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Discussion Starter · #1 ·
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Ryan
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That’s a bad ass calculator. I like how it shows you your RPM drop from gear to gear on a graph. I also like that it calculates using your converter slip as well.
 
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That's way better than the wallace one.
Can really dial in here . Nice .
A keeper lol
 

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1968 Malibu sport coupe, 489 ci. 590 hp 600 tq, RV T-400 Freakshow 3200 stall, 3.73 12 bolt posi
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I was wondering about slippage too, how do you figure that? I have a 3,200 stall conv. but no idea of percent of slippage, call shop I bought it from?
 

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1970 El Camino SS396, VortecPro 467, ATI TH400, Moser 12 bolt /TruTrac 3:42, Hedman headers
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Mark Williams, of 9” fame, used to sell a simple circular “slide rule” type at a VERY reasonable price, input tire size, rear gear, RPM’s and get mph or any other value depending upon which 3 values you imputed. Would not calculate for converter slippage though. Worth a look if still available. ($3.00)
 

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On every car that I've owned with a stock lockup converter, the RPM difference between lockup and non-lockup has been approx. 200 RPM when the trans is in final drive ratio
 

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I was wondering about slippage too, how do you figure that? I have a 3,200 stall conv. but no idea of percent of slippage, call shop I bought it from?
Yeah they should know that even if it's an off the shelf converter
 

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How much does a stock convertor slip . Is it different for a high stall unit??
No . And the stamped number on an off the shelf converter really has little to no correlation with where the vehicle will actually stall.
Put a "3500 stall " converter in a 4300 lb 55 Chevy with a 3:36 gear and then put that same "3500 stall" converter in 2800 lb 71 vega with 410 gears and those 2 cars will "stall" a mile apart .
These numbers they stamp on these off the shelf converters are little better than marketing bullshit. If you want a converter that's designed for YOUR car and engine and driveline you call an actual company who makes converters for specific weights gears and engines and for the customers specific needs . If you want to roll the dice and get whatever then buy a "B and M hole shot" converter with a stamped number on it .


So with that out of the way on to slippage .
It has zero to do with where your car stalls .
5000 rpm or 1800 rpm is of no consequence as to slip . Less slip = more mph at a given rpm regardless of what rpm the vehicle stalls .Thats another factor that would be discussed with a real converter company .

Leave all other inputs the same in the calculator but change the slippage only from one extreme to the other and you'll see what it does to mph as in relation to rpm
 

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Mark Williams, of 9” fame, used to sell a simple circular “slide rule” type at a VERY reasonable price, input tire size, rear gear, RPM’s and get mph or any other value depending upon which 3 values you imputed. Would not calculate for converter slippage though. Worth a look if still available. ($3.00)
Here is a calculator for $0.0
I know it by heart lol

Rpm=( mph x 336 x rear dif) ÷ rear tire diameter .
Then take that and multiply it by whatever transmission ratio you want .
1:1
1.52
2.52
Or whatever ratio the gear is
 

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Ryan
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I was wondering about slippage too, how do you figure that? I have a 3,200 stall conv. but no idea of percent of slippage, call shop I bought it from?
Freakshow says they shoot for at least 8 percent or under if I recall. I don’t remember where I saw that however.
 
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Discussion Starter · #12 ·
I don't know if there is a set percentage of slip except for maybe a stock factory converter but I am only guessing. I would say any of these are just a tool to help get an idea of what you're combo will do. I know my combination up doesn't track exactly like the calculator at zero slip % . If you plot what you have vs the calculator and ad slip until you get the correct numbers, you're probably close to knowing you're slip percentage

I was just looking at the changes tire size and different gears made to RPM at typical highway speeds.

Thanks
Joe
 
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Hello,

I was playing around with a RPM, tire size, speed calculator looking at the effect of various combinations. I knew about the Wallace calculator but I found another one that was pretty nice,


Thinking about changing the rear gear for a more highway friendly ratio

Thanks
Joe
Interesting calculator that has been around for some time now. Thanks for refreshing our memory.
 
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