Transmission flush, yay or nay?

Searched and only found 1 thread regarding flushes and it was nay.

So I've neglected the transmission (auto) and the fluid is pretty burnt (multiple steep forest/desert roads, no aux trans cooler :doh. Jeep shifts fine, no slipping, 70k miles. Would it be better to get it completely flushed (including torque converter, etc) and swap the filter or just drop the pan for the next couple of oil changes? I'd like to to replace all the fluid if possible

Read multiple posts on this subject regarding other vehicles, and it's seemed pretty split evenly. One reason against it was since the fluids already burnt, stuff could get dislodged and damage the transmission.

And I'll be installing a cooler this time around.

No flush just drop pan

Smokinjoe said:

No flush just drop pan

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Agree drop the pan, do not flush.

2011 JKU 3.5 R.E. Longarm lift.

Elaborate a little on why you say not to flush.

when it's flushed the trans fluid is sucked out through the fill tube - doing this will also pull any debris in the bottom of the pan back up through the transmission fluid path. The bearings that control the transmission are very sensitive to debris and you don't want to risk getting one stuck.

Pulling the pan keeps all the debris in the bottom of the pan and everything comes out without passing up through the transmission - much better and safer way to make sure all the fluid is drained and debris doesn't get back into the trans.

Also, I believe Chrysler voids the warranty if they find the trans was flushed.

jeeeep said:

when it's flushed the trans fluid is sucked out through the fill tube - doing this will also pull any debris in the bottom of the pan back up through the transmission fluid path. The bearings that control the transmission are very sensitive to debris and you don't want to risk getting one stuck.

Pulling the pan keeps all the debris in the bottom of the pan and everything comes out without passing up through the transmission - much better and safer way to make sure all the fluid is drained and debris doesn't get back into the trans.

Also, I believe Chrysler voids the warranty if they find the trans was flushed.

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One of the shops I got a quote at uses the transmission line, is that any better?

jeeeep said:

when it's flushed the trans fluid is sucked out through the fill tube - doing this will also pull any debris in the bottom of the pan back up through the transmission fluid path. The bearings that control the transmission are very sensitive to debris and you don't want to risk getting one stuck.

Pulling the pan keeps all the debris in the bottom of the pan and everything comes out without passing up through the transmission - much better and safer way to make sure all the fluid is drained and debris doesn't get back into the trans.

Also, I believe Chrysler voids the warranty if they find the trans was flushed.

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Dealerships flush the transmissions all the time, in fact the service departments recommend it vs. dropping the pan and changing the filter. Even though the service booklet says to change the filter and oil at the service interval.:crazyeyes: My guess is that it's more cost effective and easier to do a flush vs. a pan drop. The dealership I've delt with is one that unhooks the tranny line and starts the engine and lets the tranny pump the old fluid out as you add new fluid till you have nothing but fresh fluid coming out.Which this is imo the most appropiate way to change out your fluid. I did mine at 60,000m and am at 110,000m right now with no issues. If you do this you should also drop the pan and change the filter. That way you have fresh fluid and filter. Now, if your tranny fluid is not burnt and still smells ok I would say just change the filter and add the 3-4 qts of oil you lose with a pan drop.

TRAUMAhead said:

One of the shops I got a quote at uses the transmission line, is that any better?

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Imo opinion this is better at draining a tranny than sucking. But in your case you may want the full treatment.

x2 - if they use the line and let the engine pump it out as they fill it until the fluid is clean then yes. I forget the machine T-???? that does this but it'll also extract the clean fluid from the pan and stores it so they can drop the pan, change the filter and put the fluid back in.

That's how I have mine done - 78000 miles and no issues - I should have differentiated between flushing and sucking but that subject could quickly deteriorate so I'll stop here.