Transmission Swap
#1
03-10-2009, 01:56 AM
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#2
03-10-2009, 07:06 AM
Straight out of the FSM: "The 42RE is a four speed fully automatic transmission with an electronic governor." "Fourth gear range is provided by the overdrive unit" ... you sure your O/D is enabled?
What year is it? 94-97 ... the O/D defeat button is on the dash. 98-01 is on the end of the shift lever.
What year is it? 94-97 ... the O/D defeat button is on the dash. 98-01 is on the end of the shift lever.
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03-11-2009, 12:55 AM
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03-11-2009, 01:05 AM
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#8
03-11-2009, 01:12 AM
I did some research and found this to be a relatively common request. I found this information and am pasting it verbatim ... not ALL of it will apply but there are some tasty bits that are good information:
"Dodge introduced the 4 speed automatic in late 1989. This was also the time that the cummins turbo was introduced, and second year for the 239/3.9L. (The 3.9L is a chopped version of the 318/5.2L, same bore and stroke minus 2 cylinders) There are 3 automatics that were around in this year forward. The first one was the A500 which was a basic 3 speed automatic from the A904/998/999 family of torqueflites. It had an overdrive unit bolted on and was controlled by the SMEC in the truck. The torque converter lockup with computerized control was introduced in 1988 for all 904/998/999 and 727 automatics and carried though to the overdrives. The second transmission was a basic 727 design with an overdrive and this was the A518. The third transmission was the A618 and saw use ONLY behind the cummins diesel engine.
The original 904/998/999 was the smallest automatic during this time before overdrives. The 904 family was designed to fit behind the slant 6, V-6 and some applications for the 318. There are 2 different bellhousings as a result of this. The 727 was found mostly behind the 318 and 360. All of the newer overdrives were 4 inches longer than the 727 so yes, a total of approximately 8 inches less drive shaft would be necessary.
You can certainly find an automatic overdrive and provided it matches the engine application, it will bolt up. The old SB automatics for the LA engines and magnums are the same bell housing and so the SB and V-6 overdrives will bolt to an engine that originally had a 3 speed automatic provided it is not the slant 6. Bellhousings for the slant were different. If you have a 360 then you need a 360 overdrive tranny versus the 318 or 239 overdrive because of engine balancing being different. The 239 and 318 were internally balanced and the 360 was externally so which tranny you use does matter if you are looking for a bolt and go type of installation.
Your truck is a 1990 model and has a computer to control engine functions and the torque converter lockup. Unfortunately you ended up with a model that used the A998/999 automatic and as far as I know, Dodge contrinued to make some of it's trucks (mostly vans) with the 3.9L with the option of a 3 or 4 speed automatic well into the late 90s and early 00's. Why I don't know, but this is the type you have. Your transmission was called the A998/999 depending on the internals it had and its intended use. Obviously, the 999 was a stronger unit but very similar. Name designation in 1992 went from A998/999 to 32RH. The first number in all of these new designations stood for the number of gears. 3 for 3 and 4 for 4. As far as I know, Dodge stopped the 904/727 designation in 1989 when the last of the M-body cars rolled off the line and the carbureted LA engines ceased to exist.
The overdrive trannsmissions you will want to look for are anything from 1989 to 1995 or 1996??, not sure. They are all the same transmission. In 1992, when the LA engine was dropped for the magnum engine, which was basically the same engine with some upgrades such as different valve covers and SMPI, they also dropped the A500, A518 and A618 name for the 42RH, 46RH, and 47RH automatic names. They are the same transmission. Anything newer will be designated 42RE, 46RE and 47RE. The difference between the two is the governing systems. The RH is hydraulically controlled and the RE is electronically controlled. You want the hydraulically controlled type. 618 and 47 series automatics will not work. The bellhousing is for the cummins only.
To hook up the electrical you will need to have switches for the lockup and the overdrive. Your original automatic lockup was controlled by the SMEC but since you are adding the overdrive you will need control of when the lockup occurs. To operate these functions, install switches on the dash from the grounds of these functions. When you want the extra gear active you throw the switch and this completes the circuit and activates the overdrive or lockup.
Shift sequence for the chrysler automatic overdrives is the following.
With OD disengaged: 1-2-3-converter lockup
With OD engaged: 1-2-3-OD(4)-converter lockup"
What I gather from this is that you can swap in any 42RH or 46RH. The 47RH will not work as these were for the CTD and V10 motors and will not bolt up. No 4XRE will work as your computer cant control them. You'll have to install an O/D Defeat switch which is a simple, two wire job. Your computer will already control TC lock-up as previously stated. You MAY have to nab the driveshaft and transmission mount from the donor vehicle to ensure everything is the proper length.
