Question about GMC Envoy
2006 Envoy - when transmission is in auto mode it jerks, it's like it is switching in and out of 4-wheel drive when you excelerate and when you are slowing down.
First go to the part store and have them check for codes on the computer. Check spark plug and wires. Hook up a timing light to each spark plug wire and see if the light skips. If so then change coil packs.
Posted on Jan 18, 2009
SOURCE: engine whinning
I had the same problem on my 2005 Envoy. Turned out to be the idler pulley bearing. It is just a pulley the belt rides on. The bearing in the pulley was what was making the high pitched whine. I replaced the bearing, and the noise went away.
Posted on Mar 07, 2009
Just to clarify, the "transmission" is not stuck in 4-Lo. It is the "transfer case" that is attached to the transmission that actually engages the 4-Hi and 4-Lo modes. To properly shift your vehicle into 4-Lo, you know that you have to shift the transmission into neutral and slow down to less than 5 mph. Once your vehicle slows down to this range, your can switch your transfer case into 4-Lo mode. Due to the inner workings of the transfer case, the actual shift into 4-Lo may take a few seconds to complete. This is normal and does not signify that there is an issue. All transfer cases that have 4-Lo mode will act this way regardless of the make or model. To make a long story short, to shift out of 4-Lo you must follow the same steps that you took to shift into 4-Lo, just in reverse order. Switch the transfer case to 4-Lo mode if it isn't already there. Slow down to less than 5 mph (your vehicle must be moving, though). Then, shift your car into 4-Hi or 2WD. Give your vehicle several seconds to complete the shift. The transfer case indicator light will flash until it is complete. When it does complete the shift into the new gear mode, you will most likely hear a "clunk" (the range sleeve inside the transfer case disengages from its mating spline) from under your car. Again, any transfer case with 4-Lo (regardless of make or model) will exhibit this same noise. This should help you get out of 4-Lo. It is good practice to shift your car into and out of 4-Lo at least a few times each year to keep all of the splines free of corrosion and build-up. Based on the age of your vehicle, your transfer case may also need a complete flush and some new transmission fluid. Hope this helps.
Posted on Mar 21, 2009
They are operated by vacuum. Check to make sure the vacuum lines are connected and not ripped or anything. If that checks out fine, remove the vacuum line from the hub and apply vacuum to the hub, if the hubs lock then the problem is in the vacuum line or switch.
Posted on May 09, 2009
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