Author Topic: Transmission/Flexplate noise  (Read 2758 times)

Offline stavendirtbike

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Transmission/Flexplate noise
« on: August 23, 2010, 03:53:36 PM »
Few days ago I hopped in my truck and drove to the store. I noticed after about 15 minutes of driving, I was hearing a ticking/knocking sound at the stop lights. Oil pressure was good, about 30 psi at idle and 60 while driving.

Got home, snooped around and the noise is strong at the flexplate/converter area. I took an automotive sound tester and checked around the oil pan to make sure it wasn't a crank or rod knock. It is indeed coming from the transmission area.

The sound is noticeable at idle, park or neutral, and it seems to go away as the RPM's go up. I checked obvious things like fluid levels and all that is good. I took a flashlight and looked around the flywheel and saw no noticeable cracks. I checked the 3 converter-flywheel bolts and those were tight.

I took a floor jack and put a slight amount of pressure on the center of the 700r4 pan. The sound immediately went away. Release the pressure and the sound returns.

I was thinking a few possibilities here. Maybe you guys can give me some insight. I was thinking a cracked flexplate. I was also thinking possibly the filter in the 700r4 collapsed and is hitting the pan... making the sound travel? When I put pressure on the area, the noise stops. Also, possibly the transmission mount? I replaced this mount 2 years ago but it's already deteriorated with oil.

I did plan on having this 700r4 rebuilt this winter anyway. For $10, I think I may try a new transmission mount. If not, I will wait when the transmission is rebuilt. Hopefully at that time, the cause of the noise will be obvious.

Offline Lt.Del

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Re: Transmission/Flexplate noise
« Reply #1 on: August 23, 2010, 04:13:51 PM »
if it is your trans mount, you better check your bolts attaching the trans to the engine block.  If those bolts are tight, when jacking up the trans-it should make no difference.   Check all your bellhousing bolts. 

While you are at it, check engine mounts.  Have someone inside the truck and put it in drive and rev up while braking (power braking) and see if engine goes to side a lot.  Put it in reverse and power brake it and check the other direction of the engine. 

 

Offline Tater502

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Re: Transmission/Flexplate noise
« Reply #2 on: August 24, 2010, 12:31:24 AM »
I had the same problem with my 93 silverado. The flywheel was cracked, when it got warm the crack would open up and start knocking.
Andy

Offline chevymotocross

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Re: Transmission/Flexplate noise
« Reply #3 on: August 24, 2010, 10:06:00 AM »
Well, I was looking at the truck again and realized a new transmission mount isn't going to fix anything.

I'm going to deal with this issue when I get back home in February.

What do you guys recommend with the transmission shops? Should I pull the transmission myself and replace the flywheel and bring them my transmission out of the truck to save on labor? Or, should I just drive it to them as is and have them replace the flywheel and rebuild the transmission? I guess these are things I would have to ask the shops, but from your experiences, what works best?

Also, I was wanting to install a Trans Go shift kit. Should I purchase the kit myself and have them install?
1987 Chevy Silverado 2wd SWB: 305 TBI, 700r4, dual exhaust, tbi mods, k&n filter, belltech sway bar

Offline Lt.Del

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Re: Transmission/Flexplate noise
« Reply #4 on: August 24, 2010, 11:50:43 AM »
You're gonna rebuild the trans anyway, get r done at the same time.  I wouldn't tach the rpm's up too much in the meantime.
I personally would see what the diff in cost would be for me to yank the trans, then install, versus the shop doing 100% of the work.   

 


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