GM Tech, Heard of this???

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!!!

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?

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.

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?

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.

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?

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.

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!

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.

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!

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.

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:
[email protected]

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.

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!

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

http://autos.groups.yahoo.com/group/gmcenvoy/

see ya there!!

Hey chris, you change your rear diff oil yet? I did mine last week. What a difference!!!! No more vibration when I take off. When I drained the old oil out, it was nasty. the drain plug is magnetic and it was totally coated with gunk. Mine only has 20k on it. I hope that is just from "break in" normal wear. I guess we'll see.

Havent gotten around to it yet :( Did you order the fluid right from the company? whats the best way to get this stuff? How long did it take you to get it?

Hey chris, you change your rear diff oil yet? I did mine last week. What a difference!!!! No more vibration when I take off. When I drained the old oil out, it was nasty. the drain plug is magnetic and it was totally coated with gunk. Mine only has 20k on it. I hope that is just from "break in" normal wear. I guess we'll see.

Yup! Amsoil.com They have warehouses around the country. Only took a couple days and it was at my door.
XVG-QT is the part number you want, quantity of 2
It is their new Severe Gear Synthetic 75w-90 Gear Lube. That is it. Little over $20 with shipping. A must do!!!
Make sure you inspect your drain plug. it is magnetic and I will bet it is covered with junk!!!

So you did use the amsoil, eh? If you had good luck with amsoil (as opposed to royal purple) then I will take your word on it. Hey, i cant find the part number you mentioned on the website. I couldnt find "XVG" but i did find "SVG" is this the same thing?
SEVERE GEAR™ Synthetic Extreme Pressure (EP) 75W-90 Lubricant
Thats what it says is SVG and when I pulled the "application chart" on their website, this is what it recommended. I just want to make sure Im getting the same stuff you did. Check out the link and let me know if its the same stuff.
http://amsoil2.cpinternet.com/scripts/runisa.dll?amsoiloaf:index

Make sure you have some kind of bottle with a hose on it or squirter or something to get it up in the hole. Get under there you will see what i mean. I had an old bottle of gear lube that I keep for doing this.

would a clean turkey baster with a piece of aquarium hosing do ? :) thats what I have used in the past, lol. Hey, im trying to get ahold of my local amsoil dealer to see if they've got any. That way I can get this "did" today. Was yours really that bad?? where do you live anyways?

Cant seem to find a $*!# dealer in Michigan on the internet. The amsoil site is about as useless as tits on a bull when it comes to finding a dealer. I called my local parts stores, none of them carry the gear lube I need... getting irritated!

Order it direct from Amsoil.
http://www.amsoil.com/orderform.htm

Scroll down and use the 1 800 number. then use the part number I gave you.

Ah ah. My local amsoil independent dealer is meeting me at my work tomorrow at 3pm to sell me 3 quarts of the SVG-QT Extreme pressure synthetic 75-90 gear lube. The reason Im getting three, Im going to change my front axle too, might as well. I got it for $7.30 a quart from this guy and hes delivering it!! woo hoo. I will let you know what mine looks like coming out, I predict its going to be prettttyyyy ugly cos my binding in the rear end when taking off from a stop is getting more and more frequent and longer. I bet that fluid is toasted!!! By the way, the dealer told me there is no such thing as "XVG" he said there is only "SVG". Is that what you meant to type? I just want to make sure we are on the same page here. I bought 3 quarts of XVG-QT 75w-90 severe gear, extreme pressure gear lube with anti-slip additive in it.

Yup! that is it! Very cool. Sorry about the typo. Glad you got hooked up!!!! Did better than me. Let me know how your drain plug looked.

Well seeing that I was supposed to go out tonite (night before thanksgiving bar night) but since we are getting blasted here in michigan with snow, I changed the fluid and HOLY $*@( !!!! I cant believe the stuff that came out looked like dark brown paint and my magnetic plug was caked with fine metal particles. Took me a good few minutes to clean it off!!! I filled it back up, took the whole 2 quarts (all but about 3oz) it started to come back out the filler plug. Took it for a test drive to the parts store to get a new serpentine belt, didnt bind once! Actually was very smooth, I tested it out a few times in the snowy parking lot and it seems to be perfect now. Then I came home and replaced my belt - it was easy and only took me a whole 3 minutes, ok ok to be fair 2 1/2 minutes ;) I did make a funny mistake I wanted to tell you about... I had 1/2 a bottle of valvoline synpower fuel injection cleaner that I wanted to add to my 1/2 tank of gas (just to get the bottle off my shelf) so I grabbed the first bottle I saw and started to put it in my gas tank.. 2nd glance and it was Valvoline synpower synthetic power steering fluid!!! oopss!!!! only about 1/4 a cup got in to my gas tank, I felt like such a dumbass. I called my dealer here and spoke to a tech, he said it shouldnt pose any problems at all since its so thin. Whew. But at least my axle fluid is changed, I want to tackle my front axle and my transfer case (bought a bottle of the transfer case fluid for my 2000 Jimmy and discovered its the same part# for the envoy, its still sealed and in my cabinet). Have you changed your front axle fluid? Transfer case? The t-case looks easy, but I cant find the front axles plugs. Also, did you rear axle yoke seal look like it was slightly leaking? Mine was cruddy looking like it wasnt a fresh leak but has leaked at some point.

Man, that was a good one with the pwr steer fluid. You sure you didn't go to bar night first, then did that? HA! That is cool you got the fluid all changed. Hopefully the amsoil will handle the loads a little better. On your front transfer case, I don't know. I only have 2wd. But the goopy area you talking about, Mine was pretty clean. I have seen many though that did "weap" a little. No biggie.
Enjoy!!!

I just want to caution you all, gm uses a small pin to secure the pin that holds the spider gears in place, this bumping in the turns could be that pin loose in the pumpkin. if it is there will be a lot of big chuncks of metal in the oil. now this happened to me so pay attention, the pin finally breaks and slides out. now on gm's the pin holds the axels out against the side gears, which encloses a clip. if the pin is out the axels slide in in a curve and allows the clip to fall out. now the axle is no longer retained and it comes all the way out and passes you while your on the freeway. now you panic and hit the brakes, well i supose the calipers will hold in the axles but in 68 there wasn't any calipers to stop it. but in my case there were no brakes cause all the fluid went out with one squish of the peddle!

look for chuncks and clips

I have an '03 with a locking rear diff. It does exactly what you're describing.