To flush or not to flush

[Saved]

A while back I had my transmission rebuilt. I mostly use the vehicle to pull my boat and get it in and out of difficult places so as not to get stuck so there is not a lot of miles on the rebuild even though it has been 2.5 years since the rebuild. However it has been long enough in time to have the transmission serviced. I asked the place that rebuilt it to flush the transmission. They told me that they never flush a transmission because it can cause more problems then it fixes. All they do is drain it and replace the filter and refill.
That got me thinking and I did some research and there are others that say do not flush a transmission while some that say yes flush it then some others say only flush it if the fluid is still clean. Here is an article I found on it and each can decide for themselves. By the way I found out that some places are calling just draining the pan and replacing the filter a flush and charging for a flush so be aware.
Transmission Flushing

 

[Drcoffee]

Do not use a flush machine ever.

You can flush your own transmissin by letting the transmission pump out the fluid 2 quarts at a time. Here is a video and a thread I started about flushing my Sienna, but the principles still apply.

DIY flush

diy-transmission-flush-08-sienna-xle

 

[Saved]

Drcoffee, no disrespect, but the machines does not do anything any different then what you are describing. The transmission cooler lines are under the same amount of pressure as the machine. The machines do not power wash the inside of the transmission. They simply re-fill it. The problem is where the fluid is drained from if is by passes the filter or not and that the new fluid has the tendency to strip any tarnish or sludge from the torque converter and the valve body either clogging the system or leaving it with lose tolerances causing early failure down the road.

 

[Drcoffee]

It depends on the flushing machine. Some will force the fluid backwards through the transmission putting pressure on small valves and seals that can damage the inner workings. Other machines which bypass the pan filter may allow debri into the valves when they other wise wounldn't. If you are referring to a specific machine, post it up. But this should not be treated a general discussion on power flushing.

By the way, you dont have enough miles on your tansmission to worry about varnish anyway, so why would you worry about flushing yours? with that logic, you should change your motor oil either. Clean fluid is always a good idea. And anyone who says to leave old dirty oil in a machine is an idiot. Are you telling me that leaving dirty trans fluid, full of metallic bits and crap is better than clean fluid. If your fear is that clean fluid will ruin your transmission, then it's already ruined. No sir, power flushing with an external machine dislodges crud within the system and forces it backward into small passages. Its a bad idea to reverse fluid flow in a transmission even on a new transmission.

You will always be safe to use the internal pump to expell the old fluid and replace it with new clean fluid. If cleaning it ruins it, it was going to die anyway.

 

[GMZ]

That's why a drain and fill is the preferred course of action. The gradual introduction of new fluids slows the removal of sludge and varnish.

I can't imagine you have that much varnish on a 2 1/2 yr old rebuild. Maybe a 10 yr old neglected car but your transmission should be in decent shape and would benefit from a regimen of drain and fills maybe every 30k depending on the severity of usage.

 

[Dan.3]

You did some research but not enough research. This is a highly debated topic. What is for certian is that by performing drain and fills or by draining 1-2 quarts at a time with the motor running will not add any additional pressure.

Transmissions have been know to fail after being flushed by external machines. In some cases where the trans failed because of the the machine or if it was inevitable is unknown.

 

[brian2sun]

I did a DYI flush at 185k or so, and i really think it saved my tranny (with about 220k on it now). It shifted much better after i flushed it and has ever since. I was getting a lot of shudder before the flush and have never felt it again since.

I agree that machine flushes can be bad news, especially on high mileage trannies. There's a lot of horror stories out there.

Saved, there's no reason to flush yours since it was rebuilt not so long ago. You'd be better off just draining and refilling IMO. I personally wouldn't even drop the pan/change the filter if i were you. It's still basically new so it's not needed (or worth the hassle) at this mileage.

 

[KidVermicious]

Clear and yellow, let it mellow. Thick and bro... oh, we're not talking about that? Never mind then.