I was checking my suspension out and rotating tires after my first auto-x weekend on Monday and I found what I initially thought was bad rear wheel bearings. Well I kept checking and found when rocking at the 12 and 6 positions on the tire with the car in the air, the half shafts where actually sliding in and out a visible amount. The stub axles (yokes) and everything attached to them was moving a bit. Equal on both sides, this let the top of the tire rock in and out a little. Some deflection from this in the trailing links and lateral link.

Is this normal?

I never noticed it before. However, I have Z07 springs on the car (this past winter) so when unloaded in the air they have little tension on them unlike the heavily arched stock FE1 springs.

 

The range of movement allowed is 0.0005-0.0085". Im not sure I could see that much movement without measuring.

 

If the ends wear enough, the u-joint section of the end near the rear will hit the rear under hard turns. There's a c-clip inside the housing to keep them from falling out, but only the end of the shaft being worn will allow them to move in. I guess it's possible someone left the clips off, or they fell off inside the rear and that's allowing the wheels to drop out at the top when it's jacked up and it would show play. Either way, the rear will need to be looked into if you have that much play. You probably feel "slop" in the rear when you autocross? When it's sitting on the ground, are the wheels tilted in at top?

 

If the car is auto-x'd hard and often which it seems you do I would think there would be maintenance on the differential every year/winter. I wouldn't think it unusual that the dished spacer closest the differential side gears could collapse somewhat and that coupled with clutch pack wear would give you exactly the condition you're seeing. I would think a really tight clutch pack stack might help.

If there were recent maintenance on the differential, then when reassembled the same retaining rings were used without checking the end-play and changing the thickness of the select retaining clips.

Winter is for maintenance and the differential if the car is used like you often mention it is needs inspected every winter. A clutch pack every winter would be considered maintenance in a car used for hard auto-x-ing or drag racing for that matter. The Super 44 doesn't get attention until it fails and then it's blamed on the differential!

You can drop the half-shafts and confirm of course the amount of end-play but I'd plan on dropping the differential and doing a clutch pack while inspecting the pinion shaft and the case diameters where the pin fits. Get yourself 2 pinion washers also maybe a pinion shaft too. The specs "GSDave" mentioned are correct and it wouldn't seem that you would be able to "visually" see it!

Pinion gear washers and a clutch pack every year? Maybe. Every two years I would think a must. Dropping the half-shafts and confirming end play every year I'd think a must.

The pinion gear washers are very inexpensive and should be done everytime the differential clutch pack is serviced, in a differential that's used as yours maybe every winter or every second I'd think for sure.

 

I had a track event and it felt like the rear tire was flat. Checked for play and there was about three inches! After opening the diff the snap ring had fallen off. Six years mixed drag and road track use on the D36. Clutches were not bad! I had it rebuilt for $400 locally. They said the part that holds the u-joint wore out. I have all the parts if anyone wants to see a pic. Pic after opening it:

 

Interesting, I have NO where near 3 inches of slop. Holy crap. Was that the top of the tire or shaft moving?

Nor does the rear end feel loose at all. In fact quite the opposite.

No strange noises or anything. The rear wheels do lean in however my alignment is set at -1.25 degrees of camber in the back.

Clutch packs are tight, I checked breakaway torque last winter it was 85 on one side and 90 on the other. Limit is around 70 or so.

Note: I don't use R-comps or slicks, just street tires for auto-x and the occasional drag race.

Aardwolf, I'd be curious to see those pics as well as where you got all the parts for the rebuild.

 

That is the "Inner Stub Axle".

When you set these rear ends up for racing or performance useage you want to set the stub axle side play to the minimum (.0005) end of the spec.

If you think about what that stub axle does as the suspension goes thru it's range of motion (constantly traveling in and out).... you'll understand that you want it crashing against the spider gear cross pin shaft with as little momentum as possible.

Will

 

I guess the next logical question is how soon does this need addressed? A $1k diff rebuild with the season just getting going is not in the playbook.

Also, if the stub axles are what is wearings, should I look into the cold stablized stub axles if I'm doing a rebuild. What about the spider gear cross shaft?

Reckless? How did you build up your D44. If it can withstand your HP it should withstand stock HP and lots of corners.

 

Both of my C4's have D44's in them. I don't want to give the impression that my D44's "stand up to the kind of power I make" for either car because I have broken lots of stuff over the years.... However over the years I have figured out some stuff to keep them alive as long as possible. I have not had a failure with Posi since I have started doing what's listed below (over 3 yrs)...

Both use Yukon Ring and Pinion gears and Timken brg kits. 4.10 in the 92 and a 3.73 in the 84. The key here for drag racing is to set the R&P back lash up at the minimum.... This is to minimize the hit that the R&P take on launch..... this is not a great idea for a road racing car in my opinion or any other type of car that builds alot of heat in the diff and dosen't do har launches over and over.... For a road racing car I'd try for the middle of the spec.

On the Posi and Stub Axles.... I use all factory Dana Spicer parts. No Cryo, No shot peening ect.... The key is in close attention to detail about the set up. Like I said close the stub axle end play up to the minimum. Buy a few sets of the different thickness snap rings from Toms Differential.

Shim the clutch pack so that the Posi is a tight as possible. I only use the Spicer PN 707018X clutch pack. Only cost about $50.00. With new Spicer clutchs and a .020 shim you can get 150LBS of break away per side. You can use set up shims from the carrier brgs or make them from stock or just buy them from Toms..... A posi set up like this last all season in my 84 Drag car.

From there run good quality 75W-140 gear oil... (I use Valvoline SynPower 75W-140) and pay attention to the Posi break away TQ. I check the posi after every week of racing and I keep a log book of the break away TQ. Once it goes under 70LBS I put new clutches in it....

When you tear the diff down for maintenance. Pay attention to the wear spots.

I did this write up when I rebuilt a D44 Posi for 93 ragtop.

http://www.corvetteguruforum.com/mod...topic_id=17573

I cover most of the important spots to check for. He drag races alot and his Posi had a few yrs of racing on it with no checks.... Lots of damage so I had good examples of the damage to look for and we took halfway decent pics to show it.

Will

 

We all love pictures

 

Got the pictures!

I've been pretty happy with the D36. This is the first problem I've had with it since I got the car. I thought of picking up a used one for $300-350 but for $400 I got this one rebuilt with a warranty.

 

Ok, so after viewing your postings, let me get this stright.

The stub axles wear at the end of them inside the diff. as they rub/hit the spider cross shaft?

This causes excessive clearance and I get the in and out movement of the inner stub axles.

Not to mention clutch pack wear.

Is this correct?

I am assuming I need new stub axles, clutch pack kit, new snap rings, at a minimum.

If the bearings, ring/pinion gears, carrier, side gears, pinion gears, cross shaft are all ok, they should be able to be reused? I would think so.

I really won't know until I get into the thing, how bad the damage is.

Reckless, it sounds like with few tools I can do this myself. I've got the books and training on diff. rebuilding but that was 5 years ago when I was in school. I'm a bit rusty on it.

 

You need to remove it and inspect it to determine your needs. The disassembly will determine your needs. You could collect parts before hand but depending on what you find it could be an advantage to buy a differential. If the wear on the pinion shaft to the case is excessive it's the only fix.

If your interested in parts I have NOS "Dana" branded short axles depending on what you find, I do have I believe one pinon shaft and I believe a pair of pinion washers, I have a "Dana" branded NEW differential if it were needed. The pinion shaft and washers I quite sure I can put my hands on, I haven't in quite some time but I'd think I could. I believe I've only one "pair" of short axles but I believe a couple of extra lefts. I'd need to check.

Short axles aren't inexpensive but you don't know that they're needed until it's apart. I've got pretty near a complete set of GM select washers. They aren't as cheap as Tom's but they're the original real deal. They aren't inexpensive either, I got these when I don't believe anyone had them other than OE GM. They had to be purchased in a complete thickness range you'll find in the FSM (2 of each).

 

You have the top stuff correct.

As for what you need... like WVZR1 said, you really cant/wont know until you start the tear down and start checking everything out.

You only need new stub axles if you are unable to get the end play in spec using the different thickness snap ring retainers.

Yes its not very complicated and you can still buy the Miller SPX clutch pack tools like I own. I bought my tools on ebay, I think I listed all the PNs in that build thread so they should be easy to search for. Some people just fabricate the clutch pack spreader with all thread, nuts and some washers.
Will

 

Ok, thanks guys. I'm going to plan on ripping the rear end apart next winter. Hopefully, I have a better place to work on it then.

I'm willing to bet the exhuast/c-beam will give me more trouble than anything else.

Hopefully, I DON'T find too much, but I'll budget accordingly.

If I need a differential unit, I'm not going to mess around, TrueTrac for sure. Nothing to wear out, and at my stock HP/TQ levels I'll never hurt the thing.

 

I understand some of what you mention about "procrastinating" BUT when/if the differential pinions let go there's usually a "window" created in the "floor" of the housing besides the differential, the gear pack and the short-axles that could suffer.

It will soon be warm and I'd think a day spent tearing it down could save many $$'s down the road. If you do "break it" I have enough NOS for you to build another, I've an NOS housing, rear cover and I mentioned a couple axles etc. I've got a repaired housing also.

 

No offense but a "day spent tearing it down".

Your funny, I'd be lucky if my car was not down for a month.
The conditions I have to work in (my WOOD floor ins't even close to level end to end for petes sake, you'd be surprised buy what I HAVE done in my hell hole of a garage, ONLY by necessity), things fighting me coming apart and going together ie. exhuast, those nuts are going to come off....yeah right, torches...not to mention my luck with stuff.

I hear you loud and clear on what COULD happen. I'm not trying to give you attitude but you have to understand what I'm up against. I could tear it apart and have the car down for a month or two. I could run it and it lasts just fine. It could blow apart tomorrow which then it would be down for a month or two anyhow.

Keep in mind if I'm in there with the entire rear suspension tore apart....things are getting replaced like the stock bushings...my car would be down for at least a month maybe more.

Given all that and the fact nothing is EVER simple around here for me...I'll take my chances and ride it out till next winter. If things go south, which they always do, I have time to deal with it then. I don't in the middle of summer. If it REALLY goes south, well life is full of risks. I've always been damned if I do, damned if I don't, so I just started doing what is most convenient. Doesn't seem to matter which way I go with things. Enough of my life story....


Switching gears....are the backlash shims reusable? How about the ring bolts? Pinion/carrier shims if I put in new bearings?

Any other replaceable parts?

Reckless, in your post about rebuilding the clutch packs, do you add any shims to get that 150ft-lbs or just the spacers and such? I ask because Tom's lists shims for tuning the LSD?

I did find those Miller Tools on ebay for like 150 or less.

Also, is back lash adjustable like most GM integral diffs with shims on either side of the unit? Looking at the FSM seems to be that it is.

 

WVZR-1, I'll have to give this all some thought.

For now I have a EVO auto-x school I paid $250 this upcoming weekend. That car is doing that bar NOTHING. We'll see after that. Maybe I can pull something out of my *** like I usually do.

Not going to lie, but if the Dana 44 cannot stand up to some auto-x on STREET tires, maybe its time to move on. I love my C4 but this is kinda BS timing on me finding a bit of play.

 

How tight you get the posi depends on wear to the gears, washers and carrier... A .020 shim was enough to get over 100lbs in my 92, where it was 90lbs with just new clutches....

Backlash on a Dana is set with shims between the carrier and the carrier brgs... not on the outside (between the carrier brgs and housing) like a GM 12 bolt.

Shims are reuseable when you change gear sets.... as long as you dont mess them up.
Will

 

Hmm, interesting backlash adjustment. Kinda stinks if its off, you have to pull the bearings.

Dumb question, if my clutches are still tight 85 and 90 respectively, then the play would have to be elsewhere? Right?

I'm trying to learn as much as I can. Better to look before you leap so to speak.

Thanks for your help so far Reckless and WVZR-1. Even if I am stubborn.