ZF 6spd oil change?

[sjd_sd]

My local (non-affiliated) shop suggested that I change my gear oil even though GM says its good for 200K. (my truck has 90K). They put 90W back in and now shifting from 2 to 3 is tough when cold and it makes a brutal grinding noise if its lugged with the clutch partially depressed. The shop is willing to change to the correct oil, so I'm hoping this gets cured. Has anyone experienced gear oil changes in the ZF? How frequently should it be done?

Thanks

[jackrabbit]

I changed mine at ~ 12K, along with all of the other fluids after seeing how the back end looked (lots of small metal filings in both front and back diffs).

I switched over to a synthetic equivalent to the ATF that was recommended from Amsoil. Same weight as the ATF I believe.

Surprised that they put in 90W. Once that is out, I think it (shifting) should return to normal.

[sjd_sd]

The mechanic was unable to find the recommended lubricant unless he orders a case, which will take 10 days. No local shops or even ZF distributers carry it. He's recommending using "Redline" synthetic transmission fluid, which he puts in Porsche's and the likes. Any thoughts on this?

[DmaxMaverick]

GM recommends Transynd synthetic ATF. Any good synthetic Dexron-III+ ATF should do well, including Redline, Mobil 1, Amsoil, etc.

Hard shifting? 90 wt. gear oil in place of ~10 wt. ATF....That'll do it! Tollerances designed for a light oil won't like that.

Keep your documentation for the mix-up. If your tranny fails prematurely, you may need it.

[sjd_sd]

putting in the Redline MTF has fixed the shifting problem. Unfortunately, the nasty grinding noise with the clutch partially depressed is still there. The mechanic thinks its the throw out bearing and that I need a new clutch. Any thoughts on this would be appreciated. I'm going to pose the question on the driveline forum as well.

[DmaxMaverick]

How many miles?

If less than 100K, it should still be under warranty. The clutch, and associated components, are covered by the 5 year/100K mile engine warranty. There have been a couple issues with the clutch, and TSB's to address them.

I'm moving this topic to the drivetrain forum.