What gears with 35in. tires

[71GMC 4x4]

Maybe someone could help me out. I'm stepping up to 35's from 33's, i'm wondering what gears I should put in. Right now I have 3.07 which is ok on the freeway, gets great mileage. But goin up hills it's a dog. I probably won't do alot of freeway driving anyway. I was thinking 4.11 but someone suggested 4.56 do you think that would be too much? Any help would be appreaciated.

[misfits]

I would go with 4.56 if you aren't going to drive on the freeway.

[Bill72BB]

71GMC;
Try this site and play with the # . http://www.prestage.com/carmath/calc_Gears.asp

Bill

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72 3/4ton Custom Camper BB,400 Dynamax Cermax headers , air,ps,pb,leafsprings
tilt,3.54 . 82 chevy silverado sb ,ps,pb pw,pd,air 350/350 Flowmaster 40.
Torrance Calif.

" If I knew I was going to live this long I would have taken better care of myself "

[mkmiller1]

All depends on how much abuse you're gonna put it thru. For highways and slight mudding adventures I've been well pleased with the 3.73's in my blazer. I've got 33's on it now and plan on 35's when I put the 4" lift on next year. My blazer is mainly just for pleasure riding. Just my opinion, but with that big of tire you can tear some stuff up quick without big gears(4.10-4.56) if you do much offroading.
Matthew

[Fast68Chevy]

IMO, 3.73 would be ultimate all around useage gears with taller tires like that, I wouldnt be afraid to cruise the freeway with 4.10's with those tires either, as long as is 2800 or less RPM.

randysringandpinion.com has an rpm calculator to play around with:
http://www.randysringandpinion.com/calc-rpm.html

click on engine RPM to the right


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Randy- Lincoln, IL

r68c30@hotmail.com 2177353230
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[68SWB4x4]

what trans do you have? what engine? if i would drive it alot on highways and such id go 4:10, if you plan for bigger tires later on and mainly want it for around town and offroad id get 4:56

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[DINS 1]

here is a page with a chart that should help out you gear decision. my 4" lift with 35's is going to be running 4.10 mostly camper towing duty.

http://www.4lo.com/calc/geartable.htm

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72 3/4 ton 4x4 suburban
71 1/2 ton 4x4 suburban
69 1/2 ton 2wd suburban
79 Camaro RS black & white
92 GMC suburban 4x4
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[Joesjunk]

I have 35" tires and 3:73 gears. It drives great on the highway, about 2600rpm's at 70 mph. but I wish I had gone with 4:10 gears for a little more grunt off the line.

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1972 3/4T 402/auto 60k original miles, original paint
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Independence, MO

[Mudder]

I've had 3.73's adn 4.11's with 35's and I think u will want the 4.11's. If you ever go to 38's you will need 4.56's.

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67 stepside 4x4 Owensville MO mudder67@hotmail.com

[LeRoy]

I've got 4-11's with 36" tires and a Turbo 350. It's a good combo. I run around 2800 at 70. I'm putting in 5.13's, in a while, for a little more pull off the line. If you have a 4 spd. manual then 3.73 are good. My 71 with 35's, 3.73's and a 4 spd. manual, runs about the same, going down the freeway

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Add or Delete Daily

[Mudder]

All trannies and transfer cases have different ratios so it all really depends what you have and what you want.

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67 stepside 4x4 Owensville MO mudder67@hotmail.com

[71GMC 4x4]

Well to answer a few of the questions, I have a th350 and I believe a 350 with a mild cam. Eventually I want to build a motor for a little more power and alot more torque maybe a 383. Most of my driving will be around town and in the hills, not much freeway.I don't think I will ever run 38's, probably 36's would be the biggest I would go. Thanks everyone for your help.

[704x4]

i have 4.10s with 33 in tires and i love it

in my opinion any thing less than 4.10s would prabably be hard on the auto tranny.

with 4.10s at 3000rpm you'd be going 77mph

with 4.56s at 3000rpm you'd be going 69mph

got that form this sight http://www.smokemup.com/utilities/calc/mph_range2.cfm

[Mike C]

I thought 4.10 were a tad too much for the 33's but they are perfect IMO for the 35's. My truck cruises 2500 rpm at 65 with 35" BFG and SM465.

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70 GMC 3/4 ton Sierra Grande 402/TH400
72 Jimmy 4WD 4spd 4" & 35's
64 Corvette Coupe
68 Camaro 'vert TPI & TH700
69 Z/28 355 12.6's @110
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[71402BB]

I think I would choose the 4.56. Even if you do a lot of hiway driving you are only going to be spining a 3000 rpm's at 69MPH!

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71 SWB Stepside, was a 250, now is a 402 Big Block with 4 speed and 3.73's

72 LWB 4x4 350 4-speed 3.08's posi wearing army olive drab green (SOLD!)

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[Blazer1970]

With 35s, I would use 4.10s if you don't have an overdrive trans. If you do have overdrive, use 4.56s.

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Tim

[jmj4]

you guys with 33's, did you have to put a slight lift on to get them to fit? would like to put as much tire on as possible without any rubbing in the wheel well.
thanks.

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1970 GMC 1500 Custom. 307 V8. Positrac.
Brandon, Mississippi.

[bouncytruck]

My old '72 K-5 had 35's and 3.73. It was kind of a dog. My '69 K-5 had 4.10's with the 35's. I has much more get-up-and-go! I'd run with 4.10's if I were you.

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'69 K-5 Blazer - 350/TH350, 6" lift, 35" tires
Bothell, WA

[Grim Reaper]

I run 35's with a TH350 and 4.11's. Not a bad combo. I have to run a lot on the hwy to get to the trails. If I had less hwy travel I would have gone 4.56. My bud has 4.56 and basicly the same set up and it's just winding to much on the hwy. He has a 80 with lock up converter.
When you look at those Gear charts understand that a 3 speed auto without lock up converter is going to run about 250 or so rpm higher to do loss in the converter. If you have a lock up converter then it would be even. If you have Over drive then go for the 4.56 for sure.
BIG TRANNY COOLER is a must. Even with the 4.10 if you get on a long enough slope with anough grade your going to be putting some stress on the tranny. I see a 30 degree increase in temp on this long hill near my house if I try to maintain 70mph. Still stays under 200deg on the tranny but most of the time I'm running 150deg on the tranny.

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Grim-Reaper
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[trukman1]

71, Remember too, the automatic's troque converter multiplies torque until it is "all in" which means you can run a higher (numeerically lower) gear rtio and have the same performance as a higher gear (numerically lower) at low end. The 4.10 ratio should be aboput right and should provide good bottom end torque as well as decent highway cruise range. My .02 cents worth. Gary

[Dean]

I have some trucks with 4.10 and others with 4.56. All have 35" tires. Both work well. It depends on what you are going to do with the truck. The 4.56s pull a heavy trailer better, but the 4.10s do good also. I used to have a 78 K10 3.73s and 40" tires...now that was a pig. Drove it most of the time in low range....lol