69 GTX Best GEAR
- Thread starter Hammer136
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Nate S
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I didn’t see which tranny. I’d go 3.23 with an auto and 3.55 with a manual. As pointed out earlier, rear tire size is a huge factor. The above ratios I’d say are good with 27” tires (typical stock diameter).
So for those 27” tires (ground to center x 2) take 747 x your ratio and that’ll be your rpm at 60 with a manual, add about 10% for an auto.
So for those 27” tires (ground to center x 2) take 747 x your ratio and that’ll be your rpm at 60 with a manual, add about 10% for an auto.
Ceedawg
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Wow I’d like to see that, the new engineering with 3D printing and cad cam is great stuff.
Ceedawg
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That’s what I had in my 64 Plymouth 4 speed 361 engine.
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How is it on the clutch? Had a 2.80 in a 289 Mustang Fastback with a 4 speed and well, if I was trying to be smooth, there had to be some slippage but with the car being 3050 in weight I could just dump it (no popping it) and the car would just lunge with light throttle pressure. The engine had a Torker intake, headers and a 600 Holley and 8.7-1 and yet it ran a 15 flat at the track crossing in the top of 3 rd gear. Even cooler is that it got 21 on the highway running 70 but usually I was doing much faster than that when I could
Never had any highway gears in a 4 speed Mopar....Ceedawg
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Learned to feather it, later did a 3.23 but didn’t see much difference. This was late 60s so gas was much better back thenHow is it on the clutch? Had a 2.80 in a 289 Mustang Fastback with a 4 speed and well, if I was trying to be smooth, there had to be some slippage but with the car being 3050 in weight I could just dump it (no popping it) and the car would just lunge with light throttle pressure. The engine had a Torker intake, headers and a 600 Holley and 8.7-1 and yet it ran a 15 flat at the track crossing in the top of 3 rd gear. Even cooler is that it got 21 on the highway running 70 but usually I was doing much faster than that when I could
451Mopar
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With a stock 727 the 3.54 / 3.55 ratio is a good compromise, but the engine will be reving pretty good at highway speeds unless you have an overdrive.
3.55 with a 518 OD trans would be nice on the highway.
The 3.23:1 is good too, but a bit slower off the line. A low first gear in the trans would make getting the car moving easier, but I think with either, if running street tires it won't matter as both gear ratios will turn those tires into smoke.
3.55 with a 518 OD trans would be nice on the highway.
The 3.23:1 is good too, but a bit slower off the line. A low first gear in the trans would make getting the car moving easier, but I think with either, if running street tires it won't matter as both gear ratios will turn those tires into smoke.
Ceedawg
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518 is .69 under in overdrive
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When I feathered that Mudstain, it would chatter. Just a parts house clutch etc but I gave it plenty of hell and the thing stayed together. It was about that time where I 'learnt' about scatter shields when a buddy blew up a clutch on a 12 second Mustang with no shield. It about totaled that car....and he was lucky that none of the pieces got him....but got his stereo and a bunch of other things inside the car.
Hammer136
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Automatic thinking 18" wheels?
Hammer136
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Thanks for your insight.. Helpful
So far with the 3:55 gearing and the A833 manual trans. Getting up to 60 at 3000 rpm. Had thought of the 3:23 gearing but did not know just what was the best. 8 3/4 rear open diff. Maybe when I put the 489 in will go with the 3:23 gearing. 2:76 was original in this car. Know you could do at least what the speed o showed. I think.
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It's about an LSD diff....if you go with a highway gear, an open rear end is still going to smoke the right rear tire. No matter what the ratio, if you don't have an LSD, you ain't gonna do much off the line with a one wheel peel rear end. A 2.76 or any gear will always do better with an LSD diff.....
Good info for sure will keep that in mind. 
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