Bigger tires

[gmc85k10]

So I got a 85 k1500, going to put a 4 in lift on it, has a 350 hooked up to a 700r4, plan on running 35/12.50/18, has 3.73 gears right now, will I have to re gear it?

 

[SquareRoot]

No. It won't have a lot of grunt after 1st gear. I have OD, 350 Vortec and 33" tires. It's a great all around combo with 4:56 gears.

 

[Octane]

For my use I would not.To me it wouldnt make enough of a difference,besides the speedometer calibration.

 

[GTX63]

Is this a daily driver? Weekender? Trailer to car show spot?
Your location is listed as Idaho so it sounds like you would be on open road more than not. I ran 33s with a 700R4 with 4.10s and I can tell that I wouldn't have been happy with anything more than that, but I am at elevation with grades. If you are just bumping around the city I don't think it will matter much.

 

[AuroraGirl]

swap too 4.10, but i believe carrier break may potentially split that up depending on where it falls for your axles. 10bolt semi float rear and 10 bolt front axle I assume?

 

[82sbshortbed]

So I got a 85 k1500, going to put a 4 in lift on it, has a 350 hooked up to a 700r4, plan on running 35/12.50/18, has 3.73 gears right now, will I have to re gear it?

I have a 454 with a 700r4 and 275/60/15 with a 3.73 rear end. It's a good setup. I'm also thinking about going with a little bigger tire when these wear out. A bigger tire will just lower the rpms at cruise speeds. Right now it runs about 2,000 rpms at 65.

 

[AuroraGirl]

I have a 454 with a 700r4 and 275/60/15 with a 3.73 rear end. It's a good setup. I'm also thinking about going with a little bigger tire when these wear out. A bigger tire will just lower the rpms at cruise speeds. Right now it runs about 2,000 rpms at 65.

i think your tire size is much more normal is probably why lol

 

[BKING33]

4.10 ratio would be better. In overdrive you will be at probably 1700rpm at 65 mph with the 3.73 gears.
I had 4.10 in my old Small block truck without od and it was good compromise for cruising/hauling.

 

[Craig Nedrow]

Lot of money and time into swapping gears. 35 inch tires are $$$ Here is a calculator....input a few scenarios and find what you like. Me for I like the 12.5X33's

https://www.tremec.com/calculadora.php

 

[bucket]

For several years I ran a tbi 350, 700r4, 3.73 and 305/70 (33's) for daily use, along with towing and interstate travel. It was a miserable combination and I wouldn't recommend it to anyone. 35's would be even worse. God I hated that combo. Eventually I gave up and didn't run overdrive unless it was 100% flat ground at 75mph with a tail wind.

 

[Octane]

I bought 4 new Chevy trucks in the 1980s.Three had the 700r4.My manual stated not to ever tow in overdrive,to drop it down to D. I got very high mileage from all three trans.

 

[gmc85k10]

Alright thanks might just go with 33s so I don't got to swap any gears bc I plan on buying a k30 with a 6.2 which I'll be putting on 38s or 40s, so I'm running a 350 In my k15 do you think a carb or tbi would be better performance wise?