Transmission Flush, panacea or poison?

[Grif]

Did he give any thoughts about doing 2 complete flushes within a pretty short period...wouldn't that catch a lot of the particulate matter that will be loosened by the detergents?

I did not ask that, and though your suggestion sounds valid my impression was he was concerned the new fluid would have stronger concentrations of detergents and would break up any "varnishing" (ok we are getting into high temperature polymer science here) that has accumulated on the valves and gearing thus loosening the up tolerances inside causing even more problems in the near future.

Good question tho, and I'll ask him. Thanks!

To clarify, the particulates are not the only concern. Its the buildup of layers of varnish (very long string hydrocarbons formed under extreme temps) on the internal components. Once those layers are removed, everything would chatter around more.

[VXR]

I did a lot if research on this and decided not to do a flush (for some of the reasons you stated) but I did do a drain, refill and filter @ 30k with Mobil 1 ATF because I thought it may stand up to the heat better.

[VX KAT]

Sounds like a "flush" is different than a "drain & refill"...can somebody explain the difference to me? I had my tranny fluid changed at about 68k...I know he changed the filter and refilled it with Royal Purple Max ATF synth I picked up, then I had it done again about 2 months later. Is this considered a flush or drain/refill?

[Marlin]

For what its worth, I had a flush done on mine at the Isuzu dealership, tranny failed 3K miles later. Only took them 45 min to do the flush, and the truck was cold when they gave it back. That means they didn't follow the procedure, which says upon filling, it has to be running, and you shift through the gears and refill as you go along. Lesson learned, too bad the dealership closed up not long after Zu bailed on us.

[Grif]

Sounds like a "flush" is different than a "drain & refill"...can somebody explain the difference to me?

For the purposes of my original post I was using the terms pretty interchangeably, however some may consider the "backflush" procedure a flush as opposed to a drain and refill. The txmission guy didn't like either idea due to the issues described.

[VX1032]

nothing wrong with doing a drain and refill when there is no previous maintenace history. It won't hurt the tranny. The flush is better, but if you don't know the history don't do it. I flush mine but I have been doing that since I got it at 29K. It has been flushed 3 times and only havs 54k on it now, a little excessive, but I know the history.

With a flush you disconnect the trans line to the cooler, and hook it up to a michine that pushes the fluid under pressure through the entire system. AT that point you can see the change in tranny fluid in the machine as the fluid changes color from the black that it is to the red of the new fluid. Typically the flush takes a tad more fluid than the specs for the trans due to the overlap in fluid.

A drain and refill, is just that. You drain the fluid out of the trans and then refill it. All the fluid is not taken out because of the fluid in the lines and residual in the tranny. Since there is no pressure, the risk of taking anything out that has been varnished on is limited and you should not get the chunks floating around in the valve body.

You need to change the fluid on our trannys due to the breakdown of the fluid, escpcially with the heat our trannys can generate, and heat kills.

If the flush isn't done every 30K, I would never do one, drain and refills are fine.