What does a cracked flexplate sound like? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BLAZERMAN · 05-19-2008, 05:02 PM

I have a strange noise that seems to be coming from the torque convertor flexplate area. It only does this after the motor is warmed up good and doesnt do it under power. No funny noises while cranking or starting issues.

**too much stuff** · 05-19-2008, 05:11 PM

I had 2 different ones do this to me and it was most noticable while cranking. I don't recall hearing anything odd after they were running. Take the inspection cover off and look closely around the bolts. I could see where mine were cracked. Good luck, Eric
Oh yeah, check the converter bolts also...

**Stocker** · 05-19-2008, 06:12 PM

When mine cracked, I thought I had lost a rod -- it was a deep, hollow, solid knocking. I was on a duck hunting trip several hours away and had no choice but to drive it home, not knowing if it would blow up at any time...

BLAZERMAN · 05-19-2008, 07:20 PM

This is more like a squeeking sound, kinda like a belt or pulley would make but it comes from the tranny area..and only once it has warmed up good. I get no noise at all at speed or under a load.

67_C-30 · 05-19-2008, 07:24 PM

Quote:

Originally Posted by Stocker

When mine cracked, I thought I had lost a rod -- it was a deep, hollow, solid knocking. I was on a duck hunting trip several hours away and had no choice but to drive it home, not knowing if it would blow up at any time...

That's been my experience with a cracked flexplate as well. I have had the pump of the TH350 make some funky squeaking noises before, and I've heard a bad cam bearing squeak also.

LooseCannon · 05-19-2008, 09:16 PM

Quote:

Originally Posted by Stocker

When mine cracked, I thought I had lost a rod -- it was a deep, hollow, solid knocking. I was on a duck hunting trip several hours away and had no choice but to drive it home, not knowing if it would blow up at any time...

Mine sounded like a knock as well...

BLAZERMAN · 05-20-2008, 04:13 AM

Quote:

Originally Posted by 67_C-30

That's been my experience with a cracked flexplate as well. I have had the pump of the TH350 make some funky squeaking noises before, and I've heard a bad cam bearing squeak also.

What would cause the pump to squeek? and is there a fix for it besides tearing into the tranny?

EdB · 05-20-2008, 06:00 AM

I had the same noise with my 94. I was getting ready to pull things down
when the noise quit. It has not started back. It did not effect the driving
in any way. It has a new replacement engine but the trans has over
270,000 miles. It will sure be interesting to me if you find it. If mine comes back
and I find it, I will let you know.

EdB

89 crew · 05-20-2008, 06:45 AM

When I had one break it made the knocking sounds along with some squeaking noises. it was on a 77 k30 400/400 (maybe the externally balanced engine caused some of the noise since the flywheel didn't balance anymore)

jeffspower · 05-20-2008, 06:50 AM

So it will only do it hot, just in park? Will it do it in neutral? Maybe put the T-case in neutral and put in drive. If the noise goes away, I'd suspect something in the transmission, or possibly the sprag inside the converter. It's been a LONG time ago, but I seem to remember a converter making a mild squeeling noise.

05-19-2008, 05:02 PM	#1
BLAZERMAN Currently Blazerless Join Date: Apr 2000 Location: St. Joseph Mo. Posts: 4,828	What does a cracked flexplate sound like? I have a strange noise that seems to be coming from the torque convertor flexplate area. It only does this after the motor is warmed up good and doesnt do it under power. No funny noises while cranking or starting issues. __________________ 1972 C/30 133" W.B. C&C 1970 GMC 3500 157" W.B. single wheel C&C

05-19-2008, 05:11 PM	#2
too much stuff Roadtrip! Join Date: Feb 2003 Location: Grand Rapids MN Posts: 13,792	Re: What does a cracked flexplate sound like? I had 2 different ones do this to me and it was most noticable while cranking. I don't recall hearing anything odd after they were running. Take the inspection cover off and look closely around the bolts. I could see where mine were cracked. Good luck, Eric Oh yeah, check the converter bolts also... __________________ 67 gmc custom lwb dakota truck. Sold...And bought back 69 swb 4x4 project (in progress) 70 c-10 lwb texas truck 70 4x4/BB/bkts/posi/tach(retired) 70 swb (wifes) 70 jimmy camper 71 K-5 factory 2wd 71 cheyenne 4x4/tach/posi/ plow rig 71 Cheyenne20 BB, buckets, tach, tilt, 4 speed 72 jimmy CST wyoming rig 72 jimmy Colorado rig 72 lifted texas 4x4 3/4 ton burb 65 fury conv. 383/auto 65 chrysler 300 "L" 413 auto

05-19-2008, 06:12 PM	#3
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,728	Re: What does a cracked flexplate sound like? When mine cracked, I thought I had lost a rod -- it was a deep, hollow, solid knocking. I was on a duck hunting trip several hours away and had no choice but to drive it home, not knowing if it would blow up at any time... __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

05-19-2008, 07:20 PM	#4
BLAZERMAN Currently Blazerless Join Date: Apr 2000 Location: St. Joseph Mo. Posts: 4,828	Re: What does a cracked flexplate sound like? This is more like a squeeking sound, kinda like a belt or pulley would make but it comes from the tranny area..and only once it has warmed up good. I get no noise at all at speed or under a load. __________________ 1972 C/30 133" W.B. C&C 1970 GMC 3500 157" W.B. single wheel C&C

05-20-2008, 06:00 AM	#8
EdB Registered User Join Date: Jan 2003 Location: Gulfport Ms Posts: 401	Re: What does a cracked flexplate sound like? I had the same noise with my 94. I was getting ready to pull things down when the noise quit. It has not started back. It did not effect the driving in any way. It has a new replacement engine but the trans has over 270,000 miles. It will sure be interesting to me if you find it. If mine comes back and I find it, I will let you know. EdB

05-20-2008, 06:45 AM	#9
89 crew Registered User Join Date: Mar 2006 Location: Kansas Posts: 865	Re: What does a cracked flexplate sound like? When I had one break it made the knocking sounds along with some squeaking noises. it was on a 77 k30 400/400 (maybe the externally balanced engine caused some of the noise since the flywheel didn't balance anymore)

05-20-2008, 06:50 AM	#10
jeffspower Well, Whoop-dee-do! Join Date: Mar 2003 Location: Easton, Mo. pop.- me & scarcely a few others Posts: 2,302	Re: What does a cracked flexplate sound like? So it will only do it hot, just in park? Will it do it in neutral? Maybe put the T-case in neutral and put in drive. If the noise goes away, I'd suspect something in the transmission, or possibly the sprag inside the converter. It's been a LONG time ago, but I seem to remember a converter making a mild squeeling noise. __________________ '68 GMC shortbox 4x4 350/SM465/T221- bought it in '83 SOLD '72 K20 500 Cad/TH400/NP205 SOLD '92 Chevy 2500 6.5 mech TD 4L80E crusty daily driver '72 Monte Carlo... sweet low mile toy '11 Dodge Challenger IE 392 6spd... midlife car



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