3.23 or 3.55 rear end?

[fasjac]

Crawled under the car yesterday afternoon. 489 casting.



Crawled underneath yesterday. Casting is 489. (BTW - still can't upload any pics) - keep getting error message the file is too big??? Strange...

That works, if your just getting the ring gear and pinion set, it's specific to the (489) carrier. It's the largest diameter pinion. All the 8 3/4 rear ends will take 4-500 hp on the street with no issues. If you buy the entire unit you can go with either. May need to check the splines on the yoke as well.
You may reach out to one of the moderators on the photo issues.

 

[sir_veza]

If you're taking pictures with your smartphone, check your resolution settings. Phones love to take ultra-max resolution photos so those with data plans burn through them quickly. A friend is constantly running into this issue on another board, but won't listen to me that there's absolutely no need for photos that are 10240 x 7680 pixels and 15MB in size. Try resizing your photos to 2048x1536, 1200x900, or 1024x768. I don't think anyone intends to print a poster of your car from a website posting.

As far as gear selection, tire diameter plays an important part. My Valiant runs around 2,600RPM @ 60 per, but I've only got 25"-tall tires on it (P235/60R-14).

Here's a simple, easy calculator to determine your RPM at a particular speed, with a given gear ratio and tire diameter. Play around with it a bit... see what tickles your fancy.

If your tire size is P-metric, size is easy to calculate. Using my Valiant's P235/60R-14 as an example:

235 is the cross-sectional overall width of the tire in millimeters.
60 is the height of the sidewall, expressed as a percent of the width.
14 is the rim diameter.

235/25.4 (mm to inches) = 9.25"
9.25 x 60% = 5.55". Multiply that by two, since there's sidewall on either side of the wheel, to get 11.1".
11.1 + 14 = 25.1" tire height.

Thanks for the math...my tire height is 26.58" (27" for argument sake).

 

[sir_veza]

First Welcome to the site and Nice car

I had 3.23 in my Cuda for a few years and it is a good all around gear but, last year I went to 3.55 and I like it a little better. Just a little more acceleration.

Just for a little info I have a stroked 440 ( 493 ) and my RPM on the freeway at 70 MPH with the 3.23 was about 2930 RPM and with the 3.55 it is now about 3215 RPM with 26" tall tires, which is a little more than I would want for a long drive but for the short time that I drive on the freeway its just fine.

So my opinion is... go with the 3.55. You been using 3.91 and the drop to 3.55 will be noticeable but either gear will be good.

Just my 2 cents

An update from my post earlier...Got a text from a friend this morning who has a 3.23 he's willing to part with cheap...whole nine yards carrier and all - essentially pull out the 3.91 and put in the 3.23. (Not giving up on the 3.55) but this 3.23 is very tempting. What part of the 3.23 installation IS NOT obvious? Axle sleeves, bearings or anything else?? Much appreciated.

 

[fasjac]

An update from my post earlier...Got a text from a friend this morning who has a 3.23 he's willing to part with cheap...whole nine yards carrier and all - essentially pull out the 3.91 and put in the 3.23. (Not giving up on the 3.55) but this 3.23 is very tempting. What part of the 3.23 installation IS NOT obvious? Axle sleeves, bearings or anything else?? Much appreciated.

It's very easy. If you don't have a FSM, you can download one online.

 

[sir_veza]

It's very easy. If you don't have a FSM, you can download one online.

Thanks! - so straight forward couple of hours tops in other words...

 

[fasjac]

Thanks! - so straight forward couple of hours tops in other words...

Yea, unless you're replacing axle bearings too. A buddy & rack helps a lot too!

 

[413]

Let’s ask some REAL questions to better answer this.

what diameter are your rear tires? How long of a road trip do you want to take? At what MPH do you want to cruise on the freeway?

Swapping a complete carrier is pretty easy and will take a few hours.

swapping the ring and pinion in your carrier.
-its not easy
-it will take way longer than 2 hours unless you have done it many times.
it may make noise or have problems if it is your first time doing it.

 

[sir_veza]

Let’s ask some REAL questions to better answer this.

what diameter are your rear tires? How long of a road trip do you want to take? At what MPH do you want to cruise on the freeway?

Swapping a complete carrier is pretty easy and will take a few hours.

swapping the ring and pinion in your carrier.
-its not easy
-it will take way longer than 2 hours unless you have done it many times.
it may make noise or have problems if it is your first time doing it.

Thanks for your points.
*Tires are 27" diameter.
*one - four hour road trips
*Cruising - 65 - 75 MPH
And correct it's my first time at this...

 

[fasjac]

An update from my post earlier...Got a text from a friend this morning who has a 3.23 he's willing to part with cheap...whole nine yards carrier and all - essentially pull out the 3.91 and put in the 3.23. (Not giving up on the 3.55) but this 3.23 is very tempting. What part of the 3.23 installation IS NOT obvious? Axle sleeves, bearings or anything else?? Much appreciated.

Am I understanding “the whole nine yards” is an assembled third member? Right? If not, yes, the project is completely different. As far as ratio goes, you’re good from the description of how you like driving the car, you’ll like it on the open road. After all, it’s a 4 speed. If it’s a friend, I’d like to think it’s a good unit....

 

[Cojohnso]

Im still surprised that 3.23:1 gear set is considered? Especially with a performance small block build? JMO

 

[NoCar340]

This is why I posted that link to the calculator earlier--so you can play with ratios and tire sizes to see exactly where you'd land RPM-wise. No speculation, just hard numbers.

Just remember: Whatever you gain up top, you lose down low. A 3.23 provides a lot less accelerative joy than the 3.91 does. It's gonna feel like you lost 100lb/ft in first gear. Gearing is always a trade-off.

 

[413]

4 hour road trip at 75 mph means 3.23 is what you want. It will have plenty of pickup once the car is moving. You will notice a difference from a standing start. But if you launch a 4 speed hard without slicks and you just blow of the tires anyway.

You should look for a complete third member ready to install.

 

[sir_veza]

This is why I posted that link to the calculator earlier--so you can play with ratios and tire sizes to see exactly where you'd land RPM-wise. No speculation, just hard numbers.

Just remember: Whatever you gain up top, you lose down low. A 3.23 provides a lot less accelerative joy than the 3.91 does. It's gonna feel like you lost 100lb/ft in first gear. Gearing is always a trade-off.

First choice is still the 3.55 but the 3.23 is available to me for $250.00 plus 24 Heineken !!
The 3.23 came out of a Roadrunner (not sure what year). I do like the 3.91 for the fast starts though!!!

 

[fasjac]

First choice is still the 3.55 but the 3.23 is available to me for $250.00 plus 24 Heineken !!
The 3.23 came out of a Roadrunner (not sure what year). I do like the 3.91 for the fast starts though!!!

Heck of a deal for sure!