Transmission quit going down hwy 1999 mountaineer

Check your transmission fluid to make sure it is at the correct level and that it is clean. It is possible that you may have a clogged filter, when was the last time the transmission was properly serviced with a fluid and filter change?

The radiator has a built in transmission cooler, unhooking the transmission lines would have let the system loose fluid, from the lines and the cooler. Make sure your transmission is full of fluid.

Mercury Mountaineer 1997 2001 Factory Service SHop repair manual download


to solve your problem visit this link

poor gas mileage with any vehicle is usually due to lack of maintenance.
options to try:
replace fuel filter
replace air filter
spark plugs
timing adjustment?
let me know if any of this helps

Check transmission fluid. If full then sounds like electrical or internal transmission problem. Any check engine lights on? If so get codes pulled from vehicle computer.

Deifintely have the converter checked. It may be partaily restricted and when seems to be working ok it may have dislodged a piece of the catalyst allow exhaust to flow freely again.

May have head gasket leak. If so will be loosing water, possibly quite slowly. At highway speeds cylinder pressure is higher and so gasket leak more likely. Means gasket damage or loose cylinder head. Can be checked by mechanic. (pressure test and cylinder head bolt tension test)
Less likely alternatives, the spark timing is too advanced or the fuel too poor.

Try changing the transmission fluid and transmission fluid filter. It is a fairly easy but kind of messy job. Just buy the new fluid and filter, Grab your metric socket set and go at it. NEVER WORK UNDERNEATH A HOT VEHICLE. You have to pull the transmission pan to do this job. When you break the gasket seal several quarts (liters) of transmission fluid will cascade down on you. Be ready for it. Don't forget that when it stops draining there is still a lot of fluid left in the pan. When you finish cleaning up the fluid clean the gunk out of the pan. Install the new filter and reinstall the pan with a new gasket. Do not over torque the pan or filter bolts. If you strip them out or break them off you will need professional help to repair it. Refill the transmission with fluid. It should take six or seven liters.

you could have accidentally overflowed the transmission fluid. That would cause problems

transfer case needs to be taken off and brought to a transmission specialist. I had the same problem with my 99 2500 diesel, and being a transmission specialist myself, i diagnosed that the shift forks and bearings and syncro's in my transfer case had failed and after figuring out how much each part would cost on my rebuild, it was cheaper to buy a brand new transfer case out of zumbrota transmission parts out of Minnesota. The transfer case costed me $995 dollars and my parts added up over $1,100 dollars.