I have found an online calculator that will figure engine RPM based on tire size, rear gear, trans ratio, and speed. For example 60MPH with 3rd gear (1:1), a rear gear of 3.55:1 and a 26 inch tall tire yeilds 2753 RPM. I am usuming that this calculator does not take in to account for torque converter slipage.
How much slipage would you think there is?
I don't want to cruise with an RPM over 3000.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

That would depend on what converter you use and what it actually stalls at in your car.

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Official Cookie and Mater Tormentor.

Lets say it's a stock 2000 stall converter.
And lets say its an aftermarket 2800 stall converter.
Also if I have a lockup style 904 are there lockup aftermarket converters and do they lockup? I have heard about converters for lockup type trans that don't lockup.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

I have an old DeskTop Drag Program and it assumes the following slip percentages for various stall speeds:

1200 3%
1800 4%
2500 5%
3500 6%
4000 7%
4500 7%
5000 7%

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

At 2800 RPM, I would guess the 2000 stall converter would slip 5-8% and the 2800 stall would slip maybe 9-12%.

Lou

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Home of Slant6-powered fun machines since 1988

Also if I have a lockup style 904 are there lockup aftermarket converters and do they lockup? I have heard about converters for lockup type trans that don't lockup.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Don't forget that the rear axle ratio will affect converter slippage. A lower (numerical) axle ratio will require more torque for a given road load (less RPM requires more torque for the same horsepower) increasing slippage. The lower RPM also put the converter into a less efficient and more slip and heat producing operating range. This is why you do not want to have a cruise RPM below the stall speed of the converter. You end up putting a ton of heat into the fluid. That heat is just wasted fuel and if the trans cooler is insufficient, a wasted transmission. One more thing. Smaller converters are more efficient at high stall speeds than large ones.

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Joshua

Are these guys good or what. Thanks Ron Parker













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Also if I have a lockup style 904 are there lockup aftermarket converters and do they lockup?

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Yes, you can get high stall lockup converters. They are more money of course. Google is your friend.

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Joshua