My 09 Tahoe hybrid 4x4 won't shift into gear (180k miles)... here's how it happened...

It had the occasional lurch or lag, but never had any trouble shifting between gears or between electric and ICE the past 6 years. A couple weeks ago when I was on my way home from Menards with about 1000lbs of concrete block in the back it was driving fine. I had to stop for a train & all was going well. The train passed and I pulled away normally & slowed for a turn about 100 yards past the tracks. After I rounded the corner, it suddenly didn't have power accelerating, but was still going about 45mph. I slowed to around 10mph and tried accelerating again but at this point it wouldn't go over 30mph (the cutoff point for all-electric).
I came to a complete stop and tried taking off again, but it was still electric-only and wouldn't engage the ICE. At this point I stopped, put it in park, and tried shifting back into Drive. I could hear the trans trying to shift (clunking), but it wouldn't complete the shift. I put the truck back into park and shifted to reverse instead. It successfully made it into reverse and I was able to back up (which is ICE), so I tried shifting it into Drive... again clunking & wouldn't engage.
Next I shut off the Tahoe, restarted and tried Drive again... clunking. Tried going to Reverse again & now it wouldn't even complete that shift (clunking) and would kill the engine after 5-10 seconds.
After getting it pulled off the road (with the shifter in neutral), I tried starting & shifting it to Reverse/Drive a number of times, but now it kills the motor almost immediately after I start it.

I've done a fair amount of work on manual transmissions, but this 2ML70 trans is a monster in its own category and out of my realm of expertise. After doing some research, I'm wondering if this could possibly be caused by the Auxillary/Electric transmission fluid pump going bad or is would this be something more severe like the primary transmission fluid pump or stripped gears in the trans?

Any help from people with experience working on these EVT transmissions would be appreciated.

 

I don't think you're going to get a lot of answers here. not many people work on these trannys and the board isn't very active byond the battery pack info.

the little I know is, the aux pump supplies transmission fluid pressure when in auto stop. if this pump doesn't work, I don't believe it will move at all when the engine is off, I believe tranny needs to engage a cluch to drive by the electric motor. I doubt that's you're problem, once the engine is running it turns off anyways and the mechanical pump takes over.
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the tranny doesn't officially have a Rev gear driven by the engine, the electric motors move the truck in reverse by engaging a cluch pack and spinning backwards. the early models did start the engine for more electrical power, the later ones will stay in auto stop until you need more power than the batteries have and then start.

I've seen it talked about where the engine isn't actually started, but the tranny spins the motor over so well for about 5 to 10 seconds that people think it's running. but it stops cranking as soon as move the shifter so it seems like it's running and dies out. just pop the hood and make sure the engine is actually running at this point. if you wanna to check, you could drop the tranny pan and see if there's metal chunk in there. if so, you'll know. if it's clean that might be good to know too. just be careful, 3 gals of tranny fluid comes out faster than expected haha. makes a hell of a mess if you're expecting the normal 3 to 4 qt.

i don't know what broke, but it seems internal to me. you can try asking over on the other tahoe based board under the hybrid section. a tranny repair guy is active over there but he's never done a hybrid tranny. very knowledgeable overall thou. he might have an idea.

at this point probably your best case is to look for a used one. they pop at market place and car-part.com sometime.

do you have a scanner to pull obd codes? these things have codes for everything. I'm guessing you have a ton stored. don't know if they will tell you anything useful besides its broken

 

I would like to have some infos from your journey of fixing that issue