Advice from old Gearheads NEEDED (check update in comments)
This started this morning.
Since then, did the coolant flush and Oil change. Was hoping that the oil change might ‘change’ the parameters a little and that this would ‘go away’,,, Yeah,, been down that road, rare, but does occasionally happen.
I am of the opinion she has a rod knocking,,, but there’s some grey areas in my knowledge of that. So I am asking others opinions, knowing full well, you aren’t getting ‘real time information’ and that video doesn’t really deliver the sounds I am hearing on this end. I’m not ruling out a stuck lifter, but its sounds “too solid” for a lifter noise. And it does disappear when I let off the throttle, to return again at idle. Not sure if that helps or means anything to anyone.
Second question: I once, many many moon ago, replaced the connecting rod bearings on a slant6 while it was still in the truck: is that possible with a 350? I’m looking at it, and I think it might be possible, but I have never heard of anyone doing that before.
Fact is, I am WAY TOO INVESTED in Twuck to let this get in the way. And it burns me that it wasn’t there yesterday, but is today, and first thing this morning. I did NOT hear it at all yesterday, and there was one point where I had Twuck running and stopped and did a walk around, looking at the lights. I would have heard it then, but did not.
Thanks in advance for any advice/opinion on this. Chime in please, even if you have never commented before,
L.L.L.L.L!
(.’)
Dio's Workshop 
I’ve done several in the vehicle. Some RWD and a couple of FWD. and one 4WD. That one lasted 30k. It had a scored crank that I should have replaced but didn’t. Another was running a couple of owners later, but it got a new crankshaft and all the bottom bearings, timing set, oil pump and main seals. That was a pay job so he had to do what I wanted if he wanted a warranty. Bear in mind that you’ll have to replace everything questionable and other stuff as preventative repair, which means more expense. Also, working in a dirt or gravel driveway with bearings is a trial trying to keep everything clean.
Long story short, you can do it in frame. YMMV. If you pull it out, you can do a redneck rebuild. But this time of year, the weather is a huge concern. Maybe find a decent used engine and freshen it up and then do a swap when you’ve got a long clear weather weekend.
I would plan for the worst case scenario and take any better case as the Lord smiling at you. Timing set, crankshaft with bearings, oil pump, oil pan gasket and rear main seal. You’ll need to slide the transmission back about 6 inches and support it. If you use a couple of long bolts threaded through the holes in the bell housing, it’ll keep everything lined up for easy reassembly. And pull the radiator. I’ve damaged radiators trying to save time. Don’t bother, just pull it out and put it somewhere safe.
That is indeed a sucky situation.
LikeLiked by 2 people
November 28, 2025 at 5:57 pm
the part about sliding the transmission back is if it’s got a one piece rear main seal. If it’s the two piece rear main seal you might not have to.
LikeLiked by 2 people
November 28, 2025 at 5:59 pm
Its a 2 peice from all I can tell from parts available, but. Its a 5 speed, not auto, that makes its a touch trickier.
LikeLiked by 1 person
November 28, 2025 at 6:07 pm
To top it off, my resources are close to tapped out. I’m hoping conrod bearings and not mains are the issue. Mains spun or burned up, Im F!ed.
LikeLiked by 1 person
November 28, 2025 at 6:11 pm
Not sure I’d even try to do just the rods – if’n they’re bad, then I’d wanna do the mains as well just ’cause. Then again, I’m a bit more anal than a lot of folk – or so I’m told😉
And NO, you’re not F*d if that’s the case. I can assist a bit.
Y’all take care,
Mike in FLA.
LikeLiked by 1 person
November 28, 2025 at 6:22 pm
Please dont. (I say that and he’ll listen not at all: but I have to say it.)
I agree that I would prefer to do a full bottom end, because if ones down, the rest likely are too: simple brainium says so. Time space and money are the deciding factors here,
At least I have a backup, though she was supposed to be next in line, not shuffled to the bottom of the liat again.
LikeLiked by 1 person
November 28, 2025 at 6:26 pm
And a thank you to you as well Fred. I thought doing this on the truck was doable, but didn’t know. I’m gonna try the HB first, since it will be here soonest, and if need be, go full bore on the lower end. Gots to have this truck running reliable or all the effort I put forward this last month is for naught.
LikeLiked by 1 person
November 28, 2025 at 8:14 pm
Yer correct – difficult from afar. Doesn’t sound so much like a rod – at least the ones I’ve heard. Those were constant, (seriously) more when revved, less when idling, but still audibly there. Didn’t disappear when letting off the gas. Lifters – maybe (I know). Don’t dismiss something as simple as an exhaust leak, either.
And yes – the bearings CAN be done in the Twuck – don’t really recommend it though. Did it in my ’70 Challenger R/T 383 in the carport on jackstands. It’s REALLY easy to miss just 1 torque – ask me how I know. (Helluva mess, that wuz). Doesn’t mean anyone else would do it, though. YMMV.
I know I didn’t really answer anything, but I hope it helps ya narrow it down.
Y’all take care,
Mike in FLA.
LikeLiked by 1 person
November 28, 2025 at 6:15 pm
Gonna get the stethoscope out and probe around the exhaust. Its obvious around 1 and 3 area, so may be a crack or blown gasket I cant see. Maybe,,, that it disappears on off throttle cunfuzzed me so “not sure” is the game right now (this is the side with a crackedmanifold).
LikeLiked by 1 person
November 28, 2025 at 6:20 pm
🤞
LikeLike
November 28, 2025 at 6:27 pm
Thanks Mike,,, you may not have had the answer, but you pointed me in a direction I hadn’t tried. Isolate the problem, funny how that little advice slips when you are panicking about your truck breaking,,,,
LikeLiked by 1 person
November 28, 2025 at 8:11 pm
OPEN DISCUSSION;;;; Just took Mikes advice and listened closer,,,, Steth to the block, no noise, to the pan, no noise,, around the manifold at 1 and 3, no noise
from the harmonic balancer RACKET FROM HELL,,,,, I may have jumped my diag here. whatcha’ll think, could a balancer do that? Note, the noise is not a constant, mostly that hammering noise, but sometimes drops out completley for a second or so, with no changes at throttle. This might also explain the Crank position sensor error I found in the code scan.
LikeLiked by 1 person
November 28, 2025 at 6:40 pm
Dig into the nets young grasshoppa!!! A couple of Chevy forums,,, a couple of Utoobies,,, and I’ma gonna run with the ‘bad balancer’ diag.
This vid https://youtube.com/shorts/-B5hO_KocwU?si=FEeNic70Mqijizx- Sounds a WHOLE LOT like what I am hearing under the hood, and the fact that it was colder than a witches teat this AM when I started an old truck,,, yeah, something probably broke free.
Did not cancel the bearing order, as once I have them, I may never need them, but better in hand than in the mail, right? Funny thing, the balancer will be here 6 days SOONER,,, So even if I get it on and find that ‘no, not it’, I have the other option on its way already.
LikeLiked by 1 person
November 28, 2025 at 8:09 pm
I thought valve train and with having set for so long then changing out the oil… Could be chunks broke loose and clogging the sump screen or a sticky lifter. Then too, might be the reason it was parked.
but top end was my first thought.
definitely all doable while in the truck
LikeLike
November 29, 2025 at 7:18 am
Started b4 oil change. Was sudden too. I thought similar at first. But noise is from down low; not up top. Oh, and reason it was parked: original owner died and his son did not want to keep that end of the business going.
LikeLike
November 29, 2025 at 7:22 am