65chevy needs new gears

[Chevyman65]

What’s up AF. Anyways I was wondering if anyone had done a gear job before and if so how hard is it and what the process is. I want to swap out the gears I have on there now with something lower and more economical, but still has some get up and go. I have 4:11 on a 12 bolt rear right now but is this something that a person with some mechanical now how could do or should I just say screw it and take it to a shop and have them do it? I’ve never taken this car to a shop and have done everything myself and would like to keep it that way unless this is one of those things where im better off taking it in. Anyways some advice from someone who’s done this before or knows how would be appreciated. Thanks.

[MagicRat]

You are better-off taking it in. Setting up gears is like TIG-welding aluminum. It takes practice and experience to do it sucessfully. You need to read contact patterns correctly and make the appropriate adjustments based on your observations, which can get complicated..
It's easy to get something off just a bit and end up with a howling gearset or ruined gears... forcing you to do the whole job over again.

Some of my factory service manuals from the 1960's have a step-by-step process with lots of pics, because they expected the dealership mechanics to do jobs like this back then. My newer factory manuals do not show this at all...... because these days even the factory does not seem to expect the dealers to do this in-house.

[Ol'Jim]

I agree with MagicRat, (on his advice for this topic, not his religious views, lol).
I've owned numerous 66-72 Chevy musclecars for over 35 years, I build my own engines & transmissions, but I have my 12-Bolt gearsets done by guys who know what they are doing. Back in the day you could bring your new gears to the Chevy dealer, and they would change them out & set them up while you waited. Those days are gone, but you can find a drive train specialist locally, and it really shouldn't cost you too much for a good setup. I pay around $200 to have a gear guy do it on the side in his garage. Best bet for buying your parts is Randy's Ring & Pinion, in Everett (I believe?) WA - http://www.ringpinion.com/ If you buy the gearset & an install kit you'll get seals, shims, gasket, etc. Do NOT buy an off-brand like US Gear - I'm afraid you'll be sorry! I recommend sticking with Richmond, or maybe Strange, etc. I am about to do the same for my Chevelle, but going the opposite direction - It has 3.31's and I need a bit more pull off the line, but still streetable. 3.70 is going to be my choice. Make sure you buy the correct gearset for your carrier - most likely a 3-series if it came from the factory with a lower (numeric) ratio than your 4.11, but if you have a factory 4.11 you'll need a 4-series gearset. (The difference is the thickness of the ring gear and it's mating flange on the carrier).

[Chevyman65]

Thanks for the heads ups fellas. Just wanted to make sure before I attempt to get myself into something where half way through im like F$%# lol.

O'lJim how are those 3:31 anyways? 3:7ish was what I was thinking of going for. Those 4:11 only keep me in town and off the highway. In town just cruising around im at 3500 to 4000 rpm and on the highway.....pfffft im to afraid to drive it that long.

[Ol'Jim]

Yeah, I had a '66 Chevelle SS396 that was ordered by the original owner for drag racing. RPO L78 (375 HP), AM Radio & Heater, no other amenities but had all the performance goodies. With a Mncie 4-speed & 4.11's in the rear, it was barely highway-driveable, I had it in Los Angeles, back when the nationwide speed limit was 55 MPH. Good thing, 'cause it would have been harsh motoring at 70 for extended periods, lol.
3.31's are what the moderate performance cars had as standard equipment with the SS package, (most of the Super Sport cars from '68-72). They allow for good highway cruising, with better acceleration than the taller gears, and they are basically fine for a daily driver that doesn't see any dragstrip duty. But they don't give you that hard pull in the first 60 feet that you need for any type of serious action. If you are going to be cruising regularly, and doing long highway drives, 3.31's are actually a good choice, and they provide pretty decent fuel economy.

What I am doing with the old SS, is make it a weekend cruiser that I can drive to the dragstrip, race, and drive it back home. Going with a pretty stout cam choice, headers & turbo mufflers, fairly "loose" converter, Mickey Thompson "ET Street" tires, (pretty-much a drag slick with a couple of token wavy grooves in it that somehow got approved by the D.O.T. for street use). It will see very limited highway miles, so I could almost go with a 4.10 gear, but that would actually multiply the torque too much, and would likely cause wheel spin with a 10" wide tire. So I am gonna use the 3.70, which is really a compromise that leans a bit more toward streetability, but hopefully will still allow for decent 60' acceleration. I've raced against cars with 3.70's that functioned very well on the strip, but they were lighter than my 'Velle - (Older Camaro's, Duster's, etc). So that is why I will need to use a loose converter, which will almost give me the same effect as a numerically higher gear set.
Sorry, too much info, I'm sure. For your car, I'd say if the engine is stock, or a fairly mild combo - headers, carb, some moderate cam timing - the 3.31 would be a good choice, and you'll like the lower fuel cost. Especially if it's a daily driver, or sees a lot of highway miles. If you've got a more serious combination, and/or your car is a weekend warrior that will occasionally hit the track on a grudge night, and doesn't have to regularly go on 100+ mile highway trips, the 3.70 would be a better option.
Just my $.02+++ ENjoy it either way! -Jim.

[MT-2500]

4-11 rear ends are good for drag strips but not so good for hwy driving.

Chose your gear ratio from what engine car weight and transmission and tire size and the performance and type of driving that you do.

In the 3-1 ration rang would be a lot better choice.

Back in 1974 I ran a Dodge polar with a 383 HP police engine auto and setup with a 2.76 rear end.
Even Done good on a 1/4 drag strip and gave the 426 4S std engines a close run for the money

Here is a link with some rear end setup info.
But as said rear end setup is a lot of skill required.

Good Luck
And let us know how it goes.