoa wheels, so I may go with (4?) new wheels and run a set of 36" michelins, which I could probably get for cheaper than a few new 35" bfg's. I'm aware those run acceptably on a 6" rim. While the tires will probably wear like iron, I find them a bit narrow for my tastes...

    I have no requirement for an 8' bed, so I'll probably chop the frame and install a shortbox. Would dually flares fit on a shortbox? What sort of problems may I encounter?

    I really have no experience with dually's in a personal environment. The truck I drive every day at work is a dually, and I usually make it my personal truck but I've never owned one.

    Lastly, the truck has 60,000 miles on it and the original (no doubt!) 6.2 diesel. One of my work trucks had a 6.5. While quite enemic it was great on fuel, which is an underlying outline I have made. Down the road, I'll convert it to a 12 valve cummins and bomb it, but for now I'll settle for the fact it's got a 6.2 with an upgraded snail, down pipe and exhaust. What sort of power band do these engines operate in? The truck currently has 4.10's and a new 4L80E (with a 205!!). I shouldn't have a problem trading the SRW Dana 60 and 14 bolt for DRW versions, since everybody seems to have those. In OD, with 35's at 70 MPH I'd guess I'll be around 19-2000 RPM. Would the 6.2 cruise with a meagher load at that RPM? (a bed full of work gear for a few weeks) Or would it kickdown into drive all the time? An idea may be to trade up to 4.56-4.88s? I like to think of the 6.2 as a 350 that turns half the RPM, but I'm mostly unconfident and inexperienced with this motor...

    Thanks from anybody who can offer insight with this truck,
    Chad.
     
  2. azblazor

    azblazor 1/2 ton status Premium Member

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    I responded in the diesel forum. But I was thinking there is a member up in SF who runs 35's on his duallies (plural), he probably has a lot of insight into the wheel tire combos. (EricM ?)
     
  3. azblazor

    azblazor 1/2 ton status Premium Member

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    Also if it were mine I would keep the low miles D60 you have and just put dually hubs on it, you end up with exactly the same axle as a factory dually.
     
  4. camiswelding

    camiswelding 1/2 ton status

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    I bought a 1989 v3500 3+ 3 with 36k original miles about three months ago.... I wanted a single rear wheel but this truck was a once in a lifetime buy with those miles on it so I scooped it up...its still like driving a new truck,,, now I want to go the other way and convert in to srw.... and yes I looked at doing a shortbox on it
    to do so there are a number of considerations
    1) Where to shorten and how to splice properly... email me and Ill send you an attachment on that
    2) a short box doesnt work with longbed tanks so you have to do custom fuel fill relocation... the dually fenders get into that area on a shorty
    3)where to shorten the driveshaft... are you looking to do an overdrive like a gear vendor..etc...
    I am also interested in a cummins swap... after I looked at a local truck done with an nv4500, the cummins, and a gear vendor... he gets 18 mpg towing.. I get 10 out of the 454
    The 6.2 is a weak motor.. cast crank..powdered pistons.. it cant make reliable power or longevity... thats why there are so many rebuild kits around... they get decent fue mileage but Ive owned one and they are gutless... its not if its going to break but when... and 100k on many means rebuild time, less if its used hard or you try to pull with it.. my one in a new sub lasted 50k miles before needing a warranty rebuild
    Im going to do an all aluminum service body on mine... as soon as I sell the sp250 and buy the new powermig 300 with a python gun...
    I assume you can fabricate because the mods you are talking about are EXPENSIVE otherwise.
    Contact Stockton Wheel for your custom duallies.... youll have to use spacers probably if you go 8 or more... and then theres a safety issue
    You cant have it all... just most of it
    hope this helps the thought process
    cam
     
  5. 90blzr

    90blzr 1/2 ton status

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    Contact 'ken' from this site. He is in Aneheim and runs 42's on his dually. He had the rims custom made, just not sure where.
     

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