Mid~late 70s, I had a disaster from Skil, 7.2v with batteries built in. Switched to Makita shortly thereafter and and stayed for years but today it is all TOTL DeWalt for cordless as my brother works for S/B&D so they turn out cheap for pro goods.
DeWalt DCD996 dril jumps to large power boost when bogged down. I have noticed it twice, once with 2.5"holesaw cutting hardwood and the other time it snapped .5"drill bit in two when it jammed enlarging a retainer pin hole in a trailer hitch ball mount. As the drill started to bog down there was...
There is always the old racer trick of putting the correct quantity of lube in a large zip lock bag, seal it and put it inside the diff case then bolt the cover on. When the gears turn, the bag tears and the diff is lubed.