Can a transmission fluid replacement cause a transmission to fail?

I own a '98 Oldsmobile Bravada that recently had the fuel pump fail. In the process of replacing it, I had the SUV looked at by a couple of different mechanics. It was brought to my attention that the transmission was in poor shape. This was news to me because I had been told that the vehicle had received adequate maintenance on the transmission. I had never had problems shifting and had no reason to suspect that the transmission would fail. One mechanic told me that the fluid was “black” and that there was a distress code appearing on their software readout. She said that it was too late to flush the transmission, and that doing so would cause the SUV to fail to shift. The second mechanic told me that the fluid was “dirty” but not as bad as reported by the first. The second mechanic told me that a fluid exchange was strongly recommended immediately. This vehicle has 140,000 miles on the engine. I’m a broke college student who can’t afford to buy a new car right now. What should I do?

Your transmission has been neglected for the last 100,000 miles or so. This is partly the fault of the manufacturer who does not specify regular fluid and filter changes. Hence the black color. The shop knows that your transmission is likely failing and if the do ANY work on it they will be blamed for the failure. We get this type of post at least once a month.

The clerk at the first shop is wrong; transmission maintenance does not cause failure, only if the unit is failing already.

Whether you are broke or not, I would still recommend a transmission fluid DRAIN and filter change, and also a flush to get rid of the remainig balck oil. Those two are different things. A well maintained transmission only needs a fluid and filter change every 40,000-50,000 miles. No flush needed.

I would take it to a good independent transmission shop (not a chain) for this service. But be prepared for some bad news.

This is one of those situations that could be described as damned if I do, damned if I don’t. If your fluid is really broken down, it will fail outright sooner or later. So the fluid needs to be changed. Not everyone will agree with this assertion but neglected fluid breaks down and coats the internals with varnish/sludge. New trans fluid is a very aggressive solvent and will immediately start attacking these deposits. Think of it as a stroke for your transmission. Just like the stroke victim that does not know there is an underlying health problem until the blockage occurs, you’ve been going along happily ignorant of the impending problem. Then someone works on the trans, a problem develops and the owner blames the last shop to touch it. If left alone, it will fail anyway. Black fluid is no longer capable of doing the job it needs to do. Change it and keep your fingers crossed.

In fact, a large quantity of the fluid remains trapped in the torque converter if you simply drop the pan and drain the fluid. If done this way, it will take mulitiple changes to completely replace the fluid w/new. I don’t like flushes on neglected trannies and I’d suggest the repeated drains over a flush, unless the TC has a drain plug too. Then you can drain most of the fluid in one operation and be done with it.

I wouldn’t read too much into the descriptions of black and dirty as that is simply an interpretation by the person looking at it.
Black or dirty; both are bad.

The fluid/filter should have been changed every 30k miles but since that’s water under the bridge now I’d drop the pan, change the filter, and then flush the transmision or exchange the remaining fluid; however you want to phrase it.

The act of fluid exchange should not harm the transmission at all but you should keep this in mind. Transmission fluid becomes black/dirty for one reason; age and contaminants, and the contaminants are for the most part material from the friction discs in the transmission. This means wear so it’s possible that down the road the transmission could give up but it won’t be because of the fluid exchange.

Well put, this was why my mechanic was reluctant to change the ATF and filter on my 93 Caprice in 2002. He did not want to be held responsible if the trans failed after a ATF/filter change. He said once the deposits break loose, the transmission’s internal passages get clogged up (i.e. stroke).

Since the ATF was still red I had the service done. I had a second ATF/filter service done last year and the car is still shifting fine today.

Ed B.

Thank you all so very much for your prompt responses! I feel a lot better about paying to replace the transmission fluid after this!

But do know that a replacement of the fluid alone shouldn’t be done - first someone has to drop the pan from the bottom of the transmission to change the filter. Only after that should any kind of fluid exchange be done.

Your best bet is a shop that specializes in transmissions - a local, independent, not a national chain operation - since they will best be able to evaluate the condition of the fluid, filter, pan, etc. and advise you accordingly.

Time and time again someone has the same question. It is a good question, but as Doc has well explained, the car manufacturers should specify a reasonable (like 30 to 50,000 miles).

Often people will figure out the transmission if failing and or the fluid is breaking down.  They then change it and a short time later it fails.  Then they blame the closest thing around, (the oil change) rather than realizing that the change was done [b] because [/b] they already figured out there was a problem.