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Why does my Automatic truck have a manual computer?
#1773032
03/06/15 12:49 AM
03/06/15 12:49 AM
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Joined: Jan 2015
Posts: 156
San Diego
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So, my grandfather bought this truck when it was new and kept all his records for it. I looked through the folder and there is no receipt for replacing the SEMC. Anyways, is it possible the truck came from the factory like this? The computer that is in the truck is an OE#4379891 and if you look it up it's a manual trans cal emissions SEMC. I called the parts store and they said OE#4379829 is the one for my truck. I suppose I should just order the 892 one? Would a manual trans computer even work in an automatic? I drove this truck from Lake Havasu to San Diego and then drove it for a couple years before I started having problems with the truck. Here is my thread where I'm chasing the hesitation, fluctuating idle, and stalling: https://board.moparts.org/ubbthreads/show...e=0#Post8434760
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Re: Why does my Automatic truck have a manual computer?
[Re: Instigate]
#1773033
03/06/15 12:50 AM
03/06/15 12:50 AM
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Joined: Feb 2003
Posts: 1,306
Laveen, Arizona
GTSDart340
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pro stock
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Laveen, Arizona
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It could be that it has just a standard hydraulic 727 in it, therefore has no need for a computer to control it. Either that, or its been replaced incorrectly...
1949 International KB-2 "Mater" - 302/T5
1968 Dodge Dart GTS "The Drat" - 340/727
2006 Dodge Magnum R/T - Hemi
2016 Dodge Durango Limited - 3.6
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Re: Why does my Automatic truck have a manual computer?
[Re: Jim_Lusk]
#1773035
03/06/15 01:23 AM
03/06/15 01:23 AM
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San Diego
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Quote:
What year?
89
and my ID tag says I've got the A998/A999.
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Re: Why does my Automatic truck have a manual computer?
[Re: Instigate]
#1773037
03/06/15 01:29 AM
03/06/15 01:29 AM
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Joined: Feb 2003
Posts: 1,306
Laveen, Arizona
GTSDart340
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Laveen, Arizona
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That trans is hydraulically controlled. No need for a computer to run it.
1949 International KB-2 "Mater" - 302/T5
1968 Dodge Dart GTS "The Drat" - 340/727
2006 Dodge Magnum R/T - Hemi
2016 Dodge Durango Limited - 3.6
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Re: Why does my Automatic truck have a manual computer?
[Re: GTSDart340]
#1773038
03/06/15 01:32 AM
03/06/15 01:32 AM
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San Diego
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Quote:
That trans is hydraulically controlled. No need for a computer to run it.
I see, so I can get away with buying the cheaper computer?
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Re: Why does my Automatic truck have a manual computer?
[Re: Instigate]
#1773039
03/06/15 01:36 AM
03/06/15 01:36 AM
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Joined: Feb 2003
Posts: 1,306
Laveen, Arizona
GTSDart340
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pro stock
Joined: Feb 2003
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Laveen, Arizona
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I would get the one that matches what was in in it before. There are other differences than just the transmission.
1949 International KB-2 "Mater" - 302/T5
1968 Dodge Dart GTS "The Drat" - 340/727
2006 Dodge Magnum R/T - Hemi
2016 Dodge Durango Limited - 3.6
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Re: Why does my Automatic truck have a manual computer?
[Re: GTSDart340]
#1773040
03/06/15 05:30 PM
03/06/15 05:30 PM
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Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
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Balt. Md
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Its actually called a SMEC meaning Single Module Eng Controller and your trans should have a lock-up converter controlled by the PCM (SMEC) from what I remember on that model and year. The trans is hydraulic but it should use a PCM controlled solenoid that works the lock-up converter from what I remember. But I am not 100% sure without looking it up or looking at the vehicle. It could be its not working the lockup if you are right about it and the PCM does not have the terminal for the lock-up solenoid. And if thats right the PCM would not set a code since it would not be looking for a lock-up solenoid circuit. Do you know if the lock-up converter is working ? But it may be some did not have lock-up its just I dont remember seeing any without lock-up that year but my memory could be off. Ron
Last edited by 383man; 03/06/15 05:39 PM.
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Re: Why does my Automatic truck have a manual computer?
[Re: DaytonaTurbo]
#1773043
03/07/15 12:10 AM
03/07/15 12:10 AM
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Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
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Balt. Md
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Basically its all hydraulic other then the lock-up solenoid that closes the line vent so it will build presuure to move the lock-up valve over. The PCM controls when the solenoid turns on and off. I forgot what year they stared using the PCM controled solenoid to control the lock-up but the 89's have it. I think it was around 86 but it may have been earlier as I dont remember off the top of my head. Ron
Last edited by 383man; 03/07/15 12:13 AM.
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Re: Why does my Automatic truck have a manual computer?
[Re: 383man]
#1773044
03/07/15 12:29 AM
03/07/15 12:29 AM
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San Diego
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Quote:
Its actually called a SMEC meaning Single Module Eng Controller and your trans should have a lock-up converter controlled by the PCM (SMEC) from what I remember on that model and year. The trans is hydraulic but it should use a PCM controlled solenoid that works the lock-up converter from what I remember. But I am not 100% sure without looking it up or looking at the vehicle. It could be its not working the lockup if you are right about it and the PCM does not have the terminal for the lock-up solenoid. And if thats right the PCM would not set a code since it would not be looking for a lock-up solenoid circuit. Do you know if the lock-up converter is working ? But it may be some did not have lock-up its just I dont remember seeing any without lock-up that year but my memory could be off. Ron
It's hard to make out but it says "DHA Lock-Up Torque Converter" on my equipment ID tag. What should I look for on the trans? I know it does have a loom going down to the trans from behind the passenger side valve cover.
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Re: Why does my Automatic truck have a manual computer?
[Re: 383man]
#1773045
03/07/15 12:31 AM
03/07/15 12:31 AM
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Posts: 156
San Diego
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Quote:
Basically its all hydraulic other then the lock-up solenoid that closes the line vent so it will build presuure to move the lock-up valve over. The PCM controls when the solenoid turns on and off. I forgot what year they stared using the PCM controled solenoid to control the lock-up but the 89's have it. I think it was around 86 but it may have been earlier as I dont remember off the top of my head. Ron
So it is controlled by my computer? I'm pretty sure my computer that's in the truck is the one that came from the factory.
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Re: Why does my Automatic truck have a manual computer?
[Re: Instigate]
#1773046
03/07/15 12:40 AM
03/07/15 12:40 AM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
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I want to say that the 4 speed automatics had an electronic lock up solenoid. The three speeds do not. Easy enough to tell, how many electrical connectors does your trans have? One for the backuplights/neutral safety switch and one for the speed sensor to the computer. Unfortunately my bud's 89 was a stick truck. Here's a link to the lockup solenoid for an 89 D150 with a four speed auto, there is no listing for the 3 speed. Note how the connector appears, do you have that?
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: Why does my Automatic truck have a manual computer?
[Re: Supercuda]
#1773047
03/07/15 01:06 AM
03/07/15 01:06 AM
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San Diego
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Quote:
I want to say that the 4 speed automatics had an electronic lock up solenoid. The three speeds do not. Easy enough to tell, how many electrical connectors does your trans have?
One for the backuplights/neutral safety switch and one for the speed sensor to the computer. Unfortunately my bud's 89 was a stick truck.
Here's a link to the lockup solenoid for an 89 D150 with a four speed auto, there is no listing for the 3 speed. Note how the connector appears, do you have that?
Pretty sure I do. I'll double check it and post tomorrow. This is the only picture I have of the tranny. I'll check it out.
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Re: Why does my Automatic truck have a manual computer?
[Re: Instigate]
#1773048
03/07/15 01:24 AM
03/07/15 01:24 AM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
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The only connector I see in that pic is for the backup lights/neutral safety.
I think I also see the speed sensor on the tailshaft that the speedometer cable plugs into. That tells the computer the road speed and I know in FWD cars of that vintage if it goes out you tend to stall coming to a stop.
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: Why does my Automatic truck have a manual computer?
[Re: Supercuda]
#1773051
03/07/15 01:36 AM
03/07/15 01:36 AM
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Joined: Jan 2003
Posts: 18,427
UPPER MICHIGAN, MARQUETTE COUN...
NITROUSN
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I Live Here
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UPPER MICHIGAN, MARQUETTE COUN...
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Quote:
Quote:
First of all I would not trust what a part store shows as OEM for your truck. Verify the correct computer with your local dealer. 
Pretty sure he got the OEM part number off the current computer that he's pretty sure is original to the truck.
Right but he is going by an aftermarkets listing. I find lots of errors in the aftermarket world. That's why I suggested he verify what is correct for that model with his dealer.
For what its worth I have run manual on auto tbi trucks and the will run fine. Just not correct and small issues like speed control may not work and also could have emission compliance issues.
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