65 BB with F40

[Bill W.]

A friend told me that a 65 BB with F40 has a different lower rear shock mount than a standard lower shock mount . I looked in my assembly manual and didn't find anything . I have never heard of this does anyone know about F40 or F41 .

[Wayne M.]

Re: 65 BB with F40

A friend told me that a 65 BB with F40 has a different lower rear shock mount than a standard lower shock mount . I looked in my assembly manual and didn't find anything . I have never heard of this does anyone know about F40 or F41 .

Bill -- IMHO, the friend is correct; the 1965 F40 H.D. suspension (whether on F.I. or 396) should have a lower shock mount/strut rod retainer shaft (Gr 5.381, #'s 3829265 and ...66), according to my '65 P&A30, Rev 1 July.

IIRC, these do not have the angle that the standard suspension shafts have.

The 5th ed. 1965 TIM&JG does not mention this, and the AIM is useless for F40 (instructions to install same as regular suspension, or even worse, that L78 rear suspension installs same as F40).

[Joe L.]

Re: 65 BB with F40

A friend told me that a 65 BB with F40 has a different lower rear shock mount than a standard lower shock mount . I looked in my assembly manual and didn't find anything . I have never heard of this does anyone know about F40 or F41 .

Bill------


Yes, the shock mount shafts were different for standard suspension and F-40/F-41.

The standard suspension used shafts GM #3820929 and 3820930. These were the part numbers and the forging numbers seen on the un-machined portion of the shaft.

The F-40/F-41 shafts were GM #3829265 and 3829266. Both of these were machined from the same forging and the un-machined portion of the shaft of original shafts will show 3829265-66.

As far as I know, the 3820929 and 3820930 shafts were used in PRODUCTION on all standard suspension Corvettes from 1963 to 1982. However, the 3820929 was discontinued from SERVICE in February, 1978 and replaced by the 3829265. The 3820930 was discontinued from SERVICE in July, 1978 and replaced by the 3829266.

Later SERVICE examples of the 3829265 and 3829266 do not have the forging numbers embossed on them. Instead, they have either laser printing of the part numbers or nothing, at all.

I have NOS examples of all of the above but I'm too lazy right now to go out and get them to photograph. However, attached is a photo of an NOS example of one of the standard suspension shafts.
DSCN1097.jpg

[Bill W.]

Re: 65 BB with F40

Thanks Wayne & Joe .

[Tony S.]

Re: 65 BB with F40

Bill, here are a couple of photos of the '65 F40 shock mounts that will be used in the upcoming 6th edition of the new '65 JG.
Tony

[Duke W.]

Re: 65 BB with F40

What are the actual geometric differences between these two parts?

From the above photo of the base and HD parts it appears that the base suspension part has a longer distance between the shock mount shaft axis and the shoulder of the strut mount shaft, and the HD part appears to have a slightly larger diameter shock mount, but maybe these observations are just optical illusions.

Duke

[Terry M.]

Re: 65 BB with F40

What are the actual geometric differences between these two parts?

From the above photo of the base and HD parts it appears that the base suspension part has a longer distance between the shock mount shaft axis and the shoulder of the strut mount shaft, and the HD part appears to have a slightly larger diameter shock mount, but maybe these observations are just optical illusions.

Duke

Duke,
The difference is in the angle between the two shafts. The more open angle allows greater clearance for the larger diameter of the HD shock. This "feature" is most obvious on cars with side mounted exhaust as the lower shock mount(s) are visible from the rear and the greater angle is immediately obvious.

[Wayne M.]

Re: 65 BB with F40

Below big pic is a thumbnail view of std. susp. shafts that shows the slight difference in angle. Same ones as in big pic.



a

[R N.]

Re: 65 BB with F40

Duke,
The difference is in the angle between the two shafts. The more open angle allows greater clearance for the larger diameter of the HD shock. This "feature" is most obvious on cars with side mounted exhaust as the lower shock mount(s) are visible from the rear and the greater angle is immediately obvious.

Terry et al,

Would this this mean that the HD shock would not work on or fit a standard lower shock mount?

[Joe L.]

Re: 65 BB with F40

Terry et al,

Would this this mean that the HD shock would not work on or fit a standard lower shock mount?

Kurt------


Actually, the HD shocks will work with the standard mounts (in fact, Edward's situation also proves the point since I fully expect this non-HD shaft has been on the car since new).

I've never figured out why GM felt it was necessary to have a different shaft for the HD suspension UNLESS there was some other difference between the shafts (e.g. material, heat treat, etc.)

[Bill M.]

Re: 65 BB with F40

Kurt------


Actually, the HD shocks will work with the standard mounts (in fact, Edward's situation also proves the point since I fully expect this non-HD shaft has been on the car since new).

I've never figured out why GM felt it was necessary to have a different shaft for the HD suspension UNLESS there was some other difference between the shafts (e.g. material, heat treat, etc.)

Joe:

It may work in real life but might not on paper...? There are rigid clearance requirements that must be met to release a part for production.

Bill

[Jimmy G.]

Re: 65 BB with F40

Question It is said that in a revision dated 7/1/65 that the shock mount changed for F41 So I assume a car made earlier will have standard shock mounts Reason being I have a fairly original 65 396 with F41 and it has standard mounts and it was built prior to 7/1/65 Any comments ??

[Bill W.]

Re: 65 BB with F40

Hi Jimmy . My non F40 396 was built May 65 and has first design mounts . What is the vin on your 396 ?

[Jimmy G.]

Re: 65 BB with F40

Serial number is 200xx

[Joe L.]

Re: 65 BB with F40

Question It is said that in a revision dated 7/1/65 that the shock mount changed for F41 So I assume a car made earlier will have standard shock mounts Reason being I have a fairly original 65 396 with F41 and it has standard mounts and it was built prior to 7/1/65 Any comments ??

Jimmy------


Where is this revision found?

In any event, the two different sets of shock mount shafts were specified in SERVICE as early as 1963 and both sets of part numbers are consistent with a 1963 release.

Is it possible that some F-40/F-41 cars were originally built with the standard shafts? Of course. I would expect this would have been an easy mistake for the assembly plant to make. However, I think that the different sets of shafts were always specified by GM for standard and F-40/F-41.