Is there any difference between the gear boxes for MCI squirrel cage fans? MCI7, MCI8 or MCI9? I know there are different fans, but I can't find a post with that info. Thanks!!
Yes, one point is some boxes on their 3 outputs use larger style seals. I believe mainly some are bigger outside diameter, and can utilize a double lip seal as the National 470403, as opposed to the CR my covers use. Others on the site can describe better their experience in these boxes.
Floyd
Someone with parts manuals for these models could compare part numbers for each. Mainly case and shafts, although case may have been updated for larger seals. You could give Luke a call.
To follow up, I installed the gearbox from an MCI9 (6v92) into my MCI7 and everything is dimensionally the same. However, there are some design improvements. My old gearbox had a fill neck that filled near the bottom rear of the housing. It also never stood up, but would flop over to either side. The later design deleted it and put a fill directly into the top lid. On the old design there are two external oil lines to the sight gauge, and they leaked and rubbed. The new has a single (steel?) tube to the sight gauge. I re-used the original fans and squirrel cages, as I've never had a heat issue. I did keep the old fans and cages, in case of a future need.