I had the same experience with some CRC straight GL4 oil. �Back of the bottle said it wouldn't hurt yellow metal but they too lied. �It wasn't in there long because I found a thread that talked about the misleading claims that different manufacturers make. �There was a slight amount of brass color, like Carlsjeep, but any is too much. �I'm back to the mineral oil
I've been watching this thread with great interest. �This particular post from 1oldracer caught my interest because, like him, I believed what it said on the back of the bottle.



I called the Technical Service number and spoke with a tech-rep. �He told me that part of their testing and manufacturing process requires the statements on the back of the bottle to be certified. �He assured me that yellow metals are safe in GL-4.
I asked if they make a GL-1 and he said that they do not. �He said that there isn't much call for it because it's only for farm equipment. �I thanked him kindly and didn't come away very "assured". �
I completed my restoration 5 years ago. �I wasn't aware of the yellow metal problem at the time and after the transmission overhaul I put GL-5 in it. �One year later I saw the gear oil looked like matalic gold paint. �I had to go into the tranny for other reasons and by this time, after installing new brass parts, I was aware and in good faith installed GL-4. �Last fall when Carl Darnell was here, we pulled my tranny to install a new pilot bushing. �We didn't drain the oil, but had to pull the top plate and shifter. �At that time we looked for the matalic color in the gear oil but didn't see any. �I'm going to be putting my Jeep back into service soon as the days are getting nice once again. �One of the things I'll do is check the gear oil for metalic contamination. �If there is any at all I will follow so many of you now to the GL-1.
I asked this question last month when Tim got us going on this same issue, "Why are we having to discover this problem by our experience? �Why hasn't someone like Carl Walck been on top of this for some time?