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4.56 and passing gear?

Discussion in 'The Garage' started by muscle, Dec 29, 2002.

  1. muscle

    muscle 1/2 ton status

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    I have a '84 Jimmy with a 400 smblock motor built up a bit to about 360hp, a 700-R4 tranny with NP208 T case. I will be using a D44 front and 12" corp. rear ends. I plan on upgrading the gearing to 4.56 with an ARB locker in the front.

    My question is, what will passing gear be like on the highway at say 60 MPH? Seems like my RPM's will be WAY UP THERE!

    Does anybody have this set-up and can attest to what the highway driving will be like?
     
  2. outlaw612

    outlaw612 1/2 ton status

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    What size tires are you running? Ive got a 700r4 with 36" Swampers and 4.56's and its great on the highway. I wish Id went with 4.88's.
     
  3. muscle

    muscle 1/2 ton status

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    Probably the biggest tire would be a 33". This truck isn't meant for real hard core rock climbing just a good hunting rig. So the smaller tire will make the rpm's hgiher.
     
  4. outlaw612

    outlaw612 1/2 ton status

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    Yes, the smaller tire will make the rpm's higher. If you think you might go to a 35/36" tire later, go with the 4.56's. If you plan to stay at 33" tires, Id go with 4.10s.
     
  5. Highlander

    Highlander 1/2 ton status

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    I can't remenber right off hand what the RPM's are But I would say they will be close to 3000. In OD I would say you should be around 2200 @ 60/65
    I have 35's with 4.56 in my 83 and like the setup. I had a FJ-40 with a 400 sbc and 4.11's and 33's and at 65 it would be doing just about 3000, So you could be a little higher

    Eric
     
  6. muscle

    muscle 1/2 ton status

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    I would be at 2860 RPM using 33" tires and at 60 mph or 1950 in OD. What I'm concerned about is when I'm wanting to cruise at 65 and someold lady is in front of me doin 55. When I kick it down to pass her am I going to need a rev limiter to keep from goin past say 4800 RPM? /forums/images/graemlins/crazy.gif
     
  7. muscle

    muscle 1/2 ton status

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    Does anybody know what the second gear ratio on a 700-R4 is?
     
  8. Highlander

    Highlander 1/2 ton status

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    I wouldn't think you would need one. I doubt you will see 4000 when you go to pass the old lady. /forums/images/graemlins/eek.gif I wonder if there is a calc. that will help you more than I /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif I know I've seen one some place

    Eric
     
  9. florida4x4

    florida4x4 1/2 ton status

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  10. Highlander

    Highlander 1/2 ton status

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    try this site Calcs. this should help some

    Eric
     
  11. muscle

    muscle 1/2 ton status

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    Florida,

    Your calculator shows second gear ratio in a 700-R4 as 1.63 If that is correct then at 60MPH with 33" tires and 4.56, passing gear would put me at 4541 rpm! /forums/images/graemlins/shocked.gif
     
  12. Bullet

    Bullet 1/2 ton status

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    I run a healthy 383 Stroker/700R4/4.56 combo; but on 37's For that tire size, we went with 4.56 to match the best RPM range. WIth the gearing and the Stroker, it'll get on it purty good /forums/images/graemlins/grin.gif It was in third when its up to 80mph when I passed some one on the freeway the other day. Your passing capabilities will be good, but the rec's might be just a tad too high, trust me, you dont want to get your rpm's way too high...its why I have my stroker /forums/images/graemlins/crazy.gif
     
  13. Highlander

    Highlander 1/2 ton status

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    Have you forgot that you have a four speed tranny? the passing gear should be 3rd not second. But I'm think you would be driveing down the Hwy. at 65/70 in OD then go to pass the Grandma that is doing 50 if you lucky that is.

    Eric
     
  14. Bullet

    Bullet 1/2 ton status

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    700R4 Gear Ratio's...

    1st: 3.06
    2nd: 1.63
    3rd: 1.00
    4th: .70

    Hope any of this helps /forums/images/graemlins/thumb.gif
     
  15. muscle

    muscle 1/2 ton status

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    My 400 has balanced crank and rods, 91/2 to 1 hyper pistons, high vol pump, pretty serious cam. I cant remember the specs on the cam and what # heads. Machinist really hogged out the ports and put 202 intake and 175 exhaust, hardened push rods, roller rockers, wieand intake.

    Anyway,the highest I've had the motor is 4800 and she didnt even blink. Valves were'nt floating out or anything like that. Just sounded pretty high.Our race motors were 377's and 383 strokers limited out at 7200RPM but they are quite a bit more motor too.

    I just dont want to have to stay behind the friggin 'ol lady cause I dont have room to pass without kickin it up to second gear and possibly over-revin the motor. /forums/images/graemlins/eek.gif
     
  16. Bullet

    Bullet 1/2 ton status

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    Sounds like you got a nice engine in you rig. The 383 puts out plenty of power. Right now I have the ZZ4 cam, and I am curious how much it would put out with a Roller tip rocker cam.
     
  17. muscle

    muscle 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    I am curious how much it would put out with a Roller tip rocker cam.

    [/ QUOTE ]

    Depends on whether you go for a basic roller tipped rocker or a fully rollerized system. I dont use my motor for much with exception to a few stomps on the pedal when the time seems justified so I cant see putting that much into a motor that I hunt with. Its nice tho to have a little more salt in a motor when you need it.
     
  18. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    700R4's don't have a passing gear per say like a TH350 or TH400 does, 700's use a TV cable which is throttle pressure and depending on RPM and also throttle pressure it may not even downshift at all. At highway speeds you will never get it to go into 2nd gear, the only gear you will get is 3rd or 4th. There are safety features built into the design of the transmission that will not allow it to happen unless you have had it seriously modified.
     
  19. muscle

    muscle 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    700R4's don't have a passing gear per say like a TH350 or TH400 does, 700's use a TV cable which is throttle pressure and depending on RPM and also throttle pressure it may not even downshift at all. At highway speeds you will never get it to go into 2nd gear, the only gear you will get is 3rd or 4th. There are safety features built into the design of the transmission that will not allow it to happen unless you have had it seriously modified.

    [/ QUOTE ]

    Thanks, thats nice to know. I have a 77 K5 with a TH350 but never owned a 700-R4.

    At 60MPH, 3rd. gear, my RPM's should be 'round 2800 which is where my cam starts to "kick in" so it should be ok.

    If I'm passin granny and I'm about halfway, I dont want to call on Scotty for more "warp"! Who knows what granny has under the hood! /forums/images/graemlins/blush.gif /forums/images/graemlins/eek.gif
     
  20. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I doubt it would shift down to second...but even if it did it would shift up to third around 4500 anyways. With that much motor and the 4.56's you won';t need to have it hammered down for even the most agressive pass. The 700R-4 is automatic...and most shift around 4500 RPM at WOT from what I've seen.

    Rene
     

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