1963 Front Trailing Arm Bolts

[Jeff Z.]

Re: 1963 Front Trailing Arm Bolts

Tim,
Here is what I found on original April 63 chassis.
193490 Grade 5 M bolt cad/zinc
p washer bolt head 7/16x.92odx.125 thick cad/zinc not sure if 3693853 part in AIM
l washer thread end 120383 cad/zinc
271506 nut coating unknown
no p washer under lock washer.
Jeff

[Timothy B.]

Re: 1963 Front Trailing Arm Bolts

Thanks again everyone for the help.

Jeff, That's very interesting that your car has a flat washer inside and nothing outside, if you have a better picture of this washer I would appreciate if you could post. I installed one of my original bolts yesterday without any flat washers and just the lock washer and there is approx 1/4" of thread length sticking out after the nut is snug. In your picture the nut looks flush with the bolt threads, I wonder if someone was there before, can you recall if the shims were the 63 type or later style.

If there is anyone that can expand further on the dimensions of the 3693853 flat washer that may help some. The slotted nut on the newer pilot tip bolt has these flats on both ends but needs a lock washer for the slot to line properly with the cotter pin like what's noted in the 1967 AIM but if these flat washers are .125 the nut may line without the lock washer.

I posted a picture of the GM service replacement bolt with the pilot tip showing the threaded end exactly the same length as the original bolt. It's also a grade five bolt with S B headmark.

[Jeff Z.]

Re: 1963 Front Trailing Arm Bolts

Tim,

Here is picture of washer. It's essentially a thick SAE 7/16 washer and probably wouldn't have a standard 6 digit series part number. More likely 7 digit series part such as 3693853. I still had original open slot 63 shims in place. There is no evidence trailing arms have been off car as both sides had identical fastener hardware.

Thanks Jeff

[Timothy B.]

Re: 1963 Front Trailing Arm Bolts

Jeff,

I appreciate you pictures and help as removing and installing this bolt is a PIA. I want to install the original fasteners and this washer thing is something I want to be correct.

Are there any other 63 owners that can comment on the dimensions of this 3693853 washer and if it's used on this bolt inside where the bolt goes through the frame. My thoughts are that with the welded plate on both sides of the frame there is no need for the flat washer and it would be installed like in the differential front bracket but pictures don't lie. Also, there must be a reason GM started using the washers on the newer style bolt, possibly to spread the clamping load on the frame or prevent the frame from pulling in around the bolt head.

Thanks everyone.

[Joe L.]

Re: 1963 Front Trailing Arm Bolts

Jeff,

I appreciate you pictures and help as removing and installing this bolt is a PIA. I want to install the original fasteners and this washer thing is something I want to be correct.

Are there any other 63 owners that can comment on the dimensions of this 3693853 washer and if it's used on this bolt inside where the bolt goes through the frame. My thoughts are that with the welded plate on both sides of the frame there is no need for the flat washer and it would be installed like in the differential front bracket but pictures don't lie. Also, there must be a reason GM started using the washers on the newer style bolt, possibly to spread the clamping load on the frame or prevent the frame from pulling in around the bolt head.

Thanks everyone.

Timothy-----


I can only tell you this: The primary application of the GM #3693853 was associated with the generator/alternator mounting bracket. Given its size, I'd guess it was used for truck applications. It was discontinued from SERVICE in June, 1975 and replaced by GM #3954735. That part was discontinued in July, 1989 and replaced by GM #2546908. The latter is also now discontinued and I can't find a replacement for it although there might be one. So, how do the supercessive parts compare to the original 3693853? I do not know.

[Gary T.]

Hello,

I am looking for a set of 63 early trailing arm bolts/nuts if anyone has an extra set please let me know, thanks

[David B.]

193490 is 7/16 - 20 x 4 1/4 zinc
120383 is .119 thickness zinc
271506 is 7/16 - 20 zinc GM 286-M steel class 2B thread

[Gary T.]

Hi David can you PM me