Cross Member Conundrum -- Late Model 2F/4spd in an Early Frame (1 Viewer)

[TractorDoc]

I have read thru the archives about cutting/rotating the cross members in an early frame; even found a couple with removable cross members. I have installed a 1978 2F Engine, Four Speed Transmission, and Transfer Case in a 1972 Frame. I knew going in the fit between the parking brake drum and frame cross member was going to be tight. . . the result is probably close to an eighth of an inch tight!

I know this makes it impossible to pull the parking brake drum or remove the transmission/transfer case without pulling the engine. . . I am ok with that. I have a shop setup that allows me to pull the entire unit without much extra effort. What I am unsure of is how likely the brake drum will contact the cross member with street driving/minimal off road use. If the likely hood is high then I know I need to modify the cross member accordingly. If the likely hood is low then I prefer to leave things as they are.

Question 1: Should I modify the cross member? I was hoping to keep the integrity of the frame intact but the spacing is tighter than I was expecting.

Question 2: If modifying is it better to rotate and weld the cross member in place or is it just as good to make it removable? The removable design that I have in my head is to cut both sides flush with the frame and weld a square plate to each end of the "pipe" (plate is the red square in the picture below and the yellow is the weld) Id rotate the angle back to give more clearance and then drill four holes (one at each corner) to bolt the square plate to the frame (gray "bolts" in picture below within the red square).

Would this design be safe/acceptable for a removable cross member? Not sure if it would allow the frame to twist/flex as much as just the cross member tube by itself. If it is suggested that I modify it I am leaning more this direction vs. direct welding as long as it would be as strong.
I do not want to do anything that I would be mad at a previous owner for doing. . . and Id like to do it right the first time. Any and all advice or experience from others is appreciated. . . as always.

 

[Living in the Past]

Installed a four speed in my 68 more the twenty years ago. Still have the original F engine with original transfer case. Only thing I modified was added some fender washers to the front motor mounts. Installed it with the engine in. Removed the rear motor mounts and lowered the back of the engine. I did pick up a later cross member to install but ended up getting a few more cruisers, a couple have the factory installed four speed. If I ever did a frame off on the 68 I probably switch it but since it has no rust or body damage don't see that happening.

 

[4Cruisers]

Installed a four speed in my 68 more the twenty years ago. Still have the original F engine with original transfer case. Only thing I modified was added some fender washers to the front motor mounts. Installed it with the engine in. Removed the rear motor mounts and lowered the back of the engine. I did pick up a later cross member to install but ended up getting a few more cruisers, a couple have the factory installed four speed. If I ever did a frame off on the 68 I probably switch it but since it has no rust or body damage don't see that happening.

Same here. I installed a '78 FJ55 4-speed/transfer case in my '71 FJ40 (behind a '76 2F that was in the vehicle when I bought it) without changing/modifying the cross member. I also had the engine in place, I just loosened the front engine mount bolts and tilted the engine down a bit when installing the transmission.

 

[Cruiserdrew]

Same here. Ran 4 speed/case on a 71, and now run an SM420/Orion on an unmodified 71 frame. It works fine. It is an extra 10 minutes of work to pull the parking brake drum-you need to lower the rear about 1 inch. I slightly jack it up, remove the rubber isolators, set it back down and that's just enough to get the parking brake out.

If I was more energetic about this truck, though, I'd modify the cross member. That would be the right thing to do.

 

[Living in the Past]

I've measured my 73 frame once and compared it to the earlier frames. Besides being shaped differently it's a little further back. Some markets got a four speed in 73. It wasn't a H41 or H42 but something else. My guess a four speed mated to a F engine in a truck used in Japan.

 

[Roshi]

I have read thru the archives about cutting/rotating the cross members in an early frame; even found a couple with removable cross members. I have installed a 1978 2F Engine, Four Speed Transmission, and Transfer Case in a 1972 Frame. I knew going in the fit between the parking brake drum and frame cross member was going to be tight. . . the result is probably close to an eighth of an inch tight!
View attachment 1391367
View attachment 1391368
I know this makes it impossible to pull the parking brake drum or remove the transmission/transfer case without pulling the engine. . . I am ok with that. I have a shop setup that allows me to pull the entire unit without much extra effort. What I am unsure of is how likely the brake drum will contact the cross member with street driving/minimal off road use. If the likely hood is high then I know I need to modify the cross member accordingly. If the likely hood is low then I prefer to leave things as they are.

Question 1: Should I modify the cross member? I was hoping to keep the integrity of the frame intact but the spacing is tighter than I was expecting.

Question 2: If modifying is it better to rotate and weld the cross member in place or is it just as good to make it removable? The removable design that I have in my head is to cut both sides flush with the frame and weld a square plate to each end of the "pipe" (plate is the red square in the picture below and the yellow is the weld) Id rotate the angle back to give more clearance and then drill four holes (one at each corner) to bolt the square plate to the frame (gray "bolts" in picture below within the red square).
View attachment 1391369
Would this design be safe/acceptable for a removable cross member? Not sure if it would allow the frame to twist/flex as much as just the cross member tube by itself. If it is suggested that I modify it I am leaning more this direction vs. direct welding as long as it would be as strong.
I do not want to do anything that I would be mad at a previous owner for doing. . . and Id like to do it right the first time. Any and all advice or experience from others is appreciated. . . as always.

Sorry, I know this is an old thread. Whats the purpose of the steel braided lines between the transfer case and transmission here?

 

[70fj40]

Bypass line for oil that migrates between the two. Designed to be used in the case of a bad seal between transfer and transmission. Some install as a “just in case”.

 

[Roshi]

Bypass line for oil that migrates between the two. Designed to be used in the case of a bad seal between transfer and transmission. Some install as a “just in case”.

Thank you!