1963 Front Trailing Arm Bolts

[Timothy B.]

Can anyone tell me the length, grade and typical headmark of the early 63 front trailing arm bolts. I have the service replacements with the pilot tip and cotter pin but I have read somewhere that the early 63's used a different bolt. Are they all 7/16 fine thread??

TIA, Tim

[Michael G.]

Re: 1963 Front Trailing Arm Bolts

Hi Tim, The originals are 4.25" long. I'll find my originals and look at the head markings and thread pitch.

[Joe L.]

Re: 1963 Front Trailing Arm Bolts

Can anyone tell me the length, grade and typical headmark of the early 63 front trailing arm bolts. I have the service replacements with the pilot tip and cotter pin but I have read somewhere that the early 63's used a different bolt. Are they all 7/16 fine thread??

TIA, Tim

Tim------


The part number that I have for the 1963 bolt, GM #3846867, strongly implies that there may have been a predecessor part number. If so, though, I have not been able to find any record of it.

[Michael G.]

Re: 1963 Front Trailing Arm Bolts

Tim, the bolts are fine thread, grade 5, with an "M" headmarking. I was going to post a photo, but it seems beyond my capability with the upgrade....

[Michael H.]

Re: 1963 Front Trailing Arm Bolts

Tim,

As Joe mentioned, there is an earlier part/part number for the 1st design bolt and nut. Unfortunately, the original 63 AIM page that would have shown these numbers was replaced with a later sheet so we have no way of finding the original numbers.

The original was not drilled for a cotter pin and the original nut was plain, not slotted.

The undrilled design was used to at least the high 19,xxx VIN range.

[Michael G.]

Re: 1963 Front Trailing Arm Bolts

Here's a pic of the first-design parts:

Trailing.jpg

[Timothy B.]

Re: 1963 Front Trailing Arm Bolts

1963 Early Trailing Arm Bolts 001.jpg1963 Early Trailing Arm Bolts 002.jpg1963 Early Trailing Arm Bolts 003.jpg1963 Early Trailing Arm Bolts 004.jpgThanks everyone for the help, I have three bolts that are exactly like Michael's picture, they are 7/16" fine thread and 4 3/16" long, grade five with M headmark. These bolts have a 3" unthreaded portion and 1 3/16" threaded. Michael, could your bolts be 4 3/16" and not 4 1/4".

I always thought they were old motor mount bolts, two of them have lock washers and plain nuts, one nut is 5/8 across the flats and the other is 11/16 but the rust on the nuts lends me to believe they came from the trailing arm. Is it possible these trailing arm bolts are the same as the motor mount bolts on the early 63 cars. What's the length of the motor mount bolts and did they use a slotted nut on all motor mount bolts.

I will try to post pictures but now I am having problems with pictures..

[Michael G.]

Re: 1963 Front Trailing Arm Bolts

Tim, Mine are actually 4.18", the same as yours.

[Michael H.]

Re: 1963 Front Trailing Arm Bolts

Tim, Mine are actually 4.18", the same as yours.

Michael,

I think the 1st design control arm front pivot bolt is a 193490, the same bolt that was used for the differential front mounting bracket.

[Timothy B.]

Re: 1963 Front Trailing Arm Bolts

Mike,

Maybe that's how I ended up with three bolts, I will double check the length and post if that bolt will work on the snubber bracket. Can anyone tell me the length of the motor mount bolts and if they used the slotted nut on early cars.

[Joe L.]

Re: 1963 Front Trailing Arm Bolts

Mike,

Maybe that's how I ended up with three bolts, I will double check the length and post if that bolt will work on the snubber bracket. Can anyone tell me the length of the motor mount bolts and if they used the slotted nut on early cars.

Timothy------


As far as I can tell, the original motor mount through bolt was GM #3817224 which is also a part number which would be generally consistent with start-of-model year usage. However, this bolt was never available in SERVICE and I have no specs on it.

[Michael H.]

Re: 1963 Front Trailing Arm Bolts

Mike,

Maybe that's how I ended up with three bolts, .

Yup, that would explain the extra bolt.

[Timothy B.]

Re: 1963 Front Trailing Arm Bolts

Can anyone tell me if the original first design trailing arm pivot bolts used a flat washer at each end like what's shown for the second design?

[Joe L.]

Re: 1963 Front Trailing Arm Bolts

[ATTACH=CONFIG]36666[/ATTACH][ATTACH=CONFIG]36667[/ATTACH][ATTACH=CONFIG]36668[/ATTACH][ATTACH=CONFIG]36669[/ATTACH]Thanks everyone for the help, I have three bolts that are exactly like Michael's picture, they are 7/16" fine thread and 4 3/16" long, grade five with M headmark. These bolts have a 3" unthreaded portion and 1 3/16" threaded. Michael, could your bolts be 4 3/16" and not 4 1/4".

I always thought they were old motor mount bolts, two of them have lock washers and plain nuts, one nut is 5/8 across the flats and the other is 11/16 but the rust on the nuts lends me to believe they came from the trailing arm. Is it possible these trailing arm bolts are the same as the motor mount bolts on the early 63 cars. What's the length of the motor mount bolts and did they use a slotted nut on all motor mount bolts.

I will try to post pictures but now I am having problems with pictures..

Timothy------


These appear to me to be just a standard-type hex head bolt with nothing at all special about them. If required, replacements should be easy to find although not likely in the correct headmarking. Of course, observing the headmarking on these bolts is a feat that I expect few judges would even attempt.

Also, keep in mind that GM did not go to the pilot tip bolt with slotted nut and cotter pin because the 1st design worked just as well. If I had an early 1963 and I were going to go as far as restoring it with original configuration trailing arm pivot bolts I'd at least make sure that I used Locktite 242 on the threads.

[Michael G.]

Re: 1963 Front Trailing Arm Bolts

Loctite's good, you could also use a jam nut and remove it for judging. With early shims you don't want to lose clamp-load in the joint, or they'll fall out, so the jam nut may be better.