Can you harm an automatic transmission by changing fluid & filter after 130k?

I have a 1998 Ford Ranger, 3.0 V-6 with automatic transmission. I notice lately that the transmission is slipping ever so slightly. I have owned this truck since it had 25,000 miles on it, and it now has 130, 000 miles. During this time I have never had the transmission fluid or filter changed. I’m thinking of doing it now to see if it eliminates the slippage, but someone said that I might make things worse by changing the fluid and filter. Is there any truth to that? Do I run any risk of making things worse? Or, would it be a good idea to change the fluid and filter? Any advice is greatly appreciated.

Changing the fluid and filter will hurt nothing and what you heard was an old wives tale.

Sometimes what happens is that someone does the first, and well past due, trans fluid change and any problem that surfaces or becomes worse afterwards is blamed on the new fluid.

It would likely benefit you to get it serviced. It may be too late already but the slipping will definitely cause some big problems if it continues. And flushing the cooler out when servicing the filter would be beneficial. I have serviced automatics with well over 100,000 miles of neglect and seen them continue to run many miles. And I strongly discourage flushing any automatic transmission. Dropping the pan to replace the filter and refill with the PROPER amount of the CORRECT fluid is by far the best route according to most.

DO NOT let anyone talk you into a transmission “flush,” which CAN make it worse. As Rod Knox says, have them drop the transmission pan and replace the filter and fluid.

Have someone drop the pan, replace the filter and then have a complete fluid exchange performed.

If you just replace the fluid that’s removed when dropping the pan, the detergents in that new fluid can cause any gum/sludge/varnish inside the transmission to become suspended in the mix of new and old fluid. And if any of that debis finds it’s way into the valve body of the transmission, that’s when the transmission fails.


When you pull the transmission dipstick, what does the fluid look like? This information really is critical on deciding a course of action.

You KNOW the tranny is on its last legs, so you can’t do much to hurt it now…The fresh fluid and clean filter MIGHT increase operating pressure a little and that increase MIGHT squeeze the clutches a little tighter stopping the slipping…