: 2 Trans oil purge questions...or more?



Quadrasteer
06-25-04, 03:12 PM
When I look in my '99 serv.manual it says that you need to reset the trans. adapts with a scan tool after oil and filter change(screen cleaning). True??
When you purge the fld. using the lines on the radiator, does it matter which line you use. I usually use the lower because it's easier. How important is it not to let the pump go dry? When I've done this before, sometimes the amount going in the funnel is not enough to keep up with the output and you get a howling noise. Is that bad? Also, is it still necessary to drop the pan after a purge?

BeelzeBob
06-25-04, 03:19 PM
The adapts will relearn or reset with driving anyway so I wouldn't worry about resetting them with a simple fluid change.

You can use either line to purge the old fluid. I doesn't hurt the pump to "run dry" for a few seconds at idle. I wouldn't press it and rev it up or anything but running dry intermittantly while purging the old fluid will not hurt anything.

Typically you would want to drop the pan to clean the screens/replace the filter...but...with a 4T80E there is no filter to replace in the bottom pan....just the screens to clean. If they have been cleaned at least once in the transmission's life I wouldn't worry about them. Usually, on a 4T80E it would be desireable to drop the pan to drain the side cover oil as well as the bottom pan but since you are planning on purging the fluid by disconnecting the trans cooler line I would think that dropping the bottom pan would be unnecessary if you have cleaned the screens at least once in the past.

JimD
06-25-04, 03:38 PM
.... When you purge the fld. using the lines on the radiator, does it matter which line you use. I usually use the lower because it's easier.....

I prefer to use the top line as it is less messy. The top line is the return to the transaxle and the plumbing will not be dripping all over everthing.

I was not able to find a short piece of the metal line with the quick disconnect type of flare, so the fitting screwed into the radiator is removed temporarily and a brass fitting installed and a piece of hose clamped onto that.

It's easier to do than describe.

Quadrasteer
06-25-04, 08:02 PM
Why do you need the brass fitting with a hose clamped on? Also if you use the upper line does the old fluid in the rad cooler and the return line get sucked or flow into the trans so that can be replaced with fresh fluid?

JimD
06-25-04, 09:02 PM
Why do you need the brass fitting with a hose clamped on? Also if you use the upper line does the old fluid in the rad cooler and the return line get sucked or flow into the trans so that can be replaced with fresh fluid?

The temporary fitting on the top radiator connection is only an adapter to allow me to connect a flex hose to direct the transaxle fluid from the radiator into a waste bucket.

The transaxle pump is pushing fluid through the radiator from bottom to top. This method will be a 99+% fluid exchange IF you pump out 13 or 14 quarts.