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GMC Transmission Problems

Why does a GMC transmission hesitate before shifting? Are there any tips that can make GMC transmission replacement easier? How often should GMC transmission fluid be changed? Is using aftermarket GMC transmission parts a good idea? GMC transmissions are complex pieces of equipment and it is important to have reliable and accurate information available before deciding on any repair actions. The guidance and answers of Experts will provide owners with the information they need.

Read below where Experts have answered a variety of questions pertaining to GMC transmission problems.

What is the procedure for replacing GMC transmission cooling lines on a 1998 Sierra?

The job can be done with normal hand tools. Both the transmission side and radiator side have quick connect fittings. The diagrams below illustrate the release procedure.

Replacing GMC Sierra transmission cooling lines.

GMC Sierra Transmission Cooling Line Release Procedure

Generally removing the clip from the transmission side is easier and done first. But because of the lack of space, it may be difficult to reach that end. If that should be the case, there is nothing wrong in unscrewing the fitting from the radiator end first.

What will prevent a 700R4 series GMC transmission from shifting into 4th gear?

The most common problems are a stuck throttle valve or a TV cable that requires adjustment. The TV cable is the lower cable attached to the carburetor. Push the silver tab and begin to move the inner cable housing out 1/8 of an inch at a time and check to see if it will shift into 4th gear. If this does not help, drive the vehicle and check to see if the shift from 1 to 2 is at a higher than normal speed – around 18 to 20 MPH. The shift from 2 to 3 will also probably be at above normal speed. This will indicate that the TV cable is sticking in the valve body. If the shifting is at the normal from 1 to 2 and 2 to 3 is at normal speed, then the transmission will probably require overhauling.

Are there any tips that will make replacing the GMC transmission on a 1997 Savana easier?

To start with, the Savana is one of the easiest vans to work with because of the good amount of room to work under it. That being said, the following tips should make the procedure easier.

  • Before the new transmission is installed, replace the front convertor seal, the rear tail seal and install a new filter and pan gasket.
  • When removing the cooler lines from the transmission, do not lose the small clips that hold the quick connect line to the transmission. They are easily misplaced and often difficult to replace.
  • Do not forget to remove the torque convertor bolts. This is often overlooked.
  • When unplugging the neutral switch on the driver’s side of the transmission the electrical plug may appear to be frozen into place and impossible to remove. Rather than replacing the switch and connectors, remove the 2 bolts securing the switch to the transmission and slide the switch and connectors off the selector shaft and keep them aside.
  • A safety tip is to ensure that the battery has been disconnected before beginning the job.

What could cause a GMC Yukon Denali to hesitate before shifting down and often kicks hard into a lower gear with no warning lights coming on?

Most shift timing issues on a GMC transmission are caused by a valve body binding intermittently or because of dirty GMC transmission fluid or sediment in the fluid causing the valves to stick. The best way to correct this is by using a flush machine to perform a transmission flush. A cleaner will be used to ensure that all the 11 quarts of fluid are flushed out and the same quantity of new fluid is added. Dropping the pan will result in only about half the old fluid draining out. Many GMC transmission problems common on this vehicle are due to calibration issues. Have a dealer program the computer with the latest calibrations to correct any issues. If neither of these actions removes the problem, the valve body may have to be removed and rebuilt.

How to remove the transmission pan with metal tabs to change the GMC transmission fluid on a 2001 Yukon?

The solution to this common problem is to tweak over the metal tab with a pry bar enough to slide the pan out. After the pan is replaced, the tab can be tweaked back into position.

Because of the complexity of the system, the causes of GMC transmission problems are often hard to diagnose and fix. When faced with such doubts, drivers should obtain information that will guide them to the right repairs. The insights and guidance of Experts is the best way to get what is needed.

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