My wife recently put our 2004 Envoy XL into park while it was still moving....
When she did it, you could hear a ticking noise. After it stopped it would not go forward, without first putting it into reverse, then it would go forward with no problems. Since that day, intermittently it will not go forward without first put it into reverse. You don't need to move the vechile, just shift into reverse. Any thoughts of what may be screwed up?
Thanks!

First and foremost go and get your transmission fluid changed as you may have alot of particles floating around. Get someone who will look at the bottom of the pan for particles and cut the trans. filter apart to see how much is in it. Hopefully this will help. Should cost around 100.00 dollars at a transmission shop. I do this myself for about 35 to 50 dollars, but you should have someone do it for you at least this time. Take it and drive it and if that doesn't help you are in for some big expense in transmission rebuilding.

For what its worth, my Father was a trans rebuilder. I used to help him in his shop from age 9 to 23 (he retired 4 years ago when my Mom got alzheimers but still rebuilds the occasional trans)

The 4L60E is a reliable unit for the most part but is old technology. I change my trans fluid and filter every 15,000 miles period. I installed an extra magnet in the pan. I have 118,000 miles on it and it still shifts out and goes into TC lockup like the day I bought it. An external transmission cooler is an excellent idea for the 4L60E - you will definately extend the life and performance with a cooler.

I have a wierd thing going on with my transmission on my 06' envoy. as it shifts from first to second it bumps itself as if the differential is loose or the u-joints are bad. i only have 22K on it. i was wondering if that can be a fluid issue as well. should i install a external cooler and a magnet on the bottom of the pan?

Starting with basics, have you checked the trans fluid level?

If thats ok, you might benefit from a PCM flash from the dealer. Im pretty sure I saw a TSB on this.

Other than that, my 2002 and many other years tend to do that when cold. We have all dubbed it the "bump shift". The 4L60E transmission has, unfortunately, always been ridiculed for shifting like a school bus.

I was wondering about that hard shift, I get it also when it is cold. I'm amazed that people will drive so far without changing their tranny fluid. Cheap fix changing the fluid.

Firstly you should check transmission fluid level.The transmission fluid is a slippery liquid that acts as a lubricant for all of the moving parts inside your transmission system. This fluid also serves as a coolant and a viscous fluid that transmits power from the engine to the transmission system.If you don't change the transmission fluid on schedule time , you'll be lubricating your transmission with metal shavings and other contaminants.So transmission fluid should be change at schedule time .



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