Draining trans fluid

[Rattler]

Which of the two lines do I disconnect from the radiator to fully drain the trans fluid?

 

[Bob V]

http://www.dodgeownerforums.com/smf/index.php?topic=10199.0
I didn't do it exactly like this, I never let the pump run dry, and added new oil at the same time I was flushing out the old.

 

[gtoli]

If I understand you correctly Bob, you ran new fluid in until it came out clean, then dropped the pan and changed the filters.

 

[cerberusiam]

Which of the two lines do I disconnect from the radiator to fully drain the trans fluid?

IIRC, lower line is the return line.

 

[orhusky]

http://www.dodgeownerforums.com/smf/index.php?topic=10199.0
I didn't do it exactly like this, I never let the pump run dry, and added new oil at the same time I was flushing out the old.

How much fluid did you end up using doing it this way?

 

[Bob V]

I did pull the line and pumped a couple quarts out before I dropped the pan. Then I pulled the pan and changed the filters. Replace the pan and refill 5 or 6 quarts. I get 10 or so quarts ready to dump in and with the hose still attached and in a 5 gallon bucket have a helper start the truck. You might have to shift the trans to N to get better flow out the hose. Try to refill at the same rate as the flow out of the hose. Keep going till you have clean oil out the hose, or you run out of fluid. Reconnect the steel line and check fluid level.

 

[transe]

Some hopefully-helpful info:



There is no need to pump anything out of the cooler line before dropping the pan. The purpose of pumping oil out of the cooler line is to flush the converter. The pump picks up fluid from the sump (through the flat sump filter), then pumps it out to the hydraulic system (including the converter). When sitting in Park or Neutral, fluid from the converter is sent to the cooler. So if you pump oil out the cooler line (before dropping the pan), yes, you are pumping old oil out of the converter, but you are merely replacing it with more old oil, that the pump is pulling out of the pan. So the net effect is, you are just draining the pan through the cooler line (which, if you run it dry, is NOT a good thing). So just drop the pan first; you will accomplish the same result with no risk of damage. If you are adding oil through the filler tube (while pumping oil out the cooler line, BEFORE dropping the pan), then you are just mixing good oil with bad oil in the pan (kinda wasteful I think).



So drop the pan and change the filters first. Measure how much oil you drained out. Then reinstall the pan, fill it with the same amount of fresh fluid as you drained out (see below for more details), and THEN do the cooler line pump-out if you want to. You will then be feeding only good fresh oil into the converter. It doesn't matter which line you disconnect, or where you disconnect it. You just need to know which way the oil is flowing, so you know which side to plug, and which end to stick in your bucket. The oil gets pumped out of the upper line on the transmission, and comes back through the lower line on the trans. Always plug the "downstream" side when you do the disconnect, to prevent the pump from sucking air through the return line.



The converter holds two gallons of oil. If you let the trans drain (with the pan off, and the spin-on filter removed) for several hours, you can usually get half of the old oil in the converter to drain out (in which case, you should get about 11 quarts of old oil drained out, for a stock pan). Then, you should only need to pump out about a gallon of oil through the cooler line, in order to flush the converter. If you do a "quick change" on the pan (and don't allow time for the converter to drain out), you might have to pump out two gallons through the cooler line to get it flushed. Make sure you add the same amount of fresh oil to the trans as you pump out of the line.



You will ultimately use the SAME amount of fresh fluid either way; I just want you to be aware of how much you might need to pump out. If you let the converter drain down all the way (i. e you get 11 quarts out of the pan), then when you fire it up it will draw one gallon of oil out of the pan just to refill the converter (before you start getting any significant flow out the cooler line). It usually takes about 7 quarts to fill a stock pan, so if you fill it with 11 quarts (the amount you drained out), it will be WAY overfilled, but this will quickly disappear once the pump pulls out that gallon of oil to refill the converter (and you will then be OK on oil level). But if you had only dumped in 7 quarts, fired it up, and waited for oil to come out the cooler line, you would be down to only 3 quarts left in the pan (getting close to sucking air!) before the converter refilled.



So, bottom line: Add the same amount of oil back into the pan, as you drained out of the pan.

 

[gtoli]

Good info, Thanks.

 

[Bob V]

trans eng, this was the first time I did a "pre drain" of the pan using this method. I didnt drain enough that the pump ran dry- not even close. It did help with keeping the mess down when the pan was pulled.

I don't understand how the fluid FROM the cooler can get to the pump suction side. Does the port not go back to the sump?

Thanks

Bob V

 

[cerberusiam]

I don't understand how the fluid FROM the cooler can get to the pump suction side. Does the port not go back to the sump?

Not on the 6 speed autos. The cooler return fluid is routed thru the internal filter and back to the pump. It is a different setup than all previous units.

Ex: (transengineer)

 

[Bug Out]

Transengineer, is there any harm in putting on the deep aluminum finned MAG hytec pan on the 68 RFE?

 

[Cummins12V98]

Transengineer, is there any harm in putting on the deep aluminum finned MAG hytec pan on the 68 RFE?

30K and no issues here!

 

[Bug Out]

Cummins, did you see a drop in temps? I got both r/e and transmission pans before I checked the temps. neither needs them but if I sell them , I loose money. I figure WTH, go ahead and put them on. .

I have never seen the trans go over 205 and the r/e 185.

 

[transe]

Transengineer, is there any harm in putting on the deep aluminum finned MAG hytec pan on the 68 RFE?

No harm in using a deep pan (as long as you remember to leave the drain plug in, and don't drive over objects like boulders or tall stumps!). As you've already figured, it's not really necessary, but it shouldn't hurt anything.

 

[crispyboy]

This is probably a dumb question but is it necessary to do the full flush or can one just change the pan fluid (partial change) more often? Say every 30k or some other interval?

 

[transe]

This is probably a dumb question but is it necessary to do the full flush or can one just change the pan fluid (partial change) more often? Say every 30k or some other interval?

Not a dumb question at all! All that the normal maintenance schedule requires is a fluid and filter change (at 60K mile intervals for frequent trailer towing or other severe usage, at 120K intervals for "normal" usage). And the prescribed fluid change method is a simple pan drop (no flush).



Anything you do "over and above" that is OK. Changing more frequently is OK. Doing a full flush is OK. But neither is required.



Total quantity of oil in the trans, converter, cooler, and lines is about 17. 5 quarts. If you just do a quick pan drop (and don't let it sit so the converter can drain) you'll usually get about 7. 5 quarts out. If you let it set for several hours (with pan and spin-on filter removed), about half the oil in the converter should drain out also (another 4 quarts). I'm not sure whether the cooler and lines will normally drain out on their own or not (if so, that would give you another quart or so). So that lets you see how much of your fluid you are usually exchanging: 7. 5 quarts for a quick pan drop, 11. 5 quarts for a longer drain, and 17. 5 quarts for a full flush.



Be aware that the fluid you drain out isn't blatantly "bad" oil. So it's not like you need to replace it all (unless, of course, it's obviously burnt or contaminated). Usually, your old oil will still look as good as the new oil. ATF+4® is a premium-quality fluid with long life and good resistance to high temps. So just change it however often, and using whatever method, you're most comfortable with.

 

[crispyboy]

Thanks for the great explanation. I like the idea of of just dropping the pan and let it drip for awhile but do it a bit more often.

 

[walkerb]

This is probably a dumb question but is it necessary to do the full flush or can one just change the pan fluid (partial change) more often? Say every 30k or some other interval?

Thats what RAM suggests

 

[Rattler]

I finally got mine changed last Saturday. I didn't realize it had those quick connect type fittings on the trans lines. I didn't have the special tool to disconnect them, so I just pulled the pan and filters and let things drain for a while. It took right at 10 quarts to re-fill. I should be good for a while now. Thanks for the replies guys.

 

[JR]

Not a dumb question at all! All that the normal maintenance schedule requires is a fluid and filter change (at 60K mile intervals for frequent trailer towing or other severe usage, at 120K intervals for "normal" usage). And the prescribed fluid change method is a simple pan drop (no flush).

Anything you do "over and above" that is OK. Changing more frequently is OK. Doing a full flush is OK. But neither is required.

Total quantity of oil in the trans, converter, cooler, and lines is about 17. 5 quarts. If you just do a quick pan drop (and don't let it sit so the converter can drain) you'll usually get about 7. 5 quarts out. If you let it set for several hours (with pan and spin-on filter removed), about half the oil in the converter should drain out also (another 4 quarts). I'm not sure whether the cooler and lines will normally drain out on their own or not (if so, that would give you another quart or so). So that lets you see how much of your fluid you are usually exchanging: 7. 5 quarts for a quick pan drop, 11. 5 quarts for a longer drain, and 17. 5 quarts for a full flush.

Be aware that the fluid you drain out isn't blatantly "bad" oil. So it's not like you need to replace it all (unless, of course, it's obviously burnt or contaminated). Usually, your old oil will still look as good as the new oil. ATF+4® is a premium-quality fluid with long life and good resistance to high temps. So just change it however often, and using whatever method, you're most comfortable with.

Sorry for getting off topic, but I've been contemplating this for some time now. Why do the newer transmissions have such a longer service interval than the older 47/48RE? I'm guessing a lot of it has to do with today's fluids compared to what was available 15 yrs ago with my 47 but is there more to it? Since the ATF4 is all that is available is it safe to extend service intervals past 30k miles or does the internals or the design of the 47 still require the shorter service intervals?