Need help drilling hole in Truetrac carrier.

[hammer189]

I bought the Jantz kit to put the stronger JK 44 gears in my Dana 44.
http://classicbroncos.com/forums/showthread.php?t=281832&highlight=Jantz
This requires me to drill out the flange in the Eaton Truetrac to fit the 1/2" ring gear bolts. The flange is hardened steel. I tried a Milwaukee cobalt 1/2" bit and it did nothing.
Any ideas on how to do this in my garage or do I need to find a machine shop?

Thanks, David

 

[Hinmaton]

I would speak with Carl and see if he has any suggestions as step one.
I am a machinist by trade, and drilling out holes to increase their size by just a little bit is tough even when the material isn’t hardened. There is not enough material available to stabilize the cutting edges of the drill, so it is hard to get a good bite in the material leading to to chatter, cutting edge break down, heat and excessive wear. Add hardened materials and there is little chance of success.
The material is most likely case hardened and not thru hardened, so if you can get through the outer layer the rest will cut better. If it is thru hardened...
The Tool has to be harder than the material you’re cutting, which means using carbide, which are expensive. Grinding and sanding tend to work best on hard materials. If I remember correctly the D44 ring gear bolts are 3/8”-24, which would be a tough amount to try and grind out.

Again- call Carl. He’s a super smart guy, if anyone knows how to do it, it’s him.

Hinmaton


Sent from my iPhone using Tapatalk

 

[hammer189]

Thanks, I'll give him a call. David

 

[Rustytruck]

As a machinest for half my life, my first plan of attack after finding out the material is hard would be a multi flute carbide reamer. Second choice would be a carbide spot face with a proper pilot. Or a multi flute carbide drill bit.

https://www.mcmaster.com/#27515a56/=1bw1q8o

sucess will be based on drill bit speed and constant feed pressure. Too fast you wipe out. To slow a feed rate you wipe out. You need the bit to bite in and go. Only 2 flutes will probably just grab and break the bit up. You need a solid setup for each hole. Hand drill is out of the question.

Check the metal with a file if you can get it to bite you can drill it with something. If it just scates like glass your going to have a problem.

 

[Nevadasmith]

Use a reamer! No more than you are going to use it. I suspect a hss tapered repair man's reamer would do the job and cost less....also tapered reamer are much easier to use if you don't have access to a milling machine, in a hand drill for example, you might look at McMaster Carr pn 3089A15 $44, good luck!

 

[Apogee]

I have access to a CNC milling machine, so I would machine up some soft jaws, and then interpolate the holes with a 5/16" or 3/8" carbide endmill. In a pinch, you might be able to attack it by hand with a 1/4" carbide double cut burr in a die-grinder, but it won't be as pretty in the end. Thankfully the ring gear should be located by it's ID on the register of the carrier flange, so the holes really just need to clear the larger 1/2" hardware, right?

 

[EricLar80]

https://www.mcmaster.com/#3089a15/=1bwc230

 

[DirtDonk]

Just to play devil's advocate here, and even though this is a very highly stressed area, what about using sleeves in the new ring gear to take up the space between the bolts and the new, larger holes?
Is this just leaving too much of a weak point (the smaller original bolts) or even adding another weak area by adding a sleeve material that might be inferior to the bolt anyway?

Just wondering out loud. Not to dissuade you from going the proper route, but more of a "what about this" discussion.
Is the whole point of the stronger new setup in fact the larger bolts alone?

Thanks

Paul

 

[Rustytruck]

I think the problem is the JK dana 44 ring gear has 1/2" bolts the stock tru-track has 3/8" bolts thus the need to drill larger holes. You could probably find studs to make the transition too.

 

[EricLar80]

I think the problem is the JK dana 44 ring gear has 1/2" bolts the stock tru-track has 3/8" bolts thus the need to drill larger holes. You could probably find studs to make the transition too.

Right. The ring gear is threaded with 1/2" threads so the holes have to opened up. I would personally try to ream them since the holes are probably only case hardened, but you do risk damaging the reamer since it is only a little harder than the hole itself.

 

[DirtDonk]

Oops, brain fart! Sorry, I was seeing in my head the carrier being re-threaded and the straight holes in the ring gear. Totally forgot that the ring gear is the threaded part!

That's what I get for playing DA on a Friday!

Thanks

Paul

 

[Nevadasmith]

https://www.mcmaster.com/#3089a15/=1bwc230

X2, that's what I said hahaha

 

[EricLar80]

Great minds think alike!

 

[sykanr0ng]

What brand of gears do you have?
Most if not all of the aftermarket JK ring gears are drilled and tapped for more than one size of bolt, because aftermarket differentials are often drilled for other sizes of bolts than 1/2 inch.

When was your TrueTrac made?
The newer production TrueTracs are drilled with two sets of bolt holes for the older smaller bolts and one of the newer sizes Dana has used in the D44.

If it was mine I would have a machine shop make the holes larger.
Usually I am all about DIY, but the ring gear bolts are critical enough to want better and more accurate work.

 

[hammer189]

Thanks for the replies. The carrier is at a machine shop right now. Hopefully they can drill the holes out, if not I'm going with the reamer.
Studs might be a viable possibility if I can;t drill them out.
The carrier is new and the hole sizes are 7/16" and 3/8".
The Ring gears are from Dana and only have 1 set of holes, 1/2".
I'm going to call Jantz on Monday to get some more info. He is very knowledgeable.
I'll post what I find out. David

 

[sykanr0ng]

A few things I have found:

TrueTrac cases are 56 to 58 Rockwell C scale hardness.

Nitro gears do have 7/16 inch holes (or a set of 7/16 and a set of 1/2 inch)

Revolution gears are also drilled and tapped for more than one size bolt (going by pictures, most likely 7/16 inch and 1/2 inch).

 

[DirtDonk]

Interesting to see two size holes in an application like a ring gear. But good to find for just this reason!

Thanks

Paul