68/69 transmission crossmember

[Roger G.]

Given that the manual crossmember is welded in, and the automatic is removable, how about location on the frame rails? Are they in the same spot?

Is the frame indexed to accept either crossmember? I am looking at possibly converting an automatic to manual frame.

[Joe L.]

Re: 68/69 transmission crossmember

Given that the manual crossmember is welded in, and the automatic is removable, how about location on the frame rails? Are they in the same spot?

Is the frame indexed to accept either crossmember? I am looking at possibly converting an automatic to manual frame.

roger------


The crossmembers are in the same location regardless of whether welded or bolt-in. In fact, a bolted-in crossmember frame can be used to replace the welded-in type for cars with manual transmission.

A welded-in crossmember frame cannot be used for a car with an automatic transmission, though.

[Russ S.]

Re: 68/69 transmission crossmember

Joe, Yes auto can be used with welded in cross members. My 66 is a power glide with welded cross member and is an original frame.

roger------The crossmembers are in the same location regardless of whether welded or bolt-in. In fact, a bolted-in crossmember frame can be used to replace the welded-in type for cars with manual transmission.A welded-in crossmember frame cannot be used for a car with an automatic transmission, though.

On further reading I see you are referring to 68-9 which you are correct in that they would have come with (auto) bolt-in member. Welded can still be used with auto but wouldn't be correct.

[Richard F.]

Re: 68/69 transmission crossmember

Any thoughts on why they didn't use a bolt-in crossmember for both transmissions? Is the welded-in one appreciably stronger? It seems like many lives (including my own) would have been made much easier with a bolt-in for the manual trans.

[Joe L.]

Re: 68/69 transmission crossmember

Joe, Yes auto can be used with welded in cross members. My 66 is a power glide with welded cross member and is an original frame.

On further reading I see you are referring to 68-9 which you are correct in that they would have come with (auto) bolt-in member. Welded can still be used with auto but wouldn't be correct.

Russ------


All C2's, regardless of transmission, used a welded-in crossmember. The first use of a bolt-in crossmember was for 1968.

If a welded-in crossmember is used for a C3 with automatic transmission, then there is no way to remove the transmission except by removing the engine and transmission as an assembly. Even then it can be tough. This is not the case for C2 because C2 used Powerglide transmission while C3 used THM.

[Joe L.]

Re: 68/69 transmission crossmember

Any thoughts on why they didn't use a bolt-in crossmember for both transmissions? Is the welded-in one appreciably stronger? It seems like many lives (including my own) would have been made much easier with a bolt-in for the manual trans.

Richard-------


I suppose it was sort of a "transitional" thing. C2 had all used a welded-in crossmember so the same thing was carried over into C3. It could not be carried over for C3 with THM due to creating the SERVICE impossibility of removing the transmission separately from the engine. There MIGHT have been some sort of chassis rigidity issue, too, which favored the welded-in crossmember for those applications that could still use it.

However, the C3 era was a long one and things changed. Beginning about 1979 a bolt-in crossmember frame was used for all Corvettes. The bolt-in crossmember frames also became SERVICE for all 1968+ Corvettes regardless of transmission.

[John H.]

Re: 68/69 transmission crossmember

Any thoughts on why they didn't use a bolt-in crossmember for both transmissions? Is the welded-in one appreciably stronger? It seems like many lives (including my own) would have been made much easier with a bolt-in for the manual trans.

Richard -

Another consideration is that the bolt-in crossmember carried a cost penalty vs. the welded design, and the manual transmission was standard equipment, part of the "base car" package; adding product cost to the "base car" without an offset in another area always got intense scrutiny from the Finance folks, and didn't help career progress.

[Patrick H.]

Re: 68/69 transmission crossmember

Given that the manual crossmember is welded in, and the automatic is removable, how about location on the frame rails? Are they in the same spot?

Is the frame indexed to accept either crossmember? I am looking at possibly converting an automatic to manual frame.

I'd think strongly about leaving the removable crossmember and taking the nominal points hit in judging. The removable crossmember makes life SO much easier.

[Roger G.]

Re: 68/69 transmission crossmember

roger------


The crossmembers are in the same location regardless of whether welded or bolt-in. In fact, a bolted-in crossmember frame can be used to replace the welded-in type for cars with manual transmission.

A welded-in crossmember frame cannot be used for a car with an automatic transmission, though.

Joe, does the frame have an index, ie a notch or similar, where the manual transmission fit in before it was welded, or was a jig used to place it for welding?

[Joe L.]

Re: 68/69 transmission crossmember

Joe, does the frame have an index, ie a notch or similar, where the manual transmission fit in before it was welded, or was a jig used to place it for welding?

roger------


The crossmember was not welded at St. Louis; it was done at the time of frame manufacturing. I don't know if there were any index marks. I presume a jig was used for all aspects of frame assembly at the manufacturing plant.