Removing stuck trans. 8mm hex socket head bolts

Kroil (by KANO Laboratories) is by far the best penetrating oil I have ever used. Check out www.kanolabs.com for more information. I've used it for over 20 years working on airplanes & automobiles, & haven't found anything better yet. I've also used a large E-Z out (screw extractor) when internal wrenching bolt heads strip out, I've seen others cut a slot in the head to accept a common screwdriver, whatever "floats your boat"! Good luck !
Paul

Maybe not quite frozen. I recently tore apart an unmolested ZF, and the only allen wrench that worked was Unbrako brand, and it twisted 270 degrees. I snapped two others in pieces, then used the short pieces in an 8mm socket & 3/8 drive ratchet. Broke one of these too, but the thing came apart. I suspect that ZF used power tools to assemble the cases some 35 years ago and things took a set. Uhhh, you are using metric allens, I hope. There's not a prayer of unbolting the thing with an almost-the-right-size SAE allen wrench.

Sometimes if you use a flat brass punch you can smack the head of the bolt straight on and it will loosen up enough to get it to turn.The I have had a lot of practice with the pump to bell housing bolts on a Ford 4R44/55 automatic trans which are similar.
Good luck,
Ron

You may want to check your local industrial supply houses for Apex impact allen drivers. They aren't cheap, but they are stout. That is what I used on the plugs in the O2 sensor bungs. Made the hex look like a Torx, but they came out.

Thank you all for your input/suggestions, I have ordered some Kroil and looking for a hex impact drive.

Here are some of the industrial suppliers that I use in Atlanta. I think most of my impact stuff came from Ziegler. Any of these companies in New York? Snap-on also has allen drivers, but I don't think they are as stout as the Apex.
http://www.grainger.com/Grainger/wwg/start.shtml
http://www.mcmaster.com/
http://www.zieglertools.com/

Just be careful, the apex (as well as the E-Z outs) are "very stout", however they are also quite brittle. Sometimes when using an impact, they can shatter. Wear eye protection & if one does snap off you can usually get it out with a pick or place a socket over the bolt (large enough to fit over the wrench, but small enough to impact the O.D. of the bolt) & give it a good smack! BTW, the Kroil works best if you give it a little time to seep in, a buddy of mine had some suspension pieces on his Willys (sp?) truck siezed up, sprayed on the Kroil, waited overnight, success in the morning! I'm usually not that patient, but if you've got the time it doesn't hurt.
Good Luck & keep us posted.
Paul

Biggest problem with using impact drivers here is the approx. 8" depth you have to deal with, making socket extensions mandatory. And the more stuff you stack up between the bolt head and impact driver, the more the force you apply is diluted or sent at the wrong angle. You have an opportunity here to screw up your ZF cases royally. Spare diff sections where the threads are, go for about $500 and that doesn't include swapping the gears, washers & other bits from one case to another, nor any welding & rethreading required if you want to re-use your original cases. Be REAL careful with using hammers, air-guns and other power tools on ZF cases! Berore you create any problems for yourself, check with RBT Transmissions (another section of this same website). The prices will stop your heart....

Mccall is right, the best way to undo the 8mm allens is to hit the head 3-4 times with a brass punch, it will shock the bolt and help you back it out, I do it one out of two ZF's.Lloyd @ RBT