We were on vacation and was stuck in traffic. Once traffic cleared we picked up speed and stopped at a light. After that that’s when it happened. The Tahoe would shift into 2nd and just rev up. Changed to solenoids A and B also changed the filter in the transmission. Did the same thing had to have it towed home. I let it sit in the yard for a bit then replaced the transmission. Put atf in it but wasn’t enough. Added a bit more that day and drove it home. The next day it was raining so I didn’t mess with it. Then my fiancé drove the Tahoe and to Walmart and back and unloaded groceries. Went back outside to crank the car and drove it on the road and that’s when it did the same thing. So far I have changed throttle position sensor. 02 sensor. Cause it threw those codes. If anyone could help please let me know
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Welcome to Motor Vehicle Maintenance & Repair!– Pᴀᴜʟsᴛᴇʀ2 ♦Commented Jul 27, 2021 at 20:23
2 Answers
Is your car's transmission is a CVT? Maybe that isn't important but the problem seems to be that the vehicle is running in "Safe Mode". No shifting gear up further than 1st or 2nd and a max speed of 15 or 20 mph? Safe Mode might un-do itself and the vehicle runs ok for 45 minutes. But then Safe Mode returns at the next stop (red light or stop sign)... sound familiar?
My 2002 Nissan Primera CVT reports transmission errors on the dash display but not to the engine computer for OBD reading with a scan tool. The transmission has a speed sensor and the engine has a speed sensor. If one is broken the car goes into Safe Mode because they need to report the same speed.
So, ensure your all the car's computers are recognised by your diagnostics tool and report back with all eror codes.
You changed the transmission but the engine speed sensor may have been faulty...
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It’s unlikely to be limp mode if the engine revs but looses drive, more likely a clutch / transmission issue as pointed out by @Y’S Guy– Dan KCommented Aug 4, 2021 at 7:38
If it starts to rev up without matching speed increase, you certainly have slipping happening on your transmission somewhere. Seems unlikely it would be anything else.
I suspect you've either worn the clutch plates or the bands. I also suspect you'll have a hard time troubleshooting this and suggest getting a transmission technician involved in investigating this. Knowing if they are worn is hard if you've never seen the difference between new/worn.
In some cases the piston that shift the hydraulic fluid will wear out the housing and fluid will pass back lowering the internal pressure of the transmission, meaning the plates/gears will not hold - causing the exact issue you have. In almost all cases a full rebuild is necessary and in some cases its cheaper to purchase a rebuilt transmission than pay the labor.
