C2 drive shafts and half shafts

[Joe L.]

Re: C2 drive shafts and half shafts

Joe,

GM #103328 is the sol-called "hi-collar" lock washer used at multiple locations on C2s and C3s, including the bumper attachments starting in 1965. I'm just curious where you found the information about the natural finish. I agree that's correct based on another NOS lock washer I have that starts with the same 103xxx part number. The finish is quite dark, which I presume comes from its heat treatment.to achieve HRC 38-46.

Was 103328 ever available as a service replacement part? I've been searching eBay for years for an NOS example and have not yet found one.

Gary

Gary------


All GM lockwashers of series 103xxx were of "plain" finish (i.e. not electroplated or otherwise finished).

Some lockwashers of series 103xxx were once available in SERVICE but were usually only available in lots of 500 or 1,000. However, I cannot find that GM #103328 was ever available. For the most part, lockwashers available from GM in SERVICE had some surface finish and, thus, while their configuration/size might have been the same as 103xxx series, they had different part numbers. I believe this was done because of the tendency of the "plain" finish fasteners to corrode while on the dealer's shelves and dealers did not want to sell rusty parts to customers. For PRODUCTION, a few pennies could be saved and, even if rust occurred before a car was sold, it would not be noticed.

Another factor is that "in days of old" GM almost always specified no finish or black phosphate for high strength fasteners (GM 300M).

[Joe L.]

Re: C2 drive shafts and half shafts

Mark
The original trail arm bolts @ the shims were zinc plated on mid years up to and into 68. After that I don’t know. This is one of the cases where GM didn’t use phosphate on a graded bolt.

Gene------

The zinc plated trailing arm bolts were used in PRODUCTION and SERVICE through early 1977. Thereafter, the bolt was black phosphate.

The 1963-77 bolts were GM material grade 280-M (SAE grade 5; 3 radial lines). GM material grade 280-M bolts were often zinc or cadmium plated. However, when the bolt was replaced for the 1977-82 model years (and 63-76 SERVICE), it was replaced with a GM 300-M grade bolt. As was GM's general practice of the time for 300-M bolts, this bolt was black-phosphate finished.

This is not to say that no GM 280-M bolts were ever black phosphate; some were. But, for the most part, 280-M bolts were zinc plated. On the other hand, GM 300-M bolts were rarely, if ever, zinc or cadmium plated.

[Mark P.]

Re: C2 drive shafts and half shafts

Thanks Joe for clarifying what I need to search for.

[Mark P.]

[Joe L.]

Re: C2 drive shafts and half shafts

Gary - I was referring to various reproduction bolts I have bought for my C1 and C2. An example are the bolts that attach the rear spring to the differential cover. CCs are cad and Paragons are black phosphate. Both have cad lock washers. Lengths are different by 1/8” between the two sets.

Mark------


Originals were black/gray phosphate and of GM #3822486. They were GM-280M material grade. Length was 3-7/32". These bolts were a special bolt and had a shorter thread length than a standard bolt of this length.

The GM replacement bolt was GM #9428598, a standard bolt.. It was of GM 300-M material grade and phosphate finished. It was 3-3/4" long with a thread length of 1-3/8". The original length is important for these bolts. The replacements can be shortened to the original length.

[Joe L.]

Re: C2 drive shafts and half shafts

All-------


One more thing to keep in mind: there are many fasteners on the chassis of a Corvette that are SAFETY-RELATED. If there is any doubt as to the condition or integrity of these fasteners they must be replaced with new, high quality fasteners of the same or higher material grade as the originals. Personally, I would never use a used fastener that was of unknown history.

Refinishing high strength fasteners (i.e. GM 275-M, 280-M, 300-M) must be done in a way that correctly avoids the problem of hydrogen embrittlement. Some folks say just bake them for an hour at a certain temperature and all will be fine. That's not good enough for me when it comes to SAFETY-RELATED chassis fasteners. Buying re-finished, used fasteners is an absolute crapshoot that I would NEVER, EVER feel comfortable with. For me, having a factory new fastener from a reliable manufacturer ALWAYS TRUMPS correct headmarking. That's one of the reasons I always prefer new GM fasteners if I can get them. Of course, GM does not now nor ever has manufactured fasteners. But, we're pretty well assured that they obtain their fasteners from reliable, competent sources and that those sources would not want to risk "crossing" GM by supplying bogus, off-spec fasteners.

In addition, there are excellent aftermarket sources. ARP is one that I particularly favor.

[Gary R.]

Re: C2 drive shafts and half shafts

Joe I agree 100%. Good example is with RG bolts in a diff. When I build a diff I always replace them with ARP's as they are the best in my opinion and this is a part you can't see yet is very important. I have seen many rebuilt diff's with original bolts or the fully threaded kit bolts used. I firmly believe in changing this part over saving $35 to reuse the original or the kit bolts.

[Mark P.]

[Richard G.]

Re: C2 drive shafts and half shafts

I have never seen half shafts that are from GM that had any balance weights installed.
I didn't see any on yours either. I am guessing as they turn between 1/3 and 1/4 the speed of the drive shaft and the short length GM just saved the money and didn't balance them.
Nice job. I like the placebo weld heat treatment.
Rick

[Mark P.]

Re: C2 drive shafts and half shafts

@ Richard - the shop prefers to check them but they needed no weights. My new driveshaft for my 60 has no weights either. They spin them all to 3,200 RPM. The halfshafts spin so much slower I know it was probably overkill to balance them.

[Brad Hillhouse (37766)]

Re: C2 drive shafts and half shafts

The half shafts are so short that its very difficult to balance them using weights. Think of a drive shaft tube as a jump rope. The longer the rope, the more it can swing out due to centrifugal force. Think of a 10 foot jump rope held by a person on each end. It is very easy to get a large deflection in the straightness of the rope in ten feet - thats why it is easy to "jump rope" by swinging it in a circle even though your hand does not move much from its center point. Now, shorten that 10 foot rope down to 1 foot. There is little to no deflection in the rope as it is too short for centrifugal force to play as much of an effect on it.

Long story even longer. This is the reason that manufacturers started making two piece drive shafts in longer vehicles by using two short 3-4 foot drive shafts with a center carrier bearing instead of one long 7 foot drive shaft.

One last point. Prior to welding of any drive/half shaft, the run out of the tubing would be checked with a dial indicator to make sure that the yokes are running centered against the tubing. In our shop, we used 5 thousandths or less at 2 inches from the yoke as ready to weld. Post welding, the runout is checked again to make sure that it is still under that 5 thousandths. On special application short race shafts or half shafts, if there is need to bring the runout back under 5 thousandths, a heat/cool cycling to shrink the tubing back under specifications instead of adding weight is the method that is most successful. I cannot say what was done at the factory when the original shafts were done. This is the methods used in our drive shaft shop for the last 3 generations since the 1950's.

Brad Hillhouse
37766

[Mark P.]

Re: C2 drive shafts and half shafts

@ Richard - thank you for the thorough post. It helps me understand why balancing half shafts is not typically done. The shop made some extra money on me but I don't regret using them. I have heard about using heat to fix runout which is why I didn't try to use my torch to get add the blueing. I was worried about causing some distortion.