I agree since you have over 100K miles and don't know how or when the transmission was service last by the previous owner/s, I would drop the pan get the filter and fluid changed ASAP. If your old transmission fluid smells burnt, you might want to follow with a transmission flush as soon as your budget will allow it.
Afterwards, I would get transmission flushed every 25K-30K miles.
For the life of me, I cannot understand why people think a transmission flush in a high mileage vehicle will result in transmission failure? My assumption is that the transmission was giving symptoms of failure and that's why they had the flush done in the first place and they want to blame the shops. I do know that some shops will not guarantee their work if the vehicle has high mileage and they have not done regular transmission flushes on that vehicle. The other possiblity is that the shop that did the flush used the wrong kind of transmission fluid for that vehicle?
A transmission flush just replaces about 98% of the old fluid in the transmission vs a drop-the-pan fluid change that only changes about 50% of the old fluid. The flush uses a machine connected in series with the cooling lines...as the transmission pumps out each quart of old fluid a quart of new fluid is put back into the transmission. This can be done using only the transmissions internal pump pressure and does not require the use of any external pumps. No solvents or other chemicals are needed or should be used.
Some shops will offer a more expensive flush where they first pump in some kind of cleaning solution they claim gets all the dirt out of your transmission ??? That's a bunch of BS and is not needed and may even be detrimental to the transmission. Even the Ford dealership where I worked offered this service for $269. When I questioned the Service Manager about that, he just smiled and shrugged his shoulders and said "That's what the boss wanted"
Also don't use any shop that says that they back-flush the transmission to clean the filter, or use an external pump to force fluid through the transmission...that's a bunch of BS too. It is impossible to push fluid through the transmission backwards and you don't want any abnormal pump pressures forced through your tranny.
...Rich
