Dave your exactly dead on with your comments and I started writing something earlier today along the same lines....but then I had to run and did not get it fully complete.

As I referred to earlier I was last night working on my gears...in order to get them set right i had to knock the pinion race out and install some shims....in doing so you expose some of the machined casting...in what I could see were some fairly large exposed casting voids...........this exact thing came to mind which why some people experience possible failure of the housings....coupled of course with what I described before..........

I work as an engineer dealing with GM on a regular basis, while our technology is Powdered Metal engine components......castings is a direct competitor of ours....as with anything you want to know your competitions strengths and weaknesses....one of castings is voids caused by trapped air bubbles...

Is this the reason why some setups fail sooner.......perhaps...is it why all fail....probably not.

 

When I had my '90, I was consistently leaving at 4,000 rpm on Nittos and just chirped the tires. That car was stock cam/heads/clutch, but was modded out and made 365 rwtq on the dyno or about 420-430 at the crank. I had no problems with it, probably because the clutch was mushy enough to not hurt the rear. My best 60ft with that car was 1.86.

Now with the '96, I'm leaving at 4,000. It makes less torque, but has run a better 60 at 1.80. After reading this post, I think I'll start leaving at 3,000 just to be safe.

 

To Dave and Jesse, your last postings are very good explanations. I've wondered about casting errors and if it's something that can slip past quality control. I'm thinking I've got a casting error in the front differential of my '02 Tahoe, it sounds as though its eaten a second set of bearings. The two of you have substantiated that thinking. I've still got a couple of choices, not sure which way I'm going to go. Thanks to everyone who has contributed to this thread!

 

I did have some luck running a 6 speed and irs. There is no doubt that you can run faster more dependibly with an automatic. I guess I just like to do things different. If you have everything cryoed and good beam plates,urethane bushings,ect, I think you can run well in the 11's with a manual. I ran 10.70's for quite a while with a good single disc clutch, and never broke anything. Maybe I was lucky. That little bit of give in the clutch was the difference. When that clutch wore out and I put the street twin in... that's when the trouble started. I broke halfshafts, u joints and finally the D44 case. At that point I either had to slow the car down, or make the rear stronger. I ended up going the 9" route, and haven't broke anything since. If you are serious about drag racing, a solid axle is the way to go. If you plan to stay with the stock irs, an automatic would be easiest on parts. 6 speeds seem to be hit and miss, some guys have good luck while others break things constintely.

 

I have one question at this point, who do you guys recommend for cryo treating? I heard mention of a guy named Jeb, is he the man? I'm there's many, what have been your experiences with this?

Thanks,

Adam.

 

My fathers place has a large cryo setup - all automated. I put my entire rear in it about 1 year ago. Can't say it did or didn't help.....they make tool and die components that are used in HUGE 880+ ton presses....most of these tools have very intricate detail on the faces of the punches which are used in powdered metal forming. This process basically relieves the stresses induced when ANY material is machined...our differentials are no different. The process relieves those stresses....ultimately making the component less likely to fail at these stress riser areas.

That was a rather simplistic explination but no need to go into fine details of the cylces it runs the parts through....all one needs to know is it relieves the stress risers that are induced when a material is manipulated.

 

Jeb, owns deep freeze cyrogenics. I recommend going to him. Jeb helped me out with the cryoing and with some of his knowledge. With that in mind I have ran (3) 10 second passes on my 6spd car with a best 60' of 1.51. The best et was a 10.87 with my mph usually around 129 using slicks too, and no breakage(knock on wood).

Since then I went from 396 cubes(stock cams), to 428cubes and some pretty stout cams. The power should be a good bit more, therefore it's also time to make some more changes to the irs. When I'm done with my mods I will post some pictures here. I will be retaining the zf 6spd also.

Movement is the key, and as little as possible is best!

 

Neat,
I'm in the same boat with this thread with my application, an '85 D44 in a rather light '28 Model A hotrod, 3:91 gearing setup by DTS, ES batwing bushings, custom heavy duty pinion mount (no c-channel for me), a few inches narrowed to fit the Model A, Eagle adjustable coilovers, and a Muncie-M22, Motor = 530 hp aluminum Motown 427.

As such, I've got a many of your suggestions covered but you mentioned a few things in your list of things that caught my eye. Specifically,

<< -You can box in the stock batwing. >>
<< -Make sure the rear alignment is on.>>

Can you provide some more detail as to the batwing boxing (where?) and any suggestions for the rear alignment (outside of stock?) ?

It's these sorts of details that a builder/racer can't pick up from any magazine. How many times have you read a build-up how-to article where they say, "and then we set up the rear end correctly....?" WTF is "correctly?" Too many times.

Excellent thread! Thanks to all of you for sharing your valuable experience.

Chad

 

 

I heard my name mentioned... I've been off the Forum for a couple of months while I combined my company (Deep Freeze Cryogenics) with Street & Performance so I've been too busy to do much of anything. But, I'm back now.

D44's can be made to live in some pretty harsh environments but it takes some work; particularly with the stick cars. Automatics don't shock the driveline as badly and are somewhat softer when they come out of the hole. Movement is the number one cause of catastrophic failure and all movement needs to be eliminated if you're willing to go to the lengths necessary to do so. However, other components will break long before then: the drive spindles and the halfshafts being chief among them. I've never broken a cryo-treated stock halfshaft (all the way down to high 9's on a stick car) but others have. Some accept this breakage as an expendable part and replace them when necessary. I'm not one of those people; I break it, I build something stronger and look for the next place the break. With halfshafts you have several choices, you can go the expendable stock route, you can cryo-treat the stockers, or you can go upgraded. I know there are several places that make custom halfshafts and I've thrown my hat in there as well with upgraded aluminum, forged steel, and billet steel ones. With regards to spindles (outer drive spindles) they are simple pieces of shemp... They were poorly cast from Spicer and I've hardness tested a few of them that were 26-30 Rockwell; very poor heat treatment. We cryogenically treat them and seem to get very good results from most of them. Occasionally you'll see one that just got a casting inclusion and nothing you do is going to stop it from breaking. I really don't like to give a torque capacity guarantee with the cryo-treated OEM ones but typically they'll take 600 lb/ft easily and I've subjected them to over 800. Once you go over that you have to spend the big bucks. Dennis MacDonald and I worked on a joint project in designing and having some new spindles CNC machined out of Vasco 300M billet... Excellent heat treatment followed by our cryogenic treatment produces a spindle that will take 1200 lb/ft plus. Inside the case you'll burn the clutch packs and bust spider gears in the marginally decent Trac-Loc; the cross pins have a nasty habit of galling as well. You can buy the complete posi-unit, and you can buy the clutch packs, but the spiders and cross-pins are no longer available. I've had good luck polishing the posi-carrier, cryo-treating all of the assembly, and assembling it very carefully and VERY tightly! But you're still working on borrowed time with it. The only real solution is a spool; I use a standard D44 spool that I machine to fit the IAS rears. But, unfortunately if you like to drive on the street they pretty much suck; and don't even THINK about driving it in the rain! But they won't break. The major secret once the ancilliary components are taken care of (the spindles/halfshafts/u-joints) is to eliminate movement in the driveline; but that's a story for another night.
-Jeb

 

Jeb Burnett can box the stock batwing for you. It involves adding some braces to the batwing that sort of make the I beam sections square. That makes the whole unit a bit more stiff.

The alignment needs to have the rear tires with no toe. So they point straight forward.

Incidentally, I found my problem. I sent my rear, spindles, and half shafts to Jeb Burnett to have a spool installed, and some other things checked. He found that my drivers side half shaft was bent pretty badly, and that was most likely killing the spindles.

When I get it back, it will be a cryo treated case, cryo'd spindles, half shafts, a cryo'd spool, and a 4.09 gear set. The batwing will have solid bushings and be boxed. Basically, the only thing else I could do to help the indy survive is fab a cross member for the transmission to take that load away from the C-beam. If it doesn't live now, I don't know what to do. Wish me luck.

 

Hey Jeb, good to see you made it in here. I guess we were posting at the same time.

 

I got to install a set of delrin solid bushings(for the batwing) that I purchased from Jeb today. After the installation of the rear end assembly with these bushings I noticed something remarkable!

When I pushed up on the pinion yolk(with the solid batwing bushings) you could visually see the batwing bow and twist! What a piece of crap, I thought to myself! It is that weak, and a very poor design! I now understand boxing in the batwing for sure. Without the cbeam there isn't any strength whatsoever! And the cbeam is marginal to begin with.

 

Thank you Jeb! I just hope I haven't damaged a spider or the pins, seeing as how i can get them any more. Why in the world would they stop making those pieces? Thanks to all of you, I've learned a lot about the Dana 44 and the IRS in these cars.

Adam.