Engine ? noise - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GMCMAX · 03-13-2011, 04:25 PM

I'm getting a noise I think is from the engine that is making me scratch my head, hoping somebody might have some ideas to try other than a teardown...
Here's the rundown; 350 4spd, I had 3.08 rear gears and at highway speed ran about 1900 RPM. Put 4.10 gears in it and now run close to 3000 RPM down the road.
The engine runs fine like it always has, but above 2500 RPM going down the road I'm getting a tap or rattle from the front. If I'm on or off the throttle it isn't there, but just rolling along it is. Can't get it to do it in the driveway sitting still either.
The noise is heavier than a lifter, but less than maybe a rod. Doesn't do it at lower engine speeds. Oil is clean, oil pressure where it always has been, have run it up to 4000 going up throught he gears and nothing, it will rattle in 3rd gear above 2500 rpm, but not on or off throttle. Backed the timing from 12 to 8 degrees to see if it was pinging, no sign of vacuum leak either.
Has me stumped.... wristpin maybe, bad input bearing in the trans?
Thanks,
Max

ItsRandy · 03-13-2011, 04:47 PM

You only hear the noise in high gear or in any gear just over 2500 rpm?

Hottrucks · 03-13-2011, 05:01 PM

I would check U joint back lash?? you know when its not under a load it may be slaping from push to holding back

bsteenburg · 03-13-2011, 05:59 PM

If you are sure it is from the front of the engine check the timing chain and the fuel pump pushrod\fuel pump. Check fan clutch and\or blades. All sound a little heavier than a lifter but not as bad as a rod bearing. Also had a harmonic dampner make a click style noise once, the bond of the dampner was loose. Check pulleys. Just some things to check.

Bryce

GMCMAX · 03-13-2011, 06:43 PM

Randy, will do it in 3rd also,
Hott, u-joints are new,
Bsteen, forgot about the pushrod/pump, have less than 20k on double roller timing set- will check balancer too,
Thanks

ItsRandy · 03-13-2011, 10:53 PM

Do you have to be going over a given mph to hear the noise?

GMCMAX · 03-13-2011, 10:56 PM

No, just over 2500 rpm, driving

03-13-2011, 04:25 PM	#1
GMCMAX Active Member Join Date: Jan 2006 Location: Lower Mid-East Ca. Posts: 326	Engine ? noise I'm getting a noise I think is from the engine that is making me scratch my head, hoping somebody might have some ideas to try other than a teardown... Here's the rundown; 350 4spd, I had 3.08 rear gears and at highway speed ran about 1900 RPM. Put 4.10 gears in it and now run close to 3000 RPM down the road. The engine runs fine like it always has, but above 2500 RPM going down the road I'm getting a tap or rattle from the front. If I'm on or off the throttle it isn't there, but just rolling along it is. Can't get it to do it in the driveway sitting still either. The noise is heavier than a lifter, but less than maybe a rod. Doesn't do it at lower engine speeds. Oil is clean, oil pressure where it always has been, have run it up to 4000 going up throught he gears and nothing, it will rattle in 3rd gear above 2500 rpm, but not on or off throttle. Backed the timing from 12 to 8 degrees to see if it was pinging, no sign of vacuum leak either. Has me stumped.... wristpin maybe, bad input bearing in the trans? Thanks, Max __________________ Never try to teach a pig to sing; it wastes your time and annoys the pig! Gets More Chicks My lugnuts require more torque than your honda makes! 68 GMC, 4X4 conversion w/73 k20 running gear and springs, 350 4spd, 4.10's, D44 powerlok front, 14BFF govlock rear, 33" tires, lifted 4".

03-13-2011, 04:47 PM	#2
ItsRandy Registered User Join Date: Nov 2010 Location: Grand Terrace, Ca. Posts: 1,607	Re: Engine ? noise You only hear the noise in high gear or in any gear just over 2500 rpm?

03-13-2011, 05:01 PM	#3
Hottrucks Redefining LowBudget Join Date: Mar 2009 Location: lebanon Cow Hampshire Posts: 4,538	Re: Engine ? noise I would check U joint back lash?? you know when its not under a load it may be slaping from push to holding back __________________ 1970 C10 CST fleetside 472 ....big dreams little cash... http://67-72chevytrucks.com/vboard/s...d.php?t=335721 SunShine Syndicate.. Mikes Sandwich Fair Run OCT 8th 2011 http://www.thesandwichfair.com/html/...auto_show.html

03-13-2011, 05:59 PM	#4
bsteenburg Registered User Join Date: Jan 2011 Location: Illinois Posts: 34	Re: Engine ? noise If you are sure it is from the front of the engine check the timing chain and the fuel pump pushrod\fuel pump. Check fan clutch and\or blades. All sound a little heavier than a lifter but not as bad as a rod bearing. Also had a harmonic dampner make a click style noise once, the bond of the dampner was loose. Check pulleys. Just some things to check. Bryce

03-13-2011, 06:43 PM	#5
GMCMAX Active Member Join Date: Jan 2006 Location: Lower Mid-East Ca. Posts: 326	Re: Engine ? noise Randy, will do it in 3rd also, Hott, u-joints are new, Bsteen, forgot about the pushrod/pump, have less than 20k on double roller timing set- will check balancer too, Thanks __________________ Never try to teach a pig to sing; it wastes your time and annoys the pig! Gets More Chicks My lugnuts require more torque than your honda makes! 68 GMC, 4X4 conversion w/73 k20 running gear and springs, 350 4spd, 4.10's, D44 powerlok front, 14BFF govlock rear, 33" tires, lifted 4".

03-13-2011, 10:53 PM	#6
ItsRandy Registered User Join Date: Nov 2010 Location: Grand Terrace, Ca. Posts: 1,607	Re: Engine ? noise Do you have to be going over a given mph to hear the noise?

03-13-2011, 10:56 PM	#7
GMCMAX Active Member Join Date: Jan 2006 Location: Lower Mid-East Ca. Posts: 326	Re: Engine ? noise No, just over 2500 rpm, driving __________________ Never try to teach a pig to sing; it wastes your time and annoys the pig! Gets More Chicks My lugnuts require more torque than your honda makes! 68 GMC, 4X4 conversion w/73 k20 running gear and springs, 350 4spd, 4.10's, D44 powerlok front, 14BFF govlock rear, 33" tires, lifted 4".



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