Pat Goss is an automotive repair guy in the DC area, he has a radio show and does chats online for Washingtonpost.com, and is on Motorweek, etc. So basically he knows a lot about cars and his opinion is respected. I asked him about a tranny flush on high-mileage cars and his response is below --


Pat Goss: Transmission flushes, to do a flush or to not do a flush is not relative to mileage. It relative to the condition of the fluid. If the fluid still looks mostly like new and smells like new fluid. A flush is in order. If the fluid has significantly changed color or smells like varnish or has a burned odor, leave it alone.


I know that's a common question and some people might want to be aware of a highly informed opinion like his.

 

what??? I have to flush my transmission if the fluid still looks new, and leave it alone if it has changed it's original properties? just doesn't make any sense...

 

Pat Goss has his own site. Here is the quote by him.

"Coolant, transmission fluid, power steering fluid, and brake fluid should be replaced before they change color. When a fluid changes color it’s causing damage to the system it is supposed to protect."

He also says regular transmission flushes extend the life of Trans. by 2 to 3 times.

 

Pat Goss isn't exactly Mr. Credibility. While some of what he says is right, much of it is either half-truth or just wrong. If your ATF is heavily discolored, leaving it alone may or may not be the best choice. It's time to look further, and perhaps send a sample off for lab analysis ($25-50). If the fluid is merely "normally aged" then there should be no problem, and in fact a great benefit, in doing a change. If the trans is damaged, then it's time to look deeper and make some decisions. And don't forget, what he's really saying is, in effect, "give up and wait for it to die," fearing that an ATF change might accelerate the coming failure. I wouldn't let my car get that bad in the first place, but I wouldn't accept that answer either.

 

That's the point people are failing to get. Once the tranny fluid is discolored and burned, changing the fluid can do MORE damage than leaving it alone. by replacing the fluid, you're adding a bunch of detergents and etc to the system, which can possibly cause the gunk deposits inside the tranny to break loose and lodge in the shift solenoids or valve body.

a few months back I pulled the valve body out of my wife's altima.. I NEVER let the fluid get more than slightly dark (basically changed every 18 months or so using a drain/fill). It had begun shifting a little rough so I pulled the VB apart and you'd be amazed how much junk was stuck in the corners and inside the shift solenoids. cleaned up everything with brake cleaner and reassembled the tranny, and it shifted like new!

The problem with doing that on a regular car is that there are so many other deposits in there that doing a flush without dropping and cleaning the VB can/will be detrimental to the tranny.. so they recommend just leaving well enough alone. you've neglected it too much already, so what's another few months of fresh fluid goign to get you?



Also, be VERY wary of what a lot of those guys say. Just because they're on every TV station in the country does NOT mean they're right. In this case, he is.. But I'm sure you guys have all heard Car Talk on the radio.. I've heard them misdiagnose dozens of very common problems on Hondas and Nissans.. stuff that I've seen quite often in the 3 years I've been turning wrenches professionally.. Things like oil in the spark plug holes on a DOHC engine.. 95% of the time that's a simple valve cover gasket leak. They diagnosed it as a dead cylinder and broken spark plug- which basically required engine rebuild/replacement... all for a $15 gasket and 30 min of time!

 

Take anything TV shows with Pat Goss, the Two Guys Garage three old farts, the "Oil Dr.", or most anyone else, with a grain of salt. They will push anything the sponsors are willing to pay for.

Two Guys Garage sponsored by the Tornado... nuff said.

 

LOL! I saw that Tornado segment.. I was like how low can you go?

 

i read in another post that this was only true for automatic transmissions? for 5 speeds replacing the fluid with newer/cleaner fluid is always better. correct me if i'm wrong... i was planning on flushing my fluid soon and would really like to know the right answer.

thanks

 

You are correct..the same school of thought does not apply to MTs. Simply drain, clean the magnetic drain plug (where applicable) and refill.

 

You are not really "flushing" your manual trannie. You are draining out all of the old fluid and then replacing it with new fluid. This is similar to changing the motor oil in your VQ engine. You don't flush it, you change it.

There are a number of stickies here to help with how to do that on your Max. Check them out for your appropriate gereration of Max.

 

and I thought it was all based on the amount of mileage you do.

 

It is based on mileage. You should drain your manual trannie fluid at least every 30 K miles. IMO you should drain your Original fluid (and if you continue to use dino fluid) even before that distance. I was late to this first change and did not change until 30 K miles. If I could do it over, I would have gone to synthetic fluid at about 20 K miles.

 

+1
This has been a long standng theory concerning aging automatic transmissions and it is actually well founded. If you have a high mileage automatic DO NOT flush it unless you have been doing it at regularly scheduled intervals toi begin with.