A727TF Fluid

I am getting ready to change fluid and pan in my 70 SB tranny. I really don't have the proper tools to drain my Torque Converter. With the new Moroso pan, I believe my pan capacity will be 7 qts (+3 in the TC). Is it wise, or OK to add syntheic TF, to mix with non synthetic fluid?

Jack

there is no drain plug on the TC I am assuming?

Unless it's been changed, a '70 converter will have a drain plug. If no drain plug, it's permissible to mix synthetic fluid with non-synthetic.

If you want to replace the fluid in the converter, you can drain the pan, refill with a minimum amount of new ATF, run in neutral for a few minutes and then drain again. That will get the remaining fluid in the converter and the rest of the tranny diluted with flesh fluid to the point of insignificance. Unless you are dealing with contaminated fluid. Then, you can pull a line off the radiator and flush and flush that way until it comes out clean before you pull the pan.

Mixing different versions of the proper fluid is okay. Frankly, in a stockish application, there is no advantage to synthetic. Any ATF you buy today has a large amount of man-made materials (synthetic) in it. In a stockish application, synthetic vs petroleum based fluid is just a matter of percentages.

If you are planning to get as much fluid out of the converter (if not equipped with a drain plug) - when you drop the pan loosen the valve body. You will see plenty of fluid drain out from the TC then. The converter will now be half full.

Flushing the TC using the converter out (to cooler) method will not get nearly as much fluid out as loosening up the valve body due to fluid vortex within the converter when it is running. Fluid coming in is mixing with fluid within the converter before it leaves the converter.

(You can also stroke the front servo piston retainer with the valve body loose and force fluid out of the front servo this way).


This has been proven repeatedly at Chrysler (FCA).

It all just depends on how much work the OP wants to go to and how much of the previous fluid he wants to get out. Heck, if he pulls and disassembles the tranny, he will probably get even more out.

We have had the opportunity to flush a number of trannies over the years that had ingested water. And I can tell you from experience that if you drain the tranny through the cooler lines and then refill with fresh fluid and run for several minutes, then drain again, after a number of times you will get the tranny flushed to the point that you can then pull the pan and finish the job. Frankly, I don't know of a better or easier way to completely flush a tranny short of pulling it and disassembling it. You certainly will get more of the previous fluid out than you would by dropping the valve body. But to each his own.

Either way, all this is probably way overkill for what the OP wants to accomplish.

THANKS everyone. I think my question has been answered. No drain plug on TC. I am not completely sure the year of the tranny, it's in my Hot Rod. If the syntheic isn't going to help (run cooler), I probably might as well stick with "regular" fluid. Makes no sense to pay all that extra money if it doesnt't help the tranny to run a little cooler?
Again, THANKS.

Jack

Your first sentence - correct.

Second - wrong.

Third - agreed.

Tman
Yes or No OK to mix standard with synthetic fluid? Any advantage to "refill" with synthetic/standard mix?

Jack

I am not aware of any issues by mixing synthetic and non.

But don’t just believe me - a quick random search with Valvoline agrees, no issue mixing them.

You mentioned earlier that you were adding a deeper pan.
I would pop for the standard fluid and be done with it.

Transman may have been referring to paragraphs rather than sentences.

When you guys refer to standard or regular fluid
are you referring to dex-merc fluid??

I should have been more clear - standard in my book is non-synthetic, to keep costs down.

For all my high performance transmission jobs I use F.

For electronic Chrysler transmissions I use the original sped’d fluid which is mostly ATF + 4.

Yeah, what Tman said in his latest post, "F", like on my report card in High School.