Tremec TKX first cuts

[DC Dart]

I used 2.5"x .500 flat bar across the top and 3/16 to tie into the lighter weight cross member. I tried to keep it low profile and simple. Seam sealer down the sides should look clean when done?
When the transmission mount is not in place the material does not look as big.

 

[DC Dart]

Bummer about the 855. Hopefully the TKX works out as well as the tremec 6 speed has.

 

[RustyRatRod]

I used 2.5"x .500 flat bar across the top and 3/16 to tie into the lighter weight cross member. I tried to keep it low profile and simple. Seam sealer down the sides should look clean when done?
When the transmission mount is not in place the material does not look as big.

Thank you! My plan is along the same lines, but I am going to section the floor pan hoop I have, along with a second one and make one larger one out of the two. At least that's the plan. lol I am putting a World Class T5 in my car.

 

[RustyRatRod]

Bummer about the 855. Hopefully the TKX works out as well as the tremec 6 speed has.

It is a real shame. All the Chevy guys have great stuff to choose from. We have very little and some of it is pure junk.

 

[DC Dart]

You were going slant six? The T5 with slant six should be a well balanced combo. Lots of room for mechanical clutch linkage too.
The guys running the HDK or RMS suspension get some of the benefits GM has. No T bars. But the torsion bars have pluses too. Room on the bottom side not is not one of them.
Always have trade offs. The less common Mopar platform in some ways has more complications to modify than GM.

 

[RustyRatRod]

You were going slant six? The T5 with slant six should be a well balanced combo. Lots of room for mechanical clutch linkage too.
The guys running the HDK or RMS suspension get some of the benefits GM has. No T bars. But the torsion bars have pluses too. Room on the bottom side not is not one of them.
Always have trade offs. The less common Mopar platform in some ways has more complications to modify than GM.

Yes. I had mulled over a 400 swap for it....and I even have a fresh one I built, but the slant 6 has been so much fun, It's gonna stay.

 

[Arthur Sperotto]

@DC Dart , I appreciate you making this thread. I love the upper torsion bar crossmember piece you made to replace what was cut out. That is literally the ONLY thing keeping me from buying SST's TKX kit for my '71 Dart (727 car). I'm scared of the rigidity loss (not regarding drivability, but safety), I feel like the torsion bars need that upper part as well as the lower part.

A couple questions for you:

1. Did you choose to fabricate everything because SST didn't offer a PerfectFit kit for your particular application with the 400 block?

2. Would you consider running US Car Tool's frame connectors and torque boxes a good enough reinforcement, instead of fabricating the upper part like you did? I'm not confident I can make the replacement piece that you did... I just recently learned how to weld. However, I am confident I can weld on the frame connectors and torque boxes lol.

If you'd like, please also let me know your thoughts on just running the kit as they send it - with no upper replacement piece. The torsion bar crossmember would then look like this:

Thank you!
-Arthur

 

[DC Dart]

The T5 is going to make the most of that slant 6 torque curve. The fun factor should be increased over what it is now. Looking forward to seeing progress on that project. A couple less cylinders to feed will be another benefit to keeping that six.

 

[DC Dart]

Hi Arthur.
SST does make the Perfect fit kit for the 400. The transmission mounts in the same location whether its big block or small block. I chose to build my own because I wanted to set my elevation of the transmission and add the support I cut out. My tail shaft of the TKX is in the same position as the 833.
The US Car Tool sub frame connectors and torque boxes are a nice upgrade regardless. I have their torque boxes on my car.
SST and American powertrain kits only have the transmission mount for the TKX. Since their mount is stronger than OEM I believe they feel it is not necessary? Many people are running their cars that this way and seem to be fine. There is more space with nothing there for sure.
The way the US car tool subframe connectors tie in would help in not having the crossmember support.
Soo. I would prefer the support over the top as that's what I did. But I think you could get away without the upper support.
I think the subframe connectors and torque boxes are harder to do than how I did my crossmember. If I was to do it over again I may not have leaned it back. The sheet metal fit better but the inside gussets did not fit as nice. The main welds are flat and on heavier metal.

 

[RustyRatRod]

The T5 is going to make the most of that slant 6 torque curve. The fun factor should be increased over what it is now. Looking forward to seeing progress on that project. A couple less cylinders to feed will be another benefit to keeping that six.

I'm absolutely thrilled with it so far. We just did about a 150 mile cruise. One of the cars in the lineup was like a late 70s Corvette. Mild 350. I kinda know the guy. He's a cool type sort. He pulled along side of me on the way just playin around and we clamped in it.....I pulled out about a half car length on him. lol I backed out because we were already runnin over 70 and I have no over drive and 13 inch tires with a 3.23 gear. When we got there we both laughed about it. It was kinda funny.

 

[DC Dart]

That's cool. The sixes are a fun motor. They can run down the freeway all day over a 100mph too. Actually with 323s that T5 should rock.
Never liked setting points on them. Have you converted it to electronic ignition?

 

[RustyRatRod]

That's cool. The sixes are a fun motor. They can run down the freeway all day over a 100mph too. Actually with 323s that T5 should rock.
Never liked setting points on them. Have you converted it to electronic ignition?

I have, but only because everything to do it fell in my lap. I like points. They don't bother me at all. Now, when I do the T5 swap, I'm also swapping in a Ford 9" I have built with 3.00 gears. That should roll down the highway. lol

 

[Car Nut]

I have, but only because everything to do it fell in my lap. I like points. They don't bother me at all. Now, when I do the T5 swap, I'm also swapping in a Ford 9" I have built with 3.00 gears. That should roll down the highway. lol

Don’t forget to post videos, really enjoy them.

 

[RustyRatRod]

Don’t forget to post videos, really enjoy them.

I will do just that. It's gonna be a little while though.

 

[Norm.P]

Hi Arthur.
SST does make the Perfect fit kit for the 400. The transmission mounts in the same location whether its big block or small block. I chose to build my own because I wanted to set my elevation of the transmission and add the support I cut out. My tail shaft of the TKX is in the same position as the 833.
The US Car Tool sub frame connectors and torque boxes are a nice upgrade regardless. I have their torque boxes on my car.
SST and American powertrain kits only have the transmission mount for the TKX. Since their mount is stronger than OEM I believe they feel it is not necessary? Many people are running their cars that this way and seem to be fine. There is more space with nothing there for sure.
The way the US car tool subframe connectors tie in would help in not having the crossmember support.
Soo. I would prefer the support over the top as that's what I did. But I think you could get away without the upper support.
I think the subframe connectors and torque boxes are harder to do than how I did my crossmember. If I was to do it over again I may not have leaned it back. The sheet metal fit better but the inside gussets did not fit as nice. The main welds are flat and on heavier metal.

This is incredible work!! The upper cross member support looks pretty stout. You wouldn't happen to have an extra one would you? I will gladly pay you for it! Also, I wonder if there's an upper brace you can bolt on instead of welding.

 

[DC Dart]

The upper cross member is just .5"x2.5" flat bar. While very inefficient strength wise laid flat it is simple to bend with a press brake or heat and bend in vise. You can make a cardboard template to use to match bends. 2"x 3/16" flat bar lays flat in the top of the cross member. The thicker material needs a transition to the lighter material to prevent stress risers.
As far as a bolt in top cross member goes the only concept I have seen that is close is a gen 3 hemi and automatic conversion mounts bor B body made by Black Heart? Holley.
The upper side of the torsion bar cross member is cut out and replaced with a 1/2 flat bar hoop that has 3/16 ears that bolt to the original transmission holes. Looks like the lower transmission mount bolts inside of that.To me that seems backwards. If the top half fit to the inside it could be plug welded or something and not move when the trans mount was altered.
There are a lot of different ways and thoughts on how to do these installs. I just wanted to throw some ideas out there.

 

[Norm.P]

The upper cross member is just .5"x2.5" flat bar. While very inefficient strength wise laid flat it is simple to bend with a press brake or heat and bend in vise. You can make a cardboard template to use to match bends. 2"x 3/16" flat bar lays flat in the top of the cross member. The thicker material needs a transition to the lighter material to prevent stress risers.
As far as a bolt in top cross member goes the only concept I have seen that is close is a gen 3 hemi and automatic conversion mounts bor B body made by Black Heart? Holley.
The upper side of the torsion bar cross member is cut out and replaced with a 1/2 flat bar hoop that has 3/16 ears that bolt to the original transmission holes. Looks like the lower transmission mount bolts inside of that.To me that seems backwards. If the top half fit to the inside it could be plug welded or something and not move when the trans mount was altered.
There are a lot of different ways and thoughts on how to do these installs. I just wanted to throw some ideas out there.

Do you know if that SST Kit keeps the same drive line angle? I'm thinking no. And shims would have to be used.

 

[DC Dart]

I think you are correct. SSTs I believe is lower guessing 3/8 to 1/2". So I would use a flat plate with holes drilled.
The speedo cable exits the trans where the mounting flange is. So the higher the tail shaft the closer the cable gets to the inner part of the torsion bar cross member where the inner bolts are.
I set mine to the same elevation as the 833 and my cable lightly touches. I may clearance it a little more before paint.
This combined with minimizing floor work could be why SST set the trans lower.
Having an auto floor to start with

 

[jcolman]

I don't want to hijack this thread but I thought that I would offer up my thoughts about losing the top of the cross member. I've put about 200 miles on my car since I had the TKX installed. I did not reinforce the cross member except for the lower brace that comes with the TKX kit. I did have the shop install subframe connectors to help stiffen up the body. I can honestly say that I can't tell any difference in handling except that the car is a bit stiffer. I don't thing cutting the cross brace had any impact whatsoever.

 

[Arthur Sperotto]

I don't want to hijack this thread but I thought that I would offer up my thoughts about losing the top of the cross member. I've put about 200 miles on my car since I had the TKX installed. I did not reinforce the cross member except for the lower brace that comes with the TKX kit. I did have the shop install subframe connectors to help stiffen up the body. I can honestly say that I can't tell any difference in handling except that the car is a bit stiffer. I don't thing cutting the cross brace had any impact whatsoever.

View attachment 1715945726

I wouldn't expect you to feel a difference from the lack of the upper crossmember part, it's not a handling enhancer, it's a structural part that has more to do with safety than anything else imo. After I've seen how thin our floors are, I've decided I'm gonna fab something in its place. I also wouldn't expect your *** to suddenly fall through the floor in 200 miles. But I would be scared of hitting, say... an ondulation on the highway at speed, or maybe coming down from a wheelie at the strip. That's when your seat cushions meat the floor. Having that section triangulated is super important, and the frame connectors do not help with that either. They'll make the chassis stiffer, but they won't help the crossmember from tugging down on the floorboard when the suspension compresses and the t bars rotate. It's hard to explain in words, I hope this makes sense.

 

[jcolman]

I wouldn't expect you to feel a difference from the lack of the upper crossmember part, it's not a handling enhancer, it's a structural part that has more to do with safety than anything else imo. After I've seen how thin our floors are, I've decided I'm gonna fab something in its place. I also wouldn't expect your *** to suddenly fall through the floor in 200 miles. But I would be scared of hitting, say... an ondulation on the highway at speed, or maybe coming down from a wheelie at the strip. That's when your seat cushions meat the floor. Having that section triangulated is super important, and the frame connectors do not help with that either. They'll make the chassis stiffer, but they won't help the crossmember from tugging down on the floorboard when the suspension compresses and the t bars rotate. It's hard to explain in words, I hope this makes sense.

I hear you and understand your concern. I guess my feeling is that the cross brace was never triangulated to begin with....it's a metal "bar" that is bent up in the middle. My thought is that if you replace the bend with a solid lower section, it should be just as strong or stronger. But I'm not an engineer. I just hope that the engineers who sell this stuff know their business. ;)

 

[plumkrazee70]

I hear you and understand your concern. I guess my feeling is that the cross brace was never triangulated to begin with....it's a metal "bar" that is bent up in the middle. My thought is that if you replace the bend with a solid lower section, it should be just as strong or stronger. But I'm not an engineer. I just hope that the engineers who sell this stuff know their business. ;)

And really if you look at it. It's barely tack welded to the floor.

 

[Arthur Sperotto]

I hear you and understand your concern. I guess my feeling is that the cross brace was never triangulated to begin with....it's a metal "bar" that is bent up in the middle. My thought is that if you replace the bend with a solid lower section, it should be just as strong or stronger. But I'm not an engineer. I just hope that the engineers who sell this stuff know their business. ;)

That bend in the bar is the triangulation. I've edited a picture from google to try and illustrate. The red forces at the torsion bars represent the forces that occur when your suspension compresses. The red arrows in the middle of the bend represent where those forces end up, and why that bend is important. The forces squeeze that section together; it's stable and strong. Without that upper section, you have the blue arrows showing where the forces end up. They just tug down on the floor. No matter how strong the lower section is, it's still a downward force with no counter-acting force. To be completely honest, and I hope I am not offending anybody when I say this, I don't think the folks at SST are engineers. You don't have to be one to design something like that. I do believe the folks who created the ToddRon crossmember ARE engineers - and as you can see from the cost of that unit, that's why I believe SST aren't including it. It drives up the cost and complexity.
As a mechanical engineer, I can assure you that part is important. If you can drive down the street with peace of mind without it, more power to you!

And really if you look at it. It's barely tack welded to the floor.

You're correct. It doesn't even have to be connected to the floor to do its job. As you can see in the pic above, it's just about dealing with the forces from the t bar movement. Tack welds are all that's needed.

 

[Norm.P]

I hear you and understand your concern. I guess my feeling is that the cross brace was never triangulated to begin with....it's a metal "bar" that is bent up in the middle. My thought is that if you replace the bend with a solid lower section, it should be just as strong or stronger. But I'm not an engineer. I just hope that the engineers who sell this stuff know their business. ;)

I was thinking the same thing. I was thinking the updated lower crossmember would absorb the load from the torsion bars. But I'm no engineer so I have no idea.

I hear you and understand your concern. I guess my feeling is that the cross brace was never triangulated to begin with....it's a metal "bar" that is bent up in the middle. My thought is that if you replace the bend with a solid lower section, it should be just as strong or stronger. But I'm not an engineer. I just hope that the engineers who sell this stuff know their business. ;)

I was thinking the same thing. I've spoken to a few people who run it without replacing the top crossmember. I don't know because I'm not an engineer. I was thinking maybe the updated lower cross member would absorb that load.

 

[Norm.P]

Tdrivesnd in the bar is the triangulation. I've edited a picture from google to try and illustrate. The red forces at the torsion bars represent the forces that occur when your suspension compresses. The red arrows in the middle of the bend represent where those forces end up, and why that bend is important. The forces squeeze that section together; it's stable and strong. Without that upper section, you have the blue arrows showing where the forces end up. They just tug down on the floor. No matter how strong the lower section is, it's still a downward force with no counter-acting force. To be completely honest, and I hope I am not offending anybody when I say this, I don't think the folks at SST are engineers. You don't have to be one to design something like that. I do believe the folks who created the ToddRon crossmember ARE engineers - and as you can see from the cost of that unit, that's why I believe SST aren't including it. It drives up the cost and complexity.
As a mechanical engineer, I can assure you that part is important. If you can drive down the street with peace of mind without it, more power to you!

View attachment 1715945764



You're correct. It doesn't even have to be connected to the floor to do its job. As you can see in the pic above, it's just about dealing with the forces from the t bar movement. Tack welds are all that's needed.

I will say I did find this. Hurst TKX, TKO Crossmember fits 67-76 MOPAR A-Bodies – Hanlon Motorsports
It's a strictly bolt on, although I'm not sure if that's a good idea either. I would think a weld would be stronger.