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  #1  
Old 07-23-2009, 06:20 PM
cudachris cudachris is offline
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Default Need info on 42RE transmission

Hi,
just got a 42re for free, minus the computer module that controls it. Does anyone know where I can get some wiring diagrams, or any kind of info on this thing? Been searching the web but didnt dig up anything useful.
Thanks
Chris
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  #2  
Old 07-23-2009, 07:02 PM
Dr. Righteous Dr. Righteous is offline
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42RE was commonly used in Jeep Grand Chrokees behind the 4.0L 6cyl engine.
It is considered a lightweight.
What is your intended use.? It must be used with a TCM.
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  #3  
Old 07-24-2009, 12:17 AM
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ehostler ehostler is offline
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Correct, the 42RE is a bad choice. It is a light weight and has way too many electronics.
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  #4  
Old 07-24-2009, 11:06 AM
dgc333 dgc333 is offline
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There is no seperate control modules for this tranny it is controlled by the same module that runs the engine.
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  #5  
Old 07-24-2009, 01:00 PM
Dr. Righteous Dr. Righteous is offline
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Quote:
Originally Posted by dgc333 View Post
There is no seperate control modules for this tranny it is controlled by the same module that runs the engine.
Not 100% correct.

Depending on the year of the vehicle, and if it had OBD1 or OBD2.
OBD1 vehicles had a seperate TCM module. OBD2 vehicles, the TCM was intergrated into the ECM.
So, in the case of Jeeps,
'93-'95 had a TCM, '96 and up used the OBD2 ECM.
Either way, the tranny is unworkable unless it goes into a vehicle already "wired" for it.
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  #6  
Old 07-24-2009, 04:29 PM
cudachris cudachris is offline
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Thanks for your replies. I´m thinking of putting the 42re into my 318 66 dart LPG-only daily driver project. I guess I´ll get me a tcm and a harness and see what happens.
Chr
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  #7  
Old 07-24-2009, 05:15 PM
cudachris cudachris is offline
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I found a manual for the tranny which contains detailed information on the operation of the transmission and the computer. The computer uses signals from half a dozen sensors to influence govenor pressure by pulse-modulating the govenor pressure solenoid. Operation of the converter clutch and the overdrive unit is controlled by another two wires. A simple microprocessor and a couple of relais should be able to give me full control of shifts.
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  #8  
Old 07-24-2009, 05:43 PM
Dr. Righteous Dr. Righteous is offline
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Quote:
Originally Posted by cudachris View Post
Thanks for your replies. I´m thinking of putting the 42re into my 318 66 dart LPG-only daily driver project. I guess I´ll get me a tcm and a harness and see what happens.
Chris
Negative. Don't do it.
A 42RE will not hold up (for long) under the torque of a V8. This is a tranny intended for 6 cylinder engine
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  #9  
Old 07-24-2009, 06:56 PM
dodger1 dodger1 is offline
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Quote:
Originally Posted by Dr. Righteous View Post
Negative. Don't do it.
A 42RE will not hold up (for long) under the torque of a V8. This is a tranny intended for 6 cylinder engines.
Don't want to be too picky here, but I'd bet the 4.0 EFI Jeep made nearly as much torque as a stocker 318. I don't have the numbers, but I do remember the nice, torquey bottom end on the Jeeps. That said, I'd still rather put a 999, or 727 behind the 318 just for simplicity's sake. Then again, how much choice do you have in Dortmund?
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  #10  
Old 07-25-2009, 12:06 AM
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ehostler ehostler is offline
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As I recall, the transmission was a major failure point on those Jeeps. I've know several people that had premature failures of the 42RE.
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  #11  
Old 07-25-2009, 01:49 AM
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JVMopar JVMopar is offline
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I have to disagree with the durability of the 42re. Well mine is a 42RH (A500)same deal though just hydraulic controlled. And it's lived a long hard life. The dakota was bought new by my dad. 150,000 miles of stop and go traffic and towing (alot of the time overloaded). At 150,000 miles I got it. I was 22 years old and lead footed so it got abused even more. At 170,000 miles I got tired of the V6 and put in a 360. Then it really got abused. Towed a Sprit from Denver, CO to Minneapolis, MN, hauled scrap metal with it (3000lb loads in the box), pull my 18' car trailer, moving horses, etc. etc. etc. I It now has 215,000 miles on it and is retired from normal service. Although I do use it to haul diesel fuel for the farm. 200 gallons at a time (it's only 1500 lbs). The trans has never been out or apart. Heck still has the original seals. I changed the fluid every 25,000 miles. The only thing is around 100,000 miles the shifts started to get really long. It does flare between shifts but holds tight. But that's my only complaint.

So in a light car like a dart it should hold up just fine, but how to control is is another problem. A 42RH would be a easier swap.
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  #12  
Old 07-25-2009, 09:21 AM
dgc333 dgc333 is offline
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Quote:
Originally Posted by Dr. Righteous View Post
Not 100% correct.

Depending on the year of the vehicle, and if it had OBD1 or OBD2.
OBD1 vehicles had a seperate TCM module. OBD2 vehicles, the TCM was intergrated into the ECM.
So, in the case of Jeeps,
'93-'95 had a TCM, '96 and up used the OBD2 ECM.
Either way, the tranny is unworkable unless it goes into a vehicle already "wired" for it.
I didn't realize the 42RE was used pre OBD2, I thought those years it was an A500 or 42RH.
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  #13  
Old 07-25-2009, 05:06 PM
70AARCuda 70AARCuda is offline
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42rh were obd 1

h meaning hydraulic...
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  #14  
Old 07-25-2009, 06:54 PM
Dr. Righteous Dr. Righteous is offline
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Quote:
Originally Posted by ehostler View Post
As I recall, the transmission was a major failure point on those Jeeps. I've know several people that had premature failures of the 42RE.
The 42RE isn't a "lemon" transmission as so many have tagged it.
But I know first hand of a bad cooler circuit designed that caused them to run hot. The drain back valve in the cooler circuit was prone to clog. This also plagued the larger 46RH/RE but killed more of the 42REs because they were lighter weight trannys.
This and also the Dexron fluid fiasco caused many to die prematurely.
I have seen many live to 200K+ miles with no problems, but like with everything good maintenance makes it last. The transmission is overlooked by most people.
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  #15  
Old 07-25-2009, 06:56 PM
Dr. Righteous Dr. Righteous is offline
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Quote:
Originally Posted by 70AARCuda View Post
42rh were obd 1

h meaning hydraulic...
Negative. Not in Jeeps.
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  #16  
Old 07-25-2009, 10:40 PM
dodger1 dodger1 is offline
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The "rh" part of the model number indicated "r"ear wheel drive, "h"ydrauliclly controlled. The "e" basically indicated that the trans. was the same, except for the fact it was "e"lectronically controlled. Why would this nomenclature be different for Jeeps?
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  #17  
Old 07-26-2009, 12:06 AM
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JVMopar JVMopar is offline
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He's saying that OBD I Jeeps were RE's not RH's.
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  #18  
Old 07-26-2009, 11:46 AM
Dr. Righteous Dr. Righteous is offline
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Quote:
Originally Posted by JVMopar View Post
He's saying that OBD I Jeeps were RE's not RH's.
Correct.
The OBD1 trannys behind the v8s were RH. But for some reason they used REs behind the 6cyl engines.
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