on my 1990 700R4 (code 0FUM), the various filters I purchased recently to complete my latest assembly don't fit, I tried several. and yes, I removed the old orange rubber sleeve out of the bore, which I now regrettably threw away. the new seal is too thin.

anyways, to make a long story short, I ended up having to remove the new ribbed orange rubber sleeve seal from the new filter, and use two o-rings instead. currently going with 17mm ID x 4.0mm thk. just have to be sure the o-ring doesn't roll over the filter tube flange when you're inserting it. it's a tight fit. use Vaseline on the o-rings, and a light coat on the bore ID where you're sticking it into.

and make sure your pan bottom is in close proximity to the filter bottom, you know, to keep the filter from falling out.

on my '90 trans, the bore ID where the seal seats is about 24.5mm (measurement obtained using a socket OD as a gage). the filter tube is 18mm. the orange rubber sleeve is about 2mm thk. it doesn't add up.

I couldn't Google-find much commentary on this, other than the sporadic report of an issue here and there on various forums, but no real discussion, and no solution. my trans can't be that unique, you know, 1 of 1. wow, should be really collectible, huh? JK.

on my previous 700R4 filter encounters, I didn't have this problem, I've done a few, spanning 20yrs. The ATSG manual does casually mention using 2 o-rings, but other than one sentence, no real details.

anyways, this is my contribution. FWIW. YMMV.

 

Try a filter for a 4l60

 

Might be a totally ordinary transmission, but an aftermarket pan.

 

I occasionally use the O-rings here because of what you describe. Two or three O-rings should work fine here.