Low gear set 904, pro’s and Con’s

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I don’t know, 4:10 here, but the low gear set also changes 2nd gear slightly. So the 2-3 split gets a bit bigger. Not an issue for me, but you can hear it. Now add a 2.94 rear ratio and you might really notice it on partial throttle shifts.
 
I don't know anything about anything.
I did run both in my Dart when I was racing.Low HP car less than 220 at the rear wheels.
Low gear set with 4.30 rear didn't help over regular gear set.
Same car, same everything, switched to 3.73 rear that's when the low gear set helped.
 
I only know one guy that used the 904 lo set in his stock lo compression 360 duster and he liked it
with 2.94 gears. I'm not a quarter miler and I think that may calculate to the equivalent of 3.30 rear gears
through 1st and 2nd gears with a regular automatic (2.45 lo gear)?
 
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ir3333 said:
I only know one guy that used the 904 lo set in his stock lo compression 360 duster and he liked it
with 2.94 gears. I'm not a quarter miler and I think that may calculate to about 3.30 through 1st
and 2nd gears?
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A 2.94 rear axle ratio and a 275 low gear is 8.09 overall in low gear.
 
I should have said a 2.75 lo gear with 2.94 rear gears is like driving a regular transmission with 2.45 lo gear and 3.30 rear gears.
 
B3422w5 said:
Giving some thought to maybe installing a low gear set when tranny gets freshened.
cars weighs 3350, always hooks, has what I consider a lazy 60.
yea or nay?
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Years ago my dart ran like 11:70-80 et.
15x32 slick which was overkill for the car, but like yours it always hooked but had a lazy 60ft of 1.80+
Over the winter I switch from the 727 with 2:45 gear to a 2:74 904 with 4600 turbo action converter, same as before.
A bit more camshaft lift from .580 to .630
Lift.
No other changes. First pass the car ran an 11:22 with same mph as before the changes.
60 ft was 1:52, so I would say that the low gear in the right combination can make big improvements. Keyword is combination.
I have seen plenty big slick big block fairly heavy cars run a 2:74 with 4:56-4:88 rear gears with a 30-32 inch slick works really well. My theory on a big tired car is that the motor can’t get up on the tire with 2:45 and the 2:74 adds more torque.
The only drawback with my car, was that it did not alway hook after the changes.
I have switched to Caltracs and double adjustable shocks to add tune ability.
My 2 cents ymmv.
 
B3422w5 said:
Decisions, decisions .
what I really wish is I had a spare good footbrake transmission to swap in, and shelve my brake tranny after freshening it( don’t use the brake in it currently)
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Just quoting what the gentleman said who built my trans brake transmission. You can't footbrake off of a transmission that is setup for a brake.

Your car works very , but removing the brake just might be the ticket alone
 
67mprfan said:
Just quoting what the gentleman said who built my trans brake transmission. You can't footbrake off of a transmission that is setup for a brake.

Your car works very , but removing the brake just might be the ticket alone
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my transmission is setup for a brake. Has an A&A brake in it and was built by Cope, he used these until a few years ago, went to his own brake now for his builds.
Every pass I have ever made in the car was off the foot. Have yet to ever use the brake except to push the brake button to back the car up.
So whoever told you that is dead wrong.
Other cars I have had with a brake I have used the brake and the foot both, depending on the event/rules….
 
Ya I definitely disagree with that in its entirety about not being able to footbrake a trans brake transmission.
 
That's why I used I'm quoting statement.
And also mentioned Don's car works very well
 
My 727 has a Cope trans brake, it works in low or second, Cope even said I could foot brake it in second. It's been 1.34 60', so it seems to work okay.
 
B3422w5 said:
my transmission is setup for a brake. Has an A&A brake in it and was built by Cope, he used these until a few years ago, went to his own brake now for his builds.
Every pass I have ever made in the car was off the foot. Have yet to ever use the brake except to push the brake button to back the car up.
So whoever told you that is dead wrong.
Other cars I have had with a brake I have used the brake and the foot both, depending on the event/rules….
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Hook the brake up and let it rip!!!!!
 
Most of the time this car foot brakes, it REALLY drags the bumper when he uses the brake.

C0E8EB09-D044-4A12-9B90-9CD799A701F5.jpeg
 
furrystump said:
Most of the time this car foot brakes, it REALLY drags the bumper when he uses the brake.

View attachment 1716047530
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My W5 Duster was the same way. Pull the tires about a foot using footbrake, much more( and sometimes on the bumper) using the brake.
But the car 60 footed identically either way, and ran the same number either way, unless it was on the bumper.
 
So do you think your going to give the 2.75 a try? I will be trying it this year and think it may be too much but it’s already in my trans. Cope trans brake, 2.75, 4.1 rear gear with 29.5 tall tire. 418 small block
 
1bad360duster said:
So do you think your going to give the 2.75 a try? I will be trying it this year and think it may be too much but it’s already in my trans. Cope trans brake, 2.75, 4.1 rear gear with 29.5 tall tire. 418 small block
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Chances are, if a deeper low gear hurts your short times it’s a chassis/converter issue. I suppose it could be an engine combination issue as well.

You will have more torque at the rear tires, which makes the same chassis/shock tuning deal with the added speed and force caused by the lower gearing.

I lived through the huge migration to the powerglide. Most of that was caused by the limited selection of shocks and most guys were using SS springs and pinion snubbers (Chrysler guys) or a ladder bar.

Both have a relatively short, high instant center and if you can’t move it forward and down or at least control axle movement with your shocks the lower (higher numerically) low gear can hurt your short times.

The tire just can’t deal with the added forces.
 
1bad360duster said:
So do you think your going to give the 2.75 a try? I will be trying it this year and think it may be too much but it’s already in my trans. Cope trans brake, 2.75, 4.1 rear gear with 29.5 tall tire. 418 small block
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Gonna leave it up to the tranny guy( who‘s family are all very good Mopar racers). Let him know everything with the car and see what he thinks.
Right now, I am actually leaning against it. I bracket race the thing, so consistency is the main thing( can’t believe I am saying that..lol) but I do intend to move the convertor, which might by itself, help me.
The other factor is I still have an 8.75 in the car. Broke it once already. I do now have a much better center section but it isn’t gonna last forever.
Lord willing, a Dana is next, but not this year.
 
B3422w5 said:
Gonna leave it up to the tranny guy( who‘s family are all very good Mopar racers). Let him know everything with the car and see what he thinks.
Right now, I am actually leaning against it. I bracket race the thing, so consistency is the main thing( can’t believe I am saying that..lol) but I do intend to move the convertor, which might by itself, help me.
The other factor is I still have an 8.75 in the car. Broke it once already. I do now have a much better center section but it isn’t gonna last forever.
Lord willing, a Dana is next, but not this year.
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B3422w5 knows a lot about my car. With a 2.77 first gear my car hit the wheelie bar so hard it'd lift the rear tires off the ground. With a stock 2.45 it was drivable and went 1.31 at sixty feet. It'd still squeak the tires when it hit the wheelie bar. I had Keith Long at 727 specialist build me a transmission with a 2.13 first gear. It's much calmer in first gear and goes 1.30 at sixty feet. My experience with the 2.74 first gear is that if you have a 3.73 or less rear axle ratio it will help if not it doesn't help and in some cases it might slow you down. This is assuming that you already have the right converter in the car.
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