The Stovebolt Site Forums The Shop Area The HiPo Shop Do I Keep or remove this Crossmember for V8 swap?

Should this come out? I will be adding a crossmember for the rear of the 700r4, and side mounts for the 305. But it looks to me like i will need to cut this out, to get it all to fit.

http://i1022.photobucket.com/albums/af342/scotphotobucket/crossmember.jpg

Yes, remove it. It is not needed if you are using side mount motor mounts and a transmission cross member.

Removing it will also make routing the exhaust a bit easier.

That crossmember also braces the frame at the rear spring hangers. If you remove it you'll get a lot of flex in the frame rails and possibly break them after putting some mileage on the new setup. I'd recommend fabricating a tubular crossmember with enough clearance to accommodate the new engine/trans assembly.
Jerry

Removed mine, bought a tubular one from CHASSIS ENGINEERING and fit to my frame rails. They come in different drop heights. Built very strong and fair priced. Just remember, make sure it is removable after the truck is done. IE, do not mount inside the trade rails. Don't ask me how I know.
Running a SBC W/700R4. Two piece drive shaft. Good luck!

ctheusa, I have mine removed and I am using the side motor mounts and crossmember under the rear of my 700R4.
However, I agree with what Jerry said about the spring attaching in that area and it may stress crack later.

I've thought/wanted to put some "strength" back in that location. I've thought about re-enforcing the chassis with some plating or something similar but your cross member sounds interesting. Is the one you mentioned specifically for going where we took the one out?? If so, can you give a little more detail. I can look up their site but like some "hands on" information when I can get it.

thanks

I see two answers to this question depending on what front suspension will be used.

If you are keeping the stock leaf springs and front axle, then you will need to put in some sort of reinforcement or replacement crossmember at the spring mounts.

If you are changing to an independent front suspension, it will have it's own crossmember, so the rear transmission crossmember should be sufficient.

I will be keeping the front leaf springs, and will be using the CE 2 piece engine mounts, with the 700r4 crossmember at the tail end of the trans.

Or should I change my plan , and get a crossmember style engine mount as well, if I take the stock one out?

I won't be off roading, just take it easy driving mostly.

Achipmunk, not sure on your vehicles (37 and a 52). Mine is a 47. When in question add some more steel. The CE trans support goes where the mount for the 700R falls.
Scotricker, the engine adds a lot of strength in itself. If you plate the frame in the spring mount areas you will be fine. The trans cross brace also adds rigidity.
The frames were designed to flex back then anyhow. I do not think you will have any problems. Remember, the axle is also a cross member. Good luck with your build and just use common sense.
Like you said; it's just a driver! 😎

I put a 350/TH400 in a 47/48 frame. I did not touch that crossmember. I also used the bolted-on original transmission crossmember for the TH400 by unbolting and sliding it back until it was centered under the transmission tailshaft mount. I did not have to cut it either. When I mounted the cab, I had to slightly massage the lip of the forward edge of the transmission hole.
After reading about all of the "aftermarket cross member this" and "cut out that", I was surprised how easily my method of installation worked.
Carl

I would take a sawzall to the crossmember outlined in the photo link, about 3" inboard of the frame rail on both sides, then fabricate a 2" square tubing cross piece that bolts into the remaining stubs. Put enough drop into the new piece to clear the flywheel and bellhousing, and the job should be good to go with about 3-4 hours' worth of fitting and fabricating.
Jerry

I have the same problem with my 55 2nd with Pontiac V8. The bellhousing is a full circle one with out removeable bottom. Some day when I need to replace clutch, The stock crossmember is in the way of removing the bellhousing. My thought is to try and remove rivets from the crossmember and replace them with bolts. Don't know if I can reach all rivets or if crossmember will be able to come out from the bottom. I think a couple of the rivets are common with the rear spring mounts. I have thought about cutting out enough of the crossmember to allow clearance, but I'm not sure that wouldn't compromise the integrity of the frame. The Pontiac V8 has mounts at the midpoint of the block, which are setting on a fabbed up crossmember, and the Muncie 4speed is also setting on a crossmember. So the stock rear crossmember bears no weight, but it does attach to the frame rails at the spring mounts. And it is a heavy duty gusseted part of the frame.

I think Jerry is on the right track. When I removed the '52 crossmember I cut it back about 3" to get it out of the way. Then I took the rivets out and stored the ends for later use just as Jerry suggests. In the meantime, until I have everything together, I "lost" the two end pieces...and still lost. I replaced some rivets with grade 8 bolts.
I still plan to fab me a cross member. It is currently doing fine but I don't want to get under the panel later and see damage I could have avoided. I will fab one up.
Quite simple really, I like "insurance" when I'm tooling down the road and all over the country side!

I guess I will figure out why I can't actually get away with not cutting the cross members when I finish assembling my truck. I'm pretty sure that I didn't just have a dream about pulling it off. But then again it has been hot as blazes...
Carl

Scot: We can't say "looks to me like". The secret is to put the motor in there as best you can and see what it looks like. See where everything lands, tranny mount, motor mounts, tranny shifter, pinion angle and all potential firewall, frame and steering box interferences. Mock up or mess up. The aftermarket tubular cross members are pretty nice and can be bolted in...for later removal. $50-$60. Don't start cutting until motor/tranny/exhaust is cherry picked in there. You have the clip off which is absolutely perfect. Maybe you have mocked it already. If you do have to cut the old cross member out, you will be replacing it with another thus re-strengthening. I would guess Carl must have mocked it up somehow or did some extreme cyphering and saved time and structure. Good job Carl (that hurts my brain!)

Thanks, all. I will post as the project progresses.

Went to the Brothers truck show today in So. Calif. Lots of nice Chevy and GMC trucks there! Looked at all the TF pick ups like mine, with stock front axle, for the ones with the crossmember removed. Interestingly, found two, both had the rear bellhousing crossmember completely removed. One had a 265/283 engine with the front birdleg mounts and only a crossmember back in the rear of the trans. Nothing inbetween bracing where the spring mounts on the frame rails are. That's over four feet with out any crossmember. Wasn't able to hook up with the owner of either truck, to get their input. One guy was a member of the Old Farts Club of Riverside, Ca.

If you guys are still out there this 7+ years later, I'm curious how it turned out. I am in the same situation with a 56 31300, 700r4. Instead of cutting the rivets I am considering cutting the crossmember vertically along the frame to leave in the rest of the crossmember on either side since that is where the leaf springs attach. Then possibly shape a couple piece of sheet metal to weld over the cut cross section. Performance online says I don't need anything but this kit which might have not been available in 2015.

https://www.performanceonline.com/1...ransmission-crossmember-kit-with-mounts/

I am dropping the front end 2" or so and hope none of this drags.

I was concerned about removing the cross member on my '50 3600 for all the reasons discussed. I am using an NV3500 transmission so not the same but the same problem as my transmission have a full bell housing and an external clutch slave that further interferred with the cross member when I located my SBC engine where I wanted it (as close to the firewall as possible).

I made vertical cuts in the cross member inboard of the frame on both sides, welded plates to the remaining portions that remain rivited to the frame, and then attached plates to the removed center section that allowed the center to be moved down and back.

I needed to modify the transmission clearance in the cab to clear the transmission bell housing and fabricate a different transmission cover.

For posterity, here is my solution. I used a tubular engine mount and modified with angle iron. I used some iron pipe as spacers for the bolts to the frame. I don’t notice any flexing. Feels solid but time will tell.