Do I still have to do the "drain thru the hose" RFE technique?

[wjpatton]

Following the last transmission drain and filter replacement, I bought a PML pan from Geno's. Now that I have a transmission drain, can't I just pull the plug and start the engine to extract most of the fluid without having to do the 3/4 inch heater hose drain thing prior to dropping the pan? What, if anything, am I missing here? Thanks! TDR is the only way to go.



Mr. Bill

 

[cerberusiam]

Not if you want to do a fluid exchange. The fluid returned from the cooler doesn't go to the sump it goes right back to the pump, to flush it you want the cooler return to not dump back into the trans until it has flushed as much from the TC and lines as possible.

 

[wjpatton]

Thanks! I drained the pan, then disconnected the return (bottom) line and ran a hose from the return line to a large oil drain pan. Ran the engine in neutral for about 30-45 seconds, with no fluid visible. Do I need to run the engine longer?

 

[cerberusiam]

In order to get th erest out of the TC you will have to put the pan back on and fill the sump. Once it starts sucking air it won't pump any more out of the TC, it has to have a supply to flush the old fluid out.

 

[wjpatton]

Thanks! Now I know better! Drain through the hose first, THEN drain the pan. I just keep learning... .

 

[Bob V]

actually that would still leave old fluid in the TC and cooler. Drain, filter change, and refill. Then with the line disconnected start the truck and let a 2-3 quarts drain into the bucket, shut off the truck and refill the trans. Repeat this until fresh fluid comes out of the line. What you want to accomplish is flush out the old fluid with fresh fluid.
You do not need to get 100% of the old fluid out every time, but the more you get the better. it's about 17 quarts to completely change out the fluid with the stock pan.

 

[wjpatton]

Great info Bob, thanks. I got all the fluid out last time when I drained with the hose BEFORE dropping the stock pan. Obviously I wasn't thinking straight when I drained the new aftermarket pan first this time. But now I know how to drain the TC so I will proceed. Thanks again! TDR is worth its weight in gold.