2009 Cadillac DTS

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#1
I have 96000 miles on this car and the owner's manual tells me it is time to change the transmission fluid. Should I just drop the pan, replace the filter, put it back together and add new fluid or should I do the above plus flush the torque converter/cooler? I am not having any trouble with the transmission at all but the manuals tells me it is time.
 

billr

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#2
My opinion? You may do more harm than good trying to flush it; just change the fluid and filter.
 
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#3
My opinion? You may do more harm than good trying to flush it; just change the fluid and filter.
But, if I only do a change and filter then I would be mixing this new oil with 5 plus qts. of old oil. That sounds wrong don’t you think???
 

billr

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#4
I don't think there is any definite "flow" through the converter, there is no effective way to flush it quickly. Old fluid is going to remain in there (the converter) unless you remove it and turn it hub-down to dump the fluid. Flushing the rest will require opening a couple of lines, with new chances for leaks. Any changes to normal flow, during the flushing, might disturb crud from where it is resting benignly and move it some place where it causes a problem. I think the safest flushing, if you insist, is to simply change fluid/filter again after a very short interval (a few weeks or so). That will give the new fluid a chance to "migrate" into the converter diluting the old fluid there and everywhere else where it remained. As I said, "my opinion"...
 
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#6
This topic has been "kicked around" for years and I happen to agree with Billr, especially since you have no problems, I would not want to interject a new problem. As they say, "if it ain't broke, don't fix it"
 

nickb2

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#7
And since I am the guy that kicks around a lot of shyte, I happen to agree with both bill and jack.

Billr said it the best, safer just to change a few liters at a time.

On these caddies, probably 13lt, only way to properly flush that is with a flushing machine, or do it by cooler lines. Either way, you run a risk. If fluid is nice, trans is not acting up, leave it alone as jack said.
 

nickb2

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#8
This is actually a very old debate. As a technician, I don't recommend flushes on these gm cars, they have good transmission. I get into it almost every day when a service guy sells a flush on these cars. I say why? He says we need to fill up the service bays. I say why again? If it is doing fine, lets sell the client on a 4 wheel brake lube job instead. These caddies suck large in that dept.
 

nickb2

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#9
Oh, and god forbid, a rear wheel bearing. Last time I did one of those on a caddy like this, I wanted to shoot myself in the head.

That took 8hrs to do. Wow. So basically, I would heed the advice, and leave it alone.

Keep you money for other things that will happen to this car. Such as an injector flsh, or a good rinse of the coolant system. Those things are fine to do as routine maintenance, but in the trans dept, as Jack said
As they say, "if it ain't broke, don't fix it"