Early 63 Trailing arm bolts / washers

[Alan D.]

Re: Early 63 Trailing arm bolts / washers

Mike, I went back and looked at some of my old notes & yes early 63 only had the lock washer under the nut. One head marking was reported as "SBC"
The picture I have seen shows the nut with about 6 threads showing.

[Stephen G.]

Re: Early 63 Trailing arm bolts / washers

I found my original bolts from my February 63 car. It's 4 1/4 in length. Has a lock washer only and a M head mark.

Also its a grade 5

[Michael G.]

Re: Early 63 Trailing arm bolts / washers

Stephen, your parts are the same as mine, although my lock washers disappeared over time...

They must have used the same bolt on the differential attachment that Rich mentioned also. I'll just have all three of my old bolts re-plated with cad and go with them, as well as a single lock washer and hex nut.

Thanks all.

[Stephen G.]

Re: Early 63 Trailing arm bolts / washers

Unfortunately I only have one. One had to be cut off to remove. I've found lots of 4-1/2" grade 5's out there. Just no 4-1/4".

[Michael H.]

Re: Early 63 Trailing arm bolts / washers

As a side note, the conventional nut, bolt and lock washer configuration continued almost to the end of 63 production.

Cars in the 20,xxx VIN range may have been the first to receive the drilled bolt and slotted nut with cotter pin.

[Michael G.]

Re: Early 63 Trailing arm bolts / washers

Rich, here's pic of the head of the trailing arm bolt. The differential bolt is the same.

[Michael H.]

Re: Early 63 Trailing arm bolts / washers

Rich, here's pic of the head of the trailing arm bolt. The differential bolt is the same.

Michael,

I'm pretty sure the part number for the original trailing arm bolt was the same as the bolt in the differential. My original GM 63 AIM has the original page that showed that bolt in the trailing arm. The reprinted copies of the AIM do not. Unfortunately, I don't have that AIM here.

[Michael G.]

Re: Early 63 Trailing arm bolts / washers

Thanks Michael, I don't need to see it - I'll just go with it. I've found you have a pretty good memory for these things...

[Stephen G.]

Re: Early 63 Trailing arm bolts / washers

Spoke to Long Island today. Their bolts are 4". "I must be doing something wrong. My 4-1/4" can't be original. They have sold hundreds with no complaints.."

Gee, I never heard that before!

[Michael G.]

Re: Early 63 Trailing arm bolts / washers

Stephen, Its pretty tough for you to "do something wrong" in installing this part. The frame width is the frame width; either the part is long enough to go through the frame or it isn't. I guarantee it'll be way too short if you use the 3 washers LI supplies with the bolt.

I'd suggest that the fact that LI may have sold hundreds of these 4" bolts is between them and their customers, its immaterial to any discussion of the correctness of the part. They are too short, from both a design and manufacturing standpoint.

I've attached a pic of the LI bolt installed with just the lock washer, no flat washers. As you can see, only the chamfer on the end of the bolt is sticking through the nut in the installed condition. GM doesn't, and never did, design attachments without at least one extra thread on the back side of the nut.

From my perspective, it not worth the shipping to send the parts back to them, but they should correct them for the future.

[Michael H.]

Re: Early 63 Trailing arm bolts / washers

I've attached a pic of the LI bolt installed with just the lock washer, no flat washers. As you can see, only the chamfer on the end of the bolt is sticking through the nut in the installed condition. .

Alan Drake sent this pic of the bolt, nut and lock washer on the Lance miller car. Thanks Alan.

By the way, this unrestored late production car is in the 19,XXX VIN range. I don't think the new drilled bolt and slotted nut appeared before the 20,000 VIN range.

[Michael G.]

Re: Early 63 Trailing arm bolts / washers

Thanks Michael. As you probably already know, that pic is consistent with the five extra threads you'd expect from the 4.25" long bolt.

[Kenneth S.]

Re: Early 63 Trailing arm bolts / washers

To answer Michael's original question about the finish of the bolt, my parts description lists the bolt as part number 3846867 and 7/16-20 X 4 1/4" Reg Hex Bolt Gr5 CAD.
Ken

[Timothy B.]

Re: Early 63 Trailing arm bolts / washers

You would think GM would use a grade eight bolt at this location. I can't remember what grade the newer pointed bolts are, these are what's on my 63 now.

[Rich P.]

Re: Early 63 Trailing arm bolts / washers

You would think GM would use a grade eight bolt at this location. I can't remember what grade the newer pointed bolts are, these are what's on my 63 now.

Grade 5 all the waty to 82. They started useing grade 8 on the pinion snubber to rear bolts in 69.

Rich