Is there a way to calculate the rpm drop for when a torque converter locks up? Like if a 3200 stall converter locks up? I probly need to list more info so. 24 in tall tires 373gears 200-4r tans. ---------- Post added at 09:54 PM ---------- Previous post was at 08:45 PM ---------- Never mind I figured out what I needed. And I don't know why I posted this.
I have a lot of experience with the lockup converters so I can help. At a given speed: When I used a stock converter in my 700R4 trans it went from 2300 RPM on the highway to 2150 RPM with the lockup. When I used a 2500 stall converter in my 700R4 trans it went from 2400 RPM on the highway to 2150 RPM with the lockup. When I used a 3200 stall converter in my 700R4 trans it went from 2500 RPM on the highway to 2150 RPM with the lockup. So the point is that the converter will be 100% locked up when the lockup is engaged. I run a toggle switch so I can control the lockup and make sure it only locks when I want it to. With a loose converter there is more slippage at all RPMs bellow the stall speed although the lockup converter eliminates all the slippage. I tend to gain to about 2 MPG with the lockup engaged on the highway when running a 3200 stall converter and only 1 MPG when running the stock converter... So yes a loose converter hurts fuel mileage but is also the perfect match for a lockup converter.
Thank you very much that's the kind of data I needed. I'm planning on going with a different cam from ta I believe it's the C113-350 and it recommends a use a 3000 stall converted. So I'm going to go with a 2800-3200 converter. Any expirance with that cam?
700R4 here as well. 2800 RPM converter. Spot-on with my experience (a couple hundred RPM), except, my fuel savings tend to be much more with the lockup engaged.
Well my numbers are in a 4x4 3/4 ton truck so it does not get too great of mileage anyways LOL... Best I can get is 19 MPG at 65 MPH, but I also get 17 MPG at 75 so I just drive it fast LOL. The biggest thing to note is that with a higher stall converter the more the lockup will help lower the RPM and increase the fuel mileage. The other thing to consider is being in the propper RPM band for the engine, trans, rear end combo. The truck drives great at 80 MPH but only gets about 15 MPG. For example that TA-113 cam would not be happy cruising at anything under 2800 RPM likely, there as if a TA-212 cam was used it would cruise nicely at 2300 RPM. Matching the gearing and tire size to get the RPM in the sweet spot when going your desired speed on the highway is the trick to getting good fuel mileage. Another example is my olds 307 with ported heads, headers, and some other mods. It is a really low RPM engine, it loves being at 1800-2200 RPM on the highway and it is matched with a 2004R trans and a 2.56 gear... With this combo it easily drives 80-90 MPH without wasting much fuel. I average 22 MPG on the highway with a heavy 4 door 88 Cadillac.
While your 3.73 gears should be about perfect with the 2004r Tranny, I question your use of 24 in tall tires. That seems awfully short to me. The GSs usually run a 26 1/2" tire and even Pony cars like Camaros and Mustangs run 26 inch tires standard. What kind of car do you have to be running a 24" tire?
Lockup converter will effectively remove the loss you have with the converter. The mechanical ratios of your combo dictate you should be turning around 2000 RPM at 55 MPH. Any RPM higher than that at 55 while not locked up is the additional slip your converter is causing. 24 in tall tires 373gears 200-4r tans The formula is (RPM*Tire Diameter)/(Rear Gear Ratio*336*Final Trans Ratio) Plug your number in and get (2000x24)/(3.37*336*.67) = 57.2MPH. If you are showing 2200 at 55, you have 10% loss at that speed. Does that make sense? I can send you a spreadsheet you can play with to get your own numbers.
Yes, indeed. I used to turn 2000 at 40MPH, now I turn 2000 at 60MPH with the same 3.73 and 275R60-15 tires. Lockup and overdrive are great things!
