All this makes me wonder how many warranty claims GM dealerships got from the very problem we speak of. You'd think that with re-occuring problems that they'd look into it and fix what's wrong. Somewhere I read that in '68 or '69 they lowered the mounting points of the lower strut rods. Vette Brakes I think lowers them even more and claim only .3 camber change from 3.0 degrees on the original 63. GM decreased camber change from lowering the rods and I somehow think they came up with the idea in the mid 60's probably from the servicing they were having to do on there differentials. I don't know, but there's a reason they lowered those rods...still though, even with the new mounting point there's plenty of mid to late 70's cars with the same problem so i'm not sure they fixed it.

I just though of some more stuff after I posted...you're right when you say usage is where the wear comes from. Too much heavy duty usage. Com on, these are Corvette's. They going to get driven hard no matter what. I guess GM designed the IRS in 63 without thinking how hard people would bag them and then they realized somewhere in the mid 60's that they were having problems and anything short of redesigning the system would result in more comebacks. I'm guessing that they lowered the rods to cure 50% of the problems while the other 50% continued to bag drive. If you check the manual in a brand new car it will say somehwere in there that they will not warrant parts that are subject to abuse or racing. So really, they never intended us to drive these cars hard :rolleyes:


[Modified by Stingy74, 3:03 PM 12/4/2001]

 

Hi all...
I have been following this thread with interest.
If I may, I'll give you my experience.
I am the original owner of a '70. It was driven very hard for many years.
It now has almost 90K miles on it. In 1971 I was racing it fairly often and
found the stock rear spring very weak. On a hard launch it would squat
like a dog doing it's thing.
In 1971 I installed a 7 leaf F41 spring. ( Fixed the problem )

Now to the point.
I rebuilt the T/As this fall and removed the rear to change the oil and just
look inside. The yokes were worn very slightly. Still had the bevel on the
ends. I replaced them anyway, since I had a set of HD yokes that I had for
years.

Since I had the F41 spring all these years, does this support the theory
of "squat = wear"...

Or, maybe it's as simple as non consistant hardening from the supplier.
Thanks
Barry

 

Barry,
There's no doubt that your differential has lasted a long time under some hard miles but someone else may have had a completely different experience. There's too many variables to take into account to make a proper finding. The spring/wear thing makes sense but as Tom454 stated above, he's had a different experience. What works for one guy might not work for another. Everybody told me not to use a 3000 stall on the street but I love it. Another guy may complain that he burns transmissons up, I dunno. I corrected the issue we speak of with the 6 link rear suspension setup a few years back, so I have absolutley no side load on the diff. Infact if I ever get another Corvette, and even it's only got a 165 hp engine, it's getting the 6 link modification.


[Modified by Stingy74, 3:57 PM 12/4/2001]

 

FWIW, Zora actually did the initial design on the C2,C3 IRS in the late 1950's.
Will

 

I think i read somewhere the "pin" is harder than the end of the yoke this and the yoke being a "suspension member" (so to speak) is probably the reason your yokes are wearing out. The other reason may be that GM might of saved some $$ ( more like a few pennies per car) by building (or buying) a less strong yoke, those mid to late`70 cars didn`t have much of a HP rating. And you know the General save a buck at all costs.
...redvetracr