[JSchmitz]

I'm wondering about differences in A-Body crossmembers. My '64 GTO has the style in the picture. I've never cared for this design. It has these weird rubber mounts on the outside. One side a previous owner fabricated the steel bracket. Didn't do a very good job either. I also never cared for the stamped design. It accumulated dirt. My '65 Chevelle had a tubular design that I like much better. It didn't have rubber mounts on the outside. Just bolted to the frame. I'm trying to decide if I want to modify this one to eliminate the outside mounts or try to find a better design.

[JSchmitz]

Also, this crossmember works with my THM400 and Muncie. I just flip it around.

[steve25]

I don’t understand why you are posting a question and then answering it basically!

You seem fully happy with the type in your Chevy so then go with it!

[Formulajones]

A lot of Pontiacs used that design cross member with the rubber isolators, dad's 69 GTO is that way too. I'm not a fan of it.

My 72 Chevelle has a much beefier tubular bolt in design from the factory.

I modified dad's a long long time ago and got rid of the isolator setup.

Find yourself a Chevelle cross member and swap it out, that's the easiest thing to do and they are all over at the swap meets for cheap.

[JSchmitz]

Originally Posted by steve25

I don’t understand why you are posting a question and then answering it basically!

You seem fully happy with the type in your Chevy so then go with it!

I don't understand why you constantly believe that you're intelligent! Read all of what I said, "I'm wondering about differences in A-Body crossmembers.". I like the Chevelle design. I'm wondering about what all is available. Not just the two that I referenced genius. There may be another design that someone can tell me about instead of making ignorant useless comments.

[JSchmitz]

Originally Posted by Formulajones

A lot of Pontiacs used that design cross member with the rubber isolators, dad's 69 GTO is that way too. I'm not a fan of it.

My 72 Chevelle has a much beefier tubular bolt in design from the factory.

I modified dad's a long long time ago and got rid of the isolator setup.

Find yourself a Chevelle cross member and swap it out, that's the easiest thing to do and they are all over at the swap meets for cheap.

I think I will look for a Chevelle crossmember unless there's an even better design. The aftermarket ones are a little much for what you get. I thinking I might fab one from box tubing also. Thanks for the constructive intelligent comments!

[steve25]

I guess you don’t understand that those as you say weird rubber end mounts that Pontiac used where to better cushion the frame and body of the car from drivetrain full throttle hard shifts and make for a better driving experience for the average buyer.

[Formulajones]

I found them to be troublesome. Really not necessary either as the trans sits on it's own rubber mount anyway.

May have worked when new, but 50 years after the fact you're stuck with finding repo replacement rubber that doesn't fit right, it's sloppy, driveline angles move all over the place, and quite honestly is just a subpar way to hold a crossmember in the frame.

[i82much]

this is why i gotta stay off these forums. i have never given the crossmember in my 65 a second thought in over 30 years, and now all of the sudden i am convinced i need to upgrade it!

[Formulajones]

Originally Posted by i82much

this is why i gotta stay off these forums. i have never given the crossmember in my 65 a second thought in over 30 years, and now all of the sudden i am convinced i need to upgrade it!

LOL it's always something isn't it?

[JSchmitz]

Originally Posted by Formulajones

I found them to be troublesome. Really not necessary either as the trans sits on it's own rubber mount anyway.

May have worked when new, but 50 years after the fact you're stuck with finding repo replacement rubber that doesn't fit right, it's sloppy, driveline angles move all over the place, and quite honestly is just a subpar way to hold a crossmember in the frame.

Very well said!

[JSchmitz]

Originally Posted by steve25

I guess you don’t understand that those as you say weird rubber end mounts that Pontiac used where to better cushion the frame and body of the car from drivetrain full throttle hard shifts and make for a better driving experience for the average buyer.

If you were even half as smart as you think you are you'd be mildly impressive! I suggest that you go do your mental sparring with someone on the grade school forum.

This mounting design sucks! It's an unnecessary cumbersome POS! I don't care what the engineers had in mind! I definitely don't care what you think of it. I work with engineers every day that screw things up because they have no "Uncommon sense". They should stick to driving trains!

[64speed]

I have the G Force Crossmember. Mainly for exhaust clearance. Not because there is anything inherently wrong with the factory design

[Tom Vaught]

Originally Posted by i82much

this is why i gotta stay off these forums. i have never given the crossmember in my 65 a second thought in over 30 years, and now all of the sudden i am convinced i need to upgrade it!

My factory crossmember (64 GTO Convertible) is shorter in length vs the hardtop/coupe body style crossmembers. Convertible frames are boxed in the Trans Mount area. You put the biscuits on the end of the cross-member, set it on the frame supports, tighten the retention bracket bolts, and you are locked in in that location.

The factory Pontiac design has worked well for me for about 57 years.
Convertible Chassis are more flexible vs hardtop chassis (whose body has a roof). You don't attach a rigid part to a flexing component unless you want a part failure.

People who have never done the job are ALLOWED to have their opinions Steve25 but 10,000 opinions are not worth one fact. The crossmember from Pontiac worked well on my vehicle for 57 years.

Tom V.

[ZeGermanHam]

When I boxed in my '66 GTO coupe frame, I had to put some thought into what I wanted to do with the trans crossmember. The outer crossmember tabs were fairly thin from rust, and obviously wouldn't fit the newly boxed frame anyway, so I elected to trim the rusted tabs off and then fabricate some shelves for it to sit on and be bolted to. I didn't see any benefit from purchasing an aftermarket tubular crossmember, and I had some scrap metal laying around to fab the shelves.

This is one of those things that I don't think is worth changing unless you have a specific need due to whatever drivetrain, exhaust, and frame configuration you are running. If it's just typical stuff used in a standard configuration, the factory crossmember is fine, IMO. The money spent on a tubular crossmember would be better used elsewhere.

[JSchmitz]

I don't believe that the extra cushion on the outside is needed. I think that the Chevy solid bolted design helps with chassis rigidity by adding another solid crossmember. I never seen a cracked Chevy frame in this area. If you guys like the factory mount then keep it. I don't. My reason for this thread is to search out alternate designs. How many of the original parts are so good that they don't warrant improvement?

[JSchmitz]

Originally Posted by ZeGermanHam

When I boxed in my '66 GTO coupe frame, I had to put some thought into what I wanted to do with the trans crossmember. The outer crossmember tabs were fairly thin from rust, and obviously wouldn't fit the newly boxed frame anyway, so I elected to trim the rusted tabs off and then fabricate some shelves for it to sit on and be bolted to. I didn't see any benefit from purchasing an aftermarket tubular crossmember, and I had some scrap metal laying around to fab the shelves.

This is one of those things that I don't think is worth changing unless you have a specific need due to whatever drivetrain, exhaust, and frame configuration you are running. If it's just typical stuff used in a standard configuration, the factory crossmember is fine, IMO. The money spent on a tubular crossmember would be better used elsewhere.

Nice looking frame work there! Factory frame was probably just fine though! LOL!

[ZeGermanHam]

Originally Posted by JSchmitz

Nice looking frame work there! Factory frame was probably just fine though! LOL!

Thanks! Yeah, the factory frame is fine for most people, although you'd be surprised just how bendy the stock frame is when removed from the body. I've upgraded my suspension, steering, and brakes on my car, so having a stiffer frame will allow those components to function more optimally. Plus, it only cost a little bit to buy some raw steel and make my own chassis boxing plates. I figured why not, I'm building my forever car set up exactly how I had always wanted.

Tom's earlier comment about bolting something to the frame that was originally designed to have some flex is a valid consideration generally, but in this application I do not think it's cause for concern. People have been solid mounting crossmembers to A-body frames for all eternity and it has not been an issue. The extra frame stiffness is welcome, IMO.

[Tom Vaught]

Originally Posted by ZeGermanHam

Tom's earlier comment about bolting something to the frame that was originally designed to have some flex is a valid consideration generally, but in this application I do not think it's cause for concern. People have been solid mounting crossmembers to A-body frames for all eternity and it has not been an issue. The extra frame stiffness is welcome, IMO.

I would question that in some cases.
Ever look at the "crease" that develops top of rear quarter to wheel house molding. Nice vertical (easily seen) indicator that the body is flexing because the open channel frame is not strong enough in the center (under the doors) area. Some racers ordered the Heavy-Duty (convertible) frame under their "Roof Cars" when they knew they were to be raced. ON THE STREET with a good tire. Why would they do that if they thought the open frame was adequate for high performance use as is? The Engineers/Old Racers were NOT stupid, as some imply in this thread.

I was referring to a engine/transmission unit mounted in a frame with no "flex" components. See how long that lives before something breaks/cracks. Put your "chevy design" stuff on your pontiac, I really do not care, YOUR vehicle.

Tom V.

[ZeGermanHam]

Originally Posted by Tom Vaught

I was referring to a engine/transmission unit mounted in a frame with no "flex" components. See how long that lives before something breaks/cracks. Put your "chevy design" stuff on your pontiac, I really do not care, YOUR vehicle.

Tom V.

Hey Tom. Part of my previous comment was indeed referring to your comment specifically about solid mounting the trans crossmember to the frame. To that end, if you can offer a logical explanation of how a Pontiac A-body is somehow different from a Chevy A-Body in terms of how energy from the engine is transferred to the crossmember, I'm certainly willing to listen & learn. I've just never heard of people cracking their frames with solid-mount trans crossmembers. Maybe I'm naive here (wouldn't be the first time!). Also keep in mind that by solid mounting the trans crossmember to the frame, it does not automatically imply that there are no flex components present. For example, I still use rubber engine & trans mounts.

As for general frame flex and the adequacy of the stock open c-channel hardtop frames, when I said it is fine for "most people", I do not include racers and high-performance use in the "most people" grouping. I'd wager that most people only use their GTOs for cruising and shows, and for that I think the open c-channel frame is okay. If it wasn't, virtually all of us would have creased quarter panels simply due to vehicle age. Agree that for high-performance use, including racing, strengthening the frame is a good idea for the reason you describe. That is indeed why I reinforced my frame.