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Which is best 4.10 or 4.56 please help

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by blazentank, Jan 23, 2002.

  1. blazentank

    blazentank 1/2 ton status

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    I have a 86 blazer with a rebuilt 305 and a 700r4 with 33 inch tire's and 3.42's. i used to have 35 inch swampers but this summer i lost my second transmission in a matter of 6 months so i had to sell them and get 33's I,m looking into changing the gears out but i don't know what is overall the best performance wise and has the best fuel economy. All know is i don't want to loose another transmission. I do alot of highway driving I cruise at about 75 mph. I think that is the reason i lost my last transmssion was because of all the highway driving i do. When i drive down the freeway it feels like there is a constant strain on the motor. well what I'm asking is what is better overall 4.10 or 4.56. I know some day i will be getting 35's again so should i just plan ahead and get 4.56 or is 4.11 good enough. Also where is the best place to get new gears from and how much does it cost to get them installed. I live in texas does anybody know the going rate down south please help me out

    "When you say i drive a fullsize are you calling my wife fat."
    J/K i was bored and made that up i don't even have a wife i'am only 17.
     
  2. 74k5inVA

    74k5inVA 1/2 ton status

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    can't tell you from experience, i am still running stock gears too. god awful in my opinion with a lift and 35's. but the general opinion around here is with an automatic tranny you should go 4.56's


    If it can't be broken then I haven't had it.
    '74K5 NP203/sm465 4"Lift 35"BFGs 350ci
     
  3. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    I have 4.10s and 35" tires. Proboably would go 4.56s if I had to do it again. I pull a motorcycle trailer all over Ca and drive has plenty of range. OD with no trailer is really hauling a$$!

    You have the 700r4? You can get away with 4.10s. In fact I think 4.10s, 33" tires and a 4" lift would be good setup.

    What diffs? Did you say?

    Dave

    Rehab is for quitters.
    <a target="_blank" href=http://coloradok5.com/gallery/Daves-Pics>http://coloradok5.com/gallery/Daves-Pics</a>
     
  4. 6.2Blazer

    6.2Blazer 1/2 ton status

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    If you plan on going to 35" tires again, then I would recommend going with the 4.56 gears.

    In order to save the transmission, there are a couple of other things you can do.
    - install a big transmission cooler
    - keep the trans manually shifted into Drive around town or on back roads, basically don't shift into O/D until out cruising at a steady speed on the highway

    There is really no reason why the 35" tires and 3.42 gears would cause a properly built 700r4 to fail after only 6 months. Yes, the large tires and high gears cause a little more strain but not enough to do that.
     
  5. txbartman

    txbartman 1/2 ton status

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    My rig is VERY similar to yours. Best similarity is IT'S TEXAN! Seriously though... Mine started as an 85 w/305 and 700R4 and 3.73 gears. That was fine with 32s, but really hurt when I went to the 35s. The 305 motor has a higher RPM power band than the 350 (from experience), especially if it is old and tired. My rig was really working with the 3.73s and 35s, I can only image yours with 3.42s. You just can't turn high enough RPMs to safely use OD on the highway without burning up your tranny. And, with a weaker 305, you are probably going to have difficulty maintaining enough power from the motor to keep the RPMs up there on the highway (probably doing a lot of shifting to keep you at 75 in OD with those gears and big tires).

    I went with 4.56s and haven't looked back. With the 305, it still struggles some, but my motor was old and weak. With OD, the highway RPMs are fine. You just won't be able to go 90 or 100 (which you shouldn't be doing in a rig like this ANYWAY). The 4.56s also give a MAJORLY NOTICEABLE DIFFERENCE off the line. You will be quite pleased with those gears.

    Now, I can wait to get this danged engine finished tonight (hopefully) so that I can see how I like the combo with the new 350!

    I got my gears and install kits at <a target="_blank" href=http://www.ring-pinion.com>Randy's Ring &amp; Pinion</a>. They are very knowledgeable, have lots of resources on their website, and had the best prices. I got install kits, Yukon gears, and Detroit lockers from them.

    Search this board for "R&amp;P Install" and you will find lots of posts about costs and doing it yourself. Check those out. Around TX, you are looking at about $300 for the front and $250 or so for the rear. But, that is only labor. You could also check with people in your local <a target="_blank" href=http://www.tx4x4.org>Tx4x4 club</a> for more local info and places.

    Brian
    Check out <a target="_blank" href=http://tx85gmcguy.alloffroad.com>My Jimmy</a> with all her projects!
     
  6. blazentank

    blazentank 1/2 ton status

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    Yea i fugured it was a crappy rebuild but when it went out again the transmission guy only charged $75 in parts to fix it. I already have a cooler

    "When you say i drive a fullsize are you calling my wife fat."
    J/K i was bored and made that up i don't even have a wife i'am only 17.
     
  7. POFF

    POFF 1/2 ton status

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    I have 4.10s and 33s and I would like 4:56. If you have overdrive I'd go with 4:56 for sure. I have a 4spd so 4:56 would suck on the freeway, but you can't have too low of gears off-road especially with 35s.

    '70 K-20 San Diego, CA
    I know, I can't spell!
     
  8. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    Well check this out...
    I had 3.73's / turbo 400 and 33's
    I saw a rusted out truck for sale for $500. I looked in the window and saw a smc465 tranny !!!! YES !!!! then the guy came out and i looked under the hood. He said it is only running on 7 cylinders. He started it up and boy did it run like crap. Well from there I crawled under the front... looked at the tag on the dana 44 and it said " 4.55 " YES!!!!!!! I crawled out told him I would be back and to get the title. I drove it out of there. the truck was stock with
    dana 44 w/4.56's
    14 bolt corp w/4.56's
    SMC465 and a NP205

    Hell I swapped all body parts from mine to his... sold the NP203 and turbo 400

    Now I was running 4.56's with a stock 350 and got 14mpg and I wanted to see where the gears would stop me.. I got the truck to 108mph !!!!!!!! I traveled for 5 years highway travel and enjoyed the better gas mileage...my full time NP203 gave me 10mpg and now I am getting 14 !!!!
    well now the truck has been lifted and off the road since 1997... hopefully this summer we will see what going from 33's to 4.56's is like..........

    well my long dragged out story... also I am going to be doing a website of my buildup from 1990 to 2002...... I will post it up hopefully soon.....

    Peace...

    1978 Chevy 3/4 - 14" leafs -dana 44w/4.56's -14 bolt corp w/4.56's on 40x17x16.5 Ground Hawgs on 16.5x12 steel rims-NP205&SMC465
     
  9. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    I meant that we would see what going from 33's to 40's is like....


    1978 Chevy 3/4 - 14" leafs -dana 44w/4.56's -14 bolt corp w/4.56's on 40x17x16.5 Ground Hawgs on 16.5x12 steel rims-NP205&SMC465
     
  10. Gandolf

    Gandolf 1/2 ton status

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    I have an '89 with stock TBI 350, 700R4 and 3.73's, and use it as an almost daily driver. When I was running 33's, I would have preferred at least 4.11's so I could have used OD more. I recently went to 35's, and don't use OD at all. I guess I could use it on a level freeway at 70+ mph, but for driving around the Bay Area, I just leave it in drive. I am looking for new axles (D60/14BFF) and the gear set I hope to find is 4.56. With 35's, I just don't think 4.10's will be low enough to prevent tranny damage in OD. If I got a great deal on axles with 4.10's and had to re-gear, I would probably go with 4.88's. I think 4.88's would work well with my future upgrade plans to 38's, injected 383 and a Raptor tranny (or 4L80E, if I can find a good deal on one).



    '89 K5 Silverado..."You can’t have a real adventure, unless the outcome is truly uncertain".
     
  11. blazentank

    blazentank 1/2 ton status

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    how much does it cost to get gears changed and where is the best to get them from

    "When you say i drive a fullsize are you calling my wife fat."
    J/K i was bored and made that up i don't even have a wife i'am only 17.
     
  12. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Don't mean to bust your bubble, but going from 3.73's to 4.56's without correcting the speedometer and keeping the same size tire will give you a false reading. The odometer will show that you traveled more miles than you actually did by around 15-20%.......meaning the reported 14 mpg is probably closer to 11.
     
  13. riz

    riz 3/4 ton status

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    <font color=purple> I would definately go with 4:56's if you plan on going back to 35's ! That set up is as close to factory stock ratio as you're going to get .......... perfect !

    L8r,
    . Riz . <a target="_blank" href=http://www.geocities.com/rizmonkey>www.geocities.com/rizmonkey</a>

    <font color=purple> monkeys steal my underwear at night
     
  14. Calclips

    Calclips 1/2 ton status

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    What exactly is considered a "safe" RPM range for running in OD?
     
  15. POFF

    POFF 1/2 ton status

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    Most speedo shops will correct your speedo with a little gearbox between the cable and t-case for about $80.

    '70 K-20 San Diego, CA
    I know, I can't spell!
     
  16. JIM88K5

    JIM88K5 1/2 ton status

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    4.56-Four point five six-Fourfiddysix....
    My daily driver has front &amp; rear 4.56's. I paid $1100.00 to the
    best local 4x4 shop in town and consider it as probably the
    single best modification &amp; best bang for the buck so far....
    That price includes new gears,bearings &amp; seals frt &amp; rr.
    The CV drive shaft comes in a close second.
    Jim

    88 Silverado K5 5.7-700R-208-10 bolts-4.56-35in
    Procomp AT's- some ORD stuff & a CV driveshaft
     
  17. dysphemism

    dysphemism 1/2 ton status

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    I have good experience with this. I have a 1986 GMC Jimmy with a 350. I run 38" rubber and 4.56 gears. My mom's BF runs a 4" lift and 35's with 4.11s. I was cruising in his rig a while ago and the accel just isnt there. I bought my rig with 4.56s on 36" rubber. The 4.56s are just better. If you could drive both you'd see it after a minute.

    Beefing up my truck broken part by broken part.
    1986 GMC Jimmy 9" lift, 38" swampers, and a sarcastic liscense plate holder.
     

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