Which Transmission to use?

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kzcountry

kzcountry

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I have a 72 Demon and installing a slightly built 73 340 in the car. I am going with an auto for sure, my knees ain't what they used to be. Which one would you use 727, 904, 500, 518 ?? This will be a street car, not planning on any strip racing. Will be running a lot of 100 mile round trips. Thanks for your input.
 
904 and if I was going auto I’d get the 42RH aka the 904 with hydraulic over drive. Later was the 42RE that has electric activated OD. Lighter and less rotating mass than a 727 and will hold the power of a build 340. Plus you get over drive for those lung cruises…
 
904, unless you don’t mind some fab work for the A-500 OD. It’s a little bit of a PITA, but the reduced rpm’s at Hwy cruise will be worth it.
 
What is your rear-end gears?
One option is a 904 with lower(2,74 opposed to 2.45) first gear.
 
Once you put an overdrive trans in your car you’ll never want another street car without one. It makes them so much nicer to drive. Even 100 miles at a time will be well worth it. I vote 42rh.
 
toolmanmike said:
Interstate driving? If not you really don't need a OD.
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I currently drive a Cuda with a 727 and 3.23 rear end. When I get on the interstate for a shot run I am turning close to 3grand around speed limit. I am looking for something to drive like 30 miles or take a 150 mile trip.
 
Don’t just look at Chrysler products. The gm 200 and 700 r4 models can adapted and the floor surgery is minor. They are good transmissions and can be built to handle pretty good power. I have an 83 elcamino with a 383 and a 700r4 with 3:73 gears. Cruises at 75 mph at 2200 rpm.
 
A 518 has 727 front guts. A 727 is comparable to a C6 and th400. A 700 uses th350 low reverse clutches and planetaries. A 2004R is weaker than a 700. The A500 has the same overdrive as the 518, but of course weaker clutches; comparable to a 2004R, but it has a nice low first gear. Both A500 and A518 require floor surgery above the mount area; but it can be performed from above; for the most part. I hate using GM because then you are required to use SPECIAL parts like flexplate and starter. Good luck finding replacements when the time comes. Under 400 horse I say go with the A500, but use Kevlar front band and thin Red Eagle clutches. 5 in forward and 6 in direct. A radical 340 should use the A518; add a clutch to the direct 3 pack.
 
727 with a Gear Venders added later on. I wouild not cut a floor for 500 or 518
 
kzcountry said:
I currently drive a Cuda with a 727 and 3.23 rear end. When I get on the interstate for a shot run I am turning close to 3grand around speed limit. I am looking for something to drive like 30 miles or take a 150 mile trip.
Click to expand...
with 3.23sand 27" tires the Zero slip number is 65=2700 rpm. Allowing 3% maximum for slip, that comes to 2800. If you are doing close to 3000 at 65, Ima thinking something is wrong. That calculates to over 11% slip.
Here is the formula;
MPH = (rpm x tire roll-out)/1056 x R1xR2
Where tire roll-out could be Diameter x 3.1416, and
R1 and R2 are your gear ratios, trans and differential.
1056 is a constant so it spits out the proper answer in mph.
 
AJ/FormS said:
with 3.23sand 27" tires the Zero slip number is 65=2700 rpm. Allowing 3% maximum for slip, that comes to 2800. If you are doing close to 3000 at 65, Ima thinking something is wrong. That calculates to over 11% slip.
Here is the formula;
MPH = (rpm x tire roll-out)/1056 x R1xR2
Where tire roll-out could be Diameter x 3.1416, and
R1 and R2 are your gear ratios, trans and differential.
1056 is a constant so it spits out the proper answer in mph.
Click to expand...
I am looking for doing around 70 mph close to 2000 rpm or lower
 
kzcountry said:
I have a 72 Demon and installing a slightly built 73 340 in the car. I am going with an auto for sure, my knees ain't what they used to be. Which one would you use 727, 904, 500, 518 ?? This will be a street car, not planning on any strip racing. Will be running a lot of 100 mile round trips. Thanks for your input.
Click to expand...
At the price of gas today, and looking into the future, you really do need to get the Rs down. 2400 is a good lower-limit number cuz you can just barely give her enough timing advance to make it worth the swap. At 2400 and cruising, she may like about 56 degrees. If you modify your Vcan to 22* then you can hit 24 on the mechanical.
To hit 2400 in loc-up, with 27s you need a rear gear of 2.965.
So the closest is 2.94s. But the starter gear is just 2.94 x 2.45=
7.20 so, with a stock TC, she will be a bit of a turd off the line.
A good starter gear is at least 7.90 (3.3 x 2.45)
to get 7.90 with a 2.94, you need a first gear of 2.69. The A999 has a 2.74 as do some A998s.
So there you go;
Get yourself a 2.74low-gear lock-up, 2.94s and a lil more stall than stock, which will depend a lot on your cam and cranking cylinder pressure. Easy Peasy.
 
kzcountry said:
I am looking for doing around 70 mph close to 2000 rpm or lower
Click to expand...
2000 or lower is IMO, Not realistic from a fuel-economy standpoint, because there is no way to give the engine the timing that it wants, with the factory type distributor. So your combo is most likely to get LESS mpgs at 2000 than at 2400.
If you just want to cruise down there for other reasons, I cannot speak to that.
My combo now cruises at 65=2240 and She is about 6 to 8 degrees shy of getting the timing she wants. So I have installed a dash-mounted, dial-back, timing device, and crank it up come cruising time.
 
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