Have a ford 200 straight six with the light duty c-4 (c-3?) behind it. It's always made little rattles (sounded like loose heat shields on a late model) at certain rpm. Lately though the noise has turned to a loud ringing, just like the old fire alarm bell from elementary school, which begins full volume at around 2850 or 2900 rpm and ceases abruptly at 3000 or 3100. Doesn't matter what gear, what roadspeed, uphill, downhill or level. Works going accelerating and decelerating too, I can be driving along in third, 3500 rpm at a level cruising speed, back my foot off the throttle and, just as the tach hits 3100, the alarm goes off. It sounds like something rotating at high speed is contacting the bell housing, but i don't know what it could be. The drivetrain is set up straight, engine pitched 3 degrees on install, u joints fine, driveshaft balanced. This maybe sound like a torque converter type thing? Seems like that's the only thing spinning anywhere near the bellhousing that could possibly contact it, but a warped or misaligned one would cause a hell of a lot more trouble than a noise at 3 grand i would think. Anybody ever get this?
Look at tin shielding and at the converter to plate/flywheel bolts. Especially bolts...I think the next change in sound is going to be "ZING!!! clatterclatterclatter"
I've asked around the shop and all we can come up with is a torque converter stator. It turns loose at about that RPM. Change out the torque converter and while your at it have a good look at the flywheel and flywheel bolts like Mr. Lancaster said. Good luck.
had an O/T Ford e250 ambulance that had a constant pinging/rattling noise from the tranny, it turned out that the flexplate was breaking loose around the torque converter nuts. laid out new holes 45' off and redrilled them. noise gone. the amount of metal lost by the T/C holes popping out was negligible. it could be this on yours too.
Does it rattles in park at any rpm? or only as you're driving it? If it rattles in park, it may be converter. If it rattles as you're driving, it's in the transmission maybe the planetary gears.
thanks everybody. haven't had time to get under it, but i guess that's what i'll have to do. just thought maybe it was something c-4s did that i wasn't aware of. ihbigblock, that's a good point. haven't revved it to 3000 in park, but that'll definitely narrow things down.
drop the trans pan and look for alot of fine shavings silvery in color, that's a good indication of internal converter problems. we changed alot of c-4 converters back in the day.
thats the weird thing, actually--i just did a fluid/filter service about a month ago, and there was nothing out of the ordinary in the pan. no metal shavings, no black shit, the fluid was even still (sort of) clear.
The Jalopy Journal
