72DartGuy
Well-Known Member
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!
I’ve got 14” wheels. 265’s on the back. Would like to do 75, 80 on the freewayAll depends on rear tire diameter and how fast you want to cruise on the freeway.
Hey Joe, what’s the big difference between the 2:94 and 3:23? I’m leaning toward the 2:94’s3.23 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.
Hey Joe, what’s the big difference between the 2:94 and 3:23? I’m leaning toward the 2:94’s
500 | 2.74 | 1.54 | 1.00 | 0.69 |
A-904 / 30RH | 2.74 | 1.54 | 1.00 | N/A |
A-727 / 36RH /37RH | 2.45 | 1.45 | 1.00 | N/A |
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 case3.23'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)
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 hotHere’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.
Regular 904;
500 2.74 1.54 1.00 0.69
727
A-904 / 30RH 2.74 1.54 1.00 N/A
A-727 / 36RH /37RH 2.45 1.45 1.00 N/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.
2.94’s? **** NO! 3.55’s are the min!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
Damn, I was too slow.here, play around with this easy to use calculator and see what gear ya think you'll like best. .
Speed/Tire/RPM calculator
..
And Bingo Was His Name Oh! That’s what I was looking for. Thanks Mike!Here, play around with some numbers. Calculate GEAR, RPM, MPH, TIRE DIAMETER
3.23 with a 28" tire at 70 mph will be 2850 rpm.
So that would be 2500 with the un available 2:94 gears? I’ve learned a whole lot over the past 18 months, lolDamn, I was too slow.
I have a sure grip 489 case with 3:73 gears in it. Too hotFind 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.