New ATF in a bad transmission.

[Donald]

Originally Posted By: RF Overlord
I am SO glad to see this thread. Every board I belong to has some numbskull come on and proclaim that changing the ATF is a death sentence. I try to set them straight, but it's like convincing people Pennzoil doesn't cause sludge...they always know some guy whose father's barber's gardener's uncle knows a mechanic who once talked to a guy whose transmission died backing out of the shop after changing the fluid.


The only part that is close to being true is most mechanics do not want to change the ATF when its like driveway sealer as they just do not want to be liable and the $50 they might make is not worth it. They may come up with some lame excuse. In most cases the transmission is showing some signs of being on its last legs and the owner is hoping to prevent that by changing the ATF.

 

[dave1251]

The whole topic just gets me. Because I have seen more than once from more than one mechanic that blamed the owners transmission failure because the owner put in fresh fluid and the fresh fluid is the cause. To me it is just like a mechanic blaming a oil change and the correct oil as the cause of engine failure. This puts mechanics with sound decision making skills and a understanding of lubrication in a bind. Because most professionals do not like to tell customers that whomever gave this advice is giving some flawed advice.

 

[BMWTurboDzl]

Originally Posted By: JZiggy
I heard an argument once that an old, worn out AT will have substantial amounts of wear particles in the fluid which act as a kind of friction modifier allowing the clutches to still do their thing. Putting in fresh fluid then causes it to slip. Of course, with no maintenance it was on its way out anyway...


Supposedly this is no longer the case due to computer driven shifts. The AT is supposed to compensate.

 

[fisher83]

I think this sums it up pretty well. The customer is going to assume that the last person who touched it broke it. The shop would rather avoid the problem. Most people change their oil once in awhile when they remember and neglect all other fluids/services until something big goes wrong. Then they either point fingers at the mechanic, or swear off that brand of vehicle because it is "junk" since it didn't run flawlessly without any maintenance. I personally like to know I have fresh fluids in my vehicles and very rarely have any mechanical problems. It's much easier to budget for maintenance than be surprised by a breakdown.

 

[Zako2]

On compromise for
Originally Posted By: BMWTurboDzl
Originally Posted By: JZiggy
I heard an argument once that an old, worn out AT will have substantial amounts of wear particles in the fluid which act as a kind of friction modifier allowing the clutches to still do their thing. Putting in fresh fluid then causes it to slip. Of course, with no maintenance it was on its way out anyway...


Supposedly this is no longer the case due to computer driven shifts. The AT is supposed to compensate.


Well, we're talking about the AT that's going bad, so probably relatively old tech, possible 4-speed trany designed in 90s or earlier.

One interesting advise I have heard, about changing fluids in AT with too many miles on fluid, is not to flush all fluid at once. In most cars, if you drop the pan, change the filter, and top off the fluid, this procedure will exchange roughly half of fluid or less helping the transmission to adapt faster to the fresher fluid.

 

[weebl]

Originally Posted By: fisher83
I think this sums it up pretty well. The customer is going to assume that the last person who touched it broke it. The shop would rather avoid the problem. Most people change their oil once in awhile when they remember and neglect all other fluids/services until something big goes wrong. Then they either point fingers at the mechanic, or swear off that brand of vehicle because it is "junk" since it didn't run flawlessly without any maintenance. I personally like to know I have fresh fluids in my vehicles and very rarely have any mechanical problems. It's much easier to budget for maintenance than be surprised by a breakdown.


The logic of these same people are exactly why there are certain members of my extended family that I would never, under any circumstances, perform maintenance for them. If they ever wanted to learn how, then I will show them, but it will be on my car the next time it needs it, and they can take what they learned and apply it themselves to their car.

For very few people I am close to and can trust, I would actually help them.

 

[HerrStig]

I drain the fluid per the book my Toyota autos every 30K. One of them has almost 300K on it now. The drain procedure only replaces about 2.5 quarts out of the total, but apparently it is enough to keep the transmissions happy.

 

[zzyzzx]

Originally Posted By: Bgallagher
If you havent changed your ATF in over 180k then fresh fluid might dislodge some crud or do something to cause damage.


Or you could do what I did:

Siphon out as much as you can, then replace with new. Do this about once a month for a few months. Then drop the pan, clean it, and change the filter and fluid. This way any of the stuff you dislodged is in the pan/magnet/filter. If you changed the filter first, then added new fluid you risk clogging the filter. My method potentially cogs the filter right before you change it, not after.

 

[Moab]

Originally Posted By: tommygunn
Originally Posted By: RF Overlord
Every board I belong to has some numbskull come on and proclaim that changing the ATF is a death sentence.


Yeah I'll have to agree, this thread is nice to see people with some informed insight into the assistance they give as opposed to telephone tag of biased opinion.

But I also agree; if a car was sludged up and already knocking really bad would you suggest an oil change? No. Because you know the engine is screwed anyhow and a person is probably wasting their time, and if it blows up a week later you'll probably get blamed for it (because it was "just fine" before you said it was sludged up).

Transmissions probably the same thing because almost everyone I know NEVER services their transmissions and drives it for ages upon ages as it slips and grinds funny. Usually by the time they're looking for options the transmission is so beyond a good fluid change to fix it that the transmission will inevitably explode anyhow.

But I guarantee there is a lot of people guilted into euthanizing their transmission because someone said not to change the fluid.


The best transmission shop owner/mechanic I know told me he does an automatic transmission service on his personal cars every 15,000 miles. He said transmission fluid is pretty worn out at 30,000 miles and you only get 1/2 the fluid out when doing a transmission service, so he changes the ATF fluid on his own cars every 15,000 miles. He said servicing an automatic transmission this way results in the trans lasting a very long time. Of course all of this depends on the brand of car, how it was driven and how well it was taken care of.

Some people are weird about car maintenance. I know people who never have their automatic transmission fluid changed or serviced. They just drive the car until something blows up. I know a guy who bought a new suv and he told me he hates to change his oil so he usually just keeps it topped off instead of changing it.