Gearcase Drain Bolt Thread Pitch?

[sr12345]

I tried to change the oil in my gearcase tonight. The drain took hardly any torque to remove, and when I reinstalled it, it took very little torque to tighten, and never seemed to seat. When I removed it next, my fears were realized when I saw that gearcase threads hanging on the bolt.

I'm having a hell of a time figuring out what size bolt this is. The head is half inch, and the bolt diameter is either 3/8" or 10mm. However, I can't seem to find a good fit with either my standard or metric thread pitch gauge. I'm going to need to put in a helicoil, but it would sure help to know what size I'm looking for!

Using a metric gauge, it's very close to a 1.25mm pitch, or 20 threads per inch on the standard gauge. However, the drain plug threaded portion is so short that it's difficult to match up more than a few threads.

[Quadder]

Originally Posted by sr12345

I tried to change the oil in my gearcase tonight. The drain took hardly any torque to remove, and when I reinstalled it, it took very little torque to tighten, and never seemed to seat. When I removed it next, my fears were realized when I saw that gearcase threads hanging on the bolt.

I'm having a hell of a time figuring out what size bolt this is. The head is half inch, and the bolt diameter is either 3/8" or 10mm. However, I can't seem to find a good fit with either my standard or metric thread pitch gauge. I'm going to need to put in a helicoil, but it would sure help to know what size I'm looking for!

Using a metric gauge, it's very close to a 1.25mm pitch, or 20 threads per inch on the standard gauge. However, the drain plug threaded portion is so short that it's difficult to match up more than a few threads.

The manual doesn't say what the thread pitch is, but it does say that the torque on transmission drain/level plugs is 30 - 45 INCH pounds. That's not very much. I suspect you will have to get the rest of the information from your dealer. Good luck.

[sr12345]

Quadder,
Thanks for the reply. I eventually figured out that the threads are 3/8 - 24. Now I've got to try to get a Helicoil in there...