jeepinit23

I am looking for anywhere on the internet to find a used or refurbished transmission control module. Or if any one has one they are willing to part with that would be great and I will pay all cost. My part number is 56027218 and its for the 42re trans. Also if there is anywhere i might be able to send the tcm to get it rebuilt that info would be great as well. To answer any questions that might arise about my trans problem i have already replaced the tps and the speed sensor and changed the fluid and filter and adjusted the bands as well. It shifts erratically sometimes, not all the time and shifts at high rpms from 2 to 3 or if i let off the gas it shifts like normal before the rpms get to high. If anyone has any insight to any other possible sensors that could be replaced or any other fixes on anything to solve this pain in my *** problem, any help will be aprpreciated. thanks.

wingless

Welcome to the forum.

This ATSG 42RE Manual is well-written and complete. It is superior to the FSM and is a nice complement to that document.

97grand4.0

A refurbished TCM? Almost never the problem. Try a junkyard if you suspect yours is bad, but it probably isn't. Jeeps and 42re's are not a spectator sport. You did fluid filter and bands, but how about the governor pressure sensor, the rcm lockup solenoid and the shift solenoid, these get clogged up. I was able to cure 95% of mine just by taking the gov. sensor out and cleaning the screens with carb cleaner. Then it wouldnt downshift but cleaning up the lockup solenoid , more carb cleaner, and back in business worked like nothing. I did eventually replace them, but you need to do about 4 fluid filter changes and band adjustments too. Mind you its old, but mine has 200k on it ..daily driver.

jeepinit23

Thanks I will try that and see how it goes seeing as it is in worse condition all of a sudden today wont shift past second.

97grand4.0

Is your fluid low? Filter plugged up? There is a very specific way you check the fluid on these, in N, warmed up, and shift thru the gears first. Also only ATF +4 on these. But for sure you need to give the gov pressure sensor some attention as I say above. You can search many videos on this procedure.

jeepinit23

Changed all solenoids out and works better but the the Haynes book I have said to use Dex mercon for the 1993 what is the difference and would it hurt it at all

wingless

The correct fluid is ATF+4, as defined in TSB 21-010-06.

wingless

IMO, toss the Haynes book, get the correct Factory Service Manual and don't look back.

Again, the ATSG 42RE Manual is well-written and complete. It is superior to the FSM and is a nice complement to that document.

97grand4.0

^This.

Adjust the bands, fluid and filter changes, and drive it. BTW it's one pressure sensor, and two solenoids.

jeepinit23

Alright thanks. I'll have to get that manual. Driving it was dex Merc in it for a little bit won't hurt it though. Right. Or should I just swap it out tomorrow

jeepinit23

did all that got the transmission upgrade kit from cascade transmission

wingless

Per the linked TSB:

NOTE: ATF+4® must always be used in vehicles that were originally filled with ATF+4®. DO NOT USE ANY OTHER FLUID.

NOTE: ATF+4® is backward compatible with ATF+3 , ATF+2, and ATF+. Additionally, ATF+4 can be used to top off vehicles that used ATF+3, ATF+2, or ATF+.


The Dexron / Mercon is not supposed to be inside the transmission. Even after dropping the pan and after blowing out the external coolers, there is over a quart of fluid lingering within the torque converter, the passages and the cavities.

The appropriate remedy is to drain and blow out the lines. More fluid would be freed if removing the valve body.

Yes, I would suggest a drain / fill cycle, followed by another in the near future.

jeepinit23

Sounds good thanks for the info

jeepinit23

So now this happened. Drove ten miles down the road had to get to work and now it won't stay I gear at all and manually shifting it does nothing. It started off fine and then all of sudden nothing. Any suggestions on where to start looking for a cause of this problem. Just replaced solenoid and pressure sensors as stated above. Engine still runs and and stays running even when out of gear.

wingless

That's all very bad.

So now there is a no drive condition, in all forward and reverse gears.

If this repair will be performed by the OP, then there are diagnostic steps defined in the listed manuals. I would recommending getting both.

There are four pages of tests defined while the transmission is installed. Those include pressure measurements on the test ports, using two different high-pressure gauges with different ranges and long flexible hoses.

Armed with that information a rebuild / repair is implemented. Here is my 46RH Rebuild Topic. Clearly it is lots of work, many specialized tools are required, but following the instructions results in a properly working transmission.

Or, bring it to the shop for repair...