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4.10’s or 4.56’s with 700r4, 35” tires

Chris Ziemer

Chris Ziemer

Daily Driver
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Location
Galt CA
I’ve ran the numbers through the gear ratio calculator. On paper, the 456 gears seem like they’d work well, but the 411 gears would be a little less risky, in my inexperienced opinion. It’s about $2000 to switch both pumpkins out. So I’m hoping to only do this once.

I’d love some real world experience about what kind of RPMs people are pulling with this combination.

Trans type: 700r4
Tire size: 35”
Gear ratio:
Rpm’s at 65mph
Happy with them?

She’s a daily driver and I need to be able to cruise at 65-68mph down the highway, sometimes for 300 miles or so. But also pull a small trailer up long grades.

Currently have an old 350 and 3.08 gears. I can tell you going up over mountain passes is a painful experience. Depending on the grade, I’m in second gear doing 40 miles an hour!

I know 4.56 gears are pretty popular, but I hate to go too low. Anyway, any information you guys can provide I’d be super appreciative!

Whatever the consensus is is what I’m going with.

Thank you!IMG_7605.jpeg
 
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I have run a K5 with a 700R4 and 36” tall tires and 4.56’s - this brought things very close to the original 3.73 gear ratio with 31” tall tires which was perfect.

The difference between the two ratios is not gonna cause any regrets of too much gear - your trans will benefit from the proper ratio and it will also help fight wind resistance.
Go with 4.56’s with confidence!
 
yeah is only @200 rpm difference. I say 4.56. All engines are different if yours has any kind of performance cam you'll want to have the engine turning a little higher rpm to match the power band.
My next set of tires will be 35-37's. Even with the 4.88 and 33's, I pull 6% grades and @3k trailers in 3rd 3600 rpm at 65mph, cruise 4th 2700 at 75mph
 
Well it depends on the gear ratio your truck was equipped with, but in the 80's GM built these truck with gearing that had no business in a 4wd. For example 2.73. Many came with 3.08 still not a good gear for a 4wd, with larger tires.
Above 3.5 would be getting there. If you wanted 3.73 in 4th you would need 5.33. 4.88 in 4th is 3.42.
I couldn't do 5 up the pinion is very small in the ratios, and I have 14bff.
Looks like your rig is still on 10 bolts. If you have a g80 rpo traction aid, you'll want to upgrade your differential when you do the gears. The g80 in a 10bolt is not strong enough for big tires.
 
Wow, understanding that is really helpful. Mine came with 3:08 originally. No traction/locker goodies. At some point, I may upgrade to a 14 bolt, but it’s going to have to stop ringing my wallet out for a while, first.

So using 4:56 is similar to using a 3.42 gear set with the stock tires. Seems like that’d be a huge upgrade and certainly would make my trans happier.

Super appreciate you all.
 
Chris Ziemer said:
Wow, understanding that is really helpful. Mine came with 3:08 originally. No traction/locker goodies. At some point, I may upgrade to a 14 bolt, but it’s going to have to stop ringing my wallet out for a while, first.

So using 4:56 is similar to using a 3.42 gear set with the stock tires. Seems like that’d be a huge upgrade and certainly would make my trans happier.

Super appreciate you all.
Click to expand...


So, you're spending money on a 10 bolt?

YMMV, but swapping in a 14b with your choice of gears may be cheaper than the 1000 you're allocating to the gearing swap.

:dunno:
 
If ya find a 14Bolt that already has a 4.56 ( and possibly a Detroit Locker from a CUCV ) you will be money ahead and only have to gear your front axle.

We’ve all been down the road of spending money on parts that we later upgraded and wished we waited a little while and spent that money only once.

The point the guys are say’n is that a rear 10Bolt is the absolute smallest axle ever put in our squares and is known for breakage with small tires - larger tires are gonna add even more stress.
If you can hold off find that upgraded axle and spend that money once.
 
4.56 x .72 = 3.28
In overdrive your effective rear end gear ratio will be 3.28.
 
I ran 37s with 4.10s and a 700r4. It wouldn't stay in overdrive if there was even a slight incline. To the point I would keep it in drive not OD on the highway which defeated the purpose of having it in the first place. If you add anything to the vehicle (winch, bumpers, ect) tow and small trailer, boat or camper it will be worse. I would definitely do 4.56 or even 4.88s in my opinion.
 
formercruiserhead said:
I ran 37s with 4.10s and a 700r4. It wouldn't stay in overdrive if there was even a slight incline. To the point I would keep it in drive not OD on the highway which defeated the purpose of having it in the first place. If you add anything to the vehicle (winch, bumpers, ect) tow and small trailer, boat or camper it will be worse. I would definitely do 4.56 or even 4.88s in my opinion.
Click to expand...
I’m in a similar situation. Even on flatland, if a stiff breeze comes up it shifts down in the third. I do have a front bumper and winch. Spare tire, a box full of fix it gear…
 
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