Loud bang during hard acceleration - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Rangerman · 11-30-2015, 12:51 AM

79 C10, truck runs great but have had a weird noise lately.

Twice the last few days if I hammer it at about 30 miles an hour there is a loud bang/slam, it feels and sounds exactly like someone pulled up the tailgate handle and let the gate just fall open. It's definitely a WTF moment.

Any ideas?

Matt Man · 11-30-2015, 01:03 AM

Does it make a bang/clunking sound when going from P to R or R to D? If so your u joints might need to be replaced.

Rangerman · 11-30-2015, 01:08 AM

No sound when putting in gear.

Dead Parrot · 11-30-2015, 08:00 AM

My old tailgate had that feature. More than one tailgater took evasive action when it would decide now was a good time to drop open.

Very loose spare tire? Check all your cab bolts and mounts. Bed bolts. Might only have two or three left due to rust. Loose exhaust?

Less likely could be a lean mix backfire.

Rangerman · 11-30-2015, 09:12 AM

Quote:

Originally Posted by Dead Parrot

My old tailgate had that feature. More than one tailgater took evasive action when it would decide now was a good time to drop open.

Very loose spare tire? Check all your cab bolts and mounts. Bed bolts. Might only have two or three left due to rust. Loose exhaust?

Less likely could be a lean mix backfire.

No spare, removed for new tank. Cab bolts and mounts are tight, all 8 bed bolts are tight.
New exhaust is solid.

Liberty · 11-30-2015, 11:38 AM

Quote:

Originally Posted by Rangerman

No spare, removed for new tank. Cab bolts and mounts are tight, all 8 bed bolts are tight.
New exhaust is solid.

Well shoot, I was going to guess the cat might be plugged.

Maybe they 007'd your Truck and put a gun in the back.

ddr11 · 11-30-2015, 11:44 AM

Leaf Springs?

Rangerman · 11-30-2015, 12:08 PM

Ha ha, wish it was 007'd.

I lowered the truck, all leafs and u bolts are tight.

Its just like the tailgate dropped open, really hard bang.

Matt Man · 11-30-2015, 12:59 PM

How is the condition of the transmission mount?

**MikeB** · 11-30-2015, 02:24 PM

Check to see how much the engine lifts up on the drivers side when you rev it.

Had something similar happen on a 55 Chevy sedan that had been converted to side motor mounts. I never did determine where the "bang" was coming from. But replacing the old rubber mounts with polyurethane mounts fixed the problem, and reduced the engine movement substantially.

11-30-2015, 12:51 AM	#1
Rangerman Registered User Join Date: Sep 2015 Location: Norman OK. Posts: 54	Loud bang during hard acceleration 79 C10, truck runs great but have had a weird noise lately. Twice the last few days if I hammer it at about 30 miles an hour there is a loud bang/slam, it feels and sounds exactly like someone pulled up the tailgate handle and let the gate just fall open. It's definitely a WTF moment. Any ideas?

11-30-2015, 01:03 AM	#2
Matt Man Registered User Join Date: Oct 2009 Location: Buhl, Idaho Posts: 1,438	Re: Loud bang during hard acceleration Does it make a bang/clunking sound when going from P to R or R to D? If so your u joints might need to be replaced. __________________ 86 c30 crew cab dually 454/400 4/6 drop SOLD 1-8-11 1981 chevy K10 short Bed Scottsdale SOLD 10-26-2020 67 GMC Stepside Straight six/3 on the tree "The Peach" 2020 Silverado Double Cab LT Z71 5.3 8 speed Daily Driver K10 build http://67-72chevytrucks.com/vboard/s...d.php?t=671934 The Peach build http://67-72chevytrucks.com/vboard/s...d.php?t=733903

11-30-2015, 01:08 AM	#3
Rangerman Registered User Join Date: Sep 2015 Location: Norman OK. Posts: 54	Re: Loud bang during hard acceleration No sound when putting in gear.

11-30-2015, 08:00 AM	#4
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,611	Re: Loud bang during hard acceleration My old tailgate had that feature. More than one tailgater took evasive action when it would decide now was a good time to drop open. Very loose spare tire? Check all your cab bolts and mounts. Bed bolts. Might only have two or three left due to rust. Loose exhaust? Less likely could be a lean mix backfire.

11-30-2015, 11:44 AM	#7
ddr11 Registered User Join Date: Nov 2013 Location: sumter sc Posts: 79	Re: Loud bang during hard acceleration Leaf Springs?

11-30-2015, 12:08 PM	#8
Rangerman Registered User Join Date: Sep 2015 Location: Norman OK. Posts: 54	Re: Loud bang during hard acceleration Ha ha, wish it was 007'd. I lowered the truck, all leafs and u bolts are tight. Its just like the tailgate dropped open, really hard bang.

11-30-2015, 12:59 PM	#9
Matt Man Registered User Join Date: Oct 2009 Location: Buhl, Idaho Posts: 1,438	Re: Loud bang during hard acceleration How is the condition of the transmission mount? __________________ 86 c30 crew cab dually 454/400 4/6 drop SOLD 1-8-11 1981 chevy K10 short Bed Scottsdale SOLD 10-26-2020 67 GMC Stepside Straight six/3 on the tree "The Peach" 2020 Silverado Double Cab LT Z71 5.3 8 speed Daily Driver K10 build http://67-72chevytrucks.com/vboard/s...d.php?t=671934 The Peach build http://67-72chevytrucks.com/vboard/s...d.php?t=733903

11-30-2015, 02:24 PM	#10
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,597	Re: Loud bang during hard acceleration Check to see how much the engine lifts up on the drivers side when you rev it. Had something similar happen on a 55 Chevy sedan that had been converted to side motor mounts. I never did determine where the "bang" was coming from. But replacing the old rubber mounts with polyurethane mounts fixed the problem, and reduced the engine movement substantially. __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!



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