07 Tahoe Transmission Problems - No Foward Drive

[mwalkertx320]

All,

I've got an 07 Tahoe (5.3L non-flex fuel) with 110k miles that tried to lay down on me today. Leaving the Truck Stop, I heard a lound bang, pop, something - I thought I had hit something or something hit me. I stopped, and looked, but didn't see anything. When I got back in, Drive wouldn't work, only reverse, so I reversed the mile or so back to the truck stop and played around and realized I had 1st, 2nd. I took off determined to drive the 200 miles back home in 2nd (I initially thought I was going to have to drive back home down I-10 in reverse). It seems I now have a manual transmission. Reverse works fine, and as long as I shift from 1, to 2nd, and then 3rd, and finally drive it works (manually shifting at around 2k RPM) no unusual sounds, smells, feels - however, passing gear seems to be broke. If I try to start out in Drive, or kick it in the a** to pass or pull a hill, it's like it is in neutral. If passing gear trys to kick in, it just readlines, backing off, will eventually catch drive and go. OnStar diagnostics are negative for anything Transmission related.

I'm thinking Sprag gear from what I'm reading online, but have been told by some friends that it might be the Selnoids? Anybody have any ideas? I'm hoping this is only a $1k repair.

BTW - My Check engine light has been on for 6+ months now, which is related (as reported by OnStar) to a Throttle Position Sensor, I haven't had any issues with this, other than the remote start doesn't work - could this cause the shifting problems? The dealer wanted $800 for the Throttle Body (you can't get just a sensor), and it just doesn't seem to be that big of an issue.

Thanks!

UPDATE: Looks like it was a Sprag Gear and I think they said a retainer pin from the reverse assembly chewed up a couple of clutches. They also changed the Torque Convertor since they said it contained clutches that would be in the same shape as the clutches in the transmission. All told, $2400 with a 24month/24k mile warrenty.

[Jimmiee]

Welcome to the Club!

Sounds like the input sprag went south. You are looking at a major repair here. Also your transmission relies on the TPS to set the shift points and pressures. So don't think your TPS problem had nothing to do with the failure because it did.

[Steve]

Yeah, sorry about that but the new fully modularized systems are all 100% interdependant to give the best performance/fuel economy and they shift the tranny depending on a number of factors coming out of the system ... I'm not sure what damage is done, but I'd have it looked at and not try to drive it as a "manual" transmission so you can get it fixed and back on the road.