79 t-top

does anyone know who on the assembly line decided that in 1979 the 4 speeds needed to be welded in and the autos not... Has anyone modified their crossmember with bolt in style? If so how hard was it Changing the clutch is going to be a little bit more difficult.

Bob Onit

It started long before 1979
There are kits available for conversion.

I'm Batman

All C3s were that way. Why, I don't know.

69427

Why Chevrolet made the decision to make and stock two different part number frames is beyond me. I know it's not necessarily Chevy's fault for not considering the future uses of the car, but the welded in crossmember sure made it a major PITA for those of us with aftermarket five and six speed transmissions.


ps: 79 t-top: I bought my '69 in Anchorage years ago when I lived there. Loved driving it on the winding roads there (Seward to Fairbanks).

TopGunn

My 75 is the same way also but you won't have any problems removing the 4 speed with the welded X-member, it comes right out easily. Remove the shifter assembly and bracket, right hand exhaust pipe, pull the transmission back then lower the front down and to the right. I've done mine 3-4 times,(screwing around with my Centerforce II clutch ) The problems start when installing 5 or 6 speed upgrades, then I'd either install a removable one or modify it with flanges so it can be unbolted.
Bill

I'm Batman

Seems like any potential greater costs of the bolted crossmember would be negated by the PITA of buying and stocking two different frames. From a business view, GM made some odd decisions in that era.

73 red vette

Bill
Thanks for the info my 73 will be needing a new clutch soon and I was wondering about that welded x-member as it doesn't seem to have enough space to move it back enough to get the spline out. Really not looking forward to doing this in my garage, but nobody works on my cars but me.
Rich

Graemeinvette

I used the Bowtie crossmember when fitting a Tremec T56 box.

TopGunn

Yup I hear you, same here. I use jackstands and get it up in the air enough so you can move around under the car. I can pull it out by myself using a small floor jack to lower it down but I need help getting it back up in place. My old muscles aren't as good as they used to be! It's not too bad a job.

Good luck with it.

Bill

TopGunn

Hey what's you opinion on that crossmember??? I looked at a picture of one and I was wondering if the strength was comparable to the stock GM design. Hard to tell from your picture but it looks like you may have welded something to it in the trans mount area. ??

I'm thinking of doing a trans swap this winter.

Thanks, Bill

myoriginal77

I'm also interested in a crossmember swap, not sure what to do yet but the LS1 & T56 is getting ready ....

Frank

Graemeinvette

Yeah we had to change the mount slightly to take the Tremec box, photo shows it before painting of course!

Bullshark

I elected to modify my welded in crossmember for easy Tremec TKO access. Here are a few pics of how I did it.













Bullshark

BarryK

it started long before '79......... I think ALL C3's are that way aren't they?

don't complain though - at least the guys (like me ) with auto's are lucky enough to have a removable tranny crossmember. On the C1's and C2's NONE of the crossmembers are removable short of a cutting torch. They are all welded in

exdrag77

I looked at those a while back. I like them since you don't run the exhaust through the crossmember. I'm planning on a 4 speed auto soon and plan on using the "bowtie" type as well.

TopGunn

Thanks.....file to fit huh!!

TopGunn

Bullshark...... Really nice job. Looks like you might have a CNC program for the flanges, they're nicely done.

Why didn't you elect to put a 4th bolt on the radius side?? Or am I not seeing something??

Bullshark

thanks, All I really did was take my sketch and the center section into a friends machine shop who has a high pressure water jet cutting tool.
He generated the program based on my sketch and matched the inner flange cuttout to the crossmember cross section. I then had him weld the two inner flanges to the center section properly squared. It was then very easy to slide the outer flanges on each of the outer sections, bolt up the center and then tack weld the outer flanges in place. I removed the center section and finished the weld on the outer sections. You don't have access to the upper forward corner due to the seat floor board profile. That is why no 4th bolt. I had one of our strength guys here where I work look at it and tell me all is fine. I did have to do a little grinding, cause he didn't follow my sketch exactly. Oh well, you get what you pay for In, this case I got much more than I paid for

Bullshark

TopGunn

Yes, I'd say you made out real well. I'm tempted to try that instead of cutting mine out then trying to get the new one in the right spot. If I can cut the thing square and make up some flanges like that I'd be happy. Thanks for the tips!!
Bill

Bob Onit

Believe me
I have replaced tons of four speeds/clutches on GM cars with bolt on X members
When it came to my current 73' I paid the $400 in labor to have someone else do the job

If I had a lift I would have done it myself but after multiple back surgerys I refused to spend a day on my back
To each his own