HELP.....Stripped Xfer Housing at Drain Plug

[casbuffs2]

CRAP....Anyone have experience on the specifics of re-threading the drain hole on a 1978 transfer case? Looking for appropriate thread size and what kind of bolt to procure as a substitute.

I'm looking to avoid replacing the whole housing due to lack of income. Hope I'm not the only idiot to ever do this!

I found NAPA has a self-tapping drain plug, will this work in the transfer case? The sizes are standard, not metric. OEM plug thread 17mm w/ 24mm head. Will 3/4 inch self-tapper have enough bite (17mm=~.70 inch vs. .75)? Anyone know where to locate a metric version? Anyone suffer this fate before, or am I the only lucky bastard?

Or should I go with the ol' tap and die....Is there something else (tool/process) better?

Thanks in advance for any help or advice


Craig
'78 FJ40, stock drivetrain.

 

[handcannon]

go to your local auto parts store and check on a heli-coil to fit your drain plug size and thread. heli-coil requires special size drill bit and tap to drill and tap the drain hole, then you put in the heli-coil and then you are back to stock size and threads for a stock drain plug. Good luck on the fix.

 

[Pin_Head]

Try the self tapping oversize plug first. We used al ot of these in the shop when drain plugs got stripped and they worked fine.

 

[casbuffs2]

Thanks...and follow-ups

Do you think the 3/4 inch (.75) self-tapper will get enough bite on a hole that is roughly .7 inches in diameter or will I need to go bigger? Next size up is 7/8 and it is a BIG mama bear....I dont want to crack the housing!

They come with a rubber gasket, so I'm not so worried about leakage, just want to make sure the bolt doesn't fall out in the middle of nowhere. I can live with the problem if the truck is in the garage!

.05 inches (.75 - .70) is equal to a 1.1 mm, or only .55 mm on either side of the bolt. I'm sure the metal displaced from the tapping will fill-in some of the gap. Call me paranoid, but I want to make sure. Any thoughts?

If I try the self-tapper, will I still be able to do the heli-coil as a back-up? My unlearned opinion would be "yes".

Thanks again for the expertise!

 

[e rock]

Do you think the 3/4 inch (.75) self-tapper will get enough bite on a hole that is roughly .7 inches in diameter or will I need to go bigger?

If I try the self-tapper, will I still be able to do the heli-coil as a back-up?

I'd say yes and yes. If you have to work it in slowly, backing it out occasionally, it'll probably be fine.

One thing to watch out for is the depth of the aftermarket drain plug. I don't know if the J40 gears are the same as the J30, but if they are, there isn't much room between the inside edge of the housing and the teeth of the big gear right there. So you might need to shorten the plug. You don't want to find out the hard way by stripping out the new one by driving it into the gear.

 

[65swb45]

I'd say yes and yes. If you have to work it in slowly, backing it out occasionally, it'll probably be fine.

One thing to watch out for is the depth of the aftermarket drain plug. I don't know if the J40 gears are the same as the J30, but if they are, there isn't much room between the inside edge of the housing and the teeth of the big gear right there. So you might need to shorten the plug. You don't want to find out the hard way by stripping out the new one by driving it into the gear.

That's what I was thinking about the helicoil option: with the spacing of the gears being so tight, if you were gonna go the helicoil route, you'd be better off disassembling the housing to run a tap good and proper thru the case. BUT, if you're gonna strip the case down anyways, you might as well have a welding shop weld up the hole and re-tap it stock.

Just my .02

 

[casbuffs2]

My thought exactly...

The length of the self-tapper scares me as well. I believe I will use the self-tapper to carve the new threads and then back it out and replace with a regular 3/4" drain bolt that is the same length as the OEM.

Heli-coil looks like it would work as long as you make sure the insert is the same depth/thickness as the housing. There appears to be plenty of "meat" to the case around the plug area.

Thanks for the input.

 

[casbuffs2]

Won't bite....

OK, I got the 3/4 self-tapper, but I can't get the bastard to bite into the case housing. I used the butt of a claw hammer wedged against the bolt and the floor to provide upward pressure while I turned the bolt. I got a small sliver of housing, but it will not completely catch.

A pro mechanic buddy of mine suggested filing the drain hole out just a fraction. I'm nervous about making the hole any wider than it is now. I was thinking that perhaps flaring the hole slightly wider toward the outer wall (towards the bolt head, away from the interior of the case) would work best to minimize metal shavings inside the case.

Any suggestions for proper technique on this chore?

Anyone know where to find a 3/4 tap?

Thanks.

 

[e rock]

I'd go for the file trick. Just go slow and keep checking. I'm more of a Dremel fan myself, but whatever floats your boat.

At this point, if you don't get that plug in, you have bigger issues than whether or not the hole is 1mm wider. A welder doesn't care if the hole is 18mm or 19.


And I wouldn't stress too much about aluminum filings in the case. Once you get the plug to work right, you can remove it and dump a few ounces of gear oil into the fill plug and let it run out into a drain pan. Besides, it's just aluminum - it won't hurt much. When I swapped in my SM420, I pulled the PTO gear out and didn't realize that there was a spacer that was supposed to come with it. I found the spacer a few thousand miles later when I rebuilt my tcase - because I ripped the drain plug out dragging it over a rock. The spacer was dinged up and a little munched from playing with the gears, but there was no evidence of damage to anything else.

 

[casbuffs2]

Ahh...the Dremel

Why didn't I think of that earlier? I need a new excuse to pull that tool out. This will be perfect!

Any particular bit that is your favorite for a job like this?

I was thinking of using the ol' bottle jack to (carefully) apply upward pressure on the bolt. Seems like the perfect application....

Any reasons why not?