Add a REAR Pump to 4L80- to enable PUSH starting ?
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From: Alaska
Add a REAR Pump to 4L80- to enable PUSH starting ? Looking at the extension housing for 4x4 4L80, looks like plenty room for a small-ish shaft mounted OIL Pump.
Could one incorporate a spline driven, output shaft mounted oil pump - about like the one used in Transfer cases?
- If the pump drew fluid from it's own pick-up tube and filter IN the transmission oil pan, with ball check valve in the pressure line TO the valve body: could one develop sufficient line pressure from the rear shaft turning to engage first gear while ROLLING, and thus get PUSH START capability with a modern Auto Transmission ?
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The ability to PUSH start would be pretty cool.
Could one incorporate a spline driven, output shaft mounted oil pump - about like the one used in Transfer cases?
- If the pump drew fluid from it's own pick-up tube and filter IN the transmission oil pan, with ball check valve in the pressure line TO the valve body: could one develop sufficient line pressure from the rear shaft turning to engage first gear while ROLLING, and thus get PUSH START capability with a modern Auto Transmission ?
.
The ability to PUSH start would be pretty cool.
I have vague memories of some old chrysler auto trans that allowed push starting, but it was more like push with another car to start, not push with a couple of friends. Even with the fluid pressure up, you still have torque converter slip to overcome.
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From: BERWICK PA
the pressure you could probably make but to really make it semi practical you would need the lockup clutch to be on during the push start.
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From: BERWICK PA
My thoughts were mabe just a why not lol . Sometimes people just do things because lol. Years ago I worked on the idea of using the rev input drum as 3rd gear in the 60e. figured out the hydraulics easy enough . But with place I worked they were not big on lots of time spend trying figuring out new stuff so never got to really work out the timing and they why was well why not lol .
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Frank formerly of Performabuilt, Now just me, What can I build for you today? Call or message me. Click sig pic for my facebook
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My thoughts were mabe just a why not lol . Sometimes people just do things because lol. Years ago I worked on the idea of using the rev input drum as 3rd gear in the 60e. figured out the hydraulics easy enough . But with place I worked they were not big on lots of time spend trying figuring out new stuff so never got to really work out the timing and they why was well why not lol .
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From: BERWICK PA
True me too , That is why I say its a why not lol.
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Thread Starter
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From: Alaska
.
It would give the Automatic Transmission the ability to transmit power backward TOWARD the engine flywheel, enabling push start capability.
The ONLY practical disadvantage of the modern TCC auto transmission as compared to a manual transmission is that the manual box allows easily roll starting if the starter breaks, or battery is discharged.
For remote, extreme weather or mission critical operation, an auxilliary way to quickly and easily start your vehicle engine could be a lifesaver.
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I had a 1974 Mercedes Diesel with 4 speed automatic that DID have a rear pump, and would easily roll start... which is a pretty cool feature.
It would give the Automatic Transmission the ability to transmit power backward TOWARD the engine flywheel, enabling push start capability.
The ONLY practical disadvantage of the modern TCC auto transmission as compared to a manual transmission is that the manual box allows easily roll starting if the starter breaks, or battery is discharged.
For remote, extreme weather or mission critical operation, an auxilliary way to quickly and easily start your vehicle engine could be a lifesaver.
.
I had a 1974 Mercedes Diesel with 4 speed automatic that DID have a rear pump, and would easily roll start... which is a pretty cool feature.
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Ha ha ha, I guess only us old timers remember the rear pumps. In the 50's I think most all GM automatics had them. Push start ? No you don't need a lockup clutch to do so. Because I think the only transmission in those days to have one was the Powermatic in 1957 GM medium trucks.
I coast started many old cast iron and corvair power glides back in the day. The manuals all say you needed to be at 35 minimum miles per hour to do so, and the normal old torque converters had no problems transferring the torque to the engine to successfully start it.
Had to use that many times to break an oil starved engine (it leaked a lot) free to get us high school buddies back home or on the road, the starter couldn't turn the engine. Oh the good ole days.
If you did get a pump to fit, just study some of the older transmission fluid circuits and see how they accomplished it.
Its a great idea to reintroduce the rear pump.
I did a rebuild many years ago on a cast iron dynaflow, the key for the rear pump was sheared. The guy had all carpet out of the car, and complained about the new noise the transmission made. I should have not fixed the rear pump.
I miss those old transmissions, simple and easy, and no corrugated tin cans for clutch drums.
I coast started many old cast iron and corvair power glides back in the day. The manuals all say you needed to be at 35 minimum miles per hour to do so, and the normal old torque converters had no problems transferring the torque to the engine to successfully start it.
Had to use that many times to break an oil starved engine (it leaked a lot) free to get us high school buddies back home or on the road, the starter couldn't turn the engine. Oh the good ole days.
If you did get a pump to fit, just study some of the older transmission fluid circuits and see how they accomplished it.
Its a great idea to reintroduce the rear pump.
I did a rebuild many years ago on a cast iron dynaflow, the key for the rear pump was sheared. The guy had all carpet out of the car, and complained about the new noise the transmission made. I should have not fixed the rear pump.
I miss those old transmissions, simple and easy, and no corrugated tin cans for clutch drums.
Last edited by bob4360; May 14, 2025 at 09:47 PM.
