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Discussion Starter · #1 ·
I have a Nissan Sentra in really good shape with an automatic trans. My thought is to dis assemble the trans, remove all un-needed components, pump, valve body, torque converter, first gear cluster, third gear cluster, band solenoids etc. Lock it in second gear gives me a 5.5 to 1 final ratio with differential. This would give me 99.2 MPH @ 8000 RPM. Does this sound practical or am I off in lala land.
 

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What would lubricate the transmission, without the fluid and pump?

It seems like it would easier to swap in a manual transmission and leave it in whatever gear is most suitable (so you wouldn't need to set up a clutch or shifter).
 

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Discussion Starter · #3 ·
I would put enough oil in for simple splash oiling. The pump is for torque converter and to operate the servos for band tightening.
 

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I would put enough oil in for simple splash oiling. The pump is for torque converter and to operate the servos for band tightening.
It usually doesn't work that way. When an automatic transmission vehicle is towed with the drive wheels on the ground (so they're turning) and the engine stopped (so the pump driven by the input shaft isn't pumping) - with a normal fluid level - the transmission is usually destroyed. Splash lubrication is not normally sufficient for an automatic.

Also, just out of curiosity, how old are we talking about... modern transmissions use multi-plate clutches (and some dog clutches), not bands.
 

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Discussion Starter · #5 ·
It is an 87 FWD. I plan to replace any clutches or dogs with solid attachments so the transmission is nothing but a non shifting gear box in an automatic transmission shell.

When my kids were little and racing out law go karts, I removed the clutch from a CR 125 motorcycle engine and made a winner from a mid pack kart. I made a small torque plate to take its place thus removing all that flywheel weight.

There will not be anything in the transmission shell that will need any oil pressure. I am confident that this is possible but it is still a theory.

I have been building goofy things all of my life and most of them were successful.
 

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It is an 87 FWD. I plan to replace any clutches or dogs with solid attachments so the transmission is nothing but a non shifting gear box in an automatic transmission shell.
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There will not be anything in the transmission shell that will need any oil pressure. I am confident that this is possible but it is still a theory.
Okay, so it's not a modern transmission, but I think you're still underestimating both the complexity of an automatic, and the need for lubrication. I still vote for any random manual transaxle that fits a Sentra and doesn't make grinding sounds, and locking that in one gear... it will be lighter, more reliable, and less work.
 

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Discussion Starter · #7 ·
You may very well be right. Unfortunatly, I am a very stubern jerk and have to find out for myself. I will keep you advised.
 

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I don't get why you want to stick with the Auto anyway if you are locking it in one gear? What advantage does it give you? Why not switch to the equivalent manual box from the same model?


That is what I have done with a Nissan Pulsar which I suspect is quite similar to the Sentra.
 

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You may very well be right. Unfortunatly, I am a very stubern jerk and have to find out for myself. I will keep you advised.
I'm also very interested. I plan to get rid of the entire transaxle in a FWD Dodge Intrepid. I want to replace it with a rear differential from a Dodge or Chrysler or Ford. It'll be a direct drive, so I won't need the all original gears except the final drive bit in the differential. But, replacing the transaxle like this means I'll have to customise the half shafts.
It just might be an easier job to gut the original transaxle as you suggested and keep just the gears required for one speed. Please let us know how your project goes..
 

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It just might be an easier job to gut the original transaxle as you suggested and keep just the gears required for one speed.
The degree of "gutting" is not a trivial choice. All those bits are designed to work together, so for many parts just removing them is not an option; for example, if you remove a gear splined onto a shaft you probably need to replace it with a spacer to keep everything else on the shaft in place (axially). A typical planetary-gear automatic will likely be significantly more difficult to modify this way than a typical manual transmission/transaxle. In either type, since all of the shafts and housing are retained, the weight saving won't be dramatic.
 

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Removing gears may also leave part of a shaft less supported or with uneven radial loads, which could result in undesirable forces across bearings, other gears or the the shaft itself.
 

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I plan to get rid of the entire transaxle in a FWD Dodge Intrepid. I want to replace it with a rear differential from a Dodge or Chrysler or Ford. It'll be a direct drive, so I won't need the all original gears except the final drive bit in the differential. But, replacing the transaxle like this means I'll have to customise the half shafts.
It just might be an easier job to gut the original transaxle as you suggested and keep just the gears required for one speed.
While it would be more straightforward on some ways to keep all of the original configuration (and stock axle shafts) by keeping a gutted version of the original, an automatic is not a good starting point. Unfortunately, I don't think there was ever a manual transmission in these "LH" platform cars, and the automatic is especially unfortunate for this application because it has a chain drive stage.
 

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I think you and Emyr are both right Brian. Just looking at the innards of an automatic transmission it's enough to make you dizzy. I guess I'll have to stick with a differential from another vehicle instead
 

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Discussion Starter · #16 ·
Hi,
I have been reworking the transaxle and things are going really well. I decided to use the oil pump so that the bushings along the input shaft would not suffer.

Took out the first/reverse planetary and band
Removed the valve body
Replaced pan with flat plate to reduce oil volume
Fixed second gear to drive always
Pluged pump discharge port and redirected it to center of input shaft
Cut up the torque converter and used the parts to fab a drive shaft that returnes the oil back inside the case insted of supplying the non existing converter

I have a small dc motor that I am going to set up and bench run the transaxle to see if it oils ok. So far, the 130 lbs starting weight, is around 95 lbs not including oil.
 

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Hi,
I have been reworking the transaxle and things are going really well. I decided to use the oil pump so that the bushings along the input shaft would not suffer.

Took out the first/reverse planetary and band
Removed the valve body
Replaced pan with flat plate to reduce oil volume
Fixed second gear to drive always
Pluged pump discharge port and redirected it to center of input shaft
Cut up the torque converter and used the parts to fab a drive shaft that returnes the oil back inside the case insted of supplying the non existing converter

I have a small dc motor that I am going to set up and bench run the transaxle to see if it oils ok. So far, the 130 lbs starting weight, is around 95 lbs not including oil.
This is really interesting!.. I do wonder how it will perform under full load though.
Also, have you any pictures of the innards of the new "fixed speed transaxle"?
 
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