2.45 1st gear in A500 OD trans
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I did. I put a low compression 360 with a very mild cam in a 95 dakota. It had been a 4cyl. 5 speed. I did not like the rpm drop with the 2.74 low in the a500, so I put a 2.45 out of a 904 in it.
I also took apart an old 904 VB that I had put a B&M Manual Pak in, and used parts from it to make a forward manual VB for the a500. I used a toggle switch to activate the OD.
It was driven a couple years and sold.
There may be reasons that I am unaware of like spline differences that make it wrong, but it worked fine behind the almost stock 360.
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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but why would you want to?
I know you're a smart man and have considered the options, so I'd honestly like to know what your thinking is.
Also, as Mopar Sam mentioned you would have to be very careful with the donor 904, cuz somewhere in the 70s they changed the spline shapes, but not the count. I did not know that, and my swap went 20 miles until I floored and Ziiiing, she stripped all the splines out of the rear planetary. Ok, so now I did some research and figured it out.
Here's the tricky part;
A had many 904s in the shed several that were torn-down, both late and early styles. For the life-of me, I could not tell one from the other. IDK the change-over year but it might have been 1976; mightabin.
BTW the gearing is on that tiny gear at the center of the sunshell, together with the planetaries. If you swap out first, it automatically takes second with it. If you want a mixed gear set, I think A&A has it.
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I'm thinking of going with an A500 instead of my 727, and if the deeper 1st proves to be too much just want options especially since you got to cut up the floor to do it.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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On the street
The deep low-gear works very well with up to 3.91s and 28" tires. Taller tires will like more gear. After that, more gear can get kindof aggravating , as the rpm climbs seemingly fast.
With a stout engine, the touring-splits are no big deal at low rpm, but they grow with rpm. At redline the 1-2 shift drop difference is noticeable.
I like to think of the
2.45-1.45-1.00 as the close-ratio gears, and the
2.74-1.54-1.00 as the wide ratio gears. The difference in percent is, 11.6% in first, 6% in second, so at least it is progressive.
So from 3.91s , plus 11.6% in first starts like 4.36s, and plus 6% in second feels like 4.14s..
>If you don't run enough rear gear, and if that lack of rpm causes your engine to cruse with the intake in reversion, you will actually lose mpgs. Plus with the factory timing controls, the lower your cruise rpm gets, the more impossible it is to give the engine the timing it wants, so again you lose fuel economy.
>With 22* modded into my Vcan, All I can get out of the factory parts is 50*@2800, 47 at 2400, 44* at 2000. Meanwhile the engine is wanting in the range of 52 to 60. You will lose more fuel economy to loss of optimum timing than that which you gain from the lower cruise rpm.
>My 230* cammed 367engine vacuum-peaks at ~2100, and I cruise it at 65=2240, but the most timing I can give it, with the factory D, is 45*, and she is wanting close to 60*, so the rest has to come from my dash-mounted, dial-back, timing retard gizmo. But as soon as I come off cruise, I have to remember to dial it back out. It is for this reason that she has 3.55s instead of 3.23s, which would lower the rpm to 2040, but the timing would be another 3 degrees less.
>So, unless you have a programmable computerized timing system, it's kindof a tight balancing act.
> with an automatic, you might be able to increase the PT timing to say 28*@2200 and you might be able to get another 2* out of the Vcan, so plus 6* to my 45=51* is about the best you can get at 2200, which is still far short of what she wants.
But 2240 is a real nice cruise rpm
With 3.91s and 28s, 65=2100, about as low as you might want to go.
To get that with an A999, you would need 2.69s rounds up to 2.76s and 65=2160 locked up. Have you considered this with the 2.74-1.54-1.00 ratios?
The starter becomes 2.74 x2.76=7.56, and second becomes 4.25, sounds sick right?
But with a lock-up there is no good reason to run a whimpy 2200TC. Why not try a 3200 or something and pick up say 10%torque, which will make your 7.56 starter feel like 8.32 on take off. this would be the equivalent of running 3.39s with a 904 and around a 2200TC.
Here's how that works out:
Say at 2200 your engine makes 120 hp/280ftlbs, I mean let's just say. So with the 2.76 x2.74 and 28s this looks like 2117 ftlbs into the rear axles/1818 to the road.
Say at 3200 it makes 180 hp/300ftlbs , so 2270 into the axles/1945 to the road. You won't be spinning 28s with that, but recall that 65=2160 in LU
2.94s would increase everything be 3.94/2.76= plus 6.5%, so
65=2300, and now 2072 ftlbs to the road, with the 3200..
Lets try 26.5 tires . I get 2190 to the road and 65=2430 in LU. Ima thinking 2190 will spin 26.5s, maybe not far; but 2430rpm is still not bad for cruising.
And I did not factor in any TM from the TC, and recall that I pulled the power numbers out of thin air.
Lets do one with 2.76s again, 26.5 tires, the A999LU, and lets factor in some TM in the convertor.
First;65=2280rpm
then; 300ftlbs at 3200x2.74x2.76x24/26.5=2055 ftlbs to the road before the TC. So at zero mph lets factor in a TM of 1.8 =3700 oh yeah! that will bust 'em loose. Now; a couple of car lengths out, lets say the TM has dropped to 1.3, so 2672 will sustain the spin if not all the way thru first, at least a respectable way. And really; how far do you want to spin?
Ok but, I pulled those torque numbers off a 5.2M. So if you have a 273, I don't think 2.73 gears are gonna do it for you, even with the 3200; but, you get the idea. Unless maybe you specifically built a hi-torque 273, lol.
The deep low-gear works very well with up to 3.91s and 28" tires. Taller tires will like more gear. After that, more gear can get kindof aggravating , as the rpm climbs seemingly fast.
With a stout engine, the touring-splits are no big deal at low rpm, but they grow with rpm. At redline the 1-2 shift drop difference is noticeable.
I like to think of the
2.45-1.45-1.00 as the close-ratio gears, and the
2.74-1.54-1.00 as the wide ratio gears. The difference in percent is, 11.6% in first, 6% in second, so at least it is progressive.
So from 3.91s , plus 11.6% in first starts like 4.36s, and plus 6% in second feels like 4.14s..
>If you don't run enough rear gear, and if that lack of rpm causes your engine to cruse with the intake in reversion, you will actually lose mpgs. Plus with the factory timing controls, the lower your cruise rpm gets, the more impossible it is to give the engine the timing it wants, so again you lose fuel economy.
>With 22* modded into my Vcan, All I can get out of the factory parts is 50*@2800, 47 at 2400, 44* at 2000. Meanwhile the engine is wanting in the range of 52 to 60. You will lose more fuel economy to loss of optimum timing than that which you gain from the lower cruise rpm.
>My 230* cammed 367engine vacuum-peaks at ~2100, and I cruise it at 65=2240, but the most timing I can give it, with the factory D, is 45*, and she is wanting close to 60*, so the rest has to come from my dash-mounted, dial-back, timing retard gizmo. But as soon as I come off cruise, I have to remember to dial it back out. It is for this reason that she has 3.55s instead of 3.23s, which would lower the rpm to 2040, but the timing would be another 3 degrees less.
>So, unless you have a programmable computerized timing system, it's kindof a tight balancing act.
> with an automatic, you might be able to increase the PT timing to say 28*@2200 and you might be able to get another 2* out of the Vcan, so plus 6* to my 45=51* is about the best you can get at 2200, which is still far short of what she wants.
But 2240 is a real nice cruise rpm
With 3.91s and 28s, 65=2100, about as low as you might want to go.
To get that with an A999, you would need 2.69s rounds up to 2.76s and 65=2160 locked up. Have you considered this with the 2.74-1.54-1.00 ratios?
The starter becomes 2.74 x2.76=7.56, and second becomes 4.25, sounds sick right?
But with a lock-up there is no good reason to run a whimpy 2200TC. Why not try a 3200 or something and pick up say 10%torque, which will make your 7.56 starter feel like 8.32 on take off. this would be the equivalent of running 3.39s with a 904 and around a 2200TC.
Here's how that works out:
Say at 2200 your engine makes 120 hp/280ftlbs, I mean let's just say. So with the 2.76 x2.74 and 28s this looks like 2117 ftlbs into the rear axles/1818 to the road.
Say at 3200 it makes 180 hp/300ftlbs , so 2270 into the axles/1945 to the road. You won't be spinning 28s with that, but recall that 65=2160 in LU
2.94s would increase everything be 3.94/2.76= plus 6.5%, so
65=2300, and now 2072 ftlbs to the road, with the 3200..
Lets try 26.5 tires . I get 2190 to the road and 65=2430 in LU. Ima thinking 2190 will spin 26.5s, maybe not far; but 2430rpm is still not bad for cruising.
And I did not factor in any TM from the TC, and recall that I pulled the power numbers out of thin air.
Lets do one with 2.76s again, 26.5 tires, the A999LU, and lets factor in some TM in the convertor.
First;65=2280rpm
then; 300ftlbs at 3200x2.74x2.76x24/26.5=2055 ftlbs to the road before the TC. So at zero mph lets factor in a TM of 1.8 =3700 oh yeah! that will bust 'em loose. Now; a couple of car lengths out, lets say the TM has dropped to 1.3, so 2672 will sustain the spin if not all the way thru first, at least a respectable way. And really; how far do you want to spin?
Ok but, I pulled those torque numbers off a 5.2M. So if you have a 273, I don't think 2.73 gears are gonna do it for you, even with the 3200; but, you get the idea. Unless maybe you specifically built a hi-torque 273, lol.
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I had to pick this part out to ask....
Are you referring to the condition where a car is operated at a speed below the RPMs where the camshaft becomes efficient?
If so, I understand the principle.
I'm going with a 5 speed in my '70 Charger. The OD ratio is .64. Some have asked me why I didn't opt for the 6 speed but to me, a .050 OD gear would only serve to allow a higher top speed. Rolling along at 75 mph at 1800 rpms with a 440/493 and a solid lifter MP 528 cam seems like I'd be well under the point of efficiency and probably get the same freeway mileage as a .64 OD gear and 2200 rpms.
moparmat2000
Well-Known Member
You dont have to cut up the floor to do this. Just the torsion bar crossmember loop.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Hyup you got it.
That sixth gear is pretty pricey. and like you say, to properly use it, you gotta be cruising High speed. .
I followed a Corvette in 2004, coming home from Minneapolis. He blew by me, as I was doing 75 on the Interstate. Well, said I, I bet he has a radar detector. So I let him get up on the horizon, and that is where we trucked along. With my A833od and GVod behind it; 100 maths to 2440.
But I no longer use that combo. These days I run the Commando 3.09 low box still with the GVod.. One overdrive is enough.
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