I have a 1960 Impala with around 80k miles. The drive line is all original, with a 283, Turboglide tranny and a positrac rear end. I have just had the front end rebuilt as well as complete new front and rear suspension bushings installed. Also new carrier bearing and U joints. My question: when you accellerate hard from a standing start, the drive line makes a horrible scraping noise, like the bumper would make scraping on concrete. It did the same thing before the suspension overhaul. What could be causing this?
I think I know. I think you need new motor mounts and here’s how you find out:
Plant your foot firmly on the brake, set the parking brake, and start the car. Put it in drive (still keeping the brake depressed) and give it a little throttle. If it makes the noise, then I am going to say that it’s a bad motor mount and the sound is your radiator fan scraping the fan shroud when the motor is torqued to one side.
I would be surprised if this thing has an O.E. fan shroud. It could be the fan is hitting the radiator, but you should be able to see the clean metal.
Has the engine or trans been out recently? Is there any way the flex plate could be scraping the bell housing?
When you powerbrake it to check the motor mounts, leave the hood open so you can watch for engine movement. Does it have leaf or coil springs in the back?? If leaf springs, check to see that the Snubber the prevents the rear axle from rotating upward is there. It’s on the nose of the “3rd member” near the rear U-joint…The rubber snubber may be mounted on the body above the rear end. Coil spring suspension will not have this snubber. They use a control arm to limit rear axle movement.
With an all original powertrain and 80k miles, I’ll bet you a 6 pack that it has the original fan shroud. My '70 Chevy 3/4 ton has the original shroud and it’s been around the block a couple of times.
EDIT: Although it could well be the differential rotating and letting the drive shaft rub, like Caddyman said…
No, what I am saying is that it never had a shroud. When did they start putting shrouds on them? IIRC it used to be just a fan behind the radiator with nothing else hooked onto the back of the naked radiator.
I hadn’t thought of that. I think they did though, they were big funky circular things, I think I remember seeing them back in to the late '50s (note that I’m 23, I wasn’t there or anything…)
Thank you all so much for your responses. I must apologize; we have been without electricity since last Sunday, so things have been very hectic around here. The 60 is still in storage, so I haven’t had a chance to get it out and check some of the things you have suggested. Yes, it does have a shroud, and I believe all of the V8’s did. The fan is a good 6 or 8 inches from the radiator, so that’s not a problem, and I couldn’t find a place where it had rubbed the shroud. The car has 4 wheel coil springs, and a control rod on the pumpkin. All of the bushings have been replaced, so I can’t rightly lay it on loose bushings anymore. I have not checked the motor or transmission mounts, but that increasingly is the focus of suspicion. The shift lever is steady as a rock, though, and if the tranny was moving, I would expect it to jump around a bit. In any case, I am still baffled. I will make the powerbrake check as soon as I get caught up on things, and can get t he car out. Next stop, get it up on a lift and look for spots where the drive shaft might have contacted the frame or tunnel. Oh, this car has a two piece drive shaft with two U joints. Thanks again, I will check in again soon.
If after checking the Chevy out again and don’t find the fault, go ask on this site (if you don’t already know about it): http://www.chevytalk.org/fusionbb
The universal joints could be making the noise too, so check them. If they are hard to move or clunk around, they should be changed. You have to remove the driveshaft to check them.