I heard a clicking in my rear end...when I got it up on the lift I see where the half-shaft u-joint bolts are hitting a flange on the rear end (pass. side, 9 o'clock position). I don't see anything loose or any way to adjust this. Any help is greatly appreciated!! Thanks!

 

can you get a pic of what your talking about?

Here is a pic i dug up of mine.

 

What kind of lift do you have it on? If the wheels are hanging down freely, this can happen- too much halfshaft angle. This would be unrelated to your noise.

Rich

 

mine did that also.... come to find out that halfshafts were hitting the plate that in on top of the t-arm for the bump stop....... it would only make the noise on angled inclines i.e. parking lot entrances.......


b

 

[QUOTE=luerja]can you get a pic of what your talking about?

Here is a pic i dug up of mine.

Where mine is rubbing is on the Pass. side of the diff. housing. I can get some pics tomorrow...

 

If Your talking about what I think Your talking about it means Your
stub shafts that come out of the sides of the differential are wore
out. As the end inside the diff. wears down the half shaft moves closer
to the diff. housing until it begins to make contact. I f this is Your
problem only fix is new stub shafts.

 

I agree check that and fix it before the yoke grinds the face of the boss off the housing and hits the seal.

 

Yes, that can happen. Ask me how I know.

 

Here is a close up of the LH yoke on a Differential I just blueprinted. I dialed in the yoke end play to .002-.004" You see the clearence between the yoke and housing and the seal too.

 

How hard is this to fix? I may have the same issue on my drivers side that I was told was due to a sagging leafspring that changed the geometry and has forced the halfshaft inward told the diff. I'm planning to replace the spring/strut rods/shocks real soon...

 

Just discovered the same wear problem on mine. You detect a noticable clunk and can see the the axle yokes move in and out when rocking the tire at the 6 and 12 positions.
Looks like you have to drop the differential/crossmember/spring to take off the rear cover. Then replace the yokes (minimally).
Do a seach in C3 tech section on "differential + yoke" and you'll get all the info you need.
Gary

 

got it..thanks! Suppose I replace the spring/shocks/rods and it raises the car to relieve the pressure on the side of the differential case. Would this be a safe (although in need of repair) condition until I can get to it or should I not bother with the suspension until I do the diff? I'm a woos of a driver so I don't expect I'll suffer performance wise. My hope is that the lift in the rear will change the geometry favorably and give clearance between the yoke and the case and I can just enjoy the car without getting into the diff.

 

Raising the car wont relieve much pressure on that yoke. There are probably others who can answer better than me. But it seems your camber will vary depending on side load on the tire, if there's significany play in the yoke.
I say do the whole thing at the same time. You're just going to have to remove all the stuff again when you do the differential.
Gary

 

I don’t think a spring replacement will help at all. The C3 uses the axle as a suspension component, much like the upper A-arm on other independent suspension cars. The length of the axle and the length of the strut rod determine the camber of the rear wheel. Slack in the yolk causes a shift in camber when you drive. When you turn to the left the right axle is bulled out of the diff and the left is pulled into the diff, and when you turn right the opposite happens. Changing the spring and the geometry of the axel doesn’t relieve the forces on the axel.

 

Well, just goes to show you, never trust guys who work on Ferrari's (ie my expert). Although a bit disheartening, it's good to know what my real problem is (I'll post some pix that don't have any phantoms in them...I hope!) just to verify I need to do the yoke swap. I'll review Gary's post form yore, but what is the minumum I need to do the job right? I expect since I'll have the half shafts off I'll press on some new U-Joints, but as far as trading out the yokes do I need anything besides the yoke and the seals? Bushings/bearings? I realize this assumes there is no differential damage but that's how I'll begin...

Is it cost effective to swap out the whole diff? Full rebuild by a pro? Cost?

Thanks loads..back to the drawin' board!

 

IMO the biggest PITA on these cars, after possible birdcage rust, is the IRS-differential setup. You start a simple job back there and it will likely open up a whole can of worms. I brought my diff. to a shop that specializes in differentials and they told me it was junk since the side yokes had worn to a point that the case got ruined. I found a good used one on Ebay and put that in. Hopefully yours isn't as bad as mine was so you'll have other options (Van Steel, gtr1999 or his paper, local shop, etc). My point is don't try to scrimp on things while you have it apart. Do it right and you won't have to worry about it again for a long time.

 

If I may suggest a few things to help you out.
1st it sounds like you're new to these cars and you have one that needs rear suspension/Differential work. Probably a late 70's vette that hasn't been touched in the IRS?
The 1/2 shafts joints are pressed in pretty tight so you may find they do not just press out. Unless you have worked on vette 1/2 shafts they can be a PITA, they are not like replacing joints in the common driveshafts. The best way is not to press them out but to cut them out. Use an oxy-ace torch and burn those suckers out,polish the yokes, then lightly press the new caps in. You have to support the flange or it will bend for sure. Look at the shafts to see if there are any flat spots on them near the yoke ends. This is a good sign that someone replaced them before and crushed the tube in a vise. If that's the case you may find the flange is already wrecked.
Here is how I work on them. This is a shaft I installed Spicers in for my buddy Jim in FL.





As for a cost effective way of rebuilding the differential or rear suspension that's like building an engine. You can take it apart, buy a cheap master kit, slap it together or check all tolerences, use quality parts, spend the time on it. What you get out of it is what you put in.
The diff and suspension are the same. You can try it yourself, exchange it or build it better then it was new. The cost increases as you progress up the "ladder."

If the yokes are worn then the metal ended up in the oil,bearings, gears,etc. Most who know me probably knew I would say this!LOL Point is it may be time for an overhaul and unless Chip comes and gets your car you're going to have to pay.HOw much is the question.

If you just replace the yokes and do the labor it will cost you about $250. If you do a basic rebuild maybe $600. If you detail and blueprint it and can do what I list in my paper the parts alone will still run between $800-$1,000 depending on what you use.This doesn't account for the cost of any tools you need to buy.

There are differences in the level of the work no question, but the first thing you should ask yourself is what you plan to do with this car? Are you going to keep it a while and drive it or maybe sell it shortly? If you plan on "marrying" the car then do the job right now and drive it. If not, then you're going to have a hard time recovering the cost of repairs if you sell in a short time.Keep in mind there is always,always something that fails on these cars, drivetrain, body, headlights, brakes,etc. Just be prepared if this is your first vette.

I hope this helps, if you have any questions let me know.

 

Many many thanks...here's what I'm up against. My assessment when I bought my '79 last August was limited to the newbie checklist...the IRS seemed pretty good, especially since the trailing arms/spindles/rear calipers had all been replaced.





The strut rods had been bent so well that I didn't realize it had been done until told by a Vette shop. The camber adjust had obviously been exceeded so, why replace the rods when you can heat and bend? Thanks Bubba...





They also pointed out where the bolt holding the U-Joint was making contact with the diff housing on the driver side...red alert!





My mechanic friend suggested replacing the spring/rods/shocks to raise the rear and increase the distance between the spindle and the differential, effectively pulling the halfshafts away from the differential housing...maybe not.

I'm interested in a solid, reliable 10 footer for Sunday driving and local cruise nights...not an autocross or high performance guy. So far it fits the bill perfectly but I'm not looking for perfection. However, if I fix it, I want it to be off the list so I don't have to worry about it again.

Thoughts from the forum?

Thanks again,
Steve

 

Folks,

Assuming the worst, any recommendations for Vette mechanics in central Jersey that have experience with differentials? I'm familiar with Corvette Paramedics...

S

 

It is not that you needed new rods....but you do now!!!. They bent them to dial in the camber. Why was the camber out so much? Because your yokes are worn. Don't ever go back to the shop that did this!!!! Now you need new rods and a diff rebuild.