Quote:
Originally Posted by sclor
I have been reading how such oils may damage "yellow metals" in the tranny due to high sulphur content. The tranny that I installed didn't have a drain plug, so I am a bit hesitant to go through changing the fluid unless I have created a real problem for my synchros. No problems with shifting or performance with the gear oil, but I am a bit concerned that I could be harming it through this choice. Have you seen this discussion and do you have any advice?
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Yes, that story is true. GL5 lubricants contain sulphur-based extreme pressure additives which are harmful to some copper alloys. As you correctly concluded, that would include the brass synchro rings. They won't get eaten today or tomorrow, but it will happen eventually.
I have never seen a GM 3 speed + OD transmission that didn't have a drain plug, but if you have a SM318, I strongly suggest that you do whatever is necessary to get that GL5 out of there as soon as possible. The synchro rings in a SM318 are an integral part of the 2-3 shift sleeve (GM calls it a clutch) and that part is no longer available from GM. If you have a SM326 (Saginaw), that has the normal type of synchro rings and those are still available.
Ray