02 Astro AWD transfer case fluid change advice

I am planning to replace the transfer case fluid with Auto-Trak II per the TSB and earlier threads on this forum. I am unfamiliar with this vehicle. Are there any gotchas? The Auto-Trak II comes in quart bottles. The dealer here quoted $11.78 per quart. Having not been under the vehicle yet, I can only imagine the clearances are limited. Is there any trick to pouring the fluid in the fill hole? An earlier poster mentioned getting a gadet from wal-mart to help him fill the transfer case.

Thank you in advance for any help you may offer.

Donny B

Welcome Aboard!

Actually, the oil is in one-liter bottles, but that's close enough. You will need two of them. You'll also need the tapered cap from a gear lube bottle, and about 18" of hose that fits that cap. Using the cap and the hose, you should be able to squeeze the oil from the bottle through the hose and into the transfer case.

It is also recommended thqat you use new drain and fill plugs, but if you are careful not to distort the originals, they can be used again. The housing is magnesium, so be careful to limit torque when the plugs are installed.

There is enuogh space to get the job done with nothing other than what's been listed.

http://72.19.213.157/files/TransferCasePlugsLg.jpg

THANKS! Blue Bowtie,

I had thought, from a previous post, that the Auto-Trak II came in liter bottles. But when I called the parts counter at the Chevrolet dealership and asked the counter person if they had any liters in stock and what the price was, he said it came in quarts not liters, and that the price was $11.78. The computer at the Advance Auto Parts store said the transfer case held 3.2 pints or 1.5 Liters. From your experience how much fluid does the transfer case hold? Was it wrong about the fluid quantity specification too? I bought the Astro used and have no manual to get specs from. Do you just fill the transfer case up to the fill hole?

Do you think the 5 mile transfer case warm up drive between the two fluid changes is long enough? The dealership said they have had better luck using a 30 mile drive to warm up the transfer case for removal of the possible contaminants spoke of in the TSB.

Again, thank you.

Presuming the transfer case is still a NPG136GM, if you drain it completely, 1.9L should refill it to the bottom of the fill hole - The proper level. Drive the vehicle BEFORE you drain the old oil to warm/thin it and enable it to flush out as much as possible. Draining it with the front of the vehicle elevated higher than the rear should help drain it faster and more thoroughly, but make sure the vehicle is level front-to-rear when refilling so the fill plug level is correct.

When I changed mine to AutoTrak II, it was during the regular change interval of 30,000 miles. It solve the minor "grabbing/chuggle" problem I was experiencing right away, without the flush procedure. It's been changed again at 60,000 miles, and is approaching another change at 90,000 miles. The second change likely rid the transfer case of any remnants of the original oil. If you're experiencing serious grabbing, you may want to follow the factory procedure of draining and filling it again after a short drive, or you may want to wait a few weeks (or even years) if the problems are solved with the first fill of the synthetic AutoTrak II. Having the mixed remains of the old mineral oil for a longer period shouldn't hurt anything.

I also went directly to synthetic gear oil in both axles at 10,000 miles to prevent any problems there. I'm a little strange that way, I suppose. I'd rather spend money on better (synthetic) lubricants than metal parts. Drain sample analysis doesn't lie.

Blue Bowtie,

Your informative replies have given me much confidence to tackle this procedure myself. Thank you. I had called two shops to have it done. One wanted $260.00, the other $118.00 plus fluid. Our family's budget is very tight, I couldn't afford that. I must do this myself.

I called another Chevrolet dealer's parts department. They also said Auto-Trak II is sold in quarts. But they wanted $6.60 per quart. I also asked for the drain and fill plugs to replace them as you suggested. They said they were the same. $7.00 a piece. But they only had one in stock. I will reuse the two old ones for the first change. I will then use the new one in the drain hole following the second fluid change. That way when the second plug comes in I can replace the fill plug without fluid loss.

I asked the parts counter person if he could tell me the torgue specs for the fill and drain plugs. He said it was in the owners manual. Which I don't have. Do you recall them?

Thanks,
Donny B

I don't recall the torque specification, but I believe it is cast right into the rear cover of the case.

http://www.wwdsltd.com/4L60/TransferCasePlugsLg.jpg

Hey Blue Bowtie,

Kudos to you!

I just got done doing the fluid change. You were absolutely correct, the fluid came in liter bottles. They look like quart bottles, so I guess that's why the parts persons at the dealerships that I spoke with confused the liter bottles as quart bottles.
file:///C:/Documents%20and%20Settings/Steve/My%20Documents/My%20Pictures/201209.jpg
Within 10 miles of driving, the shudder disappeared. Even the horrendous sound while performing the low speed sharp turns has vanished. I was sure, as badly as it sounded, that it would not have improved so drastically. I was thinking I would still have to replace a CV joint or two.

Donny B

Amazing, isn't it? It's like running a cone-clutch posi axle on plain gear oil, then squeezing in a tube of friction modifier and hearing all the moaning and groaning disappear.

Hello, I know this is an old thread but I hope that some one can help. I have an 2004 Astro AWD with 40,000 miles. I purchased this vehicle used at 20,000 mile. The last couple of days I noticed this thumping when accelerating from a stop and also sharp turns at very slow speeds. After finding all this info on the transfer cases I changed the fluid using the Auto-Trak II fluid. I believe that this was already used in this vehicle. After changing the fluid I noticed a big difference, a great deal of the thumping was instantly gone. I still have some left. Will this go away? Do I need to change the fluid again? Or do I have permanent damage? Any thoughts on this would be appreciated. Thank You.

Their exist a Technical Service Bulletin concering the transfer case fluid. It said after changing the fluid, to drive the vehilce for a minimum of 5 miles. To get the new fluid to normal operating temperature. Then change the fluid again. The TSB states that the vehicle may require 100 miles of driving before the condition is corrected. But perhaps you have more than one problem with your vehicle. Have you checked your idler arms? They are weak with this vehicle. My passenger side idler arm was about to fall off when I purchased my Astro used from a car dealer.

Hi, thanks for your reply. I just had the front end aligned and no mention of a bad idler arm. I thought this problem with the transfer case was solved by 2004. My manual even says to use the Auto-Trak II. The stuff that came out was green/blue. So should I change it again? Thanks.

I have a '95 AWD Astro. I found the best way to fill the transfer case is by improvising a funnel. I took about 3.5 feet of an old thin garden hoes. I securely duct taped the hose to the bottom of a plastic funnel. I fed the hose from behind the radiator top shroud, past the serpantine belt, past the lower pulley and into the transfer case filler hole. I already know (from reading the forum) the case will hold no more than 1.9 quarts so I just poured the first quart into the funnel from the top, then poured small amounts in and let them flow until the fill hole showed the case full. No fuss, no muss, no bumping knuckles! The first time I did it, I found the case had never been opened and what was left of the fluid was almost bone dry. It certainly made a big difference in the noise and rumbling!:rofl: 160.000 miles and still cruising!