So I'm swapping an NV4500 trans into my 74 W200 crew. It is a divorced transfer case model so the trans and crossmember is like a 2WD truck. I have the original crossmember and a crossmember from 93 RC 2WD that had a 46RH in it. There was just no way to make either one of those work without major fabrication as they didn't provide enough center drop to align the trans with the transfer case using my short 4.75" intermediate shaft. So I recalled Holley makes a Hemi swap crossmember for the 72-93 2WD trucks. So I watched their video again and it looked like it would work but Holley couldn't provide any dimensions for me. I bought it anyway along with their GM style trans mount and an adapter for a 46RH trans.

I get the crossmember and it's a very stout piece that uses thick plates that bolt inside the lower frame flanged area. Everything fits, mount bolts directly to the trans and sits down on the crossmember in nearly perfect alignment. I had to clearance the frame a little for the bolt heads to sit flat to the adapter plate.

Now my question is, there is no brace to the upper frame flange, I'm not sure if I should make some or not worry about it. The adapter plates spread the load on the lower flange for about 8" maybe, but I also realize the crossmember wasn't designed for a 4WD. I used the 46RH adapter to mount the transfer case shifter so nothing was wasted. I figure if I'm going to make brackets now is the time as drilling the upper frame flange will be easy while the floor is out. Here are some pics.

I would tie the upper frame flange into the cross member. Might be over kill but the factory did it maybe for some reason we are unaware of.

The original 4x4 crossmembers bolted to both the top and the bottom flanges for a reason.

In my welding shop I've had the pleasure(?) of repairing the lower frame flange on 2 different Dodge 4x4 trucks where the owners (or someone) didn't think the bolts on the top flange were important enough to reinstall them after a trans rebuild. I don't believe the lower flange is strong enough to take the forces involved with the transfer case in action. Those two trucks may have been the strange ducks of the bunch, and who knows what extremes they may have seen, but I doubt Dodge would have invested the money to add that extra bracing if they didn't think it was needed. The extra cost of the extra bracket pieces and the extra bolds X the number of 4x4 trucks Dodge build was a big investment they would not have make if it wasn't deemed necessary.

Add the extra brackets. Especially since it looks like your crossmember bolts to the bottom side of the lower flange. Gene

The plates sit on top of the lower flange and the crossmember bolts on top of the plates so those plates are spreading the load on the lower flange. The factory crossmember bolts to the inside of the top frame flange with only the bolt heads supporting it at the flange. The factory braces support the crossmember from underneath to the inside of the lower frame flange. Just to be clear, this is not like a regular married transfer case 4x4, the transfer case has it's own crossmember about 12" behind this one that is riveted to the frame rail sides near the top flange. The crossmember you see here only supports the trans.

It is a truck so weight isn't really an issue. Add a vertical plate to tie into the top flange, or box the frame in that area, or build a different lower plate that has a vertical section (90 degree bend) that sits on the lower flange but also bolts to the vertical part of the frame rail.

I see what you are saying. It would be pretty easy to weld a vertical flat plate to the lower plate and bolt it to the frame rail rather then bend one.
Thank you.

I'd add the bracing to keep the rails from twisting.

good advice.
a C channel frame twists more than one thinks, no matter how thick the material is.

That was my main concern.

That's nice! Did part of the floor come out with the hump or are you repairing the floor too?

It has the removable trans hump, the floor had to be repaired.

I agree the top rail needs tied in to the lower rail like stock 4x4 chassis. frame twisting and flexing is why most trucks have a tweaked frame just forward of the crossmember and behind front leaf-rear shackle same spot a 2x chassis tweaks with out the 8 extra bolts and 2 supports boxing the frame in that area.

look down the lower frame rail and see if it already has a slight dip in lower rail. looks like a crescent wrench was used to pull down on frame rail edge.. this frame tweak also contributes to the dodge truck lean on driver side along with all the other reasons they lean on drive side and need a spring spacer on 1 side.

I have watched a chassis shop chain a frame down on the frame rack and re-tweak the frame in that spot to make it flat and straight again, then add the 2 braces & 8 bolts along with the steering box brace & front coil spring rubber spacer on driver side to correct the doge lean.

I find it hard to find any truck frame after 35-40 yrs that does not have that small tweak on the frame lower rail in that area and is one of the first spots I eyeball on the chassis. what's bent & what's missing tells you a lot about a trucks life.

like poorboy said I have repaired a few bolt holes in the frame and beat the rail flat after snatching bolts thru the hole or shearing them off. manual shift can be brutal with a 12 pak and a good clutch. it scratches or it breaks.

I ran into crossmember issues with my 47rh-np205 combo, basically the front driveshaft dropping down to the diff with he 6" lift interfered with the crossmember. I was going to notch the crossmember, but it was hitting right where the bracket from the top frame rail attaches to the crossmember, so notching would have meant losing that bracket. Instead I did a 2 piece front driveshaft, the brackets look like they stop the frame rails from twisting out .