Junkyard Transmission: Should You Drain the Converter?
Techline: Fluids and filter need your attention when you buy a used transmission.
I bought a used automatic transmission from a junkyard. I don't have the money to rebuild it, but I plan to put a new filter and gasket on it. Should I drain the converter or leave it because it still has some clutch material? And does anyone suggest installing the pan gasket dry or use sealer?—Joe K.
Inspecting a Junkyard Transmission
Junkyard automatic transmissions are a sketchy proposition, as there's very little you can do to inspect or test the transmission short of looking at the fluid. We rarely opt for the warranty that's offered at most self-serve salvage yards, but transmissions and engines are the two components where'd we pony up the few extra bucks. While we'd encourage you to rebuild the transmission before stabbing it in, we also understand budgets are tight and sometimes you just have to roll the dice.
You definitely want to drain both the transmission and the converter as much as you can. Pull the converter and let it drain for several minutes, or even an hour or two. The same goes for the transmission pan. We've heard of automatics starting to slip after a fluid change because the fluid was thicker than the fresh stuff due to clutch material and so on, but those transmissions were most likely on their last legs. It's better to change the fluid and start with fresh stuff than it is to continue running contaminated, old fluid. While you have the pan off, take a close look at the filter and any debris in the bottom of the pan. The condition of the filter is going to be as good an indicator of the transmission's health as anything short of a testdrive before pulling it out of the donor vehicle. Be sure to install a new filter, and the pan gasket should be installed dry. Remember, the torque spec for the pan bolts is pretty low, so look up the spec if you can or be conservative on torque so you don't deform the pan.