As a matter of fact Bryan, it wasn't a nightmare - the T-Jets were very well engineered, which is why they were so successful at the time, and why they lasted so long! The gear train was very smooth running and friction losses minimal, given the setup. But it did make it hard to change the gear ratio!
The cars generally ran very smoothly right from the beginning, with just minimal maintenance, and it turned out they could be hopped up, which made them more fun, contributed to their longevity and led to the later versions, like the AFX, which actually continued to outperform for awhile cars like the TycoPro that should have been faster (conventional inline pinion-crown gear setup, chassis influence from 1/24 "pro" cars, etc.).
The one "weakness", although relative, was the skinny rear tires, and lesser traction, which explains why you find a lot of these cars with the rear wheel wells hacked out and bigger tires fitted. In fact, Aurora's own hop-up kit included a set of their truck tires... And AJ's came out with screw-on silicone wheels/tires at some point, which were very popular and highly effective.
Yes, the 1/48 set was called Super Model Motoring and it used a larger version of the T-jet - which was also used on the second version of A.C. Gilbert's 007 James Bond set, which had an Aston Martin and a Mustang in 1/48 scale.
PS: the multi-gear arrangement was not that unusual on HO cars, because of the limited space. While Tyco used worm gear drive, Atlas and Marx used a multiple gear train with an inline motor, because the motor was higher than the center line of the rear axle. I think Lionel used a worm gear as well.