Opinions on gear ratio?

[dvdswan]

IMO, I would go with the 4.56s, just because of the hills. I would also suggest, instead of rebuilding the rear 10 bolt, get a 14 bolt SF out of a GMT 800 heavy half or light duty 3/4T. They are 6 lug axles but a lot sturdier than the 10 bolt.

 

[Jrgunn5150]

My daily driver came with a 245 tire and 4.10's.

I would absolutely run a 4.56 with a 33" tire, and 4.88 with a 35.

I've never in life wished I hadn't done such a deep gear, but I have regretted not going shorter.

 

[4WDKC]

So we have basically the same setup. Yeah I can go fast on the highway all day at low RPMS and not burn a lot of gas, but man if I mash the thing to the floor going up a hill or something it can't get out of its own way, sometimes it won't even downshift because the 700r4 is geared so high as it is. I live in new england, there are moron drivers everywere, sometimes you gotta pick up speed to pass or merge or whatever. Towing is also a nightmare.



Yeah the 700r4 is not a super good trans for towing. It can overheat easily, but that's why I have a B&M trans cooler and an AT temp gauge instead of a clock. It does alright I guess.

here ya go

RATIO: 4.10:1
TIRE HEIGHT: 33"
SPEED: 70
AUTO*:3000
AOD*: 2046
MANUAL*: 2922
5 SPEED*: 2338

using this calculator in D while towing you will not be able to down shift on big hills, when it slows down and down shifts and the hill is big enough you will overheat. Google towing with a tbi its quite common and why they have 8:1 compression. If you want to tow you need to get that cam out at a min. and preferably get better heads.

 

[RoryH19]

IMO, I would go with the 4.56s, just because of the hills. I would also suggest, instead of rebuilding the rear 10 bolt, get a 14 bolt SF out of a GMT 800 heavy half or light duty 3/4T. They are 6 lug axles but a lot sturdier than the 10 bolt.

I'm in the process of this rear axle swap. Found a light duty '94 3/4 4x4 14 bolt 6 lugs and per the RPO it's 3.73 with locker.
My k5 was born with a 305, 700r4 and 3.08 gears with 31" tires from the factory. I'm sure it was a dog. PO switched engine and trans to a 350/th350.
I'll probably stay with 3.73 with my 33" tires. But I also have a Escalade 6.0 and 4L65e trans now.

 

[Madhorn]

I am running a 5.3 with a NV4500 trans (5 SPD OD) on 35s and 4.56 gear. 70mph at 2400 rpm. I don't do a lot of highway driving, but its nice that I can. Thought about regearing to 3.73, very glad I did not. 4.10 maybe, but right now 4.56 is just fine. With the 700r4, I would lean towards the 4.56 JMO. Didn't know they made a 4.27 gear? If so, they may work well with 33in tire.

 

[RecklessWOT]

Thanks for all the responses guys. I think I'm gonna trust my gut and go with 4.56, I'll let you know how it pans out

 

[Rusty Nail]

4.56, all day.

That's the go-to gear what gets stuff done!

 

[Doubld]

I have an '87 Silverado. Unless you have had the 700R4 modified, you don't want to tow in overdrive. Stock, there is no fluid sent through the radiator to cool it.
I found that out the hard way towing a U-Haul trailer on a 103 degree day. Blew the front seal out of the tranny, had to trailer it 200 miles. 3:73 gears are plenty in Drive, and you get fluid sent out of the tranny to cool it. Not sure who the genius was at GM who thought that was a good idea. When I had the tranny fixed, the shop modified the valve body so it's always cooling.

 

[Arkansas_V8]

Thanks for all the responses guys. I think I'm gonna trust my gut and go with 4.56, I'll let you know how it pans out

Then I expect those big tires, and to see you on the trail one day.

Good decision man. Very versatile(towing, and bigger tires for the trails).

 

[DoubleDingo]

RPM = MPH x Gear Ratio x 336 divided by tire diameter. Run that equation for every single scenario you can think of in relation to tire diameter and gear ratio, and make a spread sheet if you need to, but at least write down each result, and then mull over the numbers to figure out what will work for your specific setup. Nobody will be running the exact same thing as you are, and only you have to live with your decision.

 

[gmbellew]

RPM = MPH x Gear Ratio x 336 divided by tire diameter. Run that equation for every single scenario you can think of in relation to tire diameter and gear ratio, and make a spread sheet if you need to, but at least write down each result, and then mull over the numbers to figure out what will work for your specific setup. Nobody will be running the exact same thing as you are, and only you have to live with your decision.

With or without OD? I think your equation is for no OD, but I wanted to verify

 

[DoubleDingo]

With or without OD? I think your equation is for no OD, but I wanted to verify

If you have OD you factor that into it.

 

[vintovka]

If you aren't worried about the MPG, just run in D on the highway instead of OD. It will keep it in 3rd gear.

If the issue is around town, different gears would be needed to make an improvement.

This is true. I run a 84 GMC 1500 with a new GM 350 crate 700r4, 32" tires and (unbelievably ) the stock 3.08. Cruise at 60 at 1100 rpm and damn thing down shifts at the hint of a grade. I run it on side roads and in town out of OD and its fine.

 

[DoubleDingo]

Around town OD isn't needed but for some reason any automatic will still go into OD cruising around town.

 

[gmbellew]

Around town OD isn't needed but for some reason any automatic will still go into OD cruising around town.

Around town, i run in D to keep it out of OD. I figure it keeps the tranny from shifting more, saving wear and tear, and I doubt I would notice the MPG difference. On the highway, unless towing, I run in OD. I dont tow usually, and nothing heavier than a 3000-4000 pounds when I do. If I were running the highway with a trailer, I'd probably keep it in D and keep the speed at 65.