Stripped transmission pan bolts

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Hey, where the transmission pan bolts up on the transmission, the threads are stripped. Without having to buy a re-threading kit, what would be a good way to seal it and stop the leaks? The bolts screw in but will not go tight so it leaks transmission fluid. Will JB weld work? And is a car jack a sufficient way to keep enough pressure on It to get a tight seal? And how should the JB weld be applied?

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have the same problem?
Monday, April 17th, 2017 AT 7:48 PM

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Slow down a minute. Floor jack? You are going about this all wrong, partly because you are not as wise and experienced as I am. My early experience translates to "frustration".

The first problem is the bolt hole stripped out because at some point someone over-tightened the bolt. All you need is a quarter-inch drive hand ratchet and one hand. I have used quarter-inch-drive air ratchets, and that is way more than strong enough to strip a bunch of holes. As I recall, the torque spec for these bolts is only ten inch-pounds, which is very little.

The proper way to address the hole is to install a Heli-Coil insert. I get the feeling you are familiar with them. If you are not, I can explain how to use them. The main thing to watch out for is to leave no part of the insert sticking up beyond the gasket surface. That will hold the pan up and prevent it from sitting flat and sealing.

The second-best way to handle this is to run in a bolt that is slightly larger in diameter. Use a cotton swab first with a little grease on the end, and work it around in the hole to gather up any metal chips.

The least-preferred way I've solved this is to stick a piece of solid copper wire into the hole, then run the bolt in alongside it. 14 gauge house wire works well. It is soft enough to form threads and to be pushed into the hole's threads.

The bigger issue is how you are trying to stop the leaking. One totally missing bolt will not result in a leak if you seal the pan properly. The biggest cause of leaks that you absolutely must not overlook is the pan and the flange must be perfectly clean of any hint of transmission fluid residue. Some people use a cork or fiber gasket, but that is not how professionals do it. The oil residue problem should not cause trouble if you use a gasket, but instead, just follow what I have done and observed.

You will notice that even if you let the transmission fluid drain overnight, when you come back, there is going to be a 1/2"-wide trail of fluid still running across the middle of the lower back-side of the flange.
That is what will cause a leak if it is not taken care of. One coworker would clean up the pan, spread the bead of gasket sealer on it, then stick a rag into the hole where that fluid was running out of. Next, he would clean the flange with brake parts cleaner, (that evaporates slower than carburetor cleaner, so you have a little more working time). On the count of "three" one of us would yank the rag out, and the other would slap the pan into position. That method gives you about three to five seconds before the fluid starts running out again. If it does, give up and start the cleaning all over because if you do not do it now, you will be doing it later.

My method is less stressful and gives you about a minute of working time. Clean up both mating surfaces and spread the gasket sealer on the pan. Reach a finger up into the hole where the fluid is running from. Splash around on both sides of that hole and you will get a lot of fluid running out. Now take your time and re-clean just that area to remove all of the fluid residue. There's a well up there that has to fill with the draining fluid. That takes about a minute to fill up before fluid will run over and onto the flange again.
Place the pan in position and push it up to squeeze the sealant. Start a few bolts by hand to be sure they are not cross-threaded. If you use air tools on those bolts, just run them up snug. I prefer to use a 3/8" air impact butterfly tool because I can stop it before it starts its hammering action. I like to hold the pan up with one hand, then start every bolt by hand first in case I need to slide the pan slightly to one side so a hole will line up. Then I go around with the butterfly and "zip, zip, zip", and they are all done.

Since I worked for a very nice family-owned Chrysler dealership, I used their products and became very familiar with them. They have two silicone gasket sealers. If you use the black stuff, that cures more "rubbery" and is a little easier to scrape off next time, but it absolutely will not seal anywhere there is oil residue. That includes valve cover gaskets and other engine gaskets. They also have a gray sealer that will adhere and seal through a film of oil as long as it is not real bad, but you still want the goal to be to have perfectly clean surfaces.

One tube is plenty to do an entire transmission pan. When I spread the bead, I like to make a circle around every bolt hole. That is not necessary, but in the rare event the transmission's flange has a hairline crack by a bolt hole, fluid could find its way to the bolt head. That little extra loop of sealant will stop a leak there.

You do not have to wait for the sealant to cure. You can pour in the new transmission fluid right away.

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Monday, April 17th, 2017 AT 9:06 PM

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