GM Tech, Heard of this???

[b00001]

I have an '02 Envoy 2WD. Love it. I will be taking it in for some minor warranty stuff but this rather troubles me. Bare with me, it is hard to explain. Say I am running on the interstate and exit off the ramp and come to the light. I sit there waiting on the light to change so I can turn. the light changes and as I depress the accelerator, lightly, I FEEL something very odd a vibration as I just begin to move. It really feels like I am running over one of those rumble strips, you know before stop signs sometimes. I know it is nothing on the ground, it is something in the trans. or the rear end. Like the diff gets play in it on stopping then when you apply pressure to it the ring and pinion are meshing back together. Or something similar within the transmission, gears that are not quite exactly meshing for just a second, causing a vibrating feeling just for a sec. It lasts about 1 second then it is fine. It shifts fine, pulls fine and only does this on occasion.
Also (may or may not be related) Again on interstate cruising, It feels as if the trans "hiccups". It is like maybe the torque converter is engaging/disengaging. Say you crest a very very slight incline and you let off the gas just a little you can feel it. I seem to notice both of these things happening more and more now.
Any one felt either of these or had any corrective action for these symptoms??? Are there maybe TSB for either???
Thanks so much!!!

[Chriznat20@msn.com]

My 02 Envoy 4x4 with 65,000 miles does the SAME EXACT THING!!! I want to know what it is also, seeing that you have 2 wheel drive and I have 4. Does anybody know?

[b00001]

Hey chriznat-Look in your glove box on the glove box door there should be a big rectangle white sticker with a bunch of codes pretty much in alphabetical order. Look for "G80" in yours. I'll bet you have it. I have a pretty good repoire going at the edmunds site, under the envoy section. Check it out, I think we may have found at least what we have making the noise. Trying to figure out if they all do that or what. I am also trying to get with Amsoil to see if their new gear oil is compatible with our rear diffs. Went to GM yesterday and they wanted $26 per qt. HA! I laughed at them.

[Chriznat20@msn.com]

Oh, so you think it might be the rear axle? Geez, go figure. Hold on... I will go check right now for the G80 code. YUP sure does have it. Does that mean I have the locking rear axle? Is this going to cause a bigger problem in the future?

[b00001]

Nah, I dont think so. I think that is a GOOD thing. I am just trying to figure out if this is something that is common with this rear axle or if it is a pending problem or what. I am going to swap out my rear diff oil and see what that does. Have you always felt this or just recently or what? I only have 20k miles on mine.

[Chriznat20@msn.com]

LOL I bought mine with <gasp> 64,000 miles. It has done this since I got it last month. Not all the time, but usually after I get off the expressway, just like the other person. Even though the GM fluid is expensive ( i went to edmunds and read the posts over there), wont it still be better than the stuff I have in there? I cant get a GMPP warranty, instead the dealer (non gm dealer) gave me a "guardian" warranty but it doesnt look like they cover anything "in detail". So if I can change the fluid and prevent any problems, Im all game for it! Let me know how that synthetic fluid works for you. When are you planning on changing it?

[b00001]

I have to get with Amsoil's tech people to make sure there is not a problem or conflicts with GM's specifications. Then I will order it up. I am sure that you have the factory GM spec fluid in yours. No one ever changes that stuff. I am sure I have the GM Spec fluid in mine with this low of miles. I am thinking it may be somewhat contaminated from normal clutch wear and not giving us the optimum protection. We'll see. That is why I was asking the GM tech guy if he had ever heard of this.

[b00001]

Just got off the phone with Amsoil Tech. He pulled it up and said their Severe Gear Syn. Lube is approved for the Eaton Rear diff. Cool!

[Chriznat20@msn.com]

So how much is the amsoil gear lube? Am I still going to mix in an additive? How am I to be sure this is going to not screw things up? Just out of curiousity, I brought the Envoy to a local ring and pinion (axle) repair shop around here and let the owner drive it. He, as you will agree, told me its time to change the fluid, he felt the vibration from the ass end.

[b00001]

The Amsoil is like $9.25 a qt, you need 2. You do not need the additive with the Amsoil stuff. I called their tech dept. AGAIN, and spoke with a different person and he confirmed. I have heard of a couple people using the Royal Purple as well, but I have used Amsoil for years in many of my vehicles and have been pleased with performance. You will prob. have to order it direct from them though. No biggie, it will ship right to your door for LESS than one quart of the GM crap! HA!

[Chriznat20@msn.com]

Hey I just called Royal Purple also, sounds promising. I am going to my local Pep Boys and they will order it for me for the same price ($9.25) . You have changed the axle oil on your envoy/trailblazer? Was it hard? The only experience I have with changing axle oil was with my very first car... a 78 fairmont. Could never get the axle cover to seal up!!! leaked for the whole time I had the car. Let me know.

[b00001]

Easy, pull the plug on the bottom to drain, and there is a fill plug on the side to fill, fill to bottom of top plug. Let me know how yours works after the refill. e-mail me at:
b00001@juno.com

[Chriznat20@msn.com]

Get out!! the rear axle is that easy to do!??! thank god. Will it take the full two quarts? hey, are you on the gmcenvoy yahoo group too? if not you should check it out.

[b00001]

Yup, it is that easy. I think you can use a 3/8'' extension to remove the plugs.
i will check out the yahoo group. Been wondering if there were more groups out there.
thanks!

[b00001]

Hey, give me a link to the Yahoo thing you are talking about. I dont see it.