Rebuilding C4 Dana 44, what clutches for the diff?

IROC-Z · 11-02-2009, 11:14 AM

Hey guys, I'm rebuilding a Dana 44 for road racing, auto-x, and street use. I have an honest 500lbsft at the flywheel and a TKO600 5 speed trans. What do you guys typically use for limited slip units? Is the stock unit with stock clutches and shims OK? Stock unit with upgraded clutches and more preload? Is the torsen type unit the only one to go with? I'm a Camaro guy so I don't know what you guys normally use for this type of use. Thanks for the help.

vetteoz · 11-02-2009, 02:08 PM

Any time you run a Vette D44 with power you are rolling a dice.
Most prone to breakage with man cars and clutch dumps on slicks but..............
Torque kills them ; not Hp.Have never seen anyone report problems with stock posi and clutches set up correctly.

Those that have installed the Eaton ($800+ install ) have reported good results

Too many other things to break before posi bcomes a problem
Carrier cases split in 2 , side gears shatter ,broken uni's , twisted halfshafts then you get to the outer end problems

IROC-Z · 11-03-2009, 10:31 AM

Wow, I got this unit because it is stronger than the axle I'm currently using and its stronger than the Dana 36. (I'm putting this in the back of a Camaro, fire up the ban stick

) I haven't managed to break my stock 7.625 R&P yet and was hoping this would hold up with good bearings and upgraded U joints.

COPO · 11-03-2009, 05:20 PM

Quote:

Originally Posted by IROC-Z

Wow, I got this unit because it is stronger than the axle I'm currently using and its stronger than the Dana 36. (I'm putting this in the back of a Camaro, fire up the ban stick

) I haven't managed to break my stock 7.625 R&P yet and was hoping this would hold up with good bearings and upgraded U joints.

lets see some pics!!!!

IROC-Z · 11-03-2009, 06:54 PM

Here is a pic. I'll post my progress pics once I get started in a few weeks.

I was told by another C4 owner that I should also upgrate the universal joints in the half shafts. Anyone know a good source for those?

COPO · 11-04-2009, 06:12 PM

Nice looking car!! Never seen those wheels on a 3rd gen before. Are you planing on installing C4 rear suspension under the rear?

95blklt1 · 11-04-2009, 08:18 PM

Quote:

Originally Posted by IROC-Z

Here is a pic. I'll post my progress pics once I get started in a few weeks.

I was told by another C4 owner that I should also upgrate the universal joints in the half shafts. Anyone know a good source for those?

I love the IROC's. Your's is sweet lookin

IROC-Z · 11-04-2009, 08:54 PM

Thanks for the kind words guys, I appreciate it. Yes the Dana44 is going in the back of this car. My 383 is making enough power that it will eventually destroy my stock rear axle. It is already starting to whine, leak, the pinion is getting sloppy, and the Zexel Torsen diff does not have the bias ratio to spin both rear tires coming off a corner on slicks. (I auto-x and HPDE the car as often as I can)

My options for upgrading the rear axle are a 12 bolt or a 9". Both options will cost upwards of $3k, add lots of unsprung weight, and make my handling worse. So about 2 years ago I decided to considering other options and the D44 seemed like a wise choice. I can swap it in for the same or less money, reduce weight and improve performance.

This fall I stumbled on a great deal on a complete unit from disc to disc, so I picked it up. I've seen Dana 36s swapped into one 4th gen firebird, and 2 3rd camaros, but the cars were not raced and the swap was done for novelty instead of performance.

I'm going to execute the swap and keep all of the stock driveline angles so I have a "clean slate" to begin dialing the car back in on the track. I'm planning to begin the swap in about 2 weeks, I'll post pics for those interested.

Few people know this but GM built a test mule of sorts with the D44 IRS. Here is some info about it. Sadly there are no pics of the install...
http://www.gtasourcepage.com/91FirefoxTest.html
http://www.thirdgen.org/firebird_fir..._december_1991

I still need to find a Z51 rear leaf spring, and a 3.54 ring and pinion. The diff I currently have has a 4.09 gear in it that appears to be in fantastic shape, but a 4.09 is way too low for my engine. If anyone has a complete and useable 3.54 diff, I'm willing to trade my 4.09 unit to get the gears I want.

vetteoz · 11-04-2009, 09:03 PM

Quote:

Originally Posted by IROC-Z

I still need to find a Z51 rear leaf spring,

The is no one "Z51" spring

All rear springs interchange 84- 96 and the rates softened over the years so that a late 51 / Z07 spring was softer than the base spring on a earlier model
Going to a Z51 or heavier swaybar is mentioned as a 1st option before spring change for handling improvement

http://www.corvette-guru.com/modules...d=8605&forum=1

http://www.idavette.net/hib/c4/sustunch.pdf

Run a adv over on CF for sale ; always performance guys with 6spd cars looking to swap out their 3.5's for 4.09's

IROC-Z · 11-05-2009, 10:54 AM

Yes I should have been more specific. I have the chart you posted a link to and know I need the early Z51 spring. With wheel rates factored in, the spring rate comes out to only slightly stiffer than my original IROC springs. The rear sway bar that came with it is a 24mm which is the same diameter as my stock IROC unit, but I dont know how long the arms are or anything like that to compare stiffness. Sway bars are easily swapped anyway, I'll try to use a stock Camaro or Corvette bar if I can, that way larger units are easy to find. My only other option would be to make a custom one with circle track parts.

This weekend I'll get some pics of the unit and post over on the classifieds. I'd love to trade someone their 3.54 for my 4.09.

again, thanks for the help guys.

COPO · 11-06-2009, 07:38 PM

C4 suspension is pretty cool, but have you thought about C6. For just a lil more money and since the fab work should be in the same level....It would be kick ass.

IROC-Z · 11-07-2009, 07:27 AM

I've thought about it but not really taken any measurements. I'm afraid the fab work will be 10x the amount required to fit the C4 setup. On the C4 setup the batwing tips will mount right where my rear coil springs were, already a load bearing part of the car. The "ladder" that comes off the pinion will be mounted to the trans tunnel like my current aftermarket torque arms is. The only actual cutting needed is to cut off my panhard bar mount, and I have to cut the lower front of each rear wheel well to mount the control arms. SO yes there is some cutting and lots of welding to do, but its not like back-halving the car either. I'm afraid a C5 or C6 setup would require me to move the fuel tank, cut the rear of the trans tunnel out, cut the tops of the wheel houses out for upper control arm clearance. Then I'd have to figure out how to get the torque tube, trans, and clutch to interface with my Gen 1 SBC. By the time I bought everything plus a fuel tank and all the other small items I'm afraid I'd have 3x the money in a C6 swap than I will in the C4 swap.

If I can trade someone my 4.09 diff for a 3.54 diff straight up, I'll be able to do the C4 swap for under @2k. I stumbled on the complete D44 setup from disc to disc for $1500, which I think is a deal for a D44.

I'm going to get pics of the inside of the diff this weekened so I can post them in the classifieds.

COPO · 11-07-2009, 08:20 AM

You dont have to use the torque tube, there are other ways of doing it. never been under a camaro so I dont kno what it looks like. If possible take some pics under the car. sent u a pm

IROC-Z · 11-22-2009, 06:57 PM

COPO, got your PMs, looks like you guys do some incredible work on some incredible machines, I love it.

Here are a few preliminary shots of the swap as it stands right now.