Question: 79 rear end / axle stub shafts

[chuck evans]

I purchased this car sight unseen and found excessive internal wear in diff and top of wheels kicked in badly. I've been advised that the stub shafts wear on the ends where they ride against the spyder pin in the differential. I've purchased a new spring assembly and plan on replacing shocks and any other external parts, however, I could sure use any advice on this repair and where to buy parts. Also, has anyone heard of an update on the out-board axle shaft support bearings ?

 

[Vettehead Mikey]

It is true that the yokes do wear, and especially so on later C3s such as yours. Typically the entire diff is inspected and possibly overhauled when this has happened depending on what the metal particles have done to the insides. Possibly you got lucky and can just replace the two yokes. Gary R of this forum does excellent work and can set you up.

For the rear wheels bearings, there's no real 'update' in technology if that's what you mean. They should be serviced every 30-40K miles or so and are very reliable accordingly. If you're not sure when they were done last, now is a good time.

 

[chuck evans]

Vettehead Mikey, thanks for the info. I've already got a new rear spring and was planning on insp. and rebuild as necessary. I was however, curious about the availibilty of parts. I purchased a shop manual and it refered to a special tool to repack outer axle bearings and wondered if I would still need that tool or if they was an update on that.

 

[Vettehead Mikey]

Rebuilding rear axle bearings requires a series of specialized tools, skills and procedures including setting end clearances with an accuracy of .001". Most owners choose not to bother buying/renting these tools and farm the job out. It's an area where 2nd best won't cut it.

Beware Bubba fixes that try to inject grease into the bearing housing without disass'y.

 

[JohnZ]

I purchased a shop manual and it refered to a special tool to repack outer axle bearings and wondered if I would still need that tool or if they was an update on that.

The design was the same from mid-'63 through 1982; the only way to repack the bearings is to completely disassemble the spindle and bearing support, which is not a DIY job due to the special tools required and the tight tolerances.

 

[GTR1999]

Hi Guys,
I can help shed some light on this for you.
First off look over the car from top to bottom. I've seen many people buy sight unseen and get into huge issues. Personally I know of two people who ended up with rotted frames, one also had a blown engine. If the car checks out ok and your only issues are the diff then it probably would be best to remove it and do the correct rebuild on it. More on this in a second.
If the car needs more work, then stop and really think about it, 79's are nice but they made a of them and they're not going to be high dollar cars if you find you're in too deep and want to sell.

Now for the diff. The 79 diff's were the last of the solid iron units. They are much better then then later units that followed but do have a couple of areas that need to be addressed. This is why I said to do a correct rebuild, you can find exchange units everywhere- buyer beware some are good and some are bad. They are basic regardless and usually don't address the problems each version had.

79's used what I coined years ago as snowflake clutches. They were made to allow more additive to get in between them to prevent posi hammer. It did not work,only made them weaker and guys who hammered their cars broke them. They should be replaced,regardless if broken, with new solid steels. Forget about the new fiber hyped clutches,stay with tried and true results.

Next you need to replace the ring gear bolts. They are flanged heads and often back out because no loctite can be found on them.

The side yokes from about 74-79 were poorly heat treated,if at all, and wear out. If you have more then 050 endplay in them replace them. There are new ones on the market,beware of imported yokes, and rebuilt. I use both and they are from Lone Star, same as everyone sells. Changing the yokes alone most likely will not bring in the endplay to where I like. Some rebuilders have told customers that up to .125 (1/8") is to be expected. They are lousy rebuilders interested in your money.
I set up my yoke endplay to 005-010 for the stock yokes and closer for the HD 30 spline custom yokes I also use.

If you plan on high hp, over 350 then you need to also made some mods to the diff. Over 400 is the next level,500 is about the limit on a 10 bolt and that is with the correct mods. I do these mods all the time but would require a lot of typing. You can PM me and I'll get you the link to them. BTW, again some rebuilders have told customers a 10 bolt will hold up with up to 1000hp, this is total BS- unless you trailer the car.:eyerole

Good luck, if I can offer any advice or help let me know. I stock all the best parts I use as well.