If you own a manual trans van, this will mean very little for you, except as a horror story, or a good laugh. Over this past summer I tried fixing the mystery leak on my '85 auto trans. The actual trans is from a '91, but that matters not. Both of the transmissions showed the same condition, to whit: There was a constant leak in the trans. Sometimes not much, sometimes quite a bit. (Like a pint in 100 miles.) I used every diagnostic trick I knew to track this down. I replaced the pan seal (x3), the governor cover seal, even had to replace the 2nd-reverse actuator piston. Did not seem to make much difference. The leak still appeared. My fluid level went down. I used more trans fluid than engine oil. And no, it was not going into the final drive. Despair. I finally gave in, and was going to go for the dreaded coolant-to-trans intercooler, figuring that the o-rings in there had given up. Ran the van up on ramps, and pulled the forward trans mount. When I tipped the trans and engine down, to get access to the forward mount bolts, a rush of fluid greeted me. I had not opened up anything at this time, just changed its position. Huh? Well, after poking around on the installed trans, and on the extra transmission on the stand in the garage, I found a small steel plug that was used to block off a drilled manufacturing access hole on the top face of the trans, at the forward edge, next to the trans mount. This vertical hole allows passage of fluid from the body of the trans back into the pan, as an internal drain. The thin steel plug was placed at the bottom of a shallow hole, and since crud will collect in any depression, it did. The hole was about half an inch deep, and was filled level with oil-soaked crud. And, as it held water and electrolytes too (Michigan vehicle), gradually the plug was perforated. The passage under the plug itself is not under any real pressure, but the passages that lead into this passage are under operating pressures, so the plug is always getting some fluid pushed into it. And then out of the trans. Always at low volumes, and no real direction. But always, if the van is driven. So. I removed the remains of the old plug. It was rotted almost completely away, on both transmissions. I measured the diameter of the hole. It is a stepped diameter, with a larger diameter at the upper, plug end, than through the rest of the body of the trans. After some research, and multiple trips to several transmission shops, including VW/Audi specialists, I got nothing. No one had heard of such a thing, let alone tried to fix it, or find parts to fix it. I figured that just being a steel plug, a regular engine block freeze plug ought to work. After asking at the local Auto Parts store - not a chain, but an old fashioned Parts Store - we found a freeze plug that was compatible. A Dorfman 555-015, at 0.923" diameter. After carefully driving that into the hole, no more leak. The cost of the plug was 83 cents. So, if you have an annoying, anonymous leak in your auto trans, it may just be there. Evan Mac Donald "...in the absence of facts, myth rushes in, the kudzu of history." -Stacy Schiff |
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