Drive shaft bump

I've had my 67 'lark for about 6 months, and am slowly getting it into shape. One of the nagging problems is that the drive shaft bumps up against the floor when there's more than 2 people aboard (including driver), and we go over a medium sized bump. Its got the 300 motor with 2 speed auto. It looks as though it could have been lowered 2" max, but I can't believe that could be the issue, as I've searched this board and there's no mention of this phenomena happening even with people SLAMMING their cars to the ground. What gives? Is there such a thing as worn trans mounts?

 

Incorrect springs or old and weak correct springs is a typical cause.

 

Does it rub in the back? I'm assuming the trans is semi-rigidly mounted with a rear trans mount and the rear is the only pivot point. Is it the actual drive shaft or the yoke or what? Can you take a picture of it where the rubbing is occurring?

If it is rubbing in the front, I'd suspect the wrong rear trans mount or the trans cross member is improper or something. Either way, a picture goes a long way.

 

It's definitely hitting the tunnel. There's a ring of bare metal on the shaft, about 4 inches back from where the shaft gets wider. I was looking to see if the trans mount was aftermarket, but looks original. Now if only I can find a trans mount that's shorter...

 

So, you have a clean spot on the drive shaft. Where is it rubbing on the car? I've seen it where the shaft will rub the exhaust pipes. Are you sure that isn't where it rubs?

 

Now that I'm looking at these pictures, I guess it's possible it's hitting the H pipe. Looks spaced out quite a bit though. What then is making that awful bump noise?

 

I would suspect the tail of the trans is up due to a bent trans cross member or wrong one all together. Yes Jason floor looks cut to me too.
Check the engine mounts also.
Can you post a shot from the side of you engine compartment. I really think your transmission tail is to high, so a shot of the trans mount would be good also.
One last shot, show us the side of the car showing how it sits/ride height.

 

make sure YOUR TRANS MOUNT IS SECURE AND DOES NOT JUMP UP OFF THE TRANS CROSS MEMBER ...

aNOTHER THING be sure the crossmember is bolted to the frame securely NO MOVEMENT.

That area should NOT GO UP AND DOWN AT ALL...??? SOMETHING is not bolted down.

YES they make a short trans mount and a tall trans mount-


Start with the simple things.... JIm

 

Thanks so far for all the suggestions, gentlemen. As you can probably tell, I'm pretty green to cars, although I was a motorcycle mechanic 17 years ago. Now that I look at the trans mount, it looks like a home made solid one. What have I gotten myself into??!!!
Yes, I know the wheel arches look hideous. They're on the list too...

 

Yes that is a trans mount but all the rubber is gone...SEE if it is even bolted to the trans crossmember. Big trick is to stick a bolt in NOT even tighten or bottomed out. TAke a crow bar and pry up and down to see where the movement is
PLEASE BE SURE TO SECURELY JACK STAND THE CAR WHEN DOING ALL THIS PLEASE!!!!!

JIm

 

If you look in the second pic just above this post, you can see where the trailing edge of the x-mbr is bent up....someone hit something and bent the x-mbr up and this caused them to put a clearane hole/opening in your floor instead of swapping out the bent x-mbr.......I have a clean x-mbr for you from a 67.....I will post some pics on Tues.

 

Wow, what a backwards way of doing things! Seems easier to swap the cross member rather than cut a hole in the floor. Thanks for the offer George, I really appreciate it, but I'm doing the 200-4r swap soon, so I'll be ditching that piece. I'm looking for a cross member for that swap though...

 

Yep did not catch that- It must have taken some SERIOUS CRUNCH to bend that member that much up like that. WOW

 

I vote you still take GStage1 up on his brace. The new trans will use the factory brace, drive line and yoke without mods (you only need to move the brace back on the frame rails about 6 inches.)

 

Is that so? You can either do the Chevelle (or similar) Cross Member, or scoot the original one back? In that case George, upon Brian's advice, I will take that cross member off your hands. Just let me know what you want for it.
I learn something new here every day!

 

Mine is a convertible frame and it is closed so it was a bit harder to move the cross member back but I am told yours will just slide back then drill 4 new holes. Look at you frame rails and how the cross member bolts in now to make sure.

To swap the 200-4R in mine I modify the cooling lines, added lock up kit, TV cable to the carb, and made a dip stick tube clear the firewall. Oh, and don't forget to change the rear differential gears depending on what you got out back. I had 2.78s and changed to 3.90 so that I could get the RPMs up on the interstate. I haven't had mine out yet other than down my street and back but the first gear of the 200-4R is way more fun than the original 2 speed switch pitch.

 

I will get some pics of the x-mbr on Wed.