While in Overdrive, and after the Torque Converter locks up, I have this strange rattle at around 42 mph during light acceleration or when coasting with no acceleration. (It's like a metal clanking noise). When I had the 383 Stroker built, a new internally balanced TCI Flexplate was installed along with a YANK SS3200 TC. The 700R4 Transmission is a GM factory refurbished unit with around 5,000 miles on it since it was installed. I've checked everything in the rear suspension, and all components are tight. Over a year ago, I changed the gearing with a Yukon 3.54 Ring & Pinion, replaced all u-joints with the Spicer Brand and also installed a new balanced Driveshaft. At 42 mph, the rattle is present about 50% of the time. However, if I'm in Drive (not OD) it will not make this rattling noise at any speed. Dave at YANK suggested that there wasn't anything to rattle in the TC and is thinking possibly the Flexplate. Since the noise is only present around the 42 mph speed during light or no acceleration, I'm at a loss as to what this could be. I would think if it was the Flexplate, the noise would be present all the time and get worse when accelerating. Does anyone have a direction they could possibly point me in? I'm just trying to prevent the expense of shop looking at the Flexplate / Torque Converter area if it might could be something else. Thanks!
42 mph Rattle - 93 Corvette Auto
- Thread starter Ace57
- Start date
Is the sound present when the car is stone cold and hot (at least to operating temperature)?
The sound is only present at around 42 mph, as soon as the torque converter locks up. I don't think temperature is a factor as it rattles about 50% of the time, hot or cold, just as soon as the TC locks up and I'm barely accelerating or just coasting.
Loves302Chevy
"One test is worth a thousand expert opinions."
Does it sound like a ball-peen hammer whacking the flexplate?
If it is not a cracked or defective flexplate, then it could be that the bolts have loosened.
Or the torque converter bolts. Did you use RED Loctite?
You should be able to check without disassembling everything.
Remove the torque converter bolts and push the converter as far as you can into the transmission.
This should give you enough room to get a wrench onto the flexplate bolts to check.
Unless they are the 12 point bolts - that might prove harder.
If they are no longer fully torqued, it should not take that much to loosen them.
I had this happen once - the 6 bolt holes were now ovals. New flexplate needed.
Another thing to check, because some people get it wrong..... is the flexplate on backwards?
If it is not a cracked or defective flexplate, then it could be that the bolts have loosened.
Or the torque converter bolts. Did you use RED Loctite?
You should be able to check without disassembling everything.
Remove the torque converter bolts and push the converter as far as you can into the transmission.
This should give you enough room to get a wrench onto the flexplate bolts to check.
Unless they are the 12 point bolts - that might prove harder.
If they are no longer fully torqued, it should not take that much to loosen them.
I had this happen once - the 6 bolt holes were now ovals. New flexplate needed.
Another thing to check, because some people get it wrong..... is the flexplate on backwards?
I think you pegged this one! I'll be surprised if it's elsewhere!
Thanks to all of you that replied, I can't imagine that it could be anything else than what y'all suggested. I didn't do the work myself, I had the 383 Stroker built by McMurtry Racing Engines and another shop did the install. I don't know if they used Loctite or not, but they are a reputable shop. I'll just take it back to them and have all the bolts checked. Thanks again for your help!!!
Loves302Chevy
"One test is worth a thousand expert opinions."
Good luck. Hopefully that was the only thing they messed up.