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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: monster77k10 on March 11, 2013, 05:21:26 pm
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He guys I habe a 77k10 400cid with turbo350 automatic trans. I recently put in a 160 thermostat and a day after its started ticking. Sounds like a rocker arm or valve lash but what's confusing is it will only do it in gear. Sounds like its coming from the engine bay or dash and goes with the rpm of the engine .anyone have any ideas?
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What was the temperature of the thermostat you replaced?
Is the engine oil level and weight adequate? Could it be an exhaust leak which just coincided with the t-stat change? It could be valve lash, but I'd think even before you replaced the thermostat that there would've have some ticking as the engine warmed up to operating temperature.
When it goes into gear, there is a certain amount of load placed on the engine. Does the ticking happen whether the engine is hot or just on a cold start or all the time?
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I went from a 195 OEM to the 160. The ticking is at any temperature but like I said its only when its in gear which leads me to believe its not lash, rod or rocker. The oil was changed and topped off two weeks ago by fast track (cheaper to just have them do it). And it had a small ticking noise when I did a cold start but only for a second so I assumed it was the starter silanoid slipping back in.
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I also forgot to add that I did bypass the heater core about a week or so ago.
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OK so I started it and was looking the pully coming from the crank with the balancer on it is slopping all over the place......main bearing I'm guessing? Or please tell me it could be something less devastating....
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Here's a video of the slop in the pully.
https://www.youtube.com/watch?v=NvBwA6oaiW0&feature=youtube_gdata_player
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says video is private only.. we can't view it
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Is the balancer loose on the crank?
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Or, is the pulley cracked or loose on the balancer?
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The pulley wobles and the balancer seems to be over working itself. So I think it might be the flexplate. Unlike the 350 and 305s the 400 is externally balanced by the dampener and flexplate. It would explain the wable in the dampener and why it only makes the loud ticking when its in gear. I went to take the inspection plate off (realized the previous owner already did and never put it back on) rotated the flex plate and could not see any obvious damage. But I feel that its the problem just because all the symptoms would match up.
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The pulley wobles and the balancer seems to be over working itself. So I think it might be the flexplate. Unlike the 350 and 305s the 400 is externally balanced by the dampener and flexplate. It would explain the wable in the dampener and why it only makes the loud ticking when its in gear. I went to take the inspection plate off (realized the previous owner already did and never put it back on) rotated the flex plate and could not see any obvious damage. But I feel that its the problem just because all the symptoms would match up.
Help us out here...
What do you mean by this: "The pulley wobles and the balancer seems to be over working itself. So I think it might be the flexplate." ???
I agree that a cracked flexplate could cause a 'tick,' especially when loaded. But, please explain what pulley wobble has to do with the flexplate. Do you mean that a broken flexplate could gradually cause the balancer ring to slip cockeyed, so that it appears to wobble?
Check the end-play on the crankshaft at the balancer end. While you're there take a close look at the crank pulley. Check the pulley and balancer mounting bolts. Tell us what you find.
In addition, the video link you posted is restricted as a "Private" video. It isn't available for viewing by many of us. Perhaps if you change its setting to make it "Public," we will be able to see what's occurring, so we can track with what you're telling us and better assist you.
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Well I finally took it to a local garage. They said it is a rod knock. I agree it has the same sound however why would it only happen in gear? Just from the extra load on the crank? Would explain the play in the pully? Just want to make sure before I go spend $2500 on rebuilding the 400.