question about grinding/roar noise - The 1947 - Present Chevrolet & GMC Truck Message Board Network

azer · 02-18-2014, 01:46 AM

Picked up a 78 Chevy c20 automatic 350 2wd there is a grinding/roar noise coming from driver side floor board, if I put my food on the floor board under the brake pedal I can feel a vibration it feels like metal to metal grinding. It gets louder with speed anything above 40 it's extremely loud making sharp turns doest seem to effect the sound. I coasted down a hill with the Engine off and transmission in neutral the sound was still there even at very low speeds I can hear it (5 - 10) mph. also if the truck has been sitting for awhile like overnight the noise doesn't seem to start until driving for about 3 or 4 minutes.

Im new here any ideas very appreciated !
Thanks!

jhngardner367 · 02-18-2014, 02:17 AM

Welcome to the forum !
I think you should check your drive shaft for bad cross joints. It sounds like one(or more) is worn.

motornut · 02-18-2014, 12:13 PM

Welcome
If it's not the front brake squealers or dust shields I'd vote Ujoints,
sometimes they will "ping" going into R/D

azer · 02-19-2014, 03:27 AM

Spent most the day messing with it and I believe very much so the noise is coming from the transmission. There is a little bit of play in the shifter while driving i wiggled the shifter around and pushed it in the upwards position just a hair and the noise almost completely went away let off the shifter back into its resting position the noise instantly came back. Then i pushed the shifter down a little and the noise got extremely louder. Now im real confused of what it could be something in the shifter linkage or something more serious inside the transmission

jhngardner367 · 02-19-2014, 08:28 AM

It sounds as if the trans may have a bad output shaft bearing,or input shaft bearing.
I would drain the trans,and check for metal in the pan/filter.

02-18-2014, 01:46 AM	#1
azer Registered User Join Date: Feb 2014 Location: texas Posts: 3	question about grinding/roar noise Picked up a 78 Chevy c20 automatic 350 2wd there is a grinding/roar noise coming from driver side floor board, if I put my food on the floor board under the brake pedal I can feel a vibration it feels like metal to metal grinding. It gets louder with speed anything above 40 it's extremely loud making sharp turns doest seem to effect the sound. I coasted down a hill with the Engine off and transmission in neutral the sound was still there even at very low speeds I can hear it (5 - 10) mph. also if the truck has been sitting for awhile like overnight the noise doesn't seem to start until driving for about 3 or 4 minutes. Im new here any ideas very appreciated ! Thanks!

02-18-2014, 02:17 AM	#2
jhngardner367 Registered User Join Date: Feb 2012 Location: Austin, Arkansas Posts: 248	Re: question about grinding/roar noise Welcome to the forum ! I think you should check your drive shaft for bad cross joints. It sounds like one(or more) is worn. __________________ Always expect the unexpected,....but don't expect the unexpected to be the unexpected you expect ! I'm busier than a one-legged cat,in a sandbox! Veteran..and proud ! I can't fix what ain't broke....you want I should break it?

02-18-2014, 12:13 PM	#3
motornut 78K & 79C Jimmys Join Date: Nov 2009 Location: Ottawa Ont CANADA Posts: 7,901	Re: question about grinding/roar noise Welcome If it's not the front brake squealers or dust shields I'd vote Ujoints, sometimes they will "ping" going into R/D __________________ John 1978 GMCJimmy4X4-350/203 1979 GMCJimmy4X2-305/350

02-19-2014, 03:27 AM	#4
azer Registered User Join Date: Feb 2014 Location: texas Posts: 3	Re: question about grinding/roar noise Spent most the day messing with it and I believe very much so the noise is coming from the transmission. There is a little bit of play in the shifter while driving i wiggled the shifter around and pushed it in the upwards position just a hair and the noise almost completely went away let off the shifter back into its resting position the noise instantly came back. Then i pushed the shifter down a little and the noise got extremely louder. Now im real confused of what it could be something in the shifter linkage or something more serious inside the transmission

02-19-2014, 08:28 AM	#5
jhngardner367 Registered User Join Date: Feb 2012 Location: Austin, Arkansas Posts: 248	Re: question about grinding/roar noise It sounds as if the trans may have a bad output shaft bearing,or input shaft bearing. I would drain the trans,and check for metal in the pan/filter. __________________ Always expect the unexpected,....but don't expect the unexpected to be the unexpected you expect ! I'm busier than a one-legged cat,in a sandbox! Veteran..and proud ! I can't fix what ain't broke....you want I should break it?



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