With the BA10 there's no bronze in the case. The synchro rings are aluminum and the bearings are steel so you don't have to be concerned like with the AX5 and AX15 with GL5. Chrysler's updated spec. for the AX15 and AX5 is 10W30 motor oil because they didn't want an issue as a result of the synchros being made out of "yellow metals". With the old GL5 gear oils there were problems. You'll find that most if not all synthetic 75W90 gear oil is yellow metals safe as indicated on the bottle. Some owners use synthetic 10W30 motor oil. Having said that, I use synthetic 75W90 in my AX15 that is specifically "yellow metals safe". Since my AX15 shifts great with it I'm not going to motor oil (10W30), conventional or synthetic. I think you would get a better result using synthetic with either. It's your choice. This is additional info: http://wranglerspecs.weebly.com/yj-87-95.html
The only info. I see that isn't accurate is that the AX15 was used in YJ's starting with late 89 production with the 4.2.
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