Building A New transmission Cross Member For A 1953 – 1956 F100
By John Niolon
We lovers of old Ford trucks usually have one thing in common. We need more power. Unless you’re a die-hard restoration type guy, you’ve probably planned on replacing those old flatheads and straight sixes with something with a little more torque and horsepower… something a little more modern and reliable. Overheating and gear grinding aren’t usually in the enjoyable scope of truck ownership these days.
The installation of a new engine and transmission usually requires new mounting points. My truck had already had some "engine mounts" installed sometime in the past when a 292 was installed. These consisted of two pieces of angle iron, torch cut (complete with slag) and hammer bent to fit, then bolted to the frame rails. The transmission mount was a piece of light gauge angle iron( bed frame) with two reasonably round, torch cut holes burned thru where the mounting bolts fit. The left side was attached to the frame by a 1/4" x 2" grade 3 bolt and nut… that were loose. The right side had two turns of clothes line wire wrapped through the holes and twisted fairly tight; this probably being a road repair when the other 1/4" bolt worked out. Or, heaven forbid… the loose 1/4" bolt was replacing more clothes line wire that had broken !!
In defense of the person who did the previous install…he did use two large fender washers to cover the torched holes and make it look neater. So my master plan included a new transmission mount to hold up the C-6 that now resides between the frame rails.
My disclaimer should be up front… this is not my original design. I’ve seen it in magazines and liked it’s low profile. My fabrication guru, Dave, helped me fab up the first one for the Volare install and this one I did on my own, following his good example.
My first front suspension change was from the original straight axle to a Volare sub frame. This involved a pretty serious engine offset of 2" to the right to clear the Volare steering box. Of course the transmission had to move the same amount also. After finding some interference problems with the engine headers and aforementioned Volare clip, the Volare pieces were removed, the rails repaired and a nice Mustang II IFS unit was installed. The Mustang unit gives plenty of room for the engine, headers and possibly a Shriner’s convention under the hood. There are no interference problems now that the steering box and rack are under and in front of the IFS cross member.
The transmission cross member is a reasonably generic piece of equipment and most all engine changes in any model and make will require the purchase or building of one. There are aftermarket "universal" models that can be ordered from the rod shops…but in my limited experience, "universal" means it’s easier to build it from scratch. It’s a simple fabrication and installation job. The material list is short… one piece of 2×2 tubing about 40" long, 12" of 2x2x1/8" angle iron, and a couple of short pieces of 2x2x1/4" angle
The first step is to measure the distance across the frame rails. On my truck it measures 34" outside to outside so I plan to make my cross member 33 1/2". I want to make the bottom edge turn up at a 45° to the top at each end so I need to cut the tube longer than the finished length to have enough material to fill in the ends.
A 45° cut across a 2" tube takes about 2 1/2" of material to fill it. I cut the bottom of the tube about 3" longer (on each end) than the length of the tube actually would be. Then I bent the bottom face up to meet the 45° face. You could just as easily cut the tube off completely and cut a filler piece from flat stock and weld it in… it all dresses out the same later.
then weld up the seams…..
Dress it up pretty…..
then do the other end…
So, now the main cross member is ready for the mounting tabs and the transmission support tabs.. these are made from the 2 x 2 x 1/8" angle iron.
I cut four – two inch long sections of 2×2 angle. I then cut away one leg at a 45° angle just to pretty it up a little. You need to remember to cut the 45s in two different directions or you’ll end up with two extra that will fit only on one side. I have two extra if you need them !
Tack weld the tabs to the cross member…checked for alignment then weld in place. Of course you do this on both ends of the cross member…The degree of finish is up to you. … make them as pretty as you’d like, then you’re ready to move on to the center transmission support tabs.
Mounting holes will be drilled in the tabs for mounting to the frame rails later.
The next step is locating the center transmission supports. My transmission was in place and temporarily supported by a jack stand. My engine and transmission have a slight offset to the right as yours might. Don’t assume that the engine/transmission centerline is the same as the frame center line. Measure it. Measurements should be made from the frame rail to each mounting bolt and these dimensions are scribed on the cross member. I used 1/4" angle for the transmission mounting tabs. I wanted a little more strength there. But as an afterthought, if I rip out the transmission mounts… I’ve got a lot bigger problems somewhere else.
Again tack in the tabs and check your dimensions and alignment. The positioning of the tabs isn’t super critical… you have a two inch wide surface to drill the mounting hole. But, centered up is prettier and looks like you put some forethought and attention in your design. Finish your welds and dress as you like.
The fabrication of the cross member is complete now with the exception of the mounting holes.
Another roll back under the truck to check measurements for the mounting holes gave me a dimension of 5-3/4" center to center. If you don’t have the nice blue layout ink, a black magic marker will give you a nice contrast for your scribed lines. I scribed the mid point between the two tabs on the cross member and then measured half the distance (2-11/16") over to each tab and scribed the line. Decide how far into the tab you want the hole, allowing enough room for fingers and wrenches and scribe the cross line. Center punch the intersection and drill the holes. My mounting bolts were 7/16" so I added a sixty-fourth and drilled.
The frame mounting tab holes were merely marked on the centerline of the tabs and about one inch in from the ends. Center punch and drill these four holes and you’re done. But like your 6th grade math teacher told you…. Check your work.
One more creeper trip under the truck with the cross member and 4 clamps showed that everything lined up.
The final step is the part I dread the most … drilling the holes in the frame rails. After you position the cross member, check that it is square with the frame. I made measurements from a common point on each side… the running board mounts. Once I have the cross member the same distance on each side I clamp it again and scribed the four mounting holes. Drill the holes to match the cross member. It helps to have a right angle drill motor but it isn’t absolutely necessary. What is absolutely necessary is a sharp drill bit.
By all means wear safety glasses and plan on a hot shaving or two getting in your tee shirt. I tried drilling from the creeper, but couldn’t get any leverage… I just rolled out from under it. So with the truck on jack stands (of course you have it on jack stands, right ?) I set it to a level where I could get my ample frame under it and be able to apply some leverage on the drill motor. Frame rails are tough and even tougher drilling from the bottom. Install some good hardware to hold it (with nylock nuts or lock washers) and you’re done. Your transmission is secure and looks good in addition.
Now granted, most people won’t see this addition unless they are like me and get down on their knees looking at under carriages. But, you’ll know it’s there and detailed nicely and that’s the idea for every part of the truck, right ?? One caution… you’ll have to find another use for that clothes line wire hanging on that nail in the garage.