Today: Best Way to Change Transmission Fluid?

Dear Car Talk

Dear Car Talk | Dec 12, 2013

Dear Tom and Ray:

What is the best way to have transmission fluid changed? Around 2002, I had my transmission fluid changed by the recycle method at a quick-change oil place. About a week later, the transmission went completely out at a cost of a couple of thousand dollars. After selling that car, I bought another used car and wanted to have the transmission fluid changed.

From that first experience, I decided to have it changed by dropping the pan and changing the filter. I now have a 2005 Chrysler 300C that needs the transmission fluid changed. What do you recommend for having it changed -- dropping the pan, or the backflow recycle method?

-- Jim

RAY: We like the recycling method. That's where a machine is hooked up to your transmission's cooler lines, and then, as the transmission pumps out the old fluid, the machine replaces it with all brand-new fluid.

TOM: Then the machine attaches to the wallet cooler lines of the customer and extracts the payment. That's why we like it so much.

RAY: Using the old-fashioned method of "dropping (i.e., removing) the pan" is acceptable, but it always leaves old fluid in the torque converter. So at the end of your fluid change, your "new" transmission fluid is still, at best, only 3/4 new.

TOM: There's a myth that we've been hearing forever that changing the transmission fluid on an old car will hasten the demise of its transmission. People will say, "I knew a guy with an old car who changed his transmission fluid, and a week later, the transmission died."

RAY: Yeah, that's what Jim says.

TOM: Oh. So it is. Well, in my opinion, any transmission that will die soon after a fluid change was almost certainly on death's doorstep before the fluid change.

RAY: I mean, when do most people with old heaps suddenly decide they need to change their transmission fluid? When the transmission starts acting up, right?

TOM: That's probably what happened with you, too, Jim. So, if your transmission is already slipping, or making hard shifts, or failing to shift at all, a fluid change is not going to be a long-term, miracle cure. If you're replacing really old, burned-out fluid, it might help you for a while. But whichever method you use, you're really unlikely to make it any worse. Good luck.

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