thread repair

[SRehberg]

I need some advice, as my project is turning into a nightmare. A simple torque converter change out, but I'm fighting the Stealer's work. When the local Dodge boys rebuilt my trans (14mos. ago) I had no reason to check the pan for problems. When removing the pan on the trans, it became apparent the #*@!* mechanic had used a air impact tool with to much torque. Four of the threaded holes in the aluminum case were shot. The mechanic (and I use the term very loosley) tried a heli-coil on one but must have used the wrong drill bit or tap, as it won't hold the coil. A 3/8" bolt will slide thru clear. The obvious answere is to bolt it thru, and I would, but it just happens to be directly under the neutral safety switch; no room for a bolt head. Any ideas?



Any help you can think of would be greatly appreciated.



_____________________________



'96 auto

 

[illflem]

What a PITA. How about tapping it out to 7/16" or a larger metric size? Is there enough meat? J-B Weld could also be used to fill the hole then drilled and tapped. Stuff works great if the surface is clean and you give it plenty of time to dry.

 

[Extreme1]

Try this...

I'd go back to the squeeler and raise Cain. Since they will probably not help without charging you and making it worse...



How about make your own helicoil?



Tap the hole for a pipe plug (the allen socket, flush top type). Turn the plug into the hole until flush. You might have to play with the tap to get the depth right. Red lock-tite it in place, let that cure and then drill and tap it back to the right size. Being a pipe plug, it won't screw through the hole.



Or, you caould try a steel filled epoxy. Fill the hole completely and then drill and tap and install a helicoil (or stack 2 if the hole is deep enough) in the epoxy.



I've used both fixes over the years, the pipe plug is better for larger holes with more torque applied.



Good luck!

 

[Joseph Donnelly]

Allen pipe plugs are often hardened and thus difficult to drill and trap later. Another possibility, once you determine the hole is too big for 5/16" or 3/8" helicoils, is to make up a threaded aluminum or mild steel piece to thread into the oversized hole. For example, say the hole will clean up at 1/2 x 13 thread. For a blind hole, you can finish the tapping with a plug tap to gain depth. Take a piece of a soft steel bolt, or thread a 1/2" aluminum rod, and drill and tap the inside to 5/16 x18 (I think that is the thread for the trans pan). Thread the insert into the oversize hole in the trans case after cleaning with solvent and applying red Loctite. Let the Loctite set for a day, then put on your pan, with some RTV sealer at the plug so you can be sure it will seal properly.

 

[SRehberg]

Thanks for the great suggestions! I will definetly try them, as I am so mad at the Stealer that I could scream. I have a total of 5 bolt holes that were screwed up, 4 of which I could heli-coil back to the 5/16 as stock. The one I was asking about, a 3/8 heli-coil won't work, as to much meat has been removed. I can't imagine how the dummy could be so rough. You should see the valve body where he cranked the bolts down with the same impact; they are peeling aluminum.



It only took them three times to get the trans so it wasn't destroying itself. i. e. eating bearings etc. , with mucho debris in the pan.



Thanks again for pulling me out of a jam!



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'96 2wd about to rain on the Stealer

 

['956Wheel]

Extreme hit it on the head! You can use a pipe plug or a bolt cut flush with the sealing surface. Use a grade 5 bolt, no harder. Loctite 272 is the one you want (NO OTHER). DO NOT USE A SET SCREW as they are VERY hard. Clean your bolt and hole with a "non risidual" type cleaner, contact cleaner or any other that does NOT leave an oily feel behind. When done right you will wind up with a stronger thread than the original and this is not a "Mickey Mouse" fix as it is done all the time in the machine shop. Use your pan as a template to locate the holes, buy a good tap and lube it with anti-seize. Impacts are a great time saver but have their place... not on flat rate!



Mike

 

[barryg41]

Extreme and '956Wheel are right on about fixing the stripped out bolt holes.



I have always used Tap Magic to lubricate the tap when tapping new threads. It keeps the tap cool and that promotes chipping when making new threads. Taps are by design to make chips so you dont guald the metal that you are cutting and break the tap. Anti-seize can withstand 1400f. In some cases this can make the tap hot and make it very easy to break a tap.



I find that in cutting new threads. You should cut 1/4 to 1/2 turns, then back out two rounds. Make two rounds and clean the tap.