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3.73's and 35

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by wakedog, Jul 23, 2001.

  1. wakedog

    wakedog 1/2 ton status

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    3.73\'s and 35

    i have 3.73s and 35 inch tires, will this be a good or bad combo with a 700r4 and a 350 crate?? I don't have the money to upgrade to 4.10's or 4.56's. Is this to high of gearing (numerically lower) for my 700r4 and 35's??
     
  2. donimator

    donimator 1/2 ton status

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    Re: 3.73\'s and 35

    i had 35's with 4.10 gearing. My freeway rpm was about 2000 going 70. I would not run that unless you change the gears.

    73 3/4 ton Chevy. 383 stroker, TH350, NP 205, 14bolt FF(Detroit), Dana 44(limited Slip), 6in. lift, 36x 14.5 super swampers
     
  3. txbartman

    txbartman 1/2 ton status

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    Re: 3.73\'s and 35

    I am running 3.73s and 35s with a 305/700. I can't tell you what RPM I am actually running at highway speed, but I cna use one of the calculators available here on the web. But, I do know that I have no get up and go for passing or even getting out of some idiot's way!

    I have to go with 4.56s or run in D on the highway. And dropping to D is too high of RPM. I also think 4.56s will help me in the lower gears as well. It isn't cheap, but you should build it right. Save in the long run.

    Brian
    Click to see <a target="_blank" href=http://tx85gmcguy.alloffroad.com> My 85 Jimmy </a>
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: 3.73\'s and 35

    If you run in OD, you'll cook your tranny, not enough RPM to be above the stall speed at cruise speed.

    Go to the junkyard and get 3/4 ton axles. I swapped them in just for the 4.10 gears. You might even find a set of 4.56s. Around here they crush 4wd trucks all the time. You could probably pay $200 for the set, throw some brakes on them, and go.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  5. wakedog

    wakedog 1/2 ton status

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    Re: 3.73\'s and 35

    I just got a 14bff w/ 3.73s, i couldn't find any with 4.10 or 4.56 and i was i need of a axle cuz its my daily driver. What is a good cruising rpm at 60??
     
  6. bigblue

    bigblue 1/2 ton status

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    Re: 3.73\'s and 35

    I have 3.73's. I just cruise the highway at 85 ! hehe
     
  7. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: 3.73\'s and 35

    Good cruise rpm at 60'd be about 2000. That's about the minimum that's acceptable.

    I don't believe you couldn't have found a set of 3/4 tons with 4.10s. In fact, I don't know how you managed to find one with 3.73s. 4.10s are much more common in a 3/4 ton truck.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  8. denver75k5

    denver75k5 1/2 ton status

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    Re: 3.73\'s and 35

    I've also got 35's with 4:10's to me thats a good highway gear! with 33's i would go with 4:10's .

    <a target="_blank" href=http://www.community.webshots.com/user/wheelininco>www.community.webshots.com/user/wheelininco</a>

    " Wider IS Better!!!"
     
  9. Ross

    Ross Registered Member

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    Re: 3.73\'s and 35

    is there any way to cool the 700r4? and if so where can i buy it. i ask this because i want to run 35's with the 700r4 and 3.73. and will it not over heat if i doint go or drive fast?
    i just got to be bigger then the j**ps in town that run 33s

    1986 white K5
     
  10. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: 3.73\'s and 35

    If you want to run 35s with 3.73 gears, go right ahead. Get the 24,000 lb B&amp;M cooler like I have. I'm going to tell you right now, it's not a good idea and you could easily cook your tranny if you use overdrive. Use the cooler, drive in 3rd gear all the time and you'll be fine.

    And, FWIW, driving slower will make the problem worse.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  11. denver75k5

    denver75k5 1/2 ton status

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    Re: 3.73\'s and 35

    Try Jeg's , Summit, or you'r local trannie shop.

    <a target="_blank" href=http://www.community.webshots.com/user/wheelininco>www.community.webshots.com/user/wheelininco</a>

    " Wider IS Better!!!"
     
  12. OFFRDK5

    OFFRDK5 1/2 ton status Premium Member

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    Re: 3.73\'s and 35

    84_Chevy_K10: They aren't hard to find. A local junkyard that I was looking at had almost ALL 3.73s. Just one 4.10!! Nothing any bigger!!


    SK-15
    J**P...it's whats for dinner!
    Roads? Where we're going, we don't need any roads!
     
  13. TX Mudder

    TX Mudder 1/2 ton status

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    Re: 3.73\'s and 35

    My 3/4 axles are 3.73 stock.
    -- Mike

    <font color=blue> At some point I'll be done building my truck and can actually go wheeling. Until then, I guess sex and alcohol will have to do. [​IMG]
     
  14. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Re: 3.73\'s and 35

    While I do agree that the 700r4 should NOT be run in overdrive around town, while driving up moderate grades, or on curvy back roads, there is no reason why it should really hurt anything to slip into overdrive when maintaining cruising speeds of about 50 mph and above. The majority of the wear and heat buildup occurs when shifting in between gears, and as you know most overdrive equipped trannies will shift alot between 4th (o/d) and 3rd in the above mentioned conditions. If you are cruising at higher speeds on the freeway there really should not be any excessive heat build up in the tranny.
     
  15. nyyef

    nyyef 1/2 ton status

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    Re: 3.73\'s and 35

    you could switch to a SM465 and never have to worry about your tranny no matter what gearing combo you have.
    $.02 from a stickshift fan.

    Knife.
    knife.coloradok5.com
     
  16. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: 3.73\'s and 35

    I'll second that...I run 36" TSL's with 3.73's and my SM 465. It gets up and goes just fine but second gear in a 4 speed is way lower than the first in a 700R4 or a TH 350.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
     
  17. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: 3.73\'s and 35

    "2nd gear is way lower"

    Yeah the number is lower but a torque converter doubles the multiplication anyway, so really that's not true. We'll just compare 1st gears. The SM 465 is somewhere around 5.5:1 as far as I know. The 700R4 is 3.06:1. Multiply that by 2 (which is probably the minimum the TC adds at full slippage) and you get 6.12, which is even more than the SM 465. Although I'm a manual fan this is still fact.

    6.2 Blazer,

    I disagree on the 50 MPH comment. The trans would most likely be below the stall speed, TC slipping, making heat, killing his tranny.

    I know a guy that has a newer IFS truck with 6+3 for lift and 38s. He has a REAL hot 350 in there, a build up 700R4, but the lowest gears they make for those trucks with IFS fronts are 4.56s. He's got a tranny temp gauge and to avoid killing is $2000+ 700R4, he drives in 3rd, all the time, with 4.56s and 38s. 3.73s and 35s are even higher when combined. I've got 4.10s--but I suppose I should really have 4.56s or 4.88s.

    I'd be hard to find 3/4 ton axles with anything llower than 4.10 stock, but you should be able to find some 4.10s if you can't afford to have the gears changed. 4.10s really aren't ideal, but it's the best I could do personally, so it's at least an idea.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  18. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: 3.73\'s and 35

    A torque convertor does not change your first gear ratio. As soon as the effective stall speed is reached it might as well be a clutch in a manual. So unless you're running some sort of high stall you're still dealing with hard numbers. Try a wide open throttle blast with an auto and a manual, same tire size and rear end ratio...which one has to shift first if my manual has a 3.58 to 1 'second' and a 700R4 has a 3 to 1 first? Still think the torque convertor doubles your ratio? How about torque applied to the ground? Any auto will eat more horsepower than a manual for one, secondly the lower ratio of the manual will multiply more of my torque and put it to better use.

    My 2 cents...

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
     
  19. TwoCrowsDesign

    TwoCrowsDesign 1/2 ton status

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  20. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Re: 3.73\'s and 35

    In regards to 84_Chevy_K10's comment about the 50 mph and stall speed. The converter may be below stall speed but if it is locked via converter clutch, then it is not in a state of stall even though the RPM's are below stall speed. You can take a high stall towing converter that has a 2400 RPM stall speed and be doing 1800 RPM's with the converter locked and it will not generate heat from slippage. If it is being forced to lug however, the tranny itself will heat.

    As far as the debate of auto vs. stick. The torque multiplication factor will give an auto an advantage over it's mechanical first gear number. Take a 700r for example. It may have a 3.06:1 mechanical first gear, but when used with a high stall converter it can reach as low as (approximately) 6:1. Depending on converter and motor torque it may not be as great (closer to 4.5:1). The one big advantage is converter slip will not do as much detriment as clutch slip when trying to get a manual to multiply it's mechanical ratio by riding the clutch (not good for clutch/pressure plate and flywheel). Torque converters are designed to slip, clutches (purely speaking) were not. That is the main reason manuals were designed with a lower mechanical gear while automatics were not.

    That being said, to each his own. If you believe it's better, it is better. Remember perception is 99% of YOUR reality. If you feel driving a stick is better, drive a stick (I think my ex-girlfriend preferred the broomstick.....whatta witch!), and if you believe driving an auto is better, drive an auto.

    Getting back to the original post. 35's are a little tall with 3.73's and automatic OD (this is where a manual has the advantage because it is less likely to grenade). You will be a little sluggish off the line, but the healthy 350 should help. For highway driving just keep it in D and it should be fine (better to run a few more RPM's than grenade it trying to use OD) and you can always re-gear later (when you save up more $$$) to take advantage of the OD and also get better acceleration.


    If you didn't build it yourself, how can you call it yours.......?
     

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