7.3L Power Stroke Engine and DrivetrainDiscussion of the 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.
Seems like every time I get back on this forum, I get confused with all of the advice (sometimes conflicting).
So, I need to change my transmission fluid tomorrow. About 237,000 miles on the original transmission, and the fluid hasn't been changed for a LONG time (don't ask because I couldn't tell you).
1) I read that if you haven't changed the fluid in a long time, that completely changing it out (flushing) would be bad because it would break loose varnish or something in the engine. So should I just drop the pan and drain the torque conv. and refill so that I'm not changing it all at once? Then do the same thing in maybe another 15K or so miles (or maybe do a complete flush at 15K or so miles)?
2) Temps here are now around freezing for highs. For a flush (doing it myself), will I be able to get the trans temp high enough (just by driving on the highway for a while to bring the temp up to normal) so that the fluid doesn't puke out when I do the flush? Not sure what the puking is, but it doesn't sound pleasant.
3) If I do the flush myself, does anyone have a picture of the actual line that I'll be hooking the clear hose to? I've seen the diagram on the FAQ flushing topic, but I can't tell by that which line it is. If you try to explain the line by where it comes from or it's purpose, you're going to lose me.
4) My first step was to search this forum for the answers to all of the questions I have, so I did try that route.
1) I read that if you haven't changed the fluid in a long time, that completely changing it out (flushing) would be bad because it would break loose varnish or something in the engine.
Nonsense. That may have been true when I was a kid 50 years ago, but it's not true today. Follow Mark K's procedure in the FAQ. Nothing is better than a complete flush of the tranny system with fresh ATF.
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2) Temps here are now around freezing for highs. For a flush (doing it myself), will I be able to get the trans temp high enough (just by driving on the highway for a while to bring the temp up to normal) so that the fluid doesn't puke out when I do the flush? Not sure what the puking is, but it doesn't sound pleasant.
If you can drive it at least 20 miles before you stop and do the ATF change, you should have no problem of the ATF coming out the wrong hole. If it does come out the wrong hole, it's because either your tranny cooler is stopped up or your cooler bypass valve is defective. In either case, you need to do some repair work to relpace the cooler or the valve before you continue with the ATF flush.
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3) If I do the flush myself, does anyone have a picture of the actual line that I'll be hooking the clear hose to? I've seen the diagram on the FAQ flushing topic, but I can't tell by that which line it is. If you try to explain the line by where it comes from or it's purpose, you're going to lose me.
If you can't find the cooler return line at the back of the tranny on the passenger's side of the tranny, then you should have someone else do the job. It's a 3/8th inch steel line coming from the front of the truck and going into the back of the tranny. There is a banjo connection where it goes into the back of the tranny, and the bypass line goes into that same banjo connection. But it's very easy to tell the bypass line that comes from the front of the tranny from the cooler return line that comes from the front of the truck.
Here is another flush procedure that is very close to or exactly like the one in the faq section & it has pictures for you! Tranny Flush 4R100 just ignore the dont use Mercon V as the fluid spec has changed for it and now it is compatable with the 4R100.
But I will have to agree with Smokey if you don't feel confident have it done somewhere. Most of use work on our trucks because we enjoy it and we know we do a better job than anyone else will do. A flush at a shop will cost you around $150 without a filter change, which you should really do if it has been awhile.
Good luck
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Last edited by woodnthings8 : 11-07-2009 at 01:21 AM.
Sounds like when I look under the truck tomorrow that the line will be obvious. I do what I can (changing alternators, lube, oil/filter changes, minor stuff) myself, but this is just something new for me and I don't want to screw it up.
I checked my trans temp guage (pre-turbo) at the end of my 25-mile trip home from work this evening and it read about 110. If you say that's warm enough, then I'll trust your judgement.
1) Should I use Mercon V or switch to Synthetic ATF?
Why not kill two birds with one stone? Mobil 1 ATF is both synthetic and MERCON V. But almost all brands of MERCON V will probably be at least semi-synthetic. That's why it costs more than cheap ATF.
If you tow more than a rowboat, then you should probably use synthetic. Synthetic ATF can take the heat of heavy towing without deteriorating.
Warning: Do not buy any brand of ATF that claims it "can be used" in anything that rquires MERCON V. Be certain it says it meets the specs for MERCON V, or maybe "approved by Ford". Several major brands of ATF now claim it "can be used" where MERCON V, Allison, or even MERCON SP are required. Baloney. Nothing can meet the MERCON V specs except MERCON V ATF. However, MERCON V can be used where MERCON is required, so it's okay if it says it can be used where MERCON or DEXRON III is required.
To be safe, stick with either Motorcraft or Mobil 1. Then you'll know you have the real MERCON V. I use Mobil 1, and last time I changed the ATF it cost me $6 per quart at Wal-Mart - or $120 for 20 quarts.
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2) For added filtration, should I add a Magnafine filter and/or a Remote External Filter?
My tranny has 137K and was rebuilt a 100K.
If your tranny was rebuilt by a Ford dealer, then you already have a Magnefine in-line filter. You should change that filter every time you change the ATF, or at 30,000 miles, whichever comes first. It should be in the "rubber" part of the cooler return line over the front axle. If you don't already have a Magnefine in-line filter, then the folks that rebuilt your tranny didn't follow Ford requirements.
You can get one at any Ford dealer. Or if you plan ahead you can save a buck and order the 3/8th inch size direct from Magnefine Filters--Online Order Form
Once I was under the truck, seeing which line to connect the hose to was obvious. I used a 1/2" ID hose with a hose clamp which worked fine. Just to make sure I got all of the old fluid out, I repeated the step where you add 6 qts and then pump it out (so I pumped fluid out 3 times instead of 2).
The only messy part was dropping the pan and replacing the filter.
I have a Chilton (i.e. cheapo...to change the fluid, it says to just drain the pan and then refill with 1/3 of what the capacity of the truck is ) book that says after you add the fluid and start the engine to not run the truck through all the gears. Since the instructions posted here say to run through all the gears as the fluid is being pumped, I hope that's ok. If anyone has any knowledge about this being good or bad, I'd be interested.
Thanks to all who answered my questions. Next time I can just get right to it.
Since the instructions posted here say to run through all the gears as the fluid is being pumped, I hope that's ok. If anyone has any knowledge about this being good or bad, I'd be interested.
The guy that wrote those procedures was a Ford tranny development engineer for many years. He has lots of experience using similar procedures to change the ATF in test vehicles out in the middle of Death Valley and similar places in the southwest, so he knows his stuff.
I've used those proceduresd three times myself, plus supervised a tranny shop that used those procedures to change my ATF two other times. The only time something other than those procedures were used on my 4R100 was when BTS rebuilt it at 112,000 miles.
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) book that says after you add the fluid and start the engine to not run the truck through all the gears. Since the instructions posted here say to run through all the gears as the fluid is being pumped, I hope that's ok. If anyone has any knowledge about this being good or bad, I'd be interested.
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