Differential gear ratio

[jo 56 vert]

I have a 56 vert with a 350 engine and TH350 transmission in it, dose any know what gear ratio rear end i should use in it. I don`t know whats in it now, I think its a 3.36. Thanks Joe

[JT56]

I have a 56 vert with a 350 engine and TH350 transmission in it, dose any know what gear ratio rear end i should use in it. I don`t know whats in it now, I think its a 3.36. Thanks Joe

Hey Jo, can you tell us a little more info? Is the 350 stock, mildly stock, hot rod ect.. What are you wanting from the car?Cruiser; do you expect to take it just short trips around town? Say within 50 mile radius or just have a hot rod with performance being the main goal.

Joey

[chevynut]

Here's my rule of thumb. If you want good street performance, I would keep the overall ratio at 10-12. That is the transmission first gear ratio multiplied by the rearend ratio. So if you have a 3.00 first gear, you would want about a 3.33 rearend. For highway cruising, I'd try to keep the RPMs around 2200 or lower if you can. Your tire diameter plays a role here too.

Like JT said, a lot of it depends on how you want to use your car. If you want to cruise on the highway at lower RPM, you're going to lose street performance and vice versa. If you don't have an overdrive transmission it's hard to make a good compromise.

There is an RPM calculator at Richmond Gear's website that's pretty handy: http://richmondgear.com/101032.html

[jo 56 vert]

It is a stock 350 engine, and i`ll be using it as a Cruiser around town say with in a 50 to 100 mile radius. Thanks Joe

[JT56]

It is a stock 350 engine, and i`ll be using it as a Cruiser around town say with in a 50 to 100 mile radius. Thanks Joe

Play with the calculator Chevynut had attached to his email. Not sure what the tire size is, but you can put in different values and see. I assume its factory rear end? Not sure if they made 3.36 for them, but I do know 3.08 and 3.55 were available.

Joey

[chevynut]

Like I said, if it's for a town "cruiser" and not a highway cruiser, I'd shoot for the 10-12 overall ratio range. I look at it this way..... a muncie M20 wide ratio trans and a 4:11 give pretty good street performance. Lots of guys (including me) ran that combo in the 70's and many still do. First gear is 2.52 and multiplying that by the 4.11 rear would give you 10.36 overall. My Porsche runs like a scalded ape in first gear and it's overall ratio is 13.03. That's pretty extreme and it winds up fast. It's equivalent to the M20 muncie with a 5.17 rear.

You can get a lot of different gear ratios if you want to rebuild a rearend. Stock ones have limited availability of gear ratios. For 55 and 56 the stock ratios were 3.55, 3.70, and 4.11 and for 57 they were 3.36, 3.55 and 4,11. I think later years had 3.08s.

[Bihili]

If you just want to improve you MPG, the cheapest way to do that IMO is buy taller rear tires.
It's cheaper than changing the rear end or changing transmissions.

Another calculator:
http://tri-5.chevyrides.com/rpm.php

[jo 56 vert]

Thanks guys your a big help thanks again Joe

[JT56]

Thanks guys your a big help thanks again Joe

Jo keep us posted