67 Body - Sagging under seats

[Bill T.]

When I have a passenger in the car or on hard acceleration the rear driveshaft universal hits the underside of the body and makes a growling sound. I'm guessing that the vertical structure directly behind the seats is broken or damaged and the body is sagging down. Any suggestions for this repair???

[Edward S.]

Re: 67 Body - Sagging under seats

Bill,
I am not much of a mechanic so I hope you get answers from some people who are. I can tell you that one of the vettes I owned, when I first bought it, did the same thing. It turned out to be weak shocks and springs, which under stress allowed the driveshaft to rub. We measured the car next to other mid-years and found it to be on average about a 1" and 1/2 lower then the rest.. Don't know if thats the answer to your problem but at least it's a start. Good luck.

[Mike M.]

Re: 67 Body - Sagging under seats

When I have a passenger in the car or on hard acceleration the rear driveshaft universal hits the underside of the body and makes a growling sound. I'm guessing that the vertical structure directly behind the seats is broken or damaged and the body is sagging down. Any suggestions for this repair???

i'd check the differential rubber cushions first, then i'd get the car on a lift and see if the Muncie is centered in the tunnel. just loosen the two tranny mount to crossmember bolts and shift the Muncie away freom the tunnel contact area. mike

[John H.]

Re: 67 Body - Sagging under seats

When I have a passenger in the car or on hard acceleration the rear driveshaft universal hits the underside of the body and makes a growling sound. I'm guessing that the vertical structure directly behind the seats is broken or damaged and the body is sagging down. Any suggestions for this repair???

Bill -

If you don't find the snubber bushings deteriorated, it's probably the classic "floor sag" resulting from the rivets along the bottom of the steel luggage stop panel to the floor pan loosening; fairly common midyear problem.

[Bill T.]

Re: 67 Body - Sagging under seats

Bill -

If you don't find the snubber bushings deteriorated, it's probably the classic "floor sag" resulting from the rivets along the bottom of the steel luggage stop panel to the floor pan loosening; fairly common midyear problem.

I'm confident this is the problem. What's the best way to make the repair? Can the floor pan be jacked back into position and extra rivets added?

[Bill C.]

Re: 67 Body - Sagging under seats

Bill,
Be sure and check to see if there is a later model pinion flange on your differential, the OD is larger and under load or an additional filled seat it will sometimes hit. This was done commonly and one only needed to use an adapter ujoint, I still have the TRW # on the wall in my shop. If you do have the larger one, new correct for your year flanges are currently available and reasonably priced.
Bill Caldwell

[John H.]

Re: 67 Body - Sagging under seats

I'm confident this is the problem. What's the best way to make the repair? Can the floor pan be jacked back into position and extra rivets added?

Bill -

Yes, it can; you also want to check the top of the tunnel at the bottom edge of the center of the luggage stop panel to see if it's cracked or broken and repair that too.

[Albert P.]

Re: 67 Body - Sagging under seats

Paragon used to sell a booklet on the repair "!963-67 Bulkhead Repair Manual"; don't know if it's still available.

[Nick L.]

Re: 67 Body - Sagging under seats

As stated by others, most likely the common and dreaded floor pan sag issue. However, I have also had low quality replacement transmission mounts separate and the trans shift laterally by nearly an inch. Along with a severe driveline vibration, the output yoke actually made contact with the tunnel before I caught the problem.