Tranny Flush

[Ozarker]

Hey guys, what's the proper way to change auto-tranny fluid for an F-150 (or probably any automatic) ? $179.00

One shop said they would presurize the system and blow out the old, then in with the new. Another said no, they put in the new and the old is pumped out as the new goes in. $89.00

Which would you do?

[Buliwyf]

I haen't done an F150 tranny.

But my routine is to park the truck Friday. Drain it Saturday. Drop the pan and change the filter and gasket (if applicable). I'm not worried about whatever ATF is left in the torque convertor. If I am worried about really nasty old ATF. I'll just dump it again next Saturday if tha's the case.

All the fancy machines and pumps are useless. Just drain it like you would engine oil, the old fashioned way.

[Ozarker]

Kinda what I thought, I had the 89 buck job done at Jeffy Lube. The guy drained the oil cooler by itself and they pumped in the new and showed me the old, no metal or chunks there but it was really dark, no film or suds to it. I could tell a difference driving away, shifted quicker and maybe a little sooner, smoothly. Had the oil changed too, last change was 7/10, 1,215 miles ago when I got an air cleaner and had the new BFG T/As put on. A '99 with 72,520. Now, if I can get a bulb for the cab brake light, it'll be up to snuff.

[HenryJ]

I do all my transmission service work with a fluid exchanger. That method pumps out the old into a barrel as the new is returned to the transmission. This method is the best way to replace nearly 100% of the fluid.
I add a varnish breaker and warm everything up prior to the service. Then drain the pan and change the filter. After that refill the transmission and begin the fluid exchange. In my opinion, this is the best way to service the transmission. Be sure to use the correct fluid. Not all ATF is the same. Some can be friction modified to meet specifications required.

I have never heard of the "blow out the old" method, so I can not comment on it.

[dro805]

at work we usually "flush" all the import cars with the screen filter, and with the american trucks we do a "transmission service" usually the trans service we change the filter and top it off back to full and then we hook up a wynns trans flush machine to the trans cooler lines and flush the system,idk if that works but hope you get that idea

[RU55ELL]

Henry, are you a mechanic? How did you get your hands on your own exchanger?

[FellowTraveler]

I just warm up transmission open line from transmission to cooler add a clear hose put the hose into an empty bucket, then make ready replacement fluid, place funnel into transmission dipstick tube, start truck and fluid flows into bucket while I replace it at a good pace until fluid comes out the color of fluid I'm putting in.

[HenryJ]

Henry, are you a mechanic? How did you get your hands on your own exchanger?

Yep, "knuckle buster by day..."

The "Redneck tranny service" works too. That is described above. Poor man's fluid exchange

[Optimistic Paranoid]

A follow up related question:

Has Detroit switched over from petroleum based tranny fluid to synthetic tranny fluid?

If so, when? (I assume it is probably different years for the different companies.)

If not, and I wanted to switch over to something like, say, Mobil 1 Synthetic Tranny fluid, I need to get ALL of the old petroleum based fluid out, right?

The so called "Redneck Tranny Flush described above looks like it might leave some of the old fluid in the cooler.

Regards
John

[FellowTraveler]

The redneck aka; poor-mans way I use has always worked for me and it gets all the fluid changed out. I've always used synthetic fluids in drive-train and do all my PM, repairs, rebuilding except for transmission which I spend big $$$$ to do the way I want it. Have professionals analyze motor oil in my truck to know when to really change it out and not before!

On the cheap makes sense to me and I know I do it right most of the time and if perhaps I screw up I have only myself to blame.

Good motoring!