Gear ratio, tire size, and lift? 72 Suburban

[1 MPG]

I'm planning to install 35x12.50x15, 4 inch or six inch lift, and possibly 4:10 gears. I would still like good RPMs at highway speeds.

What's the factory tire size that came with 1972 4x4 Suburbans.
My current gear ratio is stock 3:08, 350 turbo transmission, and 350.

Let me know what works for you?

[andrewmp6]

A chart http://www.offroaders.com/tech/gear-ratio-chart.htm or if you want a calculator to play with http://www.pitbulltires.com/calculate.php

[1 MPG]

Thank you for taking your time to send me this information! It is exactly what I was looking for. Now I need to figure out what the stock tire size was?

[Bigdav160]

Do you have a SPID on the glove box door? Any tire options listed? I think a 31.5 inch diameter was close to stock on a 4x4

[vectorit]

More than likely the OE tire spec is this:

L78-16.5-BB on/off road.

There were many different options for tires and wheel size, so check your SPID to see if it says what option it was ordered with.

[andrewmp6]

If you want a easier one http://www.advanced-ev.com/Calculators/TireSize/ you put in the info on 3 and the 4th it will give you,Like your tire size gear ratio and speed it will give you rpm,Or tire size rpm gear and it will give you your speed.

[obijuan]

this calculator is the best i have ever used:
http://www.grimmjeeper.com/gears.html


id go 410 gears with a th350 for all around cruisin town, pulling a boat, typical truck stuff. maybe even 373s for managing those rpm at 70 if your motor has some low end cajones. i had 36s and 373s on my dually and it was terrible, but i always had it loaded with something.

[1 MPG]

I'm torn between 373 and 410. Lol
You guys all rock. I'm glad I became a member of this site.

[obijuan]

410s it is.

[1 MPG]

Do you think I should change my stock gears or look for used differentials?
I'm all most positive 308, 373, and 410s where the options for 67-72?

[swamp rat]

I have 4:10's (or is it 4:11's?) I have 33" BFG's and a TH350. I am at about 2600 at 60 mph the calculator says i should be at just over 2500.

What i did notice right away was the loss of acceleration from a stop in going from stock to 33's.

I think if you went to 3:73's you'd regret it.

[BigRed76]

I had 35's with 3.73's on my old '76 K10, with no overdrive and cruising rpm's down the interstate were perfect, and I never had much trouble accelerating from a stop but it always had good torque.