s10xtremist

Thank ya!

s10xtremist

It turns out that trans shop I was referred to by my friend doesn't mess with automatics. They're actually more of a gear shop (manual trans, differentials, t-cases, etc). I've called a bunch of trans shops to find those more familiar with these transmissions. The ones that weren't pretty much just said something to the effect of "I've never heard of this 'governor pressure solenoid'. But, I know those trannys are junk and it needs an overhaul. How many miles are on it and what is it in?" The ones that are familiar with it pretty much asked first if I had upgraded the usual parts in the valve body. The two at the top of my list wanted details of how the magnet and fluid looked when I dropped the pan. Being one to document this sort of thing, I took a few key pics for later reference. I'm sweating at the thought of having to shell out 100s or even 1,000+ on this thing when the problem can be fixed in my garage with a few hours of my labor.

To recap everything from when I first bought the WJ until now:

Trans seemed to operate fine during intial test drive. After purchasing and reaching highway speeds for the first time on drive home, it wouldn't downshift when it should have and CEL came on. After stopping at mailbox at end of driveway, it was sluggish and felt like it was starting out in 2nd or 3rd gear. DTC was something like "governor pressure sensor voltage low". A bunch of random diagnostics happened (details on first page). Trans fluid and filter change was done as a PM. Borg Warner solenoid, new pressure sensor, and upgraded 3-4 spring were done as well. As expected, piece of snap ring was found in pan. Research on ring's size led me to believe the piece is from the overdrive unit. Downshifting problem was not resolved by the new parts in the valve body, but was after TPS replacement. Jeep drove fine for a few hundred (500-ish?) miles, mostly highway. On a recent trip to the grocery store, the same DTC came back and trans was starting out in a higher gear again. Trans shifted normally (CEL remained on) once Jeep was restarted after being parked for a few mins at the store.

So, the problem is intermittent. I'm told that the repeat/intermittent DTC is quite possibly from the "dirty" fluid that remained after the simple filter change (mostly that from the torque converter, etc.) has contaminated the new sensor ("transducer"). I'm wondering if I could just drop the pan again and clean the sensor and solenoid. I'd also replace the overdrive and lockup solenoids/wire harness assembly that I realized afterwards I could've/should've replaced while I was in there the first time. As for the broken snap ring, it looks like it'd just be a matter of removing the OD unit from the trans myself and bringing it to a shop for them to replace the snap ring. More labor on my part, but I have no problem removing a few nuts/bolts (no rust here) to save a couple hundred bucks.

Here's what I found in the pan-

I didn't think the stuff on the magnet looked too bad for the mileage, but I've only messed with GM transmissions:


Closer look:


Took this one to show the thickness of the buildup:


Idea of color of buildup on magnet:


Piece of snap ring. Measurements compared to online references lead me to believe it's from the OD unit:



Given the history and 110,000 miles on this thing, what are y'all's assessments?

dave1123

Most of that fine powder on the magnet is shavings from the driven clutch plates and the grey color is the drive clutch plate compound. I'd say normal for the mileage. there doesn't seem to be any big chunks from broken parts and only the snap ring. The fine non-magnetic debris can plug the ports in the sensors, though. I'd say replace the snap ring and do a good flush of everything else like the valve body and the converter. JMHO.

Most of my experience is also with the GM THM 350 and 700R4.

s10xtremist

That's very reassuring to hear!

How would I perform a "good" flush? I've heard that the flushing machines at the shops are really more of a gimmick, but I don't see how they could be with such a straightforward process. I've even heard that I can buy a crap load of trans fluid, remove the fluid cooler hose from the radiator and route it to a drain pan, then idle the motor in gear while I constantly pour new fluid in through the dipstick tube. This just sounds too easy to screw up either by over- or under-filling it through the tube. I also believe that I'd waste a LOT of costly ATF+4 because the change from old to new fluid would be so gradual that I'd never know when it was all replaced.

I'll be researching transmission flushing methods...

dave1123

When I worked at Valvoline, we had the T-Tech system which consisted of a clear plastic cylinder with a piston in it. We pumped 20 qts of fluid into the cylinder, pushing out the last guys fluid, then connected it to your cooling lines. The system used the pressure of your trans to push the new fluid into it, directly transferring 20 qts, which is more than the trans takes, however, because it was a direct transfer, the same amount of fluid the trans started with was replaced by new fluid. If the trans started 1 gt low, that's the way it was at the finish. The problem with this system is it didn't address the filter. If the filter was clogged before it was started, it was still clogged when the service was done. This service cost you $150. We did this for the store manager, but he dropped the the pan and changed the filter FIRST, added 4 qts of fluid before we did it. Because the piston sealed the chamber, there was never any intermixing of the old and new fluid. We were told this system was originally used at Ford dealerships. For some reason, Valvoline no longer does it. I think it has to do with time, labor costs and wasted fluid.

s10xtremist

I read that there were basically two types of flusher systems that shops used, and that was one of them. Apparently, the idea for these machines is to be able to thoroughly replace (Well, technically not 100%, but for the sake of argument...) the trans fluid without having to drop the pan. I'd rather see what's in the pan for diagnostics purposes. Also, that at-home method of adding new fluid while the trans pumps out the old fluid through a cooler line is way more common than I thought. Since watching a few YouTube vids, it doesn't look as sketchy as I had imagined it. I believe I'm gonna do it.

So, I'll drop the pan and replace the TCC and OD solenoid/wire harness assembly. I'll clean out the governor shift solenoid and pressure sensor. I practiced with the old parts yesterday to get an idea of how to go about doing so without damaging anything. If the newer fluid looks like it was contaminated much by the original fluid that remained, I'll replace the filter. I'll be sure to take comparison pics of the pan and magnet. Then I'll do that DIY flush and go from there.

Sound like a plan?

dave1123

Yeah, but you should know by now that the converter holds more than the pan, so don't expect to see clean fluid when you drain it.

When my THM 700R4 lunched it's converter, there were silver speckles throughout the trans, so I HAD to do a total rebuild. I got away with hand flushing the valve body and praying it was clean without pulling the spools and it worked. At least it worked for 2 years before I sold the truck.

s10xtremist

That's true. I'll just worry about excessive particles considering "half" (or less than half) of the original fluid has been replaced. I hope the magnet is relatively clean. I can promise that there will be pictures. Stay tuned...

dave1123

I think the total capacity on the 42re is 11 qts and the pan drain&refill is 4 qts. BIG difference.