New to the forum so I thought I would post a very good link for anyone having problems with a ZJ's 42RE transmission.
I had searched around this forum for awhile and haven't seen the link. It is a document on sribd.com that is 130 pages long, covering pretty much everything you would need to know about the transmission and how to diagnose any problems. I have heard way to many stories of people getting ripped off by a mechanic, saying they need a complete rebuild. It's worth the time to read so you don't have to rely on a mechanic to tell you what's wrong. Read that, and you will be telling them exactly what needs fixed.
I am currently trying to diagnose fault code 21 given by the transmission control module (TCM), which means there's a fault in the Governor Pressure Solenoid Output. Symptoms being the all too common "limp mode", where the transmission drives in only 3rd gear, unless manually shifted into 2nd (reverse still works). Pretty much just going to run down the checklist in the article until I find the problem. I'm hoping it's just a bad electrical connection somewhere, or just needing to replace the governor solenoid/sensor.
Until then, waiting for sunrise and a day off work so I can fix this thing. Oh, and if you think that article in the link is worth saving, just click download, sign in with facebook, upload one of your documents to share, and boom..free 42RE troubleshooting guide (or you can pay 10 bucks for it if your too lazy to upload something).