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I NEED INPUT!!!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by JunkYardCrawler, Oct 5, 2000.

  1. JunkYardCrawler

    JunkYardCrawler 1/2 ton status

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    I am trying to firure out what gears to go with. 4.11s or 3.73s 4.11 will be better off road i know but i plan on doing alot of highway driving too. and the 3.73s would be better. a futer mod for the truck is to put in a doubler so i can gear down and a 5 speed. i got a 4 speed now with a granney low so realy only got 3 street driving gears. what do you guys think?

    <font color=red> Hey who put that grenade in there? </font color=red>
     
  2. K5 NUTT

    K5 NUTT 1/2 ton status

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    If i had to do it all over again i'd have left the 3.73's in my diffs....and went with the doubler set-up....65mph is around 2700 rpm for me these days....only option know is to go up to a 6 inch lift and add 35's to tone it down a bit...along with a 700R4. Just my 2 cents worth.

    AZBLAZER

    1979 K5
    1976 K5 Chalet
    1972 K10 Suburban
     
  3. JunkYardCrawler

    JunkYardCrawler 1/2 ton status

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    Thanx man. i'm running 3.07's now. and there is no power. is nice on down hills and flat but soon as i hit a hill mph gose down to about 35-45 and my foot is to the floor. and hey ur 2 cents might have saved me a couple of $100 of dollars later.

    <font color=red> Hey who put that grenade in there? </font color=red>
     
  4. Goto 4LOW .com and look at the tire and gear tables,they have some info there on what gears and tires vs. rpm.
    They also have what combo's are best for miledge and power.
    I hope this helps,good luck.

    IF IT AINT BIG IT AINT BAD!!!!!!
     
  5. Wheels

    Wheels 1/2 ton status

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    I'm running 3.07 gears right now with a TH350, NP 203 and 33" tires. If I can find a TH700 that has a NP 205 attached, or a 205 that has the 350 adapter,(I'll have JET build me a 700) I plan on running 4.11 gears because of the overdrive that the 700 has. If I cant find one, I'll put the TH 400 in and run 3.73. I've done a lot of research into this and these are the best two options that will work for my set up. The TH 350 probably wont last long behind the the motor that I've built, but it's a do fer until I can find the 700/205 set up.
     
  6. realsquash

    realsquash 1/2 ton status

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  7. blazer72

    blazer72 1/2 ton status

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    I run 3.73 with 35 inch tires, a NV4500 and a 203/205 useing the ORD 400 kit. At 80 MPH I'm turning about 1800 rpms. To make it work with the 3.73 you have to have a very fat tork band with lots of tork there to use. My tork is 270 at 1000 rpm, peaks at 514 LBS /2500 rpms but only drops to 509 at 3000 rpm and is down to about 400 lbs at my red line of 4500. After 4500 the tork falls fast plus 400 sb dont like to rev and live.

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  8. lowlevell

    lowlevell 1/2 ton status

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    I went from 3.42 to 4.11 with 31x10.5.My rpm's went up about 400 rpm.The 31's i have now (bfg ko's) are a bit taller than my original 31's that i had with my 3.42 gear,so this might have made maybe 100? rpm difference.I had to change my rims because of my axle swap,thus i had to change tires.My rpms are around 2400 @ 70mph.I am running the 700r (OD) tranny.Hope this helped.....later

    One From None
     
  9. Chewy

    Chewy 1/2 ton status

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    I am running 4.10 gears with 35x14.5 tires and a TH700R4 tranny. I don't have a tach, but on the highway doing about 65, the engine doesn't seem to be working hard at all. Also, I get excellent pickup when passing those slower Fords.[​IMG]

    '87 Beast
    Colorado, USA
     
  10. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I have 35's and the SM465 4 speed and the 3.73's. On the highway my truck is turning 2400 RPM at 65 MPH. My mileage is pretty good and it seems to have lotsa power (350). Most gearing charts say I should be running 4.11's or 4.56's but I do a fair bit of highway driving. The truck wheels very well with the 3.73's (granny low first helps) and I find this combo to be just about right for my truck.

    Rene

    [​IMG]
     
  11. realsquash

    realsquash 1/2 ton status

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  12. JunkYardCrawler

    JunkYardCrawler 1/2 ton status

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    i am planing on running 35's befor i get the doubler and the 5 speed. is the 5 speed as strong as the 4? is it bigger longer?

    <font color=red> Hey who put that grenade in there? </font color=red>
     
  13. tom

    tom 1/2 ton status

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    Depends on how sure you are of the doubler and the 5-speed. The nv4500 may be trouble to adapt unless you go to the the atlas II 4:1 case. I run 3.73's in a 4 speed blazer 33x12.5 and its OK on the road, but my 3.42 4 speed suburban 32's is definitely better on the road. With the doubler and 4 speed I'd consider 3.73 and 3.42 and favor the 3.42 if it gets a lot of highway driving. If you are certain that you'll go the OD 5 speed, then 4.11's are OK. You have got to decide up front what T-case and trans and tires you will eventually have, or you'll end up changeing diff ratio's twice.
     
  14. JunkYardCrawler

    JunkYardCrawler 1/2 ton status

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    not sure on the t-case, and the tires are going to be 35-37 probly. i would like to have the 5 speed w/od. but don't know to much about it. its all so far down the line that i havn't put much thought into that part. the gears are whats going on now. and then tires. then i will see from there.

    <font color=red> Hey who put that grenade in there? </font color=red>
     
  15. blazer72

    blazer72 1/2 ton status

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    You use the tb400 203 that has a female input gear which is 32 spline, a stock chevy 4500 for 4 wheel drive with a dodge tailshaft houseing, and the chepest adapter that is made be advance adapters which mates the 4500 to the 203. There no mods to the 4500 or to the 203. And yes the 4500 does have the same out put splines as the tb400. with this there is no spud shaft or trick stuf just a flat plate about 1 and 3/4 inches thick. Once you get the 203 on then you use the 400 doubler kit. Steve at ORD can get you every thing you need. Yes the 400 doubler is a bit more costly than the 350 one and a bout 2 inches longer but the 400 kit uses not cuplers. the out put of the 4500 goes in side the 203s input gear and the out put of the 203 range box goes inside the 205s input gear with more engagement thean the cuplers have so it much stronger the the 350 or 4 speed doubler kits this is needed with the 6.34 or 5.67 first that the 4500 has.

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  16. Chris Demartini

    Chris Demartini 1/2 ton status

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    <font color=blue>What would it take to put an NV4500 in front of an NP205 that originaly came behind an SM456?</font color=blue>

    http://www.chrisd71k5.coloradok5.com <font color=blue></font color=blue>
     
  17. blazer72

    blazer72 1/2 ton status

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    That would be the first step to the doubler any way you use the dodge tail housing and chnge the 205 over to the late mod 400 with the female input gear and a flat plate ada[ter from adavance the adapters for the 203 and the 205 to the 4500 are some of the cheapest made if you use the 400 input gear.

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  18. blazer72

    blazer72 1/2 ton status

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    As for the atlas it was not built to handel a 6000 lbs of real truck with 400 or 500 lbs of tork when I talked to advanced about one they would not sell it to me Said it would not hold up in the full size blazer.

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  19. jarheadk5

    jarheadk5 1/2 ton status

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    My 87 has a 305, 700R4, 3.73 gears and 33's. Most of my driving is highway and I don't have problems.

    [​IMG] Semper Maintenance!
     

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