I know it would help if you could hear it but i'm just looking for ideas! My 57 Chevy truck has developed a strange sound that i just don't recognize and can't seem to track down. It's got a 79 Trans Am subframe and rear axle. all the suspension components are new. A-arm, ball joints, shackles, etc... It has a 283 (stock except for ingnition and exhaust) and a th350. the trans is new as is the flexplate and converter. At different times (with no correlation to how fast or slow i'm going, uphill or downhill, under load or not, even sometimes when parked and not in gear) i get a very strange sound. i can only describe it as a mix between detonation and a piece of sheet metal ratteling against another piece of sheetmetal. it doesn't do it in tune with how fast the motor is revving or whether i'm turning, hitting a bump or whatever. it is more distinct when driving than when parked. I've triple checked the timing and advance, triple checked all nuts, bolts, brackets, etc... i know it's not much to go on but i have two questions: 1. anybody familiar with a detonation/metallic rattling that isn't detonation coming from somewhere in the vicinity of the transmission? (is there some horrible thing that makes this sounds before a th350 lets go?) 2. It won't ever do it when i'm parked and listening for it (maybe my weight in the truck changes it but i've had other people sit in there) so what the hell else can i do to track it down? (i've htought about putting it on four jackstands and putting it in gear but i'd have to crawl underneath it and i like to be alive) I know it's one of those "you need to be here and see it for yourself" kind of issues but i'm just hoping the description my make soembody recall a similar sound or remedy without me having to tape a skateboard to my back and be drug under my truck for a few miles to find it.
Could be as simple as linkage or exhaust rattling. Could even be your hood springs. I know the 70+ were known for that. Put a shop rag in them and see if it goes away.
that could be, you might want to go around the truck and just whack parts with your hand, see if you find a similar sounding rattle. I found a noisy catalytic converter in a later model truck that way, it made the same sound when I smacked the converter, as it did when I accelerated from a stop
Good ideas guys. i'll try the shop rags. I was wondering about the flexplate. i know it's not gm, so that probably means it's chinese. i'll pull the cover and check it. Thanks!
It's the frame crying to have the trans am subframe removed. Or, the flexplate. It's hard to see in there, but they do make a noise like that. And OEM flexplates crack too, not just aftermarket stuff.
Also check the transmission case to engine block bolts, fun things happen if they don't get tightened enough.
Had something similar with a cracked flex plate (off shore) in my '70 C10...started when I was pulling my '34 chevy home from NY. I made it home, but it trashed my trans pump in the process. Don't wait too long to investigate.
Sounds like we have a consensus. I'll pull the cover tonight and see what i can find. I'm sure it won't be that simple and i'm going to have to unbolt it all and pull the converter to get a thorough look. Damn it!
You need to pull the trans to get a thorough look. Once the converter bolts are out it only moves away from the flexplate 1/8 to 1/4 inch. Usually not enough to see the crack. BTW all the ones I've seen crack close to the crank flange, not out on the edges.
Before tearing into things, get a cheap stethascope (Kragen, Checker, Autozone, NAPA: on the "Help" tree) Raise the truck and let it run in Park, and locate the vicinity of the rattle. The stethascope will dial in on the specific area of the noise, relieving tension and restoring confidence in addressing the solution!
A wooden broom handle is your best friend on finding wierd noises. You can check the suspected areas when running and the broom will amplify the sound. Just put one handle end as close to the area you are wondering about and put your ear on the other. So, best place to check for the flex plate would most likely be on the engine block at the rear main webbing since that is the closest piont of contact. I would have someone put it in gear and hold the brakes while you listen. See if you can find the noise that way. You might also try applying light throttle while holding the brakes. Obviously(but, I'll say it anyway), stay clear of the front of the truck incase it moves while your power braker is helping you.
I'd pull the tin inspection cover and run the rig. If they get tweeked a bit, they can make bad sounds and can come and go at will. Had it happen.
nomobux, You may be on to something. the cover is one i had laying around and was a little "tweeked." I had to "massage" it a little to get all the holes to line up and the fit is so-so. i'll pop that off first and take it for a spin before i go further. Thanks!
I think you are on to something, my brother stuck his chev truck on the ranch and when we pulled it out it had a sound much like you describe, it appears the truck came to rest on the torque converter cover jamming it upwards making contact with who knows what? a new cover and problem solved, get a plastic one.
I think it is more likely to be the cover than the flexplate, they usually sound more like a rod knock with no load on, and when put in gear with the brake on the noise will diminish or go away. Also pull your dipstick and make sure it has not got bent to where the crank can hit it. Worst of that kind of noise I ever had to track down was a baffle in the oil pan had broke loose, and was rattling against the crank.
you sure torque convertor bolts are tight if so.it could be a bearing or bushing.altenator bearings,water pump bearings,power steering pump,or possibly the bushing in your distributor trying to seize to shaft.get a stethescope save youself a lot of time and trouble
Everyone here touched on good ideas and subjects. But I worked at a tranny shop for a few years flexplate would be a problem. But a bad torque converter falling apart inside could make some wierd noises. In park no noise but when in gear more fluid and pressure it will make funny noises. How old is the torque converter? What kind of fluid you using? Shifting a bit funny ?
Worst of that kind of noise I ever had to track down was a baffle in the oil pan had broke loose, and was rattling against the crank.
it could be a bearing or bushing.altenator bearings,water pump bearings,power steering pump,or possibly the bushing in your distributor trying to seize to shaft. ____________ thomas sabo ,thomas sabo charms,thomas sabo London ,
Check your forward universal joint. Had one make noises like the torque converter was rubbing against the case.
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