Flywheel Is Contacting The Inspection Cover - The 1947 - Present Chevrolet & GMC Truck Message Board Network

*JCampbell* · 04-09-2010, 11:24 PM

'88 3/4 ton Suburban 4x4 - 350/TH400

I know what the noise is...the weight on the flywheel is contacting the inspection cover. What I want to know is "why".

Brief history...

I developed a hellacious knock about two months ago around the back of the engine/front of the trans. We pulled the inspection cover and after looking around and checking a few things, found that the weight on the flywheel was striking the front of the inspection cover. I chalked it up to hitting something on the trail that weekend that must've tweaked the I.C. just enough to cause the two to make contact. We swedged/clearanced the aluminum I.C. out away from the flywheel and all was well...until a few days ago.

The noise is back, and although it's not as bad, it's getting progressively worse. I know for a fact that it is 110% a result of flywheel/I.C. contact, but I'm not sure why they are making contact. When we had it apart the first time, we (one of the equip mechs at work and myself) checked to make sure the torque converter bolts were tight (yes) and that the flywheel wasn't cracked/damaged (didn't appear to be).

Anyone experience anything like this? Anything I may be overlooking? It's driving me nuts and I'm growing fearful that this may be an indication of a bigger problem.

Restrorob · 04-10-2010, 07:41 AM

Sounds like you could have a failing crankshaft thrust bearing, Have you looked at the flywheel with the cover off and engine running to see if the flywheel may be warped ?

James McClure · 04-10-2010, 09:01 AM

Jason, sorry to say this but I think Rob nailed it. You may have hit something on the trail but tweeking the cover didn't fix it for long. You can easily check crankshaft end play with a pry bar. Simply pry the flywheel back towards the trans, then pry it forward twards the engine. The clearance should not excede .015" max. If it does, drop the pan, pull the oil pump and rear main cap and inspect the lower 1\2 shell and look up at the shaft brng flange.Both will have lines ect, but nothing deep. Remove 1\2 shell from the cap and stick it into place and try to fit a .015 feeler gage in as a backup check. From there you have to just replace the brng and or crankshaft to fix it. Most often, just put in new bearings, new seal and drive it. jim

LONGHAIR · 04-10-2010, 09:37 AM

Quote:

Originally Posted by JCampbell

....the weight on the flywheel is contacting the inspection cover.

"weight on the flywheel"? Why is there a weight on the flywheel? Only the 400s and 454s are externally balanced

cableguy0 · 04-10-2010, 10:04 AM

The 1 piece rear main smallblocks were externally balanced too.

04-09-2010, 11:24 PM	#1
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Flywheel Is Contacting The Inspection Cover '88 3/4 ton Suburban 4x4 - 350/TH400 I know what the noise is...the weight on the flywheel is contacting the inspection cover. What I want to know is "why". Brief history... I developed a hellacious knock about two months ago around the back of the engine/front of the trans. We pulled the inspection cover and after looking around and checking a few things, found that the weight on the flywheel was striking the front of the inspection cover. I chalked it up to hitting something on the trail that weekend that must've tweaked the I.C. just enough to cause the two to make contact. We swedged/clearanced the aluminum I.C. out away from the flywheel and all was well...until a few days ago. The noise is back, and although it's not as bad, it's getting progressively worse. I know for a fact that it is 110% a result of flywheel/I.C. contact, but I'm not sure why they are making contact. When we had it apart the first time, we (one of the equip mechs at work and myself) checked to make sure the torque converter bolts were tight (yes) and that the flywheel wasn't cracked/damaged (didn't appear to be). Anyone experience anything like this? Anything I may be overlooking? It's driving me nuts and I'm growing fearful that this may be an indication of a bigger problem. Last edited by JCampbell; 04-09-2010 at 11:25 PM.

04-10-2010, 07:41 AM	#2
Restrorob The One And Only !!! Join Date: Jan 2007 Location: Hole in the woods Florida Posts: 4,567	Re: Flywheel Is Contacting The Inspection Cover Sounds like you could have a failing crankshaft thrust bearing, Have you looked at the flywheel with the cover off and engine running to see if the flywheel may be warped ? __________________ 93 Jeep XJ 88 Buick La Sabra Toys; 88 TA-GTA in the works.... 97 GMC Ext. Cab 502 Crate 5 Spd......Sucks Gas But Haulz Azz ! The primary function of an Engineer is to make it difficult for the Fabricator and impossible for the Mechanic. *"Why go out preserved when you can go out beat up, worn out, sliding in sideways screaming, Holy Sh!t What A Ride" !!!*

04-10-2010, 09:01 AM	#3
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Flywheel Is Contacting The Inspection Cover Jason, sorry to say this but I think Rob nailed it. You may have hit something on the trail but tweeking the cover didn't fix it for long. You can easily check crankshaft end play with a pry bar. Simply pry the flywheel back towards the trans, then pry it forward twards the engine. The clearance should not excede .015" max. If it does, drop the pan, pull the oil pump and rear main cap and inspect the lower 1\2 shell and look up at the shaft brng flange.Both will have lines ect, but nothing deep. Remove 1\2 shell from the cap and stick it into place and try to fit a .015 feeler gage in as a backup check. From there you have to just replace the brng and or crankshaft to fix it. Most often, just put in new bearings, new seal and drive it. jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.

04-10-2010, 10:04 AM	#5
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	Re: Flywheel Is Contacting The Inspection Cover The 1 piece rear main smallblocks were externally balanced too. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.



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