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2 lo question

Discussion in 'The Garage' started by 71 Blazer, Jan 28, 2007.

  1. 71 Blazer

    71 Blazer 1/2 ton status

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    How long can you drive your truck in 2 lo? My 76 has a 350/350/203 and with the 3.08 gears and the 35's it is a dog. Their is a warning on the truck not to exceed 45 mph, but it dosen't say how long you can drive like that. I want to use this truck to tow my Blazer.
     
  2. YZEATER

    YZEATER 1/2 ton status

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    how far do you want to tow?
     
  3. goldwing2000

    goldwing2000 Guest

    Interesting question.

    I think it might not be a good idea to do it for long, though. Think about it... that'd be like having a 6.16 rear axle. Your engine is going to be screaming, even with 3.08s and 35s. And I don't think an NP203 would be up to the task.

    I think a better short-term option may be to find some smaller tires for the towing rig.
    If this is going to be a constant tow rig and not just a one-time deal, you'll need to re-gear the axles.
     
  4. Leper

    Leper 1/2 ton status

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    Your motor and the rest of your drivetrain will not like that kind of a load. IMO the heat you will generate will kill lots of things. Have you ever driven in 4 low at 45mph? The sound is enough to scare me.
     
  5. 71 Blazer

    71 Blazer 1/2 ton status

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    Not sure how long I would be towing, maybe 2hrs max. Smaller tires are out, the 35's are brand new. I guess I could just use 2lo for the back roads and 2hi for the highway. This is only a temporary fix until I put in better gears. Not sure if I want 4:10's beacuse I do a lot of highway, might go wth 3:73's.
     
  6. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    A TH350 / NP203, with 35s, and 3.08 gears in low range would put your rpms at 60 mph around 3500 rpm, which is way higher than you'd want to be running for 2 hours... Even at 45 mph, you'd still be turning 2800 rpm in low range.

    My truck used to pull around 2800 - 2900 at 60 mph with a 2wd with 31" tires, 4.10s, and a TH400, it felt like it was screaming, and got horrible milage. That, and I don't think your transfercase is designed to remain in low range for a long period of time at high speeds, I'd be surprised if you didn't wreck something, not to mention the fact that you'd get vibes from your front driveshaft turning, and loose a ton of mileage with having to turn your front diff.

    35s and 3.73s with a 1:1 final gear would put you at about 2200 rpm, which is basically right on with most SBC's sweet spot for mileage / power, but will make your truck a bit more doggy off the line as compared to 4.10s.

    35s and 4.10s with a 1:1 final gear in your transmission is still a very acceptable gearing combo. You'd be turning approx 2400 rpm at 60 mph, but have a lot more off the line power than 3.73s

    Personally, I'd go with the 4.10s, esspecially if you plan to tow with it.
     
  7. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    hell if you have to, once, use 2 lo til about 25, then kick it into 2hi and start in 2nd...
     
  8. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    I tried doing that with the NP241 in my 96 when I had way too much weight for the V6 behind it, I had no trouble going from 4lo to neutral, but it wouldn't go into 2hi, just ground until I came to a stop...
     
  9. 71 Blazer

    71 Blazer 1/2 ton status

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    You can only shift from 2lo to 4 lo and 2hi to 4hi, under light loads. I don't think the front drive shaft would be turning in 2lo, if it was, what would be the point of 2lo. I think I will just live with it, and put in some 3.73 gears later.
     
  10. goldwing2000

    goldwing2000 Guest

    With most transfer cases, there's no such thing as 2Lo.
    All you have is 2Hi, 4Hi and 4Lo but if you don't lock in the hubs, then it's 2Lo with the front driveshaft turning.

    Since you have an NP203, then you have the "Loc" settings but all in 4wd.

    Unless you've switched in a part-time kit, then I think you get 2Lo with that.

    Either way, you can't go from low range to high range "on the fly". As far as I know, no transfer case is capable of that.
     
  11. lochenjons

    lochenjons 1/2 ton status

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    I;d go with the 4.10s. I have 4.56 with 35"s in mine and thatll probably be too low for mostly on road. If I were you I'd try and find axles with the axles with the ratio you want if you can instead paying $$$$ for regearing them unless your doing it yourself or getting it down cheap or have tons of money. I regeared my dana 44 for enough money to easily have gone 3/4 ton. Oh well live and learn
     
  12. 71 Blazer

    71 Blazer 1/2 ton status

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    I have 3.73's in my blazer and future plans are to put one ton axles under it, so that is why I am going with them.
     

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