Greetings!

Car: 1970 350/350hp 4spd, comp 240/246 cam, ported heads, 650 speed demon

I recently snapped a u-joint in half during a hard 1-2 shift. The disconnected half shaft bent a strut rod, put a nice crack in the fiberglass tub, sheard the bolts off in the diff side yoke, and generally wreaked havoc.

While pulling the differential to removed and repair the side yoke, I want to make sure everything is in tip top shape. Below is a shot of my diff and the side shaft end play, 0.022". I have read this is acceptable end play, is that true? The center pin doesn't seem to be worn and there is no visible mushrooming of the side yoke. What else should I check while the diff is out and how should I go about it (test posi, backlash, etc)?

The car previously made a clunk when going from reverse to first. I suspect this may have the cross-member bushings moving around, but I want to insure it was not the diff before I bolt her back together.

At this point I only plan to do the following:
Install 5-799x Spicer U Joints
Finish drilling out sheared bolt and tap new threads
replace yoke seals
replace yoke bolts

Is my supposed factory yoke worth saving? I have heard the standard and HD replacements are weak. The Tom's yokes look nice, but are out of my budget. All my pennies are going towards a frame off restoration in the coming months and I don't want to over do this diff project.

What else to test/fix/install?

 

Can't see the pics here at work but make sure both yokes have not sheared or cracked about an inch and a half from the ends. End play should be nill for both yokes. If strut rod is bent, make sure you can still reset camber or buy another one.

 

You should shim the clutch pack and then re-check yoke end play. If it is still around 0.020 I would get a new yoke. Reason is the end is surface hardened. Once you go through the hardening it will start to wear quickly.

 

Whoops, forgot to mention that I will be replacing the strut rods. I plan to add the VB and P Street & Slalom Kit with "Smart Struts."

 

The end of the yokes and pin look to have almost no wear at all. Following your advice and shimming sounds like a good move. Are there any good write ups? The only time I have changed diff clutch packs in the past was in a BMW. It was simple, no backlash check or no end play check, just remove and replace. Something tells me the vette may be a little more complicated.

How much radial movement is allowed on the yoke? What is the method for measuring?

 

To shim the clutch pack:

Remove carrier, clutch packs and spiders.

Install one clutch pack with gear. Install ONE spider and cross shaft. Jam pry bar/big screwdriver between side gear and cross shaft (putting preload on clutch pack). Feel the spider gear play. Add shims behind clutch pack until play is almost gone. You only want about 0.001", so barely detectable play. Repeat for other side.

Also, a tip is to leave the preload springs out. It decreases the shock load on the spiders when you punch it. The posi will still work without them.

 

Nice macro picture, but...
Did you check the end play of the right side yoke? The splines on the right yoke should look like those on the left, but it looks like they're missing - perhaps the yoke was already pulled?

 

Good eye! The right side yoke was taken out for the drilling shown above.

Should I be replacing the clutch discs during the shimming process? What is the best source for shims and disc?

 

New clutch packs is a good idea. You can get clutches and shims from Mike Dyer, tracdogg2.

 

Check out these articles for detailed diff rebuilding and posi tuning.

http://www.lbfun.com/warehouse/tech_...nt_Rebuild.pdf

http://www.lbfun.com/warehouse/tech_...osi_Tuning.pdf

 

Thanks!

 

I think the articles have Gary's numbers, but if you need it you can pm me. I currently have my diff in pieces till I get the money for new gears. So I started trying that tuning process mentioned.

 

Hopefully I can just shim the posi and be on my way. I really don't want to make this a full blown rebuild.