Can I put a T-400 into a 1980 Trans Am by using the '70- '74 T-400 cross-member? It has a 1978 Pontiac 400 already and a T-350 that is acting up. I read the cross-member may be wider due to the catalytic converter after '75.
Turbo 400 into a 1980 Trans Am?
- Thread starter Bonnewagon
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No, I think they had T-350's. I remember reading that since they didn't offer Ram Air/ Super Duty type engines anymore, the standard 6.6 didn't warrant a T-400. That and the huge pellet type Cats didn't fit with the bigger T-400. I have even seen guys cut and re-weld the mounting tab on the opposite side to fit the T-400 but if the commonly available '70-'74 works that would be perfect.
The answer is yes! Front an rear unibody frames are the same in the years your talking about(70 to 81), an infact they share this with the Camaro's. My 78 Z-28 is using 75 Trans Am front an rear uni bodies, perfect fit.
I've also had Th-350, Th-400 and now a 4l80e in mine. If l remember right l didn't change the crossmember l just extended the mount tab an inch for the 400. But not 100% sure as it was years ago.
I've also had Th-350, Th-400 and now a 4l80e in mine. If l remember right l didn't change the crossmember l just extended the mount tab an inch for the 400. But not 100% sure as it was years ago.
Thanks Bob64, but '75 and '78 are in the post-cat range. I am concerned with the pre-cat subframe and cross member. Modifying the mount tab is probably the easiest way out. I have only had '77, '79, and '80 2nd gen Firebirds so I have no '70- '74 parts to compare.
Ahhh. I did some work on a '79 T/A years ago and it had a TH400 in it that looked factory. Someone must have swapped it. Thanks for clearing that up.
I always assumed the earlier cross member would just bolt up and the T-400 would fit perfectly, minus the Cat. Yet I'm searching everywhere and I can't find anywhere where that was done. You would think it is a no-brainer. I know with the '67- '69 Firebirds the two cross members interchange because you could get a strong 400 in those cars, and I have both of them. I also have an aftermarket T-400 cross member that fits my Bonnewagon but that is totally different. I know there are aftermarket cross members available for the second gens but we are trying to keep this as simple and low-buck as possible.
Hi Mark, I came across this Trans Am forum talking about the same thing you want to do...I hope it helps
http://transamcountry.com/community/index.php?topic=72041.0
http://transamcountry.com/community/index.php?topic=72041.0
The 75 was actually a Formula, same think as TA but it was a 4 speed an full duals. So it didn't have the big pancake cat an had a double hump crossmember.
I remember that l was looking into a 72 TA for the frames but 75 was cheaper. It was a big build, l bought just the cab rust free then built on. I use to have afew(4) parts cars kicking around I've had it now for 19 yrs an built an re-built it so it gets kind of "what did l do". But l'm finally somewhat clear of it May 27th as youngest daughter is getting it for her 18th b-day, so her problem now, lol! Kid always loved it, helped build it so l know they belong together. Besides l'm to old an fat an have to roll in and out of it, not a good picture, lol!
Thanks Steve- that link had the answer. I was right- all the subframes are the same- only the cross members changed. Good ol' cheap-*ss GM always made one-size-fits-all parts. And here is the winning post:
"I wish I would have read this earlier, I see some have done it successfully their way but there is an easy way, just like the factory did. And there is no need to beat the floor.
-1 F-bodies used short shaft TH400
-2 you will need the correct length drive shaft for an F-body with a TH400 engine does not mater.
-3 the last year for the TH400 was 74
-4 AND FOR THE LOVE OF PETE STOP SAYING FRAMES ARE DIFFERENT THEY ARE NOT!!!!! the only thing that changed was the location of the trans cross member holes and the rear body mount holes.
in fact the indent in the frame for the 70-74 trans cross member mount location is still in all 75-81 frames.
-5 get a TH400 cross member.
-6 install the trans with the correct TH400 cross member and measure where you need the new holes.
BOOM DONE! just like the factory did it
"
"I wish I would have read this earlier, I see some have done it successfully their way but there is an easy way, just like the factory did. And there is no need to beat the floor.
-1 F-bodies used short shaft TH400
-2 you will need the correct length drive shaft for an F-body with a TH400 engine does not mater.
-3 the last year for the TH400 was 74
-4 AND FOR THE LOVE OF PETE STOP SAYING FRAMES ARE DIFFERENT THEY ARE NOT!!!!! the only thing that changed was the location of the trans cross member holes and the rear body mount holes.
in fact the indent in the frame for the 70-74 trans cross member mount location is still in all 75-81 frames.
-5 get a TH400 cross member.
-6 install the trans with the correct TH400 cross member and measure where you need the new holes.
BOOM DONE! just like the factory did it
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