Cross member transmission support
Thread Starter
Pro
Joined: Feb 2020
Posts: 723
Likes: 71
From: Kannapolis NC
Cross member transmission support
Question about the C3s. From Chevy, did the cross member have the tubes to run the exhaust through the cross member? Or was that an aftermarket thing? I was told that Chevy ran the exhaust thru the cross member, but I don't think that is true. Were all C3 cross members for automatic transmissions (th350) the same? Mine has been "modified" to allow a little more room for the exhaust to sneak by, but I don't like it. I have seen some units made of tube, but generally they are in a kit for changing to an OD transmission or a 5 speed. Can you get a cross member with low profile for a TH350? If so, where?
Le Mans Master
Joined: Jun 2019
Posts: 7,658
Likes: 2,470
From: Indiana
Tons of variations custom and factory
my understanding
through 79 there are two holes that exhaust runs through..although not true duals since 74 i think...(using only one)
auto crossmember removable, manual not...
all can be modified
pic of what you got?
my understanding
through 79 there are two holes that exhaust runs through..although not true duals since 74 i think...(using only one)
auto crossmember removable, manual not...
all can be modified
pic of what you got?
Last edited by interpon; Oct 6, 2020 at 08:25 AM.
Melting Slicks
Joined: Aug 2003
Posts: 3,416
Likes: 291
From: dayton oh
The answer is YES and NO: GM had AT cross members for dual exhaust on C3s up to 1975 before going to the 2-1-2 routing from 1976-1982. Aftermarket companies (BTO,etc) sell cross members to not only allow true dual to be added but also support trans swaps other than TH350s. You can buy them individually or in kit form.
FAST81
FAST81
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
I 'm pretty sure my '77 is a original cross-member. Its removable, has dual pipe locations, came w/ L48 & auto. The holes line-up somewhat for header configurations.
Last edited by HeadsU.P.; Oct 6, 2020 at 08:52 AM.
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
My 72 is the same, bolt in with through holes. At some point that started to weld them in. Major pain to work on transmission but obviously cheaper to build. I eventually replaced with a nice tubular cross member to use with my TKO600 5 speed. Leaves plenty of room to run 3" exhaust pipes underneath.
Last edited by KJL; Oct 6, 2020 at 09:28 AM.
Thread Starter
Pro
Joined: Feb 2020
Posts: 723
Likes: 71
From: Kannapolis NC
I found this one.
https://www.crossmembers.com/product...ossmember-350/
Anyone have experience with it?
https://www.crossmembers.com/product...ossmember-350/
Anyone have experience with it?
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Verdad Gallardo
Race Director
Joined: May 2006
Posts: 18,740
Likes: 2,583
I found this one.
https://www.crossmembers.com/product...ossmember-350/
Anyone have experience with it?
https://www.crossmembers.com/product...ossmember-350/
Anyone have experience with it?
Drifting
Joined: Dec 2017
Posts: 1,306
Likes: 226
From: PA
I'm curious about how it was modified. If you mean one side is raised up and the other not, that was standard production on 80-82's. It was less expensive to make than the cross member with holes through it for the dual exhaust which, as others mentioned, was used up to 79 even though with use of cats starting in 75 there was only 1 pipe going through the center section of the car.
Thread Starter
Pro
Joined: Feb 2020
Posts: 723
Likes: 71
From: Kannapolis NC
It was cut about in half on both sides and a new "bottom" plate was welded in. It looks like crap. It's probably strong enough. After all, it's been like that for over 30 years. I just don't like it. I forgot to take a picture of it.
That G-Force bar looks good. It would also give plenty of clearance where I need it. If anyone has used that one, I would love to hear your thoughts.
That G-Force bar looks good. It would also give plenty of clearance where I need it. If anyone has used that one, I would love to hear your thoughts.
Intermediate
Joined: Dec 2019
Posts: 41
Likes: 5
From: Saint Johns, Florida
I ordered and received the g-force crossmember. It seems well build and was easy to install.
Does it matter which way the 5 inch bolts install that hold in the crossmember? Does anyone have a picture?
Ill post picture of the crossmember later today.
Does it matter which way the 5 inch bolts install that hold in the crossmember? Does anyone have a picture?
Ill post picture of the crossmember later today.
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
Drifting
Joined: Dec 2017
Posts: 1,306
Likes: 226
From: PA
I agree, from an engineering point of view it doesn't matter which way they go. On mine I have the bolts in with the nut facing forward. Given the length of the bolt it was easier putting it in from the back where there is no obstruction. From the front you have to deal with the seat pans. That's probably not a problem on most. But on mine there was some shipping damage on the crossmember which placed slightly pulled one of the mounting holes on the frame downward. So, the crossmember was tilted slightly. This made blindly getting the end of the bolt to align through hole in the crossmember a bit of an exercise. Bottom line, whatever is easier and, if it makes no difference on ease of assembly, putting it thread back should keep it cleaner.
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
If you have the body off the bolts need to go head to the back else you can't remove them with the body on (at least on a '70 that is the case). Same with the trailing arms, the nuts have to go on the outside. Both of these were wrong on my car resulting in grinding the heads off the cross member bolts and saws-all for the trailing arm
Highway Man
Joined: Apr 2019
Posts: 445
Likes: 188
From: Ca
If you have the body off the bolts need to go head to the back else you can't remove them with the body on (at least on a '70 that is the case). Same with the trailing arms, the nuts have to go on the outside. Both of these were wrong on my car resulting in grinding the heads off the cross member bolts and saws-all for the trailing arm
Thank you,
Richard
Race Director
Joined: Mar 2018
Posts: 10,736
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From: Golden Colorado
I found this one.
https://www.crossmembers.com/product...ossmember-350/
Anyone have experience with it?
https://www.crossmembers.com/product...ossmember-350/
Anyone have experience with it?
Burning Brakes
Joined: Feb 2016
Posts: 874
Likes: 115
From: Round Hill Virginia
Originally Posted by Haggisbash
If you have the body off the bolts need to go head to the back else you can't remove them with the body on (at least on a '70 that is the case). Same with the trailing arms, the nuts have to go on the outside. Both of these were wrong on my car resulting in grinding the heads off the cross member bolts and saws-all for the trailing arm