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3:08s 700r4 2000rpm at 80mph Did I go to far?

Discussion in 'The Garage' started by 4wheelattitude, Sep 20, 2005.

  1. 4wheelattitude

    4wheelattitude 1/2 ton status

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    I wonder? I'm putting together a 1970 GMC 4x4 stepside. Will the gears with the 700r4 be lugging the engine to much?
     
  2. atho

    atho 1/2 ton status

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    Probably won't need OD alot.

    I know it isn't a truck, but my '88 Buick DD has 2.73 gears and a 4T60E (4L60E transverse variant) with a 27% overdrive. It actually gets its best gas mileage around 75-80 mph, no idea what its taching tho. If I drive 40-50 mph steadily, I leave it in drive or it will hunt gears too much.

    Some 3.42's or 3.73's would probably be a better idea.
     
  3. 4wheelattitude

    4wheelattitude 1/2 ton status

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    I tried to set this up for daily driver when I wanted to show it off.
     
  4. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    My 89 Chevy half ton typically pulls about 2000 rpm at 65 mph, and it doesn't lug bad at all :)
     
  5. 78Suburban

    78Suburban 1/2 ton status

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    attitude,
    what size tire are we talking here?
     
  6. 4wheelattitude

    4wheelattitude 1/2 ton status

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  7. trailblazr81

    trailblazr81 1/2 ton status

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    Well using the RPM/Gear/Tire calculators back in the day when I had a stock 86 Blazer with 700R4, 3.73's and 31" tires it was turning about 1900 RPM in OD at 65. So 2000 RPM at 80 would make me think more gear. Trying to turn a big tire in a heavy truck I would think you would want a couple hundred more RPM. Maybe 2200 at 65?? Your gonna be downshifting with every molehill you come to. I might consider 2000RPM at 80 if I had a Big Block powered Tri 5 Chevy that I would drive to all the car shows!! :wink1:
     
  8. 4wheelattitude

    4wheelattitude 1/2 ton status

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    Well I'm willing to sacrifice the tire size if I need to. I also have a new set of tire standard for the truck. They almost look to small for the truck but nice 235-75-r15
     
  9. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    With 33's and 3:08's , I never used overdrive unless I was on the freeway .

    With 33's and 3:73's I can use overdrive a lot more often , and on the way to work it helps mileage .

    The real world rpm's I see is usually between 1600-1900 on most freeway trips (flatter non mountainous ) . I can bury the needle on the speedo and still never see 2500 rpm's in overdrive :D
     
  10. 4wheelattitude

    4wheelattitude 1/2 ton status

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    So 3:73s would be better for my application? I live in Illinois kind of flat land here. I put the 3:08s in and built a 350 with a shorter stroke with the manual 3 speed and it had alot of torqe. Almost spooky!! That of corse with the smaller close to stock size tire. I don't know what the rpms were though I thought it needed another gear for the hiway. I also have a th350. I think I would rather change the transmission rather than the axles. I pulled the motor and trany out and now I can't make up my mind! I also have those 4:11s out back being an eye sore.
     
  11. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    I only went 3:73 , because local members had the axles and it was dirt cheap , and I needed 2 more housings for the trail rig .

    If I had access to 4:11's , in 1/2 tons ( I am daring to be different ) , I would of preferred those :D

    I can live with 3:73 since I have a 3:06 first and a torque converter .

    Funny thing is I HAVE to buy gears now , because I put the trail rig axles under my 83 :wink1:
     
  12. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    I'd use 4.10. Driving the burb here to CO on 33's with 4.10, the thing was unstoppable. There's a hill out of Limon, CO on I70 heading to Denver that people at work were saying they always have to kick down to get up it. I had the cruise set at 75 and it kept it without even unlocking the converter.
     
  13. trailblazr81

    trailblazr81 1/2 ton status

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    I agree 4.10's with 33's would be your best bet. And if you went 700R4 with the 4.10's and 33's would be awesome. Deeper first and OD!!! I did 3.08's with 35's with a TH350 for a while. I had a 383 and manually shifted ALL the time. Then came the 4.56's, and locker, etc...
     
  14. 4wheelattitude

    4wheelattitude 1/2 ton status

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    Sooo after going through all the trouble of with trying to get better MPG on hwy, I will be lugging the engine to much? Well should I put the th350 in or switch back to the 4:11s and go with the 700r4?
     
  15. trailblazr81

    trailblazr81 1/2 ton status

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    YES!!! Definatelly put in the 700R4 and 4.11's!!! :waytogo:
     
  16. 4wheelattitude

    4wheelattitude 1/2 ton status

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    OK! OK! I'm a little hard headed sometimes! But know I have another question. What would be best for the 4th gear lockup?
     
  17. trailblazr81

    trailblazr81 1/2 ton status

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  18. pauly383

    pauly383 Daddy383 Staff Member Moderator

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  19. 4wheelattitude

    4wheelattitude 1/2 ton status

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    I know I've seen sooo many variations. I just didn't know what would work the best with less hasle? Thanks for the links :D
     
  20. trailblazr81

    trailblazr81 1/2 ton status

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    Or you could go without a lockup... just make sure you dont miss match... lock up tranny with non lock up converter.
     

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