C2 differential front mount bracket... differences between years?

[Steven S.]

From what I have seen, 1963 and 1964 used a bracket that had no reinforcements at the holes, and most of the others I see have one long reinforcement that goes across both holes, I have one that has a single thick washer/reinforcement welded at one end of each hole on opposing sides. Is this an original piece or some home brewed modification? The part looks factory original to me.

Thanks,
Steve

[Joe L.]

Re: C2 differential front mount bracket... differences between years?

From what I have seen, 1963 and 1964 used a bracket that had no reinforcements at the holes, and most of the others I see have one long reinforcement that goes across both holes, I have one that has a single thick washer/reinforcement welded at one end of each hole on opposing sides. Is this an original piece or some home brewed modification? The part looks factory original to me.

Thanks,
Steve

Steve-----


It's likely original. There were FOUR different brackets over the 63-79 period.

1963 used bracket GM #3820186 and 1964 used bracket GM #3843683. Early 1965 MAY also have used this bracket. Neither of these brackets used any washer or other reinforcement at the bolt holes.

1965-67 used bracket GM #3868799. 1968 with manual transmission also used this bracket. This is the bracket that has welded-on reinforcing washers at the forward bolt holes.

1968 with THM-400 and all 1969-79 used bracket GM #3921657. This is the bracket with the thick, rectangular steel reinforcements welded on both sides and bolt holes drilled through them. From a functional standpoint, this bracket "trumps" all the others and eliminates the problem of hole elongation and the problems associated therewith.

[Philip C.]

Re: C2 differential front mount bracket... differences between years?

Joe maybe Iam loooossing it but I dont think any 63- 67 had any reinforcements. Phil 8063

[Joe L.]

Re: C2 differential front mount bracket... differences between years?

Joe maybe Iam loooossing it but I dont think any 63- 67 had any reinforcements. Phil 8063

Phil------


63-64 had no reinforcements, whatsoever. However, 65-67 had the "washer" welded to the forward pair of holes and these washers acted as a reinforcement.

[Wayne M.]

Re: C2 differential front mount bracket... differences between years?

Here's the story; at least from 1963 to January 1965, via TSB.

[Alan D.]

Re: C2 differential front mount bracket... differences between years?

Here are two styles;

[Wayne M.]

Re: C2 differential front mount bracket... differences between years?

From what I have seen, 1963 and 1964 used a bracket that had no reinforcements at the holes, and most of the others I see have one long reinforcement that goes across both holes, I have one that has a single thick washer/reinforcement welded at one end of each hole on opposing sides. Is this an original piece or some home brewed modification? The part looks factory original to me....

Steve --- sounds original. My early '65; 014xx has the '64-type bracket (probably # 38843683, without the reinforcing washers), as it has the earlier design posi carrier cast 3818753-N [assembled AP 9_17_64], with the threaded forward holes.

[Steven S.]

Re: C2 differential front mount bracket... differences between years?

Thanks everyone, mine is just like the one pictured on the left in Alan's photo.

Steve

[Wayne M.]

Re: C2 differential front mount bracket... differences between years?

....1968 with THM-400 and all 1969-79 used bracket GM #3921657. This is the bracket with the thick, rectangular steel reinforcements welded on both sides and bolt holes drilled through them..... .

Joe -- do you recall if this C3 type bracket with the thick reinforcements ALSO had the forward "lip" removed ? [sorry, no pic] (it might have been to prevent pinching the L to R brake line if rubber cushions deteriorated).

[Joe L.]

Re: C2 differential front mount bracket... differences between years?

Joe -- do you recall if this C3 type bracket with the thick reinforcements ALSO had the forward "lip" removed ? [sorry, no pic] (it might have been to prevent pinching the L to R brake line if rubber cushions deteriorated).

Wayne------


Yes, it did. Photos of NOS examples of GM #3868799 and 3921657 are shown below. Just what the purpose was for the removal of the "lip", I do not know. But, I'm sure there was a reason for it. That change involved a revision to the basic tooling for the part which also included revisions to other configurational aspects of the bracket (i.e. an expensive change). The addition of the washer reinforcements (for the 3868799) and the plate reinforcements (for the 3921657, assuming that part had otherwise remained unchanged)) required no changes to the basic tooling for the bracket.

[Joe L.]

Re: C2 differential front mount bracket... differences between years?

Here are some other photos of the 3868799 and 3921657 brackets. Also, the 3921657 is manufactured from heavier gauge steel than the 3868799. The 3868799 is 0.12" thick material; the 3921657 is 0.17" thick material:

Some other interesting facts: While the 3868799 was, for SERVICE purposes, supercessive to both the 3820186 and the 3843683, it was discontinued without supercession in July, 1987 (i.e. the 3921657 was never supercessive to the 3868799).

The 3921657 was discontinued without supercession in August, 1993. At that time, it carried a GM list price of $90. That was an actual PRICE REDUCTION for this part, though, as its GM list price peaked in 1991 when it listed for $144.

[Steven S.]

Re: C2 differential front mount bracket... differences between years?

Joe, you are something else to say the least! I don't think there is another guy alive that knows so much about vintage GM part numbers as you. Amazing to say the least!

Thanks for the info,

Steve