I've got an 08 H3 with 120k miles. Today I was driving down the highway just fine, went to pass someone and once the auto trans shifted down to pass it increased briefly then I just lost all forward gears. No sound that I heard, nothing just went from driving to acting like it's in neutral. I coasted to the side of the road and stopped. Tried restarting numerous times, tried sifting through all gears, tried shifting the tcase through all and nothing except reverse works fine.

A few months ago the rear driveshaft went and I had to replace it along with the diff u joint ajar shaft. Once I put the driveshaft and everything back together and went to pull out of the garage it wouldn't shift into gear at first, made a horrible sound a couple times, then went into reverse just fine and has been driving prefect ever since.

I have no codes, no warning lights. Haven't looked at the fluid yet since it was dark out but the tcase is brand new fluid.

 

Check fluid level, running at operating temperature.

 

Two options:
1) Get a BIG rear view mirror and drive backwards everywhere... cops will not like it; or,
2) have a rebuild done to your transmission.

Check the trans fluid on a level surface with the engine running at operating temp per above. Is it dark, smell burnt, too low????

 

I just got home (i actually did drive it home in reverse, it broke down on the side of the road about 5 miles from my house, had no issues) checked fluid and it's not low, it is on the red tinted black side so I know it's definitely in need of a fluid change.

 

First drop pan and inspect, probably to late for fluid change.

 

Agree, you may find a few unexpected items in your pan.

May be time to see the trans shop.