2007 GMC Sierra 1500 4 Speeed transmission problem

[nevdane]

Driving in traffic, slowed and tapped brake for slow traffic, went to speed up and transmission had obviously shifted way down into lower gear, as I hit throttle, RPM's jumped to over 5 thoushand while moving about 35-40 mph. Pulled to side of road, manually shifted through all gear positions, took off, worked fine from then on. Any Ideas? 

Twice more this has happened only the transmission shifted into neutral, again shifting throught he gears made it go away EVERY time this happened, the Speedometer dropped to zero, so it must be some electrical probleme, SENSOR??? Took to GM Dealer for Air Bag Recall and told them the problem, they also checked codes, found nothing and did not seem to know what could cause the problem.

 

Edited December 5, 2021 by nevdane
Problem persists

[Jworks]

Does it have the trailering button on the gear shift handle?  Was that on?  Even if it was 5k rpms is a lot.  I've noticed in my 6 speed if the trailering option is turned on and in cruise and Im pulling the boat it will have a different feel as it downshifts when slowing.  But thats with the trailering button in ON.  But its never went down like you're talking about with 5krpms.  Was it going down a steep hill at the time?  Hope someone else can offer you more.

 

[richard wysong]

any codes? possible bad shift solenoid. I had my car do that because the shifter wasn't in the detent, it was in between 3rd and drive

[nevdane]

On 10/30/2021 at 10:06 AM, Jworks said:

Does it have the trailering button on the gear shift handle?  Was that on?  Even if it was 5k rpms is a lot.  I've noticed in my 6 speed if the trailering option is turned on and in cruise and Im pulling the boat it will have a different feel as it downshifts when slowing.  But thats with the trailering button in ON.  But its never went down like you're talking about with 5krpms.  Was it going down a steep hill at the time?  Hope someone else can offer you more.

 

Trailering button was not on, driving on flat ground, had driven about 30 miles before it happened. Auto shop drove it, said no codes. Beats me. Going to dealere nest week for Air bag recall, will ask them.  Thanks

[nevdane]

On 10/30/2021 at 10:09 AM, richard wysong said:

any codes? possible bad shift solenoid. I had my car do that because the shifter wasn't in the detent, it was in between 3rd and drive

Trailering button was not on, driving on flat ground, had driven about 30 miles before it happened. Auto shop drove it, said no codes. Beats me. Going to dealer nest week for Air bag recall, will ask them.  Thanks

[JimCost2014]

1 hour ago, nevdane said:

Trailering button was not on, driving on flat ground, had driven about 30 miles before it happened. Auto shop drove it, said no codes. Beats me. Going to dealer nest week for Air bag recall, will ask them.  Thanks

My 2008 would always downshift to 1st gear going around corners, then run very high on the revs until it shifted to 2nd.

Drove me crazy, especially when it was raining. 

4 speed with the 3.42 rear end.

[swathdiver]

On 10/30/2021 at 11:55 AM, nevdane said:

Driving in traffic, slowed and tapped brake for slow traffic, went to speed up and transmission had obviously shifted way down into lower gear, as I hit throttle, RPM's jumped to over 5 thoushand while moving about 35-40 mph. Pulled to side of road, manually shifted through all gear positions, took off, worked fine from then on. Any Ideas?

 

So when the motor went to 5K, did the transmission shift down to 1st?  If so, is normal.