can this be a transmission prob.....

i have a 2003 envoy xl slt at about 45-50 mph it starts a vibration if i dont let off the gas the abs & break light comes on if i do let off the gas the car shifts and the vibration stops and i can go on please help

Sounds like a tranny or torque converter lock up to me.

the ABS and brake light coming on suggests IMO, that its not a tranny problem. I would scan the computer and see what codes are there first, before deciding whats causing the problem. ABS shouldn't care what the tranny is doing

could be a TCS problem

thank you took the ol envoy to the dealer he suggested that 3rd gear in the tranny was going out and the vibration occored as it was trying to find 3rd can this cause a vibration (new tranny $2800.00)

thank you took the ol envoy to the dealer he suggested that 3rd gear in the tranny was going out and the vibration occored as it was trying to find 3rd can this cause a vibration (new tranny $2800.00)changed the fluid filter and had it flushed didnt help a whole lot abs & break lights are not comming on as much as they were before but the problem is still with me

the computer senses something wrong. Without knowing what it senses wrong, not much we can tell you

TCS means Traction Control System.

had the coads ran replaced arear wheel speed sensor still have the problem

like I said, sounds like TCS. ABS won't cause the engine to run funny. TCS will though

Take a look at the speed sensor...... It tells the computer how fast the car is going (obviously). The TCS will use the speed sensors to detect a slipping wheel and tell the computer to get it under control. They do this by (correct me if I'm wrong) cutting fuel to lower power output and pulsing the brakes (via ABS). You probably just need a new speed sensor (or maybe a wire broke internally and shorts out once you hit 45-50 mph). I don't think they're too hard to replace.

thank you for your responce it was a tranny problem getting a new tranny this week with an external cooler again thank you