40k miles, adding Trans cooler, should I flush the trans?

I have been reading a ton of in info and cant get any answers. I ab about to do a downpipe and uppipe soon, so I will be putting in a TruCool Trans cooler next weekend, and I was wondering, since I have never had a transmission flush and the car has 40K miles, should I do a drain and fill, or not, because I read very contradicting info about that being bad to change it now, so please give me some concrete ansewers that will help make the trans last longer, thanks.

Change it.

I personally wouldn't go more than 30k on the ATF. Matter of fact, I think it's in the manual to change it at 30K intervals. Do at least a drain if not a flush. I'd also throw in some BG additive for good measure. Use the Subaru OEM ATF, it's the bestest stuff.

ABout how many Quarts would I need for just a drain? Also, is the delarship the best place to get it? How about the BG stuff?

I wouldn't drain, I would flush. I just did at 30k. Used amsoil atf.

Prime....that's it. I've had my last UOA sitting in my car for 2 weeks. Time to drive to the post office...

 

Joe

 

Edit: Yes, it is a post office holiday...

Amsoil ain't no better than the OEM ATF from what I keep reading around here.

There was a good reason why I didn't go with a flush, it was either because most shops with fluid exchange machines pull their ATF from a 55+ gallon drum, or because SOA doesn't recommend a flush unless you have problems.

Amsoil ain't no better than the OEM ATF from what I keep reading around here.

There was a good reason why I didn't go with a flush, it was either because most shops with fluid exchange machines pull their ATF from a 55+ gallon drum, or because SOA doesn't recommend a flush unless you have problems.

 

Fish, your normal excellent logic is showing signs of strain .

 

Given a stock 5EAT the Subaru 5EAT-specific ATF is fine. Start modifiying it, with an IPT VB for example, and Amsoil ATF is arguably better. With a full IPT 5EAT I wouldn't consider anything but Amsoil ATF. Amsoil ATF at any time, however, is a good thing.

 

But as far as drain and refill compared to a complete flush, with whatever your choice of ATF is, there is no comparison.... a flush is obviously superior.

 

A GOOD shop with the proper flushing equipment and trained personnel will be able to flush your fluid with YOUR choice of ATF, not what is in their drum.

 

And Subaru has a variety of errors in their maintenance schedule, just because they do not "recommend" a flush doesn't mean diddly. They do not recommend about 100% of what goes on on this website .

 

At 40 thousand miles you are long past doing the right thing. Better late than never.

Fish, your normal excellent logic is showing signs of strain .

Too much rice in my diet lately

A drain is easier done and you can do it yourself for cheaper. If you can change your own oil, an ATF drain is just about the same ... provided you have a T70 torx bit and a funnel with some tubing. A complete flush takes 9.6-10qts according to the repair manual. A drain, I am not 100% sure but it should be around 5 quarts so there is around half of the old stuff still in the lines, transmission lines, tranny itself etc. I figured, as long as you shorten the drain interval you should be OK with just drains.

Is Amsoil really better than the OEM stuff? The impression I got that the OEM stuff is second to none is really off this site, just reading stuff here and there. If there's compelling arguments I've missed, I'll switch.

For myself, I figured if I drain the ATF once a year or around 12-14k miles, that ought to be enough?

I just don't have a lot of trust in other shops having it flushed especially when you go in with your own stuff.

Too much rice in my diet lately

A drain is easier done and you can do it yourself for cheaper. If you can change your own oil, an ATF drain is just about the same ... provided you have a T70 torx bit and a funnel with some tubing. A complete flush takes 9.6-10qts according to the repair manual. A drain, I am not 100% sure but it should be around 5 quarts so there is around half of the old stuff still in the lines, transmission lines, tranny itself etc. I figured, as long as you shorten the drain interval you should be OK with just drains.

Is Amsoil really better than the OEM stuff? The impression I got that the OEM stuff is second to none is really off this site, just reading stuff here and there. If there's compelling arguments I've missed, I'll switch.

For myself, I figured if I drain the ATF once a year or around 12-14k miles, that ought to be enough?

I just don't have a lot of trust in other shops having it flushed especially when you go in with your own stuff.

 

Fine middle of the road process, without argument. Your numbers are good. Pretty much what I was doing for three years.... until my 5EAT STB.

 

My own decision to use Amsoil is based on more than thirty years experience with Amsoil products, the recommendation of IPT, and my own input from years racing an automatic. Amsoil markets superior products, IMO. I also believe the Subaru ATF for the 5EAT is good, and I've heard nothing bad about it. But in the end I decided to go with Amsoil because it is up front and I know what it is, unlike the good but mysterious Idemitsu ATF-HP/PSF with its "Unique formulation for all Subaru Transmissions (including 5EAT) and Power Steering Systems."

 

YMMV