I will have to agree that there were some problems wit the old blue box Athearn locomotives in the time period you mentioned. I was just starting to gather up locomotives as my ted lightly with a Teflon grease. layout only had a few feet of track down when I picked up an Athearn F-7 that was undecorated that I wanted to custom paint for the Northern Pacific. At the time there were no properly painted F units. Athearn's verstion was painted green.
WRONG
This is what I ended up with. Looked good but ran like crap at first. While working on the shell, the sintered iron wheels were replaced with nickle silver wheels from NWSL. The gear towers on the trucks were the next step. There was a lot of slop with the worm gear and this was taken care of with one tiny washer. The worm gear and the gears in the truck were then lubricated with a teflon grease and the trucks were hard wired to the motor instead of using the original strap. What a difference these changes made. Out of the box the locomotive was drawing over three quarters of an amp and after the work was done to it the amperage drew was about a tenth of an amp. None of these improvements cost much except for the new NS wheels. The performance was also improved dramatically. I also had a couple of geeps and an SW-7 that all got the same work over improving their performance also.
Then, Atlas brought out their lone of Alco locomotives. Game over. I was immediately hooked on the superior performance of the Atlas locomotives.
One thing that did still bug me with the improved Athearn units was the tendency that they had to pick up so much speed on down grades and losing so much speed on upgrades with a string of freight cars. The Atlas units did not do this. As an experiment, I picked up a can motor from NWSL and put it into the F-7 mainly because it was easier to remove the shell.
It was like day and night. With the can motors the Athearn locomotives ran almost on par with the Atlas locomotives, and at almost the exact same speeds. All of my remaining Athearn locomotives then got a motor transplant.
My main motivation for this was the speed changes on the grades. If you don't have any grades or if the speed changes don't bother you, taking a few minutes to tune up an Athearn blue box locomotive will gretly improve the locomotive.
Guess I'm just a bit too picky, but this F-7 has been running like a gem on my layout for over 25 years.
