Drop the pan before or after a trans flush?

[Lumberg]

I am going to do a home brew trans flush (kind where you disconnect the cooler hoses and refill as it's getting pumped out, a little at a time).

The pan gasket is leaking from the previous yahoos, so I'll have to replace that as well. I was thinking of dropping the pan before, cleaning it and the magnets off, and replacing the filter, so whatever crud gets washed off by the flush will have plenty of surface area to stick to. But then I might be dealing with a paritally saturated filter/magnets from the get-go. If I flush first, will I be overwhelming the capacity of the magnets/filter?

The car is a 2000 Camry with a V6 with 67k miles. I presume it's had one drain and fill at around 30k, and the tech overtorqued the pan bolts, causing the leak.

 

[JohnBrowning]

Flush first then drop the pan and change the filter and clean the pan. Reinstall pan and refill. THis will ensure that you do not drive debrigh into the clean filter!

 

[Lumberg]

Thanks bro.

Just for the record this is conventional stuff both already in there and what I'm flushing with.

I'll probably start flushing every 30k and dropping the pan every 60-90k.

 

[ekpolk]

Lumberg: Lurking no longer, I see!

to this forum. Great content as you've seen (and cooler smilies too...).

John: An interesting observation. I'd never thought of it that way. I'd always thought of doing the opposite on the theory that you'd have less contamination of the new fluid by the old filter by doing a pan drop/filter change first. How do you view the balance of those two potential "evils?"

 

[Pick]

From the many auto trans pans I have seen in the past, you always seem to have a lot of crap stuck to the pan, or settled in the pan. I would think that if you cleaned the pan and changed the filter, you would have little to no crap entering your new filter. That's my opinion.

 

[JohnBrowning]

When you change the pan any fluid in the pan will come out. Most of the debrigh in the pan is too large to pass through the filter so it is stuck in the pan. I would be more concerned with what is going to be flowing out of the converter. The material in the converter is not going to be big particle of friction material or gear material.

In the grand scheme of things it proably does not matter much. I think of it like flossing first then brushing. If you floss first then brush you get to brush away any crude that the floss freeed from beneath you gums. If you brush first and then floss the stuff you losen is sitting in your moth.

I belive that transmission shops that flush and change filter flush first then drop the pan then top off though.

THe important thing is that you are changeing your fluid witch is a huge steep in the right direction!!!!

 

[Matt_S]

On the Cartalk board, there's a transmission guy who really knows his stuff. He's adimate that you need to drop the pan first. There are two reasons. The most important one is so that you can inspect the pan contents. If you flush first, you might be pulling wear items into the filter, where they won't be noticed. Then you might not be able to spot a problem in the early stages. Second, the dirt in the pan is incredible (wait until you get it off). You want to clean as much of that crud out before you circulate all that fluid through the transmission.

It might seem a little redundant to do it that way, but this guy has convinced me that it's worth it. Also, after you drop the pan, you can just fill it up with some cheap fluid, then use good stuff for the flush, so you won't be wasting a lot of money.

 

[Lumberg]

quote:

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Originally posted by Matt_S:
On the Cartalk board, there's a transmission guy who really knows his stuff. He's adimate that you need to drop the pan first. There are two reasons. The most important one is so that you can inspect the pan contents. If you flush first, you might be pulling wear items into the filter, where they won't be noticed. Then you might not be able to spot a problem in the early stages. Second, the dirt in the pan is incredible (wait until you get it off). You want to clean as much of that crud out before you circulate all that fluid through the transmission.

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I have to call BS on that one. If anything the turbulence of the fluid during flush is going to be much lower than in oepration, because the car is only idling. How would flushing cause particles that have been sitting at the bottom of the pan for tens of thousands of miles of operation to get swept up into the filter?

Second of all let's say that's true. That's great, you get the most out of that filter, which you are about to replace anyway!

I guess ideal would be drop the pan, change the filter, clean everything, do the flush, drive around for a few hundred miles, then drop the pan again and change the filter again, then top off. But that's not going to happen.

JB you're right, it probably is not something that makes a big difference.

 

[TheLoneRanger]

I agree that it dosen't matter much which is done first. However, I would clean the pan first. The pan is the lowest point in the system, and all the debris collects there by design. The rest of the transmission is relatively clean. The fluid change is what's important.

 

[Virtuoso]

I'm gong to try this on my SHO the next time I swap transmission fluid.

Drain one gallon of fluid through the cooler lines. THEN drop the pan (shouldn't be much fluid left in the pain, easy to get off without making a mess). Clean pan, install new filter, bolt up. Then add fluid and continue flush as neccesary.