Changing trans fluid and filter

You can drain the fluid from the torque convertor on your 99. At the bottom of the bell housing is an oval rubber plug. Take that out and you can see the torque convertor. Turn the engine with a breaker bar until the plug is at the bottom. I forget what size bolt head it is. Between dropping the pan and draining the TC, you will get just about all the fluid from the trannie. If you only drain the pan, you are only getting about 1/3 the fluid. They stopped putting the plug in the TC with the 02 model year. To change all the fluid after that you are kinda stuck with a flush type.

Thanks for the tip on locating the TC plug. I have wondered about the flush procedure. Some places are flushing without changing the filter. They say their machine senses the filter quality and flushes it backward to clean it. Flushing would have the advantage of exchanging all of the fluid including the cooler and lines but I'm not sure leaving the old filter in is the best thing.

Stephen N.

Well, to be sure you could do both. Drop the pan, replace the filter and drained fluid then have a flush done. You will use extra fluid, but if you want to make sure the filter is changed without the hassle of draining the TC, it might be worth it. TCs are slow to drain. On your truck, I assume you have the 4R70W transmission. You should use Mercon V fluid. If it currently has Mercon 3, make sure you drain it all and replace with the V. Don't mix them. My 04 can really only be flushed, although the pan can be dropped to change the filter.

Yes, it is a 4R70W. I believe the dipstick specifies Mercon V so I will go with that. I don't mind if it takes a while to drain, I can do it at work and just go into the office for a while and get stuff done while I wait. I think I'll just drain the system as best I can, clean the pan out and replace filter and fluid. Thanks again,

Stephen N.

I have never flushed a tranny in my life and I am not about to now. With a refresh and pan capacity and a new filter you are good to go unless fluid is badly contaminated and then you might consider a flush.

----------------- The SnoMan

None of the flush machines I have used ever flushed backwards- it's important to verify the direction of flow to perform the procedure correctly. In my dad's F-250, (and on most vehicles I maintain) I change the filter first, add new fluid then do the flush at least once, then after that I generally flush them only about once a year.