2008 w/ 4L60E No Forward Gears - Reverse OK

My son's '08 Ext Cab 1500 with 130K Miles, 4.8L and 4L60E trans, failed as he was driving it to work a couple days ago.

I have not had time to go look at it yet, but he described the event to me as follows:

"Was driving to work about 9:30 am, first drive of the day, but it was very warm weather. About 5 blocks from home, slight uphill road, believe it was on the 2-3 shift, I think it had a quick little "shudder" and an immediate Bang or loud Clunk. Felt like it hit neutral. Coasted into a parking lot. Tried all gears. Reverse works. No forward gears are working."

He had it towed home. Said fluid level is fine, no metallic sparkles or burnt smell. Fluid and filter were replaced last Fall, about 7-8K miles ago.

With Reverse still functional, but none of the forward ranges working, this is not one of the common failure modes I am aware of with this trans.

Any advice or guidance on what to look for will be appreciated.
Guessing I will need to begin with a pressure test, then drop pan and look for clues, prepare to pull trans and rebuild.

Thanks, -Jim.

It's coming out, no short cut here.

could be a electrical problem... sudden failure no problems prior ..
GM has many wiring problems on these NEW GM trucks..2007 to now..

use GM drivetrain scan tool..
possible Sprag, Forward Clutch... I think it is now made in china ..

j_cAT, that was my initial thought as well, forward clutch/sprag failure.
Good advice on running a scan to possibly identify an electrical issue or other malfunction. Truck did not throw a MIL.
I went over and started it up, tried 1, 2, 3, D - All seemed just like neutral.
No unusual noises from trans. Reverse did engage.

Truck is a 2WD, any particular issues with R & R trans, or is it fairly straightforward?

Thanks guys.

No trouble codes showed up on the drivetrain scan.
My son and I removed his trans on Sunday.
Going to rebuild it, freshen up all the soft parts, probably put a new set of bushings in it while it's apart, and see what hard parts may need replacement. I ordered an overhaul master kit specifically for this vehicle, and a new sprag.
Kit showed up, and it says right on the label, it is for "1993-2003".
This truck is an '08. The P/N on it does match what they said I needed, but that label bothers me. I know these trannies underwent a bunch of design changes over the years, so I'm thinking I need to call and return the kit, and try to get the correct one, even if from another source? (Or do you fellas think maybe the label might just have incorrect info in it)?
Thanks for your replies, they are appreciated!
-Jim.

I know you've already got the trans out, (which is good) but I know from past experience the 4L60E is notorious for a failed second gear. When 2nd fails it goes into limp mode once it tries to shift to 2nd. The failure rate is ridiculous on the 4L60E and that is even in vehicles with engines like the 4.2 I6.

There is a guy semi local to me that rebuilds them on a constant basis and sells the rebuilt ones for $900 plus the core trans. He said he easily sells one a week, if not more.

My brother had a Trailblazer with around 88k miles on it when 2nd just went for no reason.