On expressway traveling 65 to 70 mph continuously for 20 to 30 minutes. Suddenly, engine begins to stumble intensely and transmission down shifts to a much lower speed requiring me (if I'm lucky) to exit immediately. Also, check engine light energizes and begins flashing rapidly. Parked on the side of the road, with engine on or off, it recovers and I drive on to work as if nothing ever happened.

1) How's your fluid level?

2) When did you last replace your filter?

3) When it shifted, did it go trough all the gears as you accelerate or did it just stay on one gear and never shifted?

4) How's reverse, does it slip out too after 2 - 3 min?

5) As you first able to shift into gear, you can drive it for 2 to 3 mintues and it just suddenly slip out of gear?


.... could be a number of different things. Maybe even burnt out clutche(s) inside your transmission

it sounds like a transmission issue but it could be injectors how does it ilde or run without a load on the unit how does it shift are there any codes showing is your check engine lite on this gives a lot of information

takes a long time to run the rediness test since there are 6 different tests to complete...

PROCEDURE 1
EVAPORATIVE EMISSION SYSTEM LEAK MONITOR
Inspection Conditions
Engine coolant temperature: 30°C (75°F) or less (The engine is stopped before the test drive is started).
Atmospheric temperature: 5 - 30°C (41 - 113°F).
Condition of A/T: Selector lever D range.
Fuel remained in fuel tank: 30 - 50% is recommended.
Time required: 16 minutes or less after started the engine.
Drive cycle pattern: One trip monitor (from start to ignition switch to "LOCK" (OFF) position. Well be completed while traveling with the following drive cycle pattern.
Test Procedure
Engine: start.
Accelerate until the vehicle speed is 89 km/h (55 mph) or more.
While keeping the accelerator pedal opening degree constant, keep the vehicle speed at 89 km/h (55 mph) or more and travel for 16 minutes.
Return the vehicle to the shop, then turn the ignition switch to "LOCK" (OFF) position.

PROCEDURE 2
FUEL TRIM MONITOR
Drive Cycle Pattern
Inspection Conditions
Engine coolant temperature: 100°C (212°F) or less.
Atmospheric temperature: -10 - 60°C (14 - 140°F).
Condition of A/T: Selector lever D range.
Time required: 30 minutes or more.
Drive cycle pattern: One trip monitor (from start to ignition switch to "LOCK" (OFF) position). Will be completed while traveling with the following drive cycle pattern.
Test Procedure
Engine: start.
Accelerate until the vehicle speed is 89 km/h (55 mph) or more.
While keeping the accelerator pedal opening degree constant, keep the vehicle speed at 89 km/h (55 mph) or more and travel for 30 minutes.
Return the vehicle to the shop, then turn the ignition switch to "LOCK" (OFF) position

PROCEDURE 3
CATALYTIC CONVERTER MONITOR
Drive Cycle Pattern
Inspection Conditions
Atmospheric temperature: -10°C (14°F) or more.
Condition of A/T: Selector lever D range.
Engine coolant temperature: Not set.
Time required: 16 minutes or more.
Drive cycle pattern: One trip monitor (from start to ignition switch to "LOCK" (OFF) position). Will be completed while traveling with the following drive cycle pattern.
Test Procedure
Engine: start.
Accelerate until the vehicle speed is 89 km/h (55 mph) or more.
Travel for 300 seconds or more while keeping the vehicle speed at 89 km/h (55 mph) or more.
Decelerate until the vehicle speed is within 80 km/h (50 mph) or less.
While traveling at 56 - 80 km/h (35 - 50 mph) for 10 minutes or more, fully close the throttle at least once in 2 minutes and decelerate for 10 seconds or more.
Do not repeat deceleration too often.
Vehicle speed may go below 56 km/h (35 mph) after the deceleration.
Stopping and braking are permitted. (If stopped or drive at 56 km/h (35 mph) or less for more than 5 minutes the monitoring may be stopped. In this case please restart monitoring from the beginning.)
After completing the above deceleration, bring the vehicle speed back to 56 - 80 km/h (35 - 50 mph) and keep it in the range until starting the deceleration again.
Repeat the above deceleration at least 5 times.
Return the vehicle to the shop, then turn the ignition switch to "LOCK" (OFF) position

PROCEDURE 4
HEATED OXYGEN SENSOR MONITOR
Drive Cycle Pattern
Inspection Conditions
Engine coolant temperature: 100°C (212°F) or more.
Atmospheric temperature: -10°C - 60°C (14 - 140°F) or more.
Condition of A/T: Selector lever D range.
Time required: 16 minutes or more.
Drive cycle pattern: One trip monitor (from start to ignition switch to "LOCK" (OFF) position). Will be completed while traveling with the following drive cycle pattern.
Test Procedure
Engine: start.
Accelerate until the vehicle speed is 56 - 80 km/h (35 - 50 mph).
While keeping the accelerator pedal opening degree constant, keep the vehicle speed at 56 - 80 km/h (35 - 50 mph) and travel for 16 minutes or more.
Stopping and braking during this operation are permitted. Keep the accelerator opening degree constant for 1 minute or more after each acceleration.
Return the vehicle to the shop, then turn the ignition switch to "LOCK" (OFF) position

PROCEDURE 5
EXHAUST GAS RECIRCULATION (EGR) SYSTEM MONITOR
Drive Cycle Pattern
Inspection Conditions
Engine coolant temperature: 100°C (212°F) or less.
Atmospheric temperature: 5 - 60°C (41 - 140°F).
A/C switch: OFF.
Condition of A/T: Selector lever D range.
Time required: 16 minutes or more.
Drive cycle pattern: One trip monitor (from start to ignition switch to "LOCK" (OFF) position). Will be completed while traveling with the following drive cycle pattern.
Test Procedure
Engine: start.
Accelerate until the vehicle speed is 56 - 80 km/h (35 - 50 mph).
While traveling 16 minutes or more at 56 - 80 km/h (35 - 50 mph) with engine speed 2,000 r/min or above, fully close the throttle at decelerate for 5 seconds or more until the engine speed reaches 1,000 r/min or under.
Do not repeat deceleration too often.
Stopping and braking are permitted (Rapid deceleration and sharp steering are not permitted).
After completing the deceleration, bring the vehicle speed back to 56 - 80 km/h (35 - 50 mph) and keep it in the range until starting the deceleration again.
Repeat the above deceleration at least 8 times by fully closing the throttle valve.
Return the vehicle to the shop, then turn the ignition switch to "LOCK" (OFF) position

PROCEDURE 6
OTHER MONITOR (Main Components, Sensors & Switches, Wire Breakage & Short Circuit)
Drive Cycle Pattern
Inspection Conditions
Engine coolant temperature:
100°C (212°F) or less (Except engine coolant temperature sensor monitoring).
30°C (86°F) or less (Engine coolant temperature sensor monitoring).
Atmospheric temperature:
5°C (41°F) or more (Except engine coolant temperature sensor monitoring).
-10°C (14°F) or less (Engine coolant temperature sensor monitoring).
Condition of A/T: Selector lever D range.
Time required: 21 minutes or more.
Drive cycle pattern: One trip monitor (from start to ignition switch to "LOCK" (OFF) position). Will be completed while traveling with the following drive cycle pattern.
Test Procedure
Engine: start
Accelerate until the vehicle speed is 56 km/h (35 mph) or more.
While keeping the accelerator pedal opening degree constant, keep the vehicle speed at 56 km/h (35 mph) or more and travel for 16 minutes or more.
Return the vehicle to the shop.
After stopping the vehicle, continue idling for 5 minutes, and then turn the ignition switch to the "LOCK" (OFF) position. Moreover, the vehicle should be set to the following conditions for idling.
A/C switch: OFF
Lights and all accessories: OFF
Transmission: Neutral

might want to check your transmission

the reason it might be shifting so early is because of the gear ratio in the rear end of the truck. it is common in the 2 wheel drive basic model pickup because they were designed to work not travel.

I had the same problem, replacing you thermostat should do the trick, i spent 8.99 on a new thermostat and 99 cents on a seal. For some reason engine temperature affects the transmission shifting. Good luck

I too have that problem. I own a 2005 GMC Yukon. Shutters between 40 + 55 mph. I thought for sure the stumble I felt was a plug or coil pack because it only does it under a load. With A/C on the whole truck shakes! But it wasnt the plugs or coil packs. Answers anyone?

Try this relearn procedure hopefully it will help

Vehicles equipped with engine or transmission computers may require a relearn procedure after the vehicle battery is disconnected. Many vehicle computers memorize and store vehicle operation patterns for optimum driveability and performance. When the vehicle battery is disconnected, this memory is lost. The computer will use default data until new data from each key start is stored. As the computer memorizes vehicle operation for each new key start, driveability is restored. Vehicle computers may memorize vehicles operation patterns for 40 or more key starts. Customers often complain of driveability problems during the relearn stage because the vehicle acts differently then before being serviced. Depending on the type of vehicle and how it is equipped, the following complaints (driveability problems) may exist:

Harsh Or Poor Shift Quality
Rough Or Unstable Idle
Hesitation Or Stumble
Rich Or Lean Running
Poor Fuel Mileage

These symptoms and complaints should disappear after a number of drive cycles have been memorized. To reduce the possibility of complaints, after any service which requires battery power to be disconnected, vehicle should be road tested.

Vehicle Preparation

Ensure all components are connected. Ensure transmission fluid level is correct. Warm engine to normal operating temperature. If vehicle has been repaired, perform KOEO and Continuous Memory Code Self-Test and ensure fault codes are not present.

Computer Relearn Procedures

Idle Relearn Procedure

Place automatic transmission in Park or manual transmission in Neutral position. Ensure the emergency brake has been set and all accessories are turned off. Start engine and bring to normal operating temperature. Allow manual transmission vehicle to idle in Neutral for one minute. Allow automatic transmission to idle in Neutral for one minute and then to idle in Drive for one minute. Once initial relearn is complete, process will be completed during normal driving. Always complete the procedure before returning the vehicle to the customer.

Drive Cycle Test (AOD-E, AXOD & AXOD-E TRANSAXLES)

With transmission gear selector in Overdrive, moderately accelerate vehicle to 50 MPH for a minimum of 15 seconds. Transmission should be in 4th gear. While holding speed steady, lightly apply and release brake for about 5 seconds. Stop and park vehicle for a minimum of 20 seconds with transmission gear selector in Drive. Repeat procedure 5 times. Always complete the procedure before returning the vehicle to the customer.

Drive Cycle Test (E4OD)

With transmission gear selector in Drive, press Overdrive Cancel Switch (LED should light). Moderately accelerate vehicle to 40 MPH for a minimum of 15 seconds (30 seconds above 4000-ft. elevation) Transmission should be in 3rd gear. While holding speed steady, press Overdrive Cancel Switch (LED should go off) and accelerate from 40 MPH to 50 MPH. Transmission should shift from 3rd gear to 4th gear. Hold speed steady for 15 seconds. While holding speed steady, lightly apply and release brakes enough to turn brake lights on. Maintain 50 MPH for about 5 seconds. Stop vehicle for a minimum of 20 seconds with transmission gear selector in Drive. Repeat procedure 5 times. Always complete the procedure before returning the vehicle to the customer.

Hello, and thanks for choosing FixYa for assistance.

Before I would consider anything else, I would take your vehicle to a competant repair facility and get the automatic transmission fluid completely flushed. This may be all that your problem is.

one unit that operates ratio changes and is connected to the engine is that vacuum operated actuator on the transmission
it is possible that that unit is failing , vacuum hose is leaking and that will cause ratio changes as the vacuum varies
run the fault codes to check for wiring problems or VSS or TCM problems as well