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07 Forester X Transmission Vibration

('06-'08) 
2K views 3 replies 3 participants last post by  flstffxe 
#1 ·
I have a 2007 Forester X Automatic. It vibrates or shifts hard intermittently between either 1st and 2nd or 2nd and 3rd. It doesn't do it when I gun it and it doesn't seem to matter if the car is hot or cold. I had been reading on an outback forum people having the same problems with their outbacks and it quit doing it when they did a transmission flush. Now my question is could doing a transmission flush cause other problems? I've had the car since 40k and it has 94k on it right now. We haven't done a transmission flush on it. I was thinking about taking it into Jiffy Lube to have them do it. We usually do this kind of stuff ourselves but were going to trade the car in tomorrow and was kind of wanting the best we can get for it. Just worried they will give us less if it's doing this funny little vibrate thing. BTW it's been doing this for awhile and it's not caused any problems.
 
#3 · (Edited)
I have to disagree with the above sentament...

Sorry man, not tryin to be a jerk, but its a sketchy endevour...

The chances of moving a chunk of garbage from a place where its doing no harm, to a place it could do great harm, only goes up with age...

There's a 50/50 chance of problems, so i guess im only 50% disagreeing with you...lol

Sent from the other side using mind bullets...(YapaTalk)
 
#4 ·
You have exactly the same danger in doing a drain and fill. Flush machines don't do any cleaning, scrubbing so to speak, they are simply a way to replace volumes of fluid contaminated fluid with fresh. Really it is no different than some one who is doing multiple drain and fills. It is the fresh fluid that does the cleaning breaking up of settled debris, not the act of the flush machine.

A flush wont cause any problems that are not already there. If you have large quantities of debris that have settled and would create a problem if they broke loose from the detergents in fresh fluid, you already have a problem. That debris is wear material from friction surfaces.

From the link in my first reply.

Cooler line flush machine
The vast majority of what you see shops using are machines that are powered by the vehicles own transmission fluid pump. Most all of these machines require you to break into the transmission cooler lines to interrupt the flow of fluid in the circuit. Most of these machines are nothing more then a long 3-5" diameter glass cylinder(T-Tech brand) with a piston that travels inside and keeps new and old fluid separated and have a light duty pump to fill the machine from a bulk source(QT, gal, barrels). Also done via diaphragms.

The machine is filled with new fluid. It can either be drawn in via the internal pump in the machine or pumped in with a via a gun for shops that have bulk trans fluid on hand.

Once you break into the cooler lines. Typically done by unscrewing/un-clamping the cooler line fittings at the radiator or transmission cooler and connecting them to quick connect hoses that are used to connect to the transmission flush machine. A quick start of the car will have the pump in the transmission moving fluid into one of the hoses, a quick tech can connect the hoses to the machine at this time or the car can be shut down and the hoses connected.

Now that you are connected and moving fluid, what is happening?
The pump in the transmission pumps fluid as normal through the system and to the cooler. However you have spliced into it diverting the flow. The out going flow fills the bottom of this cylinder, pushing up on the piston. That piston drives the new fluid out into the cooler line that returns to the transmission. As far as the transmission is concerned nothing has changed, it pumped out 1qt it gets 1qt returned back.

This type of set up replaces exact amounts and puts no additional forces on the transmission. Essentially this is just a fancy drain and fill. The fluid may not be mixing on the flush machine side of things. However the new fluid being returned is just being deposited back into the transmission pan, to mix with the old existing fluid, diluting the ratio of old to new fluid. The same as doing consecutive drain and fills. You replace 100% of fluid by volume, but only about 85-90% of the old fluid is removed from the system.

Here is a video of a T-Tech brand which is pretty much industry standard due to the price of the machines and simplicity.
TT500 T-TECH Express Automatic Transmission Fluid Exchanger - YouTube

Pump inlet transmission flush machine
These typically require you to drop the pan and remove the filter. New fluid is supplied to the transmission via an attachment to the pump inlet(internal filter mount) and travels through the transmission. Upon returning to the would be pan the fluid is passed to a collection tank. New and old fluid do not mix in the pan like a cooler flush set up. For a 12-15 quart transmission it takes about 16-20 quarts of fluid for a finished job. Capacity of the trans to flush + capacity of the pan to refill on pan install. Though they would like you to think this replaces 100% of the fluid you still have a mixing point of new and old fluid, the torque converter. Still better then 2 mixing points, torque converter and pan. So you are likely getting 90-95%.

IMHO the reason many transmissions fail soon after being serviced(flush, drain and fill....) is that they are in bad shape to begin with. Generally people getting a transmission service are doing so because the transmission fluid is dark, burnt, or has debris in the fluid or they are trying to solve a physical symptom of a transmission problem VS keeping up on regular maintenance through out its life that may have prevented it. Much of that contamination is likely friction material suspended in the fluid. In severe cases you do the service, remove 85-95% of this suspended debris that was acting as a medium for power transfer between clutches. When the transmission fails completely within a short time it is perceived that the flush or service was the cause when in reality it is the act of having cleaner fluid. Kind of a double edge sword, it is the contaminated fluid causing further damage, but it is also what is keeping it going.

People who do drain and fills are typically doing them regularly or at least doing some thing once in a while to get fresh fluid in there before high wear levels occur.

I would have no reservations about doing a transmission flush on any thing I own. I keep up on maintenance. But why should I pay $XX to $XXX when I can do a few consecutive drain and fills and get the same result, or just keep up on it by doing a drain and fill every oil change or every other.

P.S.

Drain and fills have their advantages over a flush. You slowly add back fresh fluid(detergent) to the system to do some cleaning. Then repeat with another drain and fill removing the contaminants broken free from the previous. In the end you maintain a cleaner transmission because it is a continuous refresh cycle.

In a flush in one fell swoop you replace the bulk of the fluid at which point most go on their way thinking they are done. What about all the contaminants the new fluid is breaking free/cleaning up the old fluid left behind from when it began to wear out to the time you changed it. Are you going to do a second flush to get all this debris that is now suspended in the new fluid?

All the fluid changed out from a flush has gone through the pump inlet pick up screen, it is all filtered. When the vehicle is shut off some of the fluid in the system back flushes the screen and clears it allowing it to settle in the pan until next time. With a flush you never get this debris out, unless it is done using a pump inlet machine where the pan must be dropped.

In a drain and fill, you pull the plug and dump these contaminants out.
 
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