stripped bolt in tranny pan!

[ndamico]

The other night my buddy was installing the deep Allison pan, which calls for 18-22 ft/lbs of torque on the bolts. well my torque wrench decided to take a dump on him and not work...end reslut, 1 bolt stripped in bottom of old Ally!

we installed the deep pan as other bolts were unaffected and the problem one has about 1 thread keeping it in there....it hasn't leaked a drop and i doubt it will but was wondering if we should:

1) leave it alone
2) tap a bit larger
3) helia coil (sp?) - i've done that on old VW heads before with good results..

[hoot]

Most likely you would get by without the bolt or a leak.

I would use a helicoil.

[AKDmax]

If you have enough material to tap and install a heli-coil insert, that should do the trick. They are used extensively in the A/C industry, should be fine for the Alli. You have to start with good threads for the insert to stay though. Better than stripping a spark plug hole . (Been there)

[77TransAm]

You will have no trouble with a heli-coil. You're even lucky - since it's a pan bolt all your chips will fall down away from the trans anyway! [img]smile.gif[/img] What could be easier? M8 x 1.25 is the thread pitch.

[DieselDennis]

A helicoil would be an easy option. But for an even easier option you could go with a self tapping drain plug. You just insert them in the hole and turn'em up in there. Then it's a good idea to flush the filings back out with some fluid. If the plug is an 8 X 1.25 then you could go with a 10 X 1.25 size self tapping plug. I'd try to stay with the 1.25 thread gauge because the pan is not all that thick. The 1.25 plug will give you the most threads. You can usually find them at the auto parts store for a few dollars. Look back where the oil change stuff is located.

I stripped an oil pan plug out of a truck once. Put a self tapping plug in to tap the hole. But I put a new plug in after that because the self tapping plugs don't have a magnetic tip.

Get it changed quick and sleep at night [img]tongue.gif[/img]

[ 10-10-2002: Message edited by: DieselDennis ]</p>

[AKDmax]

There is also the option of using a keensert or keysert. Same thing, different name. Driving the pins in after the insert is installed essentially locks it in. Very very strong. Here are a couple links to check out for thread repair.
http://www.newmantools.com/key.htm
http://www.otctools.com/brochures/247-1.pdf
A google search for heli-coil or keensert will give you tons of info. My understanding is this isn't the drain plug, but one of the pan bolts. Self-tapping is definitely cheaper, or you could use permatex thread repair if that appeals to your

[ndamico]

does anyone have any idea as to how much material i need left if i do use a larger bot or helicoil? are the existing bolt holes big enough? how thick should the walls of the hole be before i risk it cracking/breaking?

thanks!

[SoMnDMAX]

Use a Helicoil insert. They work the best for your application, since they leave more of the parent material intact.

I personally wouldn't install a larger bolt. You'll still have to tap the case, then you'll have to open up the hole in the pan, find a bolt, etc. The Helicoil is the cleanest, most professional way to fix it.

Keenserts are a great product, but not for pan bolts on an aluminum transmission case. The staking pins can break the case when driven into place, plus, the hole size needed to install the insert could leave the case quite thin around the hole, further compounding the risk of fracturing the case. The more of the original case that's left intact, the better.

Trust me on the thread insert thing. I've installed thousands of them, in everything- brass, aluminum, plastic, steel, tool steel, among others. At work they call me the Helicoil King... [img]smile.gif[/img]

[SoMnDMAX]

OK... Did some research.

An M8x1.25 Helicoil tap has a 9.8 mm major diameter.

An M8x1.25 Keensert requires an M12x1.75 hole for installation. The Keensert also requires the hole to have .540" minimum thread depth to install the insert.

Ndamico, keep the hole as small as possible. A good rule of thumb for a strong hole is 1 times the diameter of the hole, around the hole. If you've got an 8mm bolt, there should be at least 8mm of material surrounding the perimiter of the hole. More is better. What's the threshold before the case breaks? I don't know. I wouldn't want to find out either.

AKDmax- I know what you mean in reference to the spark plug holes.... I had to repair a plug hole on the head for my Honda CBX. The bike is very rare, and parts are VERY expensive and VERY hard to find. Needless to say, it was a sphincter puckering experience. So far so good. Two plug changes, and the Helicoil is still where it's supposed to be....

[AKDmax]

Just trying to throw out ideas to get things rolling on a good fix. Hope it works out for ya ndamico.