New rear end gears -

[Cuse99]

My 84 El Camino is in the shop right now getting a rebuilt 200 4R trans installed. Now for a rear end upgrade. I'm pretty sure my current gear set up is 2.73 and with the new overdrive I think I can kick it up a notch. I'm thinking 3.23. Can I just buy the parts and have my mechanic install them? Or do I need a new rear assembly. I'm hoping I can just get the parts installed.

 

[L92 OLDS]

If you have 2.73 gears now your carrier is a 2 series. This is important to know when you’re buying gears as you will need to specify the 3.23 gear ratio you want but specifically for a two series. Now would be a good time to buy a 3 series posi traction carrier and change the gears at the same time. You don’t need a new axle housing.

 

[olds307 and 403]

Step up to a 3.42 at minimum with a 2004R, especially if using the lock up torque converter.

 

[Cuse99]

Step up to a 3.42 at minimum with a 2004R, especially if using the lock up torque converter.

I'm using both. So Why 3.42? Better launches? Better highway miles? My intention is a daily driver.

 

[olds307 and 403]

What size tires are you running? Even with a short tire, you will still be under 2000 rpm at 60 mph. I was around 1850 rpm with 225/70R14 and about 1950 with the stock tire size with 3.42 gears.

 

[Cuse99]

Right now I have the factory 14" wheels and standard tires. (Car is in the shop I can't look right now). Plan is to get bigger wheels and tires when these need to be replaced. Maybe another year and maybe 18" wheels. Maybe 16" or 17". We'll see.

 

[83MonteCarloSS]

I would pick 3.42 or 3.73 gears with that trans. Depends what the governor and valve body is calibrated to.

 

[Cuse99]

I would pick 3.42 or 3.73 gears with that trans. Depends what the governor and valve body is calibrated to.

OK, but why? Why these gears over 3.08 or 3.23? What's the advantage?

 

[olds307 and 403]

What are the specs on your motor? If you drive 80 mph, then maybe the 3.08 or 3.23 is ideal.

 

[1320John$$$]

I just swapped out back in May my 2.73 gear rear for a 3.73 and I’m already regretting it
Positives
Picked up half a second in the quarter
Negatives
Drinks fuel lost 2.5mpg
Sucks to drive on the turnpike and interstate
Constantly taxing the motor when driven
275/50/15 and 255/60/15 tried both the stock 205/70/14 are a joke
I have a set of 3.23 gears going to swap them out and do the apples to apples comparison
Engine is a stock 305 with summit camshaft edelbrock intake Holley 600 stock 1987 SS exhaust with cat Y pipe
15.3 @88mph