Technical To cut or not to cut

Hello,
Once again I find myself seeking advise on my 56 Chevy truck. After replacing the motor, transmission and dealing with a sensitive starter solenoid, I found myself having to replace the transom ion pan seal on the 700r4. I did not remove the old transmission crossmember but I did add a new one to fit the new transmission. Now I have a pan seal leak and cannot lower the pan enough due to the old crossmember. Since I have a new crossmember installed, can I cut out the old one? It is heavily riveted to the frame so I wanted to cut it away along the inside frame. Is this something I can do?
Thanks
Scott

 

I ended up cutting the crossmember out of my 59 a few years ago to work on the transmission. Most of these trucks that have an automatic in them, have it cut out. It'll survive ok.

 

Cut it

 

Worst case the front of the cab will settle down on the frame and your hood won't fit like what happens on most AD trucks with the crossmember removed including mine at one time.

Meaning that if the frame isn't reinforced there is a chance that the weight of the cab pushing down on the outrigger cab support brackets will twist the rails until the cab settles on the frame rails.

 

"Since I have a new crossmember installed, can I cut out the old one? It is heavily riveted to the frame so I wanted to cut it away along the inside frame".

Any chance you can remove the rivets and replace with bolts? I can't see the ends but that looks like quite a substantial part of the frame, I'd look into setting it up so you can remove as needed then replace.

 

THIS

 

The original Hydramatic crossmember had a removable center section, it bolted in. I though about welding plates to the cut ends of mine, so I could put it back in.

Another option is to use a later rear transmission crossmember from a truck, that bolts to both the top and bottom flanges of the frame rail, and provides stiffness. It's not as close to the cab mounts as it should be, but will help.

I think you'll need to do some hard driving to get the cab to settle, but that's just a guess. Yes, the crossmember is a structural part of the frame, but it's also a pretty stout frame. Maybe since mine is a long bed with a heavier frame, it's less likely to twist compared to a short bed.

 

Can you just remove the RR trans cross member bolts & lightly jack up the tail shaft area to get sufficient clearance to drop the pan out above the old cross member?

 

When my Dad put the BBC/TH400 in the ‘57 he cut the original out. Made a new x-member for the transmission from box tubing and flat plate and bolted it to the frame.

 

I would remove and replace when done. Either bolts like mentioned before or just weld it back together when done.

 

It might be possible for him to do so. Looks to me like the engine sits pretty far forward of it's original location, which would put the main part of the pan slightly behind the crossmember. With the engine back like original, the bellhousing part of the transmission case would hit the floor when trying to lift the back of the transmission.

btw removing that crossmember with the truck assembled, without cutting the crossmember, is pretty close to impossible. It's a tight fit in there.

 

If your worried about it make it a bolt in piece. You can cut it close to the frame, weld in some plate on the inside and drill some holes. I did it on a '54 truck I had.

 

Might be able to get a little more clearance to raise if he can remove the center floor pan/inspection cover.

 

Thanks. I believe I can jack up the trans and unbolt the new crossmember. I wasn’t even thinking about that. So glad I didn’t cut it. Phew. A little time and advise saved me a big headache.

 

you might still not be able to get the pan off...it has to drop a couple inches to clear the valve body.

 

Yep. I was having yet another brain fart when I thought I could do that. Since I added a new crossmember, I should be able to cut the old one? Or would you recommend grinding off the rivets and keeping the old one just as structural support?
You always have great advise.

 

I have a similar situation coming up with a build.
I’ll remove the x member rivets and bolt it in

 

Getting the crossmember out in one piece after cutting the rivets won't be easy...you're probably better off just cutting the middle of it out. If you do it right, you could then shorten the cut section a little bit, and weld a plate at each end, as well as a plate on the remaining parts that are still attached to the frame, and bolt it back in. But you shiould be able to get by without doing that.

this is what Chevy did when they installed an automatic in one of these trucks.