Suggestions for repairing drain plug
 

I guess this isn't really diesel related, but this is the only area I ever visit. Anyway I'm getting ready to install a 4spd manual in my TD as the slushbox decided to go south. As I was looking things over, I noticed that some idiot used a chisel to remove the drain plug rather than getting a 14 mm hex drive. In the process, they mangled the plug so bad, that I couldn't get the hex drive in without cleaning up the damage done. Once I finally got the plug out, I found that It has been seriously cross-threaded, and the threads are completely unusable. So, down to the real question. What are some suggestions of how to repair this. Currently, I'm thinking about tapping it to a 1" or 3/4" pipe, but there isn't a lot of material there. If I got real desperate, I could try to tig in a new bung... Let's hear some ideas
bb

are you talking about the lower oil pan then? I assume it's not the tranny since you're removing that.

If lower oil pan, just find someone who's tearing down an engine for good and get the oil pan. I'd have one for you, but it's in New Orleans and I'm about 4000 miles away from there right now.

No, it is the tranny. I'm talking about the four speed that I'm putting in. The main housing is one piece and its aluminum, thus the stripped, messed up threads.
bb

cant you just tap in new larger threads ?

that would be my thought too. Might be worth taking it to a reputable machine shop to have a look..especially if you have limited material to give it bite.

Retapping would be best, but since there's no pressure in there, that leaves room for some creativity. You may be able to find one of those rubber plugs that are used to repair freeze plugs on engine blocks. or perhaps one of those rubber plugs the boyz at Jiffy Lube use when they punch a hole in your slushbox pan to change the ATF....

As long as you check whatever you use periodically and it is secure enough to NOT catastrophically fail ( but just leak a bit)....

How about something as simple as a toggle bolt with a rubber disc backed up by a plate keeping it tight?

Rick

Rather than using a pipe tap you could use a regular National Fine tap of the closest over size and use a bolt with a copper waser and for good measure a little silicone sealent. The benifit of this is that 3/4 and 1 inch pipe taps have big threads the cut deep into that thin metal and because they are tapered will enlarge the hole even more and then when tightened put alot of outward pressure on the metal around the hole. The National Fine threads and the fact that the hole would not be cut tappered when tapping would preserve a lot more of the origional metal. Also for alot of aluminum parts regular rubbing alcohol works well as a tapping fluid.
Another way: Clean and degrease the cross threaded area. Get a new hex plug; clean and degrease the threads to to thee bare metal. Use JB weld or another epoxey that is rated for temperatures above 200 degrees and screw the plug in tight; let it harden (I believe it must be 60 degrees or above to cure correctly.) After it is hardened drill and tap out the hex plug for a smaller american NPT pipe plug.

The rubber plug is a thought, but I hesitate to put something flimsy in... I'll have to compare it to standard pipe sizes tonight. I know I have access to a 1" pipe tap, not sure about 3/4.

Fine threads are definitely better, but availability really bites. I would have to special order a tap and bolt. Does sound better than pipe threads though.

Yes and a big say 1 inch fine threaded tap will cost more than a pipe tap. I would not hurt to call a machine shop and explain the situation and ask them what they would charge as you are not obligated to have them do the work.
I favor the 2nd choice I gave with the good quality epoxy if the new plug will go in tight.
Just a thought call the dealer maybe they have a solution at a resonable cost. They might have the correct tap and if it is a tapered one the threads may clean up enough to be able retain the correct plug. If the plug can be retained tight there are alot things you can smear on the threaded area to take care of the sealing. Even the old low tech brown Permatex will do that.

re-threading kit.
 

Check out this link for an oil pan re-theading kit.
A little spendy for me, but it does look like it would do the job.


http://www.gemplers.com/product/151292/Rethreading-Kit

How about this
 

Could you take a patch piece of aluminum and tap it, put the plug in the tapped hole and heliarc the patch over the old plug hole. And don't go so big. It is a drain hole isn't it. Put in a 3/8" pipe plug. The transmission would drain fast enough. That would save getting tapping debris in the transmission, and I think it well could be done without dismantling the transmission.

In this case it is a manual transmission and there is no pan it has a metric hex type pipe plut. It looks like that kit would be nice if you owned a shop could bring in a little extra money and it would be tax deductable.

Fixed!!
 

So, I thought that I would share the solution that I used in case anyone else has this problem in the future. It turns out that a 3/4" NPT will tap into the existing hole without any problem. So I held the transmission vertically (it's normal position in the car) on the work bench and tapped the new thread in this position so the chips would fall out the bottom rather than entering the tranny. After tapping the thread, I then used a special instrument (my little finger) to sweep around the hole inside the tranny to collect any chips that made it in. I cleaned a few out, but most stuck to the tap and drained out with the residual oil in the tranny. I bought 3/4" NPT socket plug and viola, good as new. The tap cost me $20. Quite a bit for such a simple tool, but now I have it for the next time I need to tap one of these trannies:P
bb