A couple of years ago we had an '88 Suburban that we used for hauling the family around on trips. One sunday night we were about 80 miles from home when the transmission (THM 700-R4, 16 bolts) starting slipping and there was a plume of smoke following us. It was nip and tuck getting home but we made it by adding fluid and additive a couple of times. We weren't too happy about the prospect of spending $1000 or so on an exchange for an old car that had nearly 200K on it so we tried something else. We ordered a tranny pan from JC Whitney that had a drain plug and installed it and a new filter. Then we drove the car for a day or two and changed whatever fluid would drain maybe 3 more times and then the filter one more time. This cost 60 or 80 bucks and the time getting greasy but it worked. We got about another year out of that tranny when we sold the car that by then obviously needed a new transmission. The new owners bought one right away and we still see that old car around every so often. I know that this tactic would not always pull one out of the fire but it made a believer out of me for changing the fluid.