Okay, well, I have purchased a HeliCoil Kit of size M8x1.25, and I'm preparing to go ahead with this operation on my transmission pan. I'm just wondering if it is necessary to drill the hole prior to tapping the hole? Is the only reason to drill the hole to get an adequate depth? That's my understanding. Perhaps it widens the hole as well? The drill bit is supposed to be 21/64(.328). I found instructions that match the job I'm about to do:

http://www.roadstarmagazine.com/modu...rticle&sid=233

But I'd just like to hear a little more about the drilling part prior to tapping and then inserting the helicoil. Does anyone have any advice, such as perhaps skipping the drilling part? If skipping the drilling part is a bad idea, I'll have to go out and buy a drill and bit set, which I'm prepared to do so long as it's necessary.

Thanks for all the help so far.

 

You need to drill the hole to make the proper diameter for the tapping operation. The hole you drill will be larger than the previous hole because the helicoil insert occupies the additional space.
You should buy an electric drill anyway. It's a very handy tool to have for many uses. My personal recommendation would be a 3/8" variable speed, reversible corded drill. Cordless drills have their uses but if you only use it a few times a year the battery will always be dead when you need it. When drilling metal, slow speed is better. Trying to drill at high speed in metal will dull the drill and cause the hole to elongate.
The tap requires a specific sized drill bit. Buy only that size and exactly that size. An ordinary drill bit set may or may not have the correct size. Drill carefully and don't enlarge the hole by working the drill in and out or you'll not get a good result with the tap.
Oil the tap to make the cutting smoother.

 

Well, I bought a 3/8" variable-speed cordless drill last night, and I've got a block of aluminium coming to me to practice on, so we'll see. Thanks for all the advice. I'll let you know how it turns out after I've done the work on the transmission pan and got some results.

 

Well, here's how things have gone so far. I temporarily minimized the fluid leakage from my transmission pan by using a longer bolt. I then set about practicing doing helicoils on an aluminum block I got from a local welder, which was excellent preparation for doing helicoils on my transmission pan.

Now, this past weekend, I actually went about replacing two non-adjacent, stripped bolt holes on the lower end of the transmission pan with helicoils. The job went well. I even sealed up the transmission pan to exactly 165 in-lbs using a torque wrench. I had previously been doing the criss-cross pattern with a ratchet and figuring out torque by feel. Now I relied on the clicks.

Unfortunately, the end result has been a bit of a disaster. The pan is leaking more than ever. I think this may be because I used a torque wrench (165 in-lbs may be too much). I'm also wondering if there may be some burrs on the transmission pan from the drilling, though I don't recall any. The helicoils seemed to have installed nicely, with the helicoils being about a 1/2 turn below the surface. I'm going to redo the transmission fluid change job next weekend, and I'll be installing at least one more helicoil.

So it's getting tough, but I insist on fixing this. For christ's sake, it's just a matter of sealing a transmission pan. I'm going to examine the transmission pan for any grooves or nicks that may be causing this persistent leakage. The pan always leaks at the lower/bottom of the transmission pan, but I don't recall any obvious grooves or nicks on the sealing surface there. I may avoid using a torque wrench: the Haynes repair manual says to work up to a final torque of 165 in-lbs in three or four steps, and last time I did this in two to three steps. Will a more gradual four step torquing process actually be the solution? It's a brand new micro torque wrench, but maybe it applies to much torque?

I would appreciate any advice that might help me to fix this problem. It's been a great learning experience, but ultimately I must finish this job.

 

ever thought about buying a transmission pan that hasn't been destroyed?

 

back to my original question what brand of RTV are u using and how do u apply it?

 

165 inch lbs is the correct torque, per the Chrysler service manual.

 

It hasn't been destroyed. The threads on the transmission assembly were stripped. Now it's all me, I think.

 

I'm using Mopar ATF-RTV, which is a silicone rubber ATV. I think the problem is that I smeared the ATF-RTV sealant onto the transmission pan last time, instead of squeezing out a "bead". Too little sealant is probably the problem this time...

As to torquing the pan, I normally ratchet the bolts snug and then proceed to apply torque. I'll probably go with 155 in-lbs this time just to be safe, but 165 in-lbs is what's recommended in the Haynes repair manual. The problem lies with me this time, I think. Not enough of a 1/8" bead going on the pan.

 

Which Chrysler service manual is this? I have the Haynes repair manual.