Best Gears for a 408 Stroker?

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72DartGuy

72DartGuy

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Hi guys, I have a 408 Stroker in my 72 Swinger. I gave a 489 rear end with 3:73 gears. I’m pushing 3500 RPM at 65mph. Not good! What’s the best gears for both street and freeway? 3:23’s or less? Thanks for the help!

IMG_0958.jpeg
 
All depends on rear tire diameter and how fast you want to cruise on the freeway.

gear ratio without overdrive is always compromising on one end of the range. You tell us which end is most important. Bottom end or freeway RPM.
 
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Help! I’ve got a 8 3/4 rear end with a 489 case and 3:73 gears. I’m pushing 3500 RPM at 65 MPH. That’s not workin for me. What should I put in there? I’d like it to be snappy on the street, and I’d like to be able to drive it on the freeway. I gave a 408 Stroker with a 650CFM carb. What’s the best gears for this? Thanks guys!

IMG_0958.jpeg
 
76 mph 2.94s 3000 rpm 265/60/14s
76 mph 273s 3000 rpm 265/50/14
 
3.23 would be nice. i love the 2.94. either way a 408 should have enough tq to move it along pretty well depending how ya built it.
 
Ok, so is there a big difference between the 2.94 and 3.23’s? I want the best all around gears. I’m not gonna race it, but I’d like to smoke some mustangs!
 
abodyjoe said:
3.23 would be nice. i love the 2.94. either way a 408 should have enough tq to move it along pretty well depending how ya built it.
Click to expand...
Hey Joe, what’s the big difference between the 2:94 and 3:23? I’m leaning toward the 2:94’s
 
3500 rpm is 75 mph with the 265/50/14s
3400 rpm is 79 mph with 265/60/14
both with 3.23s
you need a 28 inch tire 3.23s and a 4k stall :)
 
3.23's are about the best compromise, and with the 408 you've got more than enough ink in your pen to lay down black stripes around town.

ETA: best compromise short of playing transmission games (OD or 999 w/ deep 1st and some freeway flyer gears)
 
Here’s the thing, and I’m going to be blunt and honest so suck it up butter cup, your screwed.

Now, how to get around being screwed and tattooed!
The first problem is you want it all. This will require an OD trans for a reduced rpm cruising. Now to smoke Mustangs, what Mustang are we talking about?

As an example, the A-500 has a good first gear for a good get up and go off of the line and a reasonable OD ratio for Hwy cruising.
5002.741.541.000.69
Regular 904;
A-904 / 30RH2.741.541.00N/A
727
A-727 / 36RH /37RH2.451.451.00N/A

Notice the first gear ratios. Your looking for a 10.00 ratio via first gear ratio and the rear axle ratio for best off the line performance.

3.91 X 2.74 =10.71
3.73 X 2.74 = 10.22
3.55 X 2.74 = 9.727

OD (.69) X Gear ratio for final drive ratio;

3.55 X .69 = 2.4495 (I’d call it a 2.45.)
3.73 X .69 = 2.5737 (2.57)
3.91 X .69 = 2.6979 (2.69/2.70)

Find an on line calculator to work with the final drive gear ratios and your tire diameter for probable cruise rpm at what ever speed you realistically drive at.

I hope this helps in an easy cruise rpm and getting off the line.

Now to find a guy that can build up your A-500 to hood the power. The nicer thing about the 904 & it’s variant’s (A-500) is they require less power to turn than a 727 & it’s OD variants. That means more power to the pavement and better mileage.
 
junkyardhero said:
3.23's are about the best compromise, and with the 408 you've got more than enough ink in your pen to lay down black stripes around town.

ETA: best compromise short of playing transmission games (OD or 999 w/ deep 1st and some freeway flyer gears)
Click to expand...
I’ve got a built 727 trans. Right now it breaks the tires loose in a heartbeat, but freeway is too loud and too high rpm. I’m looking for 2:94 gears but can’t find them for a 8.75 with a 489 case
 
Find the gears you want in any case and disregard looking for a case number.

If you can get a sure grip, go with it. Just my 2 cents.

You can update any single legger to SG with a carrier change.
 
rumblefish360 said:
Here’s the thing, and I’m going to be blunt and honest so suck it up butter cup, your screwed.

Now, how to get around being screwed and tattooed!
The first problem is you want it all. This will require an OD trans for a reduced rpm cruising. Now to smoke Mustangs, what Mustang are we talking about?

As an example, the A-500 has a good first gear for a good get up and go off of the line and a reasonable OD ratio for Hwy cruising.
5002.741.541.000.69
Regular 904;
A-904 / 30RH2.741.541.00N/A
727
A-727 / 36RH /37RH2.451.451.00N/A

Notice the first gear ratios. Your looking for a 10.00 ratio via first gear ratio and the rear axle ratio for best off the line performance.

3.91 X 2.74 =10.71
3.73 X 2.74 = 10.22
3.55 X 2.74 = 9.727

OD (.69) X Gear ratio for final drive ratio;

3.55 X .69 = 2.4495 (I’d call it a 2.45.)
3.73 X .69 = 2.5737 (2.57)
3.91 X .69 = 2.6979 (2.69/2.70)

Find an on line calculator to work with the final drive gear ratios and your tire diameter for probable cruise rpm at what ever speed you realistically drive at.

I hope this helps in an easy cruise rpm and getting off the line.

Now to find a guy that can build up your A-500 to hood the power. The nicer thing about the 904 & it’s variant’s (A-500) is they require less power to turn than a 727 & it’s OD variants. That means more power to the pavement and better mileage.
Click to expand...
Thanks, so you’d go with the 2:94 gears then? I see where it’s a tough call between the 2:94 and 3:23’s. 3:73’s are too hot
 
2.94’s I only see used. They may not be available new or for the 489 case.
 
72DartGuy said:
Thanks, so you’d go with the 2:94 gears then? I see where it’s a tough call between the 2:94 and 3:23’s. 3:73’s are too hot
Click to expand...
2.94’s? **** NO! 3.55’s are the min!
 
crackedback said:
Find the gears you want in any case and disregard looking for a case number.

If you can get a sure grip, go with it. Just my 2 cents.

You can update any single legger to SG with a carrier change.
Click to expand...
I have a sure grip 489 case with 3:73 gears in it. Too hot
 
one part of getting taller tires is that he's running 14's
the other part is that starts to skyjack the *** end...
 
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