Is it necessary to change all the transmisson fluid or can you drain the pan and change the filter and refill to full. 2003 Ford 150, 4.6 engine. Type Mercon V transmisson fluid. A mechanic told me it was not necessary to change all the fluid. Another mechanic told it was necessary.
Thanks for any replys.

 

There are two schools of thought on this subject. One is drop the Pan which allows much of the fluid to drain out and for one to change the filter and clean the pan.

The other is a transmission flush, which changes all the fluid but does not allow for a filter change, for this process is through the cooler lines.

I personally would only drop the pan and drain that fluid and change the filter and clean the pan every 30,000-50,000 miles and not power-flush the tranny because I have heard rummors of this being harsh on the system. Also, drain and fill the transfer case at the same time if you have 4x4.

 

Well, its better to change it all. Whether it's "necessary" depends on how often you do it.

 

Thanks for the reply, I change the fluid every 30,000 miles. I went to one quick lube and they didn't have an adapter to connect the line to flush the system, they said they had been trying to get one. I went to another lube place and they told me it was not necessary to flush the system, just drain the pan and replace the filter. I called the Ford dealer. They said that because of the high detergent in the fluid, it should be flushed as just draining the fluid and refilling was not good enough to nenew the fluid. Just trying to save some money on those high dealer prices.

 

I have experienced two trans services where they "flushed" the system to renew trans fluid. Did not service the filter, or remove the pan. Both of these resulted in the filter being pushed off the mount and lying in the pan. Both were discovered while investigating unusal trans operation. This is just a way for "quick service" places to make money because they lack the ability to do a filter/fluid service. IMO.

 

Or find a place that will do it all. I just took mine in and for $133, I got the oil changed, and the tranny COMPLETELY drained, flushed out, new filter and fluid, (about 12 quarts if I remember right). Took them long enough but it was worth it to me. The truck hasn't shifted this smooth os this solid since I bought it.

 

I would go with billyBob69, flush and change filter. The filter can get clogged and all the flushing won't properly clean it. When I changed mine i didn't flush next time I will though.

 

I fail to see how the flush would change ALL (or even close) of the fluid. If the whole tranny were like a water hose I could understand. Instead, it's more like a few water hoses running through a couple buckets (reservoirs, just like the pan and tq. converter). The new fluid mixes with and "dilutes" the old fluid in the reservoirs, it doesn't just push it out. If memory serves correct, the flushing devices don't pump much more than the total capacity of the tranny, where as you would need many times that to get it to a point of non-issue (>95% new fluid).

Experiment time: I took 2 glasses each with 2 cup capacity when filled completely. Added equal amounts of food coloring to each (I used 8 drops of green each.) and mix w/ equal parts water (2 cups each, ie: to capacity). Using a measuring cup I removed 1 cup of the mixture from glass A, then filled it back up with 1 cup clean water (somewhat simulating a "remove the pan" fluid change). With glass B I somewhat slowly poured ( in different spots so as to "stir" it) 2 cups clean water into it ("flushing" it). The victor? Pretty close, with glass A having maybe slightly more dilution (less green). Though obviously slighly flawed (not taking into account cooler lines, mixing rate, eyeballing it,and such) it seems Method A (pan change) is twice (maybe more) efficient as the "flush" as far as the ratio of new fluid to dilution goes.

I forget, what is the total tranny capacity vs. amount needed to do a fluid change (when just dropping the pan)?

 

I beleive the book called for 16 Qt completely empty and when I changed the pan it took 4 to 5 quarts.

I am not sure how the flush actually worked i was under the impression it pushed all the old stuff out and replaced it with new including the tourqe converter.

 

Maybe it does, but I highly doubt it. It just doesn't seem possible/probable with my somewhat limited knowledge of how a tranny works/is designed. It seems as though it would have to mix given similar viscosity (though they'd be different, now that I think about it, if the old fluid is hot) in addition to the transmission pumping while the service is performed (I think it is anyway) & the "reservoir effect" demonstrated.

 

th 4W70 system holds about 13 quarts. the transmission pan holds about 5 quarts of that. i have always pulled the pan, changed the filter and added 5 quarts to the system. If you do that every 30-40,000 miles you get all the sediment out of the pan, new filter, and renewing 30% of the oil. that dont sound too bad to me. someone said on the 2001 and eariler there was a 1/8 pipe plug type drain in the bottom of the converter. i checked my 2001 and it is there. i did go back and pull the plug a month later to drain the 8 quarts out and see if it had any crud centrifuged out in it. suprisingly it looked very good. i just added 8 quarts back to the system, and will continue to change the filter and 5 quarts every couple years.

 

My tranny has the converter drain plug, and when I drop the pan, drain the converter, and remove the in-line filter (Ford accessory part), I refill with 13 qts. So I get almost all the fluid without paying for, or taking the risk of, flushing.

However, I do think that just dropping the pan at about 40K intervals is adequate. That's what I do on my other vehicles.

The filter in the pan is quite coarse; more of a strainer. Although I always replace it when in there, surprisingly, Ford does not require it.

 

Good deal, sounds like soemthing I need to do since I only drained my pan, I will do the converter this week end. You are correct if it only hold 13 quarts and 5 in pan and 8 in converter walla.
Thanks

Lance

 

Hey Team,

I just got my trans "flushed" this morning from my local Ford Dealer. By the time I got home, about 20 miles, the trans just didn't "feel" right. I also noticed that the trans downshifted very hard when I kicked in the passing gear. Does this sound like the filter was pushed off the mount? The dealer is really cool about these things and willing to do whatever it takes to make it right. Just trying to give them some ideas. The trans has about 40,000 miles on it since the last service.

Thanks for all your help and ideas,

TK

 

My father has 30 years of experience as an auto mechanic and he has always told me that changing the tranny fluid is a waste of time.
He has never replace the tranny fluid on any of the vehicles he has ever owned and has never had a tranny fail on him (has owned nothing but F-Series trucks since '78).
Octane