AWD Astro

[Happy Camper]

Finewine, Many many thanks!

I purchased a 2004 GMC Safari AWD 4 days ago. It has 180,000 km and shuddered real bad on low speed slow turns, but I only noticed AFTER buying it (oversight ... no slow speed tight turns during the test drive by me or my mechanic!). I thought I had been bamboozled by the used car dealer.

Your advice fixed the slow-speed-turn-shudder sound immediately. I proceeded with new Synthetic 75-90 in the front and rear differentials then flushed (2 litres), drove and replaced (another 2 litres) the transfer case with AutoTrak II. Cost: $60 worth of oil. The shuddering sound went from downright annoying to non-existent. Thank you, thank you, thank you!!

Happy Camper

[harryevan]

Originally Posted by SeaBuzz

Hi All, as Finewine stated. I changed all three rear, front, and tranfer case with 75/90 synthetic and all is well.

Confusion is setting in (on my part?) with all the recent posts
- is the same fluid used for the front and rear differentials as the transfer case?
- I went to NAPA for the ACDelco Auto-Trak II fluid - their docs recommend 2 1/2 quarts and, after all these years, the fluid has a different stock number.
- the minimum of five miles driving during the flush - is it better with more to a maximum of say between ten to fifty miles?
- any advantage to raising the front end to drain more, possibly, from the transfer case?

Also, as I read about the AWD on this site, I see there is a swap to a different, older S-10/S-15 TC that allows for selection and engagement between 2 HI, 4Lo and 4Hi. Is this recommended or just an option that leads to more maintenance or problems along the way? It would be nice to be able to select and stay in 4WD in some winter situations around here.

[Happy Camper]

HarryEvan,

My trusted mechanic insisted I use AutoTrak II in the transfer case and the Synthetic 75-90 in the front and rear differentials. I drove 10 miles between the flushes of the transfer case. The transfer case was drained with the van level. The shudder went away immediately and after 300 miles is still running smoothly.

Happy Camper

[harryevan]

Well I did the flush after an oil change, what came out had the color of dark engine oil with a slight red tinge to it. Put 2 Liters in, drove it for 10 miles, during which it ran smooth from the get go. Drained it and put 2.5 liters back in (as per NAPA's listing). Just amazing. My first Astro had the blue fluid in it when I checked it out, but I couldn't depend on the AWD to work. Thanks again, folks.