transmission flush or service

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illregal82

Master Mechanic
Jul 4, 2006
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i heard that a flush can be bad for a transmission my girlfreind has a 03 regal ls with 80000 on it . i was told that a flush they use high pressure to flush it which can be bad . what exactly consists of a flush and a service which is better for the car ?
 
Well a "flush" at a dealership uses a machine that works like a dialasis mechine. You hook it up the the trans cooler lines that run to the radiator/trans cooler and then turn the vehicle on. After it gets good and hot then you turn it on and it removes the old fluid out of one line and pumps in the new throught the other. This way you get rid of 90% of the old trans fluid. I don't know how you could say it is bad for your transmission. You either have to do it that way or remove the trans pan and drain the fluid from the bottom; doing this leaves the torque converter full of fluid and defeats the point of replacing the old fluid. We use these mechines all the time at work, and I've never seen any problems.
 
New fluid thats not breaking down goes in, old burnt fluid and any moisture or debris comes out. Do it. Thats why dealerships advertise it. Its usually an easy sell because it does help.
 
It won't damage the transmission at all. The machines I've used work off the trans pump itself, so there is no "extra" high pressure being put into the trans.
A flush is when you tap into the cooling lines and replace the old fluid with new fluid. A service is when you drop the pan, replace the filter, replace the gasket , and top it off with about five quarts of new trans oil. Although sometimes it is suggested to reuse the old gasket if it is that rubber re-useable one.
On a car with 80k, if nothing has ever been done to the trans I would suggest both a flush and service be done. But then again it depeneds on what type of driving is being done. If there is a lot of stop and go city driving then definately do both.



Cj 8)
 
A popular repair shop here says it's always better to FLUSH the transmission, except if it hasn't received service in a very long time...like over a 100k, it's gonna go one of these days, the flush may actually aggravate it...removing all kinds of varnish that may get lodged in a bad spot.
 
Better to risk carbon build up/varnish getting lodged somewhere so it can get reflushed vs. an overhaul because the pistons were sticking due to that same varnish/carbon or poor quality burnt up fluid. I'll take my chances with a good flush.
 
I had this done with my 76 Monte thinking it was a good idea. DON'T DO IT! Trust me on this. I wasted $100 on that flush. After getting my car back, I left the dealership and got not even 1/4 of the way home before noticing the odor and smoke from burning transmission fluid. I turned around and took it back. The pan gasket was leaking real bad. They wouldn't fix it because they "didn't touch that area of the transmission." I would have had to pay for the basic transmission service if I wanted them to fix it. I drove it home, having to stop 1/2 way because I needed to add 3 quarts of fluid in the transmission. I ended up having to do the job all over again and spend even more money than I wanted.

Just do the basic service of the transmission. Trust me. I'm sure I'm not the only one that's had this happen to them.
 
Just FYI The people that have a bad experience with a transmission flush are generally flushing an abused/neglected transmission that has so much build up in it it breaks too much loose or flushes away the clutch fiber debris that the clutches had been using for "traction"... If it is in that bad of condition it needed to die anyway.
Just like using motor flush in a neglected engine will clog an oil pump screen.
 
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