I put a starter in an sbc in a 40 Ford truck for a guy. while under there I saw some strange things going on. I was laying on cardboard in the dirt, so I didn't really study it closely, I just wanted to get done and off the ground. looks like they took some C channel and capped off the ends of the x member where they cut it out to make room for the trans. the two sides are only connected by a bolt in 1x4 steel tube, just bolted in below with 4 bolts. this serves as the trans crossmember. this would seem to me to be a great compromise so far as strength and ridgidity is concerned. the truck has parallel leaves out back, and a welded in MII up front. it also appears that the sbc is only using one hole on the block where the 3 motor mount holes go, and the connection between the steering column and the rack is a mix of OEM parts, and is questionable as well, so there could very well be other oddities in ths build. again I didn't spend a lot of time under there as my job for the day was to get the starter in and fire it up. this was like 3 weeks ago. one more thing,, I didn't look at the time, but how close is the frame off the ground in relation to the running boards on these?? the last vintage truck I tried to put on my lift didn't work because the running board hung down too much from the frame. I only have so much ability to raise the rubber pads up off the arms on my lift. so what do you guys think of a 40 frame compromised in such a way? this is a finished painted truck, looks like it is from the 1980's and probably has a few miles on it this way. the MII ads soome strength up front, but i'm thinking the whole back half must be pretty wiggly -wobbly going down the road. one thing for sure, it has to be better than the F-1 I saw a while back. NO original crossmembers at all except the front and rear and one bolted in square tube for the trans. makes you wonder just what people are thinking sometimes.
I'll take a shot on some of this. My 38 and the 40 share a lot of the some dimensions, I believe the 35-40 frames were identical including the trucks. What you describe for the transmission sounds weak at best. The two halves of my X member are held together with about 3/16 steel plate top and bottom that are bolted through the X frame with about 8 bolts each side. Pix of the steering arrangement and sbc would help. As for the running boards, they don't hang below the frame...in the stock configuration. I run parallel leaf in the rear and I have no problems but I don't thrash it either. There are some places in that frame that were really prone to rust. Back where the X member rivets into the frame rails is a bad spot so twisting up a parallel leaf could do some ugly damage. I don't have many issues with wigglies in the rear.
"Pix of the steering arrangement and sbc would help." I think in that regard my main concern is the motor mounts. he said the rod from the steering column was hitting the manifold and he had someone move the motor over... I will probably be moving it back with proper mounts and move the steering over instead. he said someone told him "there is a lot of "okie engineering" going on under the car". I don't think I have seen it all yet. the steering itself is probably safe, I'm just used to seeing $300.00 worth of borgeson U-joints and stuff these days. no extreme angles or anything like that. good to hear I can put it on my lift. if I work under a car much these days I hurt the next day from alll ht getting up and down. maybe I should join a gym.
The X member in that frame is the backbone to it's strength. Sounds like they took out with out thinking.
Agreed... The frame is actually two pieces of stamped metal, In some places it is sandwiched together (front & back portions), in others split apart (I.e.l the center cross x portion). By removing the center section you have effectively lost half its strength. Doing anything to upset the integrity of the front to back portion would be a big issue
Here are some pictures of my '41 Pickup frame which is basically the same as a '40 car. I opened the area up for transmission clearance but retained the basic structure theory.
The Jalopy Journal
