Stripped Aluminum Thread, erm, Thread
Thread Starter
Pro
Joined: Sep 2024
Posts: 526
Likes: 114
Stripped Aluminum Thread, erm, Thread
So I have a McDougal Nashola 4+3 that has the typical mostly stripped out threads on the ATF pan. I have done many repairs to steel and cast with no issues. But I am thinking about this and wondering if a timesert or a Helicoil would be the way to go so I can get it snugged up tighter than the aluminum would allow.
Anyone had any success, tips, suggestions on this repair? Best gear to get? Any idea what thread pitch the bolts are?
I would like to do them one at a time with the pan already installed if possible. The gasket and gasketmaker are brand spankers new so I really don't want to have to go through that process again, if I can avoid it.
Edit, never mind about leaving the pan on. The pan is the flange, dummy. The bolt head would have nothing to squeeze against otherwise. Doh!
Anyone had any success, tips, suggestions on this repair? Best gear to get? Any idea what thread pitch the bolts are?
I would like to do them one at a time with the pan already installed if possible. The gasket and gasketmaker are brand spankers new so I really don't want to have to go through that process again, if I can avoid it.
Edit, never mind about leaving the pan on. The pan is the flange, dummy. The bolt head would have nothing to squeeze against otherwise. Doh!
Melting Slicks
Joined: May 2014
Posts: 2,891
Likes: 591
From: New Port Richey FL
When doing a OD transmission service and you pull the pan for a wipe out there is no need to get out your German tank Cor. Torque wrench and make GOOTINTIGHT the specs are around 14" pounds so a good wrist twist is just about that is needed
So get the Helicoils or next size up if possible and don't overtightened
So get the Helicoils or next size up if possible and don't overtightened
Thread Starter
Pro
Joined: Sep 2024
Posts: 526
Likes: 114
When doing a OD transmission service and you pull the pan for a wipe out there is no need to get out your German tank Cor. Torque wrench and make GOOTINTIGHT the specs are around 14" pounds so a good wrist twist is just about that is needed
So get the Helicoils or next size up if possible and don't overtightened
So get the Helicoils or next size up if possible and don't overtightened
Melting Slicks
Joined: Nov 2016
Posts: 2,237
Likes: 3,063
From: So Cal
2023 C4 of the Year Finalist - Unmodified
The existing thread is 6mm-1.0 with a 10mm wrench hex. "Next size up" (8mm) the bolt's 13mm hex head won't fit in the recessed flange. I suppose one could go to socket head cap screws.
I'd try running a 1/4-20 tap into the existing holes. 1/4-20 major diameter is .016 larger than 6.0mm. It might work. A 7/16" hex head will fit in the recess.
I'd try running a 1/4-20 tap into the existing holes. 1/4-20 major diameter is .016 larger than 6.0mm. It might work. A 7/16" hex head will fit in the recess.
Drifting
Joined: Jun 2020
Posts: 1,694
Likes: 728
From: Stay dangerous my friends
I've done hundreds of helicoils, sometimes repairs and sometimes for a more robust threading surface. Here's my suggestion for a play by play on how to install:
Remove pan -- clean hole and casting areas with acetone or similar -- use helicoil kit and drill for the larger size tap, make sure to use the best length helicoil that's at least 1/8 shorter than the depth of the hole -- tap the hole for the helicoil, be careful to keep the tap square -- chamfer hole slightly — clean with acetone or similar, don't blow alum chips into the trannie wit an air nozzle -- apply a very light coat of red loctite to the helicoil outside surface, this also makes a decent thread lube until it cures, but not so much that it can clog the inner thread surface -- install so that end is 1/2 turn below the surface, use the installation punch to break off the installation tang with a quick light hammer tap, and make sure tang falls out -- repeat as necessary.
Remove pan -- clean hole and casting areas with acetone or similar -- use helicoil kit and drill for the larger size tap, make sure to use the best length helicoil that's at least 1/8 shorter than the depth of the hole -- tap the hole for the helicoil, be careful to keep the tap square -- chamfer hole slightly — clean with acetone or similar, don't blow alum chips into the trannie wit an air nozzle -- apply a very light coat of red loctite to the helicoil outside surface, this also makes a decent thread lube until it cures, but not so much that it can clog the inner thread surface -- install so that end is 1/2 turn below the surface, use the installation punch to break off the installation tang with a quick light hammer tap, and make sure tang falls out -- repeat as necessary.
Last edited by AZSP33D; May 3, 2025 at 11:00 AM.
