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post #1 of (permalink) Old 12-23-2001, 03:12 AM Thread Starter
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Clocking Dana 300- tapping cast iron?

I am in the process of clocking my Dana 300. I am planning to drill and tap new holes in the t-case at the desired indexing.

I have tapped holes in mild steel and aluminum without a problem. Is cast iron any easier/harder to tap and are there any 'gotchas' I should know about?



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post #2 of (permalink) Old 12-23-2001, 03:52 AM
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Re: Clocking Dana 300- tapping cast iron?

I've done a fair amount of machine work in a previous life. If by some chance your going to remove the TC, use a drill press (verified with a square to be perpendicular...important) to get the holes drilled straight. Also use a new tap in the drill's chuck and turn the chuck with the handle of the chuck key to start it. This will insure the tap enters the hole straight and centered. After it's in 5-6 threads, use a tap handle to finish. My old mentor swore by "Crisco" (shortening) for cast iron and that's what I used. "Magic-Tap" is pretty good stuff, but a wee bit expensive. It's VERY important to remove the tap & clean it, blow out the hole, and re-Crisco the tap every 2-3 threads. Cast Iron seems to "load up" the tap faster and this keeps ugly things from happening.
If your NOT planning to drop the TC, well, good luck. The above can still be used if your going to freehand the holes & threads.

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post #3 of (permalink) Old 12-23-2001, 06:05 AM
 
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Re: Clocking Dana 300- tapping cast iron?

<blockquote><font size=1>In reply to:</font><hr>

If your NOT planning to drop the TC, well, good luck.
The above can still be used if your going to freehand the holes & threads.

<hr></blockquote>

How in the Wide, Wide World Of Sports is he going to get that drill press under that Jeep if he doesn't drop the T-case?? [img]/wwwthreads_images/icons/crazy.gif[/img]
-----------------

You see, there is a reason we spend hundreds of thousands of dollars on machine shop equipment.
(so we can do the job correctly on the SECOND piece you want done...)

I only have two words for you, "Milling Machine"...
Mark your locations with a TRANSFER PUNCH (drawing little circles doesn't cut it...), and take the T-case to a machine shop (so you have someone to blame when the holes aren't in the right place...[img]/wwwthreads_images/icons/wink.gif[/img].).

Transfer punch will get the pilot points in the center of the holes. If you don't, someone like me will have to get out the very expensive divining head, and boy does it cost big money to have my lazy butt hoist that heavy bastard up on the milling machine table...

You can get away with a drill press if you use a MACHINIST SQUARE (none of those carpentry 'speed squares' I see in the shops all the time) to verify the set-up before you drill.
If I were doing it, I'd go through with the correct size drill, and use a floating tap fixture in the drill press or head mill.
Use a floating tap fixture because cast iron gets 'wollowed' out as you run the tap in and out to clean it and break chips... (and you have to break chips and run in and out...)
A floating fixture keeps the tap from eating more away from the threads you already cut.
Sort of a pressure sensitive device. Keeps you from cross threading too (real common mistake beginners make).

And if you screw up, remember, there is always Heli-Coil for oversize holes...(IE: screwed up holes)
(not really a bad idea for cast iron anyway...)


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post #4 of (permalink) Old 12-23-2001, 10:00 AM
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Re: Clocking Dana 300- tapping cast iron?

<font color=red>How in the Wide, Wide World Of Sports is he going to get that drill press under that Jeep if he doesn't drop the T-case??</font color=red>

Damn, Aaron, I just about fell out of the chair laughing over that one!

He will obviously have to remove the T-case, but won't necessarily have to get the drill press under the jeep. You're just not thinking 3 dimensionally.

<font color=red>...and boy does it cost big money to have my lazy butt hoist that heavy bastard up on the milling machine table...</font color=red>

So for a few more $$$, here's how to save some time. Just flip the jeep over and put IT on the drill press. Of course, now I'm wondering what you'd charge to do this, but it may not be a lot more.

I will NEVER crawl under a jeep or Zuk again to work on a tranny, t-case, or anything else. From now on, it comes to me. These are a few pics of a friend and I removing a D300 for ZLY from one of my jeeps.





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post #5 of (permalink) Old 12-23-2001, 10:01 AM
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Re: Clocking Dana 300- tapping cast iron?

I'm a little lost on why you want to relocate the studs in the t-case. Why not just drill the extension housing in the tranny? You will have to give up one of the 6 bolts, and only use 5, but it is much easier. Another method is to drop the money on the "clocking ring" and give up about 1 inch of driveshaft length.

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post #6 of (permalink) Old 12-23-2001, 11:42 AM
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Re: Clocking Dana 300- tapping cast iron?

Ramo must be clocking the Dana 300 to an adapter. I had to drill and tap my 300 to a Novak adapter on a T-18. in order to use all six holes. The Novak adaper had a web cast in it where I wanded to drill the adapter so I drilled the transfer cas two spots amd put studs in . Like they said above make sure you go in straight and tap a little at a time and clean the tap.

post #7 of (permalink) Old 12-23-2001, 02:26 PM Thread Starter
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Re: Clocking Dana 300- tapping cast iron?

Thanks for all of the replies....I'm glad I asked.

I have a drill press and I already have the case out.

So, Crisco instead of cutting oil, or in addition to?

I'm going to make a jig to hold the case perpendicular to the press.

I like the idea of putting the tap in the chuck to make sure it goes in straight.

The tcase mates right up the nv4500 tailhousing, so no adapter. I would rather not buy one of the rings. If I screw it up, I can get another dana 300 for pretty cheap.

I think I'll be able to keep all 6 bolts/studs by making new holes in the tcase.

Thanks again.

I'll take some pics when I do it (my wife has informed me that I won't be working on the Jeep Christmas or Christmas Eve).



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post #8 of (permalink) Old 12-23-2001, 03:09 PM
 
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Re: Clocking Dana 300- tapping cast iron?

Belh, she's crazy. That's the best time to get it done.

Everyone else is upstairs cooking and getting ready and your making a racket in the garage. No one will even notice you are missing.

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post #9 of (permalink) Old 12-23-2001, 03:54 PM
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Re: Clocking Dana 300- tapping cast iron?

It doesn't take much to cross thread things and end up with a hole full of chips. I ended up having to install a heli-coil in a cylinder head for a valve cover bolt that I screwed up.
If you have some scrap cast material around the shop try a few practice holes. If you don't have any scrap laying around you could always do a practice hole in the 300 case using a drill and tap 2 sizes smaller, then redrill and tap it for the correct size, just make sure your test leaves enough material for the real hole and don't break the smaller tap.
Also, don't use the hardware store taps, go to someone who sells taps with the three different tapers, I don't remember the names other then the "Bottoming" tap, but the one you want is the one with the most taper. I think they call it a starting tap.


post #10 of (permalink) Old 12-23-2001, 04:06 PM
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Re: Clocking Dana 300- tapping cast iron?

Max said something real important, DON'T use a cheap tap, you will end up breaking it off in cast iron, real bummer! I always use my son's set, he has a complete Snap-On set, cost huge bucks, but worth it (more than I can afford!).

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