Let's talk gears for a sec

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KevinB

KevinB

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My 8.8 (not installed) currently has a 3.73 limited slip setup. Assuming a 27" tire, that puts my highway cruising in the 3000 rpm area. Having not driven the car yet with whatever engine setup I land on (320-350hp)...if I stick with these gears am I just going to have a bunch of wheel spin when I take off and high rpms on the highway?

I'm thinking about swapping to 3.31 gears. If I do that my rpms are much better, but will it be a dog from standstill? Hard to imagine it would be, lightweight car and that much hp
 
I don't think your math is right. I drove 4.30 on the street for almost four years and I could cruise at 55 about 2750 with a 275 60 15 rear tire. I also have 3.73 gears in my Ford truck and it's nowhere near 3K at 55. But it also has tall tires.
 
You should remind us of the rest of your combo. In my big block Duster the taller gears still launch pretty darn good but then it tries to spin the tires at 60 ft! That can get really squirrely. If you have good rubber and a 904 with the low first gear set you can even go with softer gears and feel good off the line. I have 2.94s in the 68 Dart with the low first and a very mild small block that hooks great with the 295-50-15 Hankooks.
 
RustyRatRod said:
I don't think your math is right. I drove 4.30 on the street for almost four years and I could cruise at 55 about 2750 with a 275 60 15 rear tire. I also have 3.73 gears in my Ford truck and it's nowhere near 3K at 55. But it also has tall tires.
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I just used a couple of online calculators, I'll keep checkin
 
mguner said:
You should remind us of the rest of your comb. In my big block Duster the taller gears still launch pretty darn good but then it tries to spin the tires at 60 ft! That can get really squirrely. If you have good rubber and a 904 with the low first gear set you can even go with softer gears and feel good off the line. I have 2.94s in the 68 Dart with the low first and a very mild small block that hooks great with the 295-50-15 Hankooks.
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Tranny is a stock for now 904 from a 68 coronet. I'm considering engine options still...I have a 318, but am thinking about magnum heads or going with a 360 magnum
 
I have 3:55 gears and 24 in tires. I rev at 3000 at 60 mph. It is a FUN ride!!
 
I think you would like the 3.73 gears a lot. It depends on how much all out highway driving you do though. If you had the low first gear and 3.31s or 3.08s it would still jump off the line good! A mild 4bbl 318 with dual exhaust in an A body with the right gears and tires makes an easy 14 second car.
 
mguner said:
I think you would like the 3.73 gears a lot. It depends on how much all out highway driving you do though. If you had the low first gear and 3.31s or 3.08s it would still jump off the line good!
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I'll think about doing that. what exactly does a lower first gear ratio accomplish? More torque in 1st I assume?
 
Peyote said:
My 8.8 (not installed) currently has a 3.73 ----

I'm thinking about swapping to 3.31 gears. If I do that my rpms are much better,
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-- If you have lots of torque, then the 3.31s may spin more. -- Not likely with a mild 318. -- Here's some RPM vs. MPH info with 27" Tires.
 

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My 15" tires on my car new measure 25" tall. I will try to get bigger tires on it but I think 26" will about max out my clearance. I have 3:73 gearset with a stock 904 and will be putting a Gearvendors OD in mine. Should give me an effective overdriven ratio of about 2:91 if I read the data correctly. I am wanting to road trip my car quite a bit when finished.
DRO:)
 
DesertRat said:
My 15" tires on my car new measure 25" tall. I will try to get bigger tires on it but I think 26" will about max out my clearance. I have 3:73 gearset with a stock 904 and will be putting a Gearvendors OD in mine. Should give me an effective overdriven ratio of about 2:91 if I read the data correctly. I am wanting to road trip my car quite a bit when finished.
DRO:)
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Hey DR -
If you don't already have your Gear Vendors setup, you might want to check out going with a 200-4R overdrive tranny in your car. That's the direction I'm going with my '69 Dart since I also want to road trip.
The 200-4R has a 0.67 4th gear which would be like 2.50 gears at the final drive ratio on the highway.
I'm seriously considering going with 4.30 gears behind my built 360 and the 200-4R. I will be like having 2.88 gears on the highway. Lonnie at Extreme Automatics is building my 200-4R and the lock-up converter. My Dart is going to both seriously launch hard, ET well, and cruise with ease.
US Car Tool has just come out with a new rear trans mount specifically for the 200-4R that makes the swap a relatively easy one with no tunnel sheet metal mod necessary. You will need to do a minor mod on the crossmember, but nothing to the tunnel sheet metal.
Check it out.
 
ocdart said:
Hey DR -
If you don't already have your Gear Vendors setup, you might want to check out going with a 200-4R overdrive tranny in your car. That's the direction I'm going with my '69 Dart since I also want to road trip.
The 200-4R has a 0.67 4th gear which would be like 2.50 gears at the final drive ratio on the highway.
I'm seriously considering going with 4.30 gears behind my built 360 and the 200-4R. I will be like having 2.88 gears on the highway. Lonnie at Extreme Automatics is building my 200-4R and the lock-up converter. My Dart is going to both seriously launch hard, ET well, and cruise with ease.
US Car Tool has just come out with a new rear trans mount specifically for the 200-4R that makes the swap a relatively easy one with no tunnel sheet metal mod necessary. You will need to do a minor mod on the crossmember, but nothing to the tunnel sheet metal.
Check it out.
Click to expand...


That's pretty slick. I've thought about an od tranny but there's so little info for early a installs. I wonder how different this kit would need to be to work in a 66
 
ocdart said:
Hey DR -
If you don't already have your Gear Vendors setup, you might want to check out going with a 200-4R overdrive tranny in your car. That's the direction I'm going with my '69 Dart since I also want to road trip.
The 200-4R has a 0.67 4th gear which would be like 2.50 gears at the final drive ratio on the highway.
I'm seriously considering going with 4.30 gears behind my built 360 and the 200-4R. I will be like having 2.88 gears on the highway. Lonnie at Extreme Automatics is building my 200-4R and the lock-up converter. My Dart is going to both seriously launch hard, ET well, and cruise with ease.
US Car Tool has just come out with a new rear trans mount specifically for the 200-4R that makes the swap a relatively easy one with no tunnel sheet metal mod necessary. You will need to do a minor mod on the crossmember, but nothing to the tunnel sheet metal.
Check it out.
Click to expand...
OC:
Thanks for the heads up! I found their website and sent them e-mail. I haven't bought the gearvendors yet so its not too late to make the change. My car is a 250 HP cruiser so I don't need anything to race with. Just got a query from Lonnie-Gotta go!O:)
 
You are on the right track
A teener in an early A won't need, that's need, 3.73s. It'll be fun around town, or at least take-off will be. But like you, I was concerned with hiway rpm. I couldn't even get used to 2600@56mph, which woulda been 3018@65. I hated it. But I am 20 to 25 minutes from anywhere(at 60), so it's always a highway trip to get anywhere. I tried a few different things, and nothing stuck. Not until I got a tranny with a little lower gear, and a GV, and 3.55s out back.
With an automatic the TC can be sorta considered an extra gear. And if it's a loc-up, you can pull the cruise down 200 or so. So if money is an issue, I highly recommend the A999 with it's 2.74 low, it will get you about 12% more punch off the line, allowing a corresponding 12% reduction in rear gear; bringing 3.31s to the table. Then with it's loc-up feature hiway Rs will be around 2678@65. Now this doesn't come without a compromise. The gear ratios are a little further apart. However in a light A, and with a modest cam you will hardly notice it. If you are able to obtain this tranny with it's matching slightly higher stall TC, It will be a pretty good alternative to the GV.
Now before I close, I should mention that the GV can be used as a gear splitter, turning your 3spd into a 6spd. This turns the wide-ratio A999 into a close ratio set-up that can be power-shifted all the way. This would allow you to fine-tune the cam LDA and go up a size or even 2 in duration. But even more importantly, it will allow you to give up a size or 2 in cams and not lose WOT performance.THe GV will pull your 3.73's down to 2.91s, bring your cruise Rs down to 2360@65. The ratios will be;
2.74-2.14-1.54-1.20-1.00-.78 O/D. The %drops will be .78-.72-.78-83-.78--.It's not ideal, but again the light A will love it.And it is far,far, better than the 2.45-1.45-1.00 of the basic Mopar ratios which has %drops of .59-.69.
The GV fit into my 68-tunnel with just a couple of dings.
Over the life of the vehicle, it's probably worth it. In terms of fun-factor it's really hard to beat. To hear the teener drop just 1350 rpm during the 1-2 shift is like" did it really shift?" and the next one is 1700, then 1350again, and then just 1040 into direct. Well you might not get there often,cuz with 3.73s that's like 109mpg@6100rpm. I gotta tell ya it's a thrill.
Still, I often wonder if a simple 4-spd auto and a slightly loose TC mightabin a better option for me.
Naw I like banging gears; don't I?
 
Peyote said:
I'll think about doing that. what exactly does a lower first gear ratio accomplish? More torque in 1st I assume?
Click to expand...

Yep. You can drop a later model sun gear and planet set into the early model 904 and it works like a champ.
 
Since you are putting a new rear end in and will probably need a drive shaft cut to correct length, why not move the rear back and inch or so to center the axle in the wheel well. You could run a 28 or 29 inch tall tire on the street for cruising and bolt on a set of 26" inch drag radials for the track.
 
DesertRat said:
-- will be putting a Gearvendors OD in mine. --
---
I have a 69 Valiant, 360/408, 255/60-15 tires, 3.91 rear, and a 46RE (727 based) OD transmission with a 0.69 4th gear. This makes the effective ratio 2.70, which at 60 MPH, I'm turning about 2,200 RPM - perfect for cruising. ---
icon14.gif
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Click to expand...
 
mderoy340 said:
Since you are putting a new rear end in and will probably need a drive shaft cut to correct length, why not move the rear back and inch or so to center the axle in the wheel well. You could run a 28 or 29 inch tall tire on the street for cruising and bolt on a set of 26" inch drag radials for the track.
Click to expand...


I've thought about that, and will likely do it, but I never could find out exactly what diameter tire would fit. If a tire bigger than 27" will fit then cool, that will help
 
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