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newbie question

Discussion in '1982-Present GM Diesel' started by fourwheelerjeff, Oct 28, 2003.

  1. fourwheelerjeff

    fourwheelerjeff 1/2 ton status Staff Member Moderator

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    i am new to diesels and have a question, i have an m1008 with the 6.2 and am contemplating using it for a tow rig, it will be lifted 4 inches and running 37 goodyear mt's (ex-hummer) tires /forums/images/graemlins/cool.gif

    should i stick with the 4.56's that are in there, or swap to 4.10's out of my 83 blazer /forums/images/graemlins/confused.gif

    thanks /forums/images/graemlins/thumb.gif
     
  2. BlueBlazer

    BlueBlazer 1/2 ton status

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    I can better answer that in couple weeks when I get my one ton done (heh, that rhymes). Anyway, its got 410s, I got some hummer tire retreads, only difference is I got a 465 so Ill turn a few less rpm's compared to a 400. I do think that if you will be running tires that tall, even with 456s and a 400, you should still be keeping highway rpm's to a suitable level for a 6.2, and you will have a little more low end obviously. If you dont mind doing the swap, you might be a little happier with 410s though I think.
     
  3. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    i am new to diesels and have a question, i have an m1008 with the 6.2 and am contemplating using it for a tow rig, it will be lifted 4 inches and running 37 goodyear mt's (ex-hummer) tires /forums/images/graemlins/cool.gif

    should i stick with the 4.56's that are in there, or swap to 4.10's out of my 83 blazer /forums/images/graemlins/confused.gif

    thanks /forums/images/graemlins/thumb.gif

    [/ QUOTE ]

    Well to put it this way:
    My friend has a dually with the 6.2/th400, and it has a 4.56 rear, with the stock tires. He tows his race car in a full enclosed trailer and he can keep it in the 70MPH at ~3000RPM's.
    He is contemplating switching to 4.10's or putting an Overdrive, but this is with the 30" stock tires.
    I think you should be fine with the 4.56 and 37" tires or you might need to go to 5.13 if you feel you need more power.
     
  4. cegusman

    cegusman 3/4 ton status

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    I am running 4.88 and sm465 and 36" swampers sx's, The engine starts to scream at about 60-65mph. I don't run mufflers so that could be why it sounds so bad.
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    [ QUOTE ]
    My friend has a dually with the 6.2/th400, and it has a 4.56 rear, with the stock tires. He tows his race car in a full enclosed trailer and he can keep it in the 70MPH at ~3000RPM's

    [/ QUOTE ]

    Either he isn't doing 70 or he doesn't have 4.56's. Do the math and you'll see 70 mph, 4.56's and 30" tall tires works out to be 3700 rpm. That's about 100 rpm past the governor limit.

    I run 4.56's, SM 465 and 39.5's and it sucks on the freeway (rpm wise) I can pull any grade in top gear, but at 65-70 it's screaming (2750 rpm at 70). In my opinion I'd go 4.10's with 37's and a TH400 (also 2700 @ 70 mph). 4.56's would be too low a gear to be useful, unless you never drive over 50-55 mph.

    Rene
     
  6. azblazor

    azblazor 1/2 ton status Premium Member

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    My 86 K30 6.2/th400 has 4.56 and 30-31s. I usually keep it between 55-60 on the freeway. Sometimes I'll catch myself running 65. It sounds like its reving pretty high ( no tach installed right now), but it will go all day - steady 200 degrees or so and the AC on, 14-15 MPG.

    My 84 K30 has a 6.2/Th400 but also has a banks and a gearvendor OD, it has 4.10 gears and ~30 " tires and will purr along at 75-80, can't hardly hear the engine (tach reads about 1500 rpm but I know its completely off). You do have to watch the EGT's if I hit a grade or push it to 85-90, the exhaust temps go up real fast. It also gets 14-15 MPG (so far but I haven't been trying for high efficiency yet)
     
  7. ducttape114

    ducttape114 1/2 ton status

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    i have a 6.5/th350/4.10s and 37s. i feel shes just a bit gutless. its fine on the free way and around town but i wouldnt want to tow with it. i think that 4.56 would be just about perfect.
     
  8. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    [ QUOTE ]
    My friend has a dually with the 6.2/th400, and it has a 4.56 rear, with the stock tires. He tows his race car in a full enclosed trailer and he can keep it in the 70MPH at ~3000RPM's

    [/ QUOTE ]

    Either he isn't doing 70 or he doesn't have 4.56's. Do the math and you'll see 70 mph, 4.56's and 30" tall tires works out to be 3700 rpm. That's about 100 rpm past the governor limit.

    I run 4.56's, SM 465 and 39.5's and it sucks on the freeway (rpm wise) I can pull any grade in top gear, but at 65-70 it's screaming (2750 rpm at 70). In my opinion I'd go 4.10's with 37's and a TH400 (also 2700 @ 70 mph). 4.56's would be too low a gear to be useful, unless you never drive over 50-55 mph.

    Rene

    [/ QUOTE ]

    Well I guess his speedo is off because he does have 4.56 gears and he just installed a tach (tiny tach) and I just talked to him he said 3300RPM at what the speedo says ~70
    I guess it's closer to 60 something.
    He put the tach because of the same reason azblazor had, he would be keeping up with the slower traffic and the sound of the engine screaming made him worry.
    Now he knows he is close but not at the limit, but he still wants the overdrive.

    By the way, the reason I said keep the 4.56, is that you want to tow with 37" tires, if you want to work you engine then go 4.10, you will have better mileage, but if you want to tow comfortably you would keep 4.56

    Just my 2 cents /forums/images/graemlins/thumb.gif
     
  9. fourwheelerjeff

    fourwheelerjeff 1/2 ton status Staff Member Moderator

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    well, thanks all for the replies, i guess i can put the 4.10's in and if i don't like it, swap them back out for some 4.56's again, all i have to do is swap axles, i guess i could run them both on 4.56s, too many choices, too many 60/14 sets /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
     
  10. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    [ QUOTE ]
    too many 60/14 sets

    [/ QUOTE ]

    You can't have too much money, or too many 60/14 sets.../forums/images/graemlins/rotfl.gif

    After doing the 1200 miles drive to and from Moab I think I'm gonna concentrate on an NV4500 swap. Best of both worlds, and I can run it on 35's for daily driver duties or long trips. For relative simplicty I'll use a 241 with a SYE kit and a "Severe duty" skid plate/crossmember.

    Rene
     
  11. fourwheelerjeff

    fourwheelerjeff 1/2 ton status Staff Member Moderator

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    [ QUOTE ]
    [ QUOTE ]
    too many 60/14 sets

    [/ QUOTE ]

    You can't have too much money, or too many 60/14 sets.../forums/images/graemlins/rotfl.gif

    Rene

    [/ QUOTE ]

    i know, i just had to brag a little, i only have 4 /forums/images/graemlins/frown.gif



    /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
     
  12. fourwheelerjeff

    fourwheelerjeff 1/2 ton status Staff Member Moderator

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    just checking to see if anyone had anymore feedback about this /forums/images/graemlins/thinking.gif
     
  13. arveetek

    arveetek 1/2 ton status

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    Personally, I would go with the 4.56 gears and swap in an overdrive of some sort. I'd at least stick with the lower gears for now, and if you don't like it, swap to 4.10's later.

    I run 4.10's with 27" tires, and it will run at 70 mph in direct gear, but it's pretty loud. Drop it down into overdrive, and it's nice, quiet, and smooth! /forums/images/graemlins/thumb.gif

    Casey
     
  14. ZZ4x4

    ZZ4x4 1/2 ton status

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    Jeff,
    Although I think the 37s and 4.56s would be about perfect with the non-turbo Diesel , I would like to graciously offer a 4.10 14BFF for trade if you need to keep your '83 intact /forums/images/graemlins/whistling.gif. Mine is nice and clean with new brakes, seals, gov-lock, and the perches are already welded to go into a one ton. /forums/images/graemlins/rolleyes.gif
    See ya soon!
    Jeff /forums/images/graemlins/usaflag.gif
    PS: Still got your M1028 title /forums/images/graemlins/doah.gif
     
  15. blasterD

    blasterD 1/2 ton status

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    I have an 86 k30 with a 6.2, 465 and 4.10s. I run a 35" tire (315/17-17) and I hit the governor at about 75mph. I dont have a tach, but I dont like to cruise much over 65 or so (maybe 2700 RPM). I recently changed the tires from the stock 235/85-16s. Even with the larger tire, I went from 10.5mpg to 13mpg. I think the fuel mileage is a lot better at a lower cruise speed. I have plans for a NV4500. IMHO 4.10s, 35s and a 4500 would be a near perfect setup. The overdrive would put you right around the torque peak in fifth gear at freeway speeds.
     
  16. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    Personally, I would go with the 4.56 gears and swap in an overdrive of some sort. I'd at least stick with the lower gears for now, and if you don't like it, swap to 4.10's later.

    I run 4.10's with 27" tires, and it will run at 70 mph in direct gear, but it's pretty loud. Drop it down into overdrive, and it's nice, quiet, and smooth! /forums/images/graemlins/thumb.gif

    Casey

    [/ QUOTE ]

    Hey Casey
    Do you have a tach?
    My friend with his 6.2 dually crew cab, 4.56 gears and stock size tires is taching 3600RPM's at 70.
    I hear that is the most you should turn your diesel although I know the governor will let it go into 4200 or even 4500RPM.
    DO you have any idea what RPM's you got at 75?
     
  17. arveetek

    arveetek 1/2 ton status

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    [ QUOTE ]

    Hey Casey
    Do you have a tach?
    My friend with his 6.2 dually crew cab, 4.56 gears and stock size tires is taching 3600RPM's at 70.
    I hear that is the most you should turn your diesel although I know the governor will let it go into 4200 or even 4500RPM.
    DO you have any idea what RPM's you got at 75?

    [/ QUOTE ]

    No, I don't have a tach and I don't really have a clue what rpms I'm turning at any given speed.

    I've never hit the governor in 3rd gear. However, in 2nd gear, I hit the governor around 50 mph, if that helps any.

    However, I don't know what rpm range my governor max's out at. I've read it can be anywhere from 3600 rpm to 4200. I think it kind of depends on what the pump was set at to start with.

    Casey
     
  18. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    [ QUOTE ]

    Hey Casey
    Do you have a tach?
    My friend with his 6.2 dually crew cab, 4.56 gears and stock size tires is taching 3600RPM's at 70.
    I hear that is the most you should turn your diesel although I know the governor will let it go into 4200 or even 4500RPM.
    DO you have any idea what RPM's you got at 75?

    [/ QUOTE ]

    No, I don't have a tach and I don't really have a clue what rpms I'm turning at any given speed.

    I've never hit the governor in 3rd gear. However, in 2nd gear, I hit the governor around 50 mph, if that helps any.

    However, I don't know what rpm range my governor max's out at. I've read it can be anywhere from 3600 rpm to 4200. I think it kind of depends on what the pump was set at to start with.

    Casey

    [/ QUOTE ]

    That's why I got the tach.
    My truck isn't running yet so I used the tach on my buddy's truck to check, that's how I got the numbers so you would be running above 3600 which I understand is something you wouldn't want to do to GM 6.2l
    I will definitely put the tach on my burb once I get it running, I want to put tires to match the gear ratio to get no more than 3000RPM in Drive at 75MPH.
    I wouldn't be driving that fast all the time and OD will drop my RPM's when I am not towing so I might get the engine to survive longer.
    and get better mileage /forums/images/graemlins/thumb.gif
     

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