Wrong type of any lube can shift badly. My experience has been for all around performance (cold and hot weather) the correct synthetic lube will out perform standard gear oil.

And as you now know the correct regular lube will outperform the wrong synthetic.

Glad you were able to improve your shifting. I'm curious what you used for an additive?

Kevin

87 Turbo Intercooled Raider, roller cam, torsen rear diff, LSD front diff, lockup auto with modified converter, V6 brakes, low transfer case gears...