Lockup 904 question

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Good question.... but does'nt the unit need to know that there is sufficient line pressure to hold? Normally this is all done within the VB and the trans itself... No ports to the case, AFAIK. How would you monitor?? Seems like a lot of trouble.
 
U could maybe delay the l u function in the valve body. Or do u want it to work on your command? Is it hydraulic or electric l u?
 
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oldkimmer said:
U could maybe delay the l u function in the valve body. Or do u want it to work on your command? Is it hydraulic or electric l u?
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It is hydraulic control. I know about the electrric control, but I have never seen one. I have several LU 904's core transmissions, but they are all hydraulic. Even my 88 diplomat. It has the wire for the electric LU, but no connector on the trans, and the LU works. It is the original trans in the car. I bought it new in 1988.
I would like to manually control the LU function.
PS: I don't have a problem with going inside the trans to modify the VB or even adding a solenoid if necessary. The trans will be apart for a build, anyway.
 
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If I did not get enough info on the site, I had planned on calling some people during the week. I just hate to take up their time, when I'm not spending money with them.
 
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There's a vacuum switch setup you can put on it that will control lockup.
Something like this.
Vacuum controller
 
the 904 LU is not built for power-handling; it is strictly a fuel-economy feature.
It gets its apply signal from the line pressure and it's cut-out signal from the combination of line pressure plus TV pressure; so it's the first thing out when you hit the gas.
Could you make it manual?
Sure, but I can't imagine why you would want to.
Plus the stock combination works pretty slick.
 
JYH and RRR both of those things referenced are for the electric controlled transmission. I have a hydraulic controlled trans.
 
Charrlie_S said:
JYH and RRR both of those things referenced are for the electric controlled transmission. I have a hydraulic controlled trans.
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that is for a hydro unit, look back at the description and read the detailed notes.

instead of using a speed sensor and TPS, you're using a vacuum switch and a oil pressure switch to engage the LU solenoid.

obviously, you won't use that whole set up but you can accomplish it with some of those parts and a small switch. somebody on here also used a NOS solenoid to do the same with a 42 or 46 RH, same idea.
 
junkyardhero said:
that is for a hydro unit, look back at the description and read the detailed notes.

instead of using a speed sensor and TPS, you're using a vacuum switch and a oil pressure switch to engage the LU solenoid.

obviously, you won't use that whole set up but you can accomplish it with some of those parts and a small switch. somebody on here also used a NOS solenoid to do the same with a 42 or 46 RH, same idea.
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I beg to differ with you. All the transmissions you referred to have an electrical solenoid inside of the trans, that controls the fluid for the lockup. They have a electrical connector external to the trans. The 904 hydraulic lock ups do not use a electrical solenoid, and do not have a electrical connecter on the trans for lockup operation. The only electrical connector is for neutral safety and backup lights.
I was wondering if it is possible to convert the non electrical LU to electrical. That would make it easy to control manually.
 
Charrlie_S said:
If you know how, please tell me.
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Define how you want to control TCC? What you could do is the tube that feeds fluid from the 1-2 shift valve, if you add an electric solenoid to stop the flow of fluid, it won't let the TCC valve engage lock up until you turn the flow of fluid back on and it will work the way of the OEM design as disengage on deceleration and hard accel.
 
I have been researching this a little since the original post. A lot of bad info out there. I hope I am not passing on more disinformation but it seems there was a one wire version that was controlled by the " lean air" module. 1988 or so. You could probably control that one.
 
Charrlie_S said:
I beg to differ with you. All the transmissions you referred to have an electrical solenoid inside of the trans, that controls the fluid for the lockup. They have a electrical connector external to the trans. The 904 hydraulic lock ups do not use a electrical solenoid, and do not have a electrical connecter on the trans for lockup operation. The only electrical connector is for neutral safety and backup lights.
I was wondering if it is possible to convert the non electrical LU to electrical. That would make it easy to control manually.
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i'm aware of that. what i'm trying to get at is you can most likely use a combination of those parts to "make" an external solenoid that you can control electronically-- like @moparlvr166 mentioned.
 
Bodyperson said:
I have been researching this a little since the original post. A lot of bad info out there. I hope I am not passing on more disinformation but it seems there was a one wire version that was controlled by the " lean air" module. 1988 or so. You could probably control that one.
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Correct. I have read about those, but have never seen one. My 88 Diplomat has a LU 904, but not electrically controled. The vehicle has the electrical solenoid control wire at the trans but it is not connected to anything. What I am trying to find out is if it is possible to somehow convert the non electrical LU feature to electrical.
Like could it be as simple as changing the valve body, or modifying the existing valve body, or something similar? I realize I would have to drill a hole in the case to make the electrical connection.
 
moparlvr166 said:
Define how you want to control TCC? What you could do is the tube that feeds fluid from the 1-2 shift valve, if you add an electric solenoid to stop the flow of fluid, it won't let the TCC valve engage lock up until you turn the flow of fluid back on and it will work the way of the OEM design as disengage on deceleration and hard accel.
Click to expand...
OK. I assume you are aware of the mods to control the OD and Converter LU on the A500 and A518 manually. I want to do the same thing on a 904 LU for the lock up function.
 
Charrlie_S said:
Correct. I have read about those, but have never seen one. My 88 Diplomat has a LU 904, but not electrically controled. The vehicle has the electrical solenoid control wire at the trans but it is not connected to anything. What I am trying to find out is if it is possible to somehow convert the non electrical LU feature to electrical.
Like could it be as simple as changing the valve body, or modifying the existing valve body, or something similar? I realize I would have to drill a hole in the case to make the electrical connection.
Click to expand...
You would buy the junk from that transmission and transfer it to your transmission.
 
You can use a TCC solenoid to vent the fluid from the tube. Drill plate for fluid in & out and T in solenoid to vent fluid out. sounds simple, I know you can make it work inside the trans.
 
Charrlie_S said:
This is what I am trying to determine. That would be simple, or are there differences in the case or other parts? Governor, maybe?
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You already have the wire, correct? 904 is a 904. Mopar was good at adapting. They didnt change the basics. Cant know for sure. Threw my 2cents out there. I really dont know. Get to hotrodding on it an tell us.
 
Bodyperson said:
You already have the wire, correct? 904 is a 904. Mopar was good at adapting. They didnt change the basics. Cant know for sure. Threw my 2cents out there. I really dont know. Get to hotrodding on it an tell us.
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The wire is on the car. But does not go anywhere. It was used on the electric controlled LU's so the lean burn computer could control the LU. But I have never seen a electric LU 904 trans. I have experience with 904's, but the early ones before LU's. I build my own "race" 904's, even the cable shifted ones. Never have had a LU 904 apart (either style), so I don't know what is different. At this point just trying to get some ideas. I have several other projects to get done before this.
 
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