1HDT Bad Clunk and Vibration: Stranded

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Hey guys,

So I am running a 1990 1HDT with a smidge less than 200k mi on it and I’m currently stranded in Alabama (luckily somewhere safe where I can work on the truck a bit). Truck has GTurbo and pump running 19-20 on boost and fitted with H151 transmission. The motor was out 4000mi ago and refreshed. New seals and gaskets, did the BEBs, rebuilt all the pumps (vac/PS/etc), new alternator new injectors, intercooler, new flywheel and clutch, new harmonic balancer …. Etc etc.

The problem started as vibration while driving that I couldn’t track down, over about 4-5 days and maybe 350mi. So it came on relatively suddenly but not all at once either. The vibration was usually worse later in the day after running up or down a mountain or running highway. In the mornings on fire roads it was not noticeable.

After a few days the vibration got worse, especially under load. Maybe there was a loss of power? The vibrations at least made it feel like the engine was trying harder.

It didn’t overheat at all. Oil pressure was steady and good.

Finally on the 5th day I shut the truck down at a store and there was a loud terrible clunk. I started it back up and there was lighter clunk on start up. It idled and revved fine. Drove it into town and shut it down and got the loud kerclunk again. I started and stopped the motor a few times in various configurations: clutch in, t-case in N, etc. It sounded like it was in the sump. Finally I shut off fuel and cranked the engine with no start to eliminate pump timing. The kerthump keclunk was still there as it turned over. I called a tow truck.

Our best determination was something crank related. Honestly it sounded like a broken crank.

I pulled the oil pan off and as best as I can tell the crank is in one piece. I can move it fore & aft a tiny bit and it all moves together. I still need to find some feeler gauges and see if that’s out of spec. But it doesn’t move very much.

I pulled a few rod bearing caps and they look as they should with only 4000mi on them. The felt a bit loose on the crank when wiggling with my fingers but I have very little experience with wiggling rod bearings. Lol. They look perfectly fine.

I’m at a complete loss at this point as to what to check next. It’s entirely possible it’s the crank main bearings but I have to pull the motor to check that. Which I can’t do here. I have to get a uhaul and drag her 1000mi north for that.

Anything I’m missing? Signs to look out for? What can I test?

Any advice or thoughts are welcome!!!

Thanks guys.
 
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Pics to show what we’re working with here. Lol! I love this rig. Just gotta figure out WTF went sideways.

88F1437F-D13F-4B94-8845-415E7D75B1D7.jpeg
 
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How does the harmonic balancer look? Was it replaced when the motor was refreshed?
Yes, harmonic balancer is new from Toyota as well. I also looked at it with the truck idling and it looked dead straight.
 
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Loose or damaged flywheel?
This also crossed my mind. Flywheel is new but could have loosened up. The only access to it without pulling the trans is through the starter hole. I pulled that and can’t get it to wiggle but leverage is limited.

Open to suggestions on testing the flywheel through the starter hole!
 
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have you done a compression and leak down test?
 

gilmorneau

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After years of always thinking the worst, I finally adjusted my troubleshooting method to start with the simple, cheap, and easy instead of the complicated, expensive, and catastrophic.

With that in mind, have you checked your motor mounts? Trans mounts?Any loose accessories Anywhere? Just spitballing here, but trying to keep it cheap for you.
 
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All mounts are brand new. But I did put a wrench on all mount fasteners to make sure they’re tight. I’m trying to get my hands on the neighbors Jack to lift them just to be sure I didn’t get a bad one.

I have vague questions on whether the exhaust shifted off road and might hit under *just* the right conditions when hot.

However that’s only one piece of the puzzle. The vibration under load is definitely not the exhaust. But there’s always the possibility of multiple problems.

Love the spitballing. Thanks!
 

bkfj40

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Is the vibration only while driving, or when in neutral? Driveshaft tight? U joints good. What about injection pump?
 
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I am very open to entertaining that I have multiple problems. Maybe my vibration and my clunking are completely separate problems.

But the clunking is still there cranking the motor with the fuel turned off. And sounds weirdly like two masses interacting. Hard to describe. So that eliminated pump timing and the rest of the drivetrain for that particular sound. Pump is new 4000mi ago

The vibration is under load. Engine revs in neutral like everything is peachy and perfect.

All u-joints are new but the DC double joint and I have my concerns with that. That’s def not the clunk in neutral but could be contributing to the vibration under load.
 
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If you have a mechanics stethoscope or can get your hands on one it might help you narrow down the engine noise. An extension held up to your ear can do it too. Try different areas on the engine and see if you can pinpoint it.
 
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Wild guess but I wonder if this could be a clutch issue? It could cause rotational clunking and also a vibration...
 
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I’m putting the bearing caps and pan back on and will be starting over from diagnostic zero now that I know the crank is in one piece.
 
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Wild guess but I wonder if this could be a clutch issue? It could cause rotational clunking and also a vibration...
Would the sound of the clunking change with the clutch in or out? The clunking is there either way. But I know that there was always slight clicking/ticking with the clutch out that would go away with it in.
 

bkfj40

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Is there an inspection cover at the bottom of the flywheel like on a 2f?
It would be helpful to know if the noise is from the front of the engine or the rear. I like the rec about the stethescope
 
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Is there an inspection cover at the bottom of the flywheel like on a 2f?
It would be helpful to know if the noise is from the front of the engine or the rear. I like the rec about the stethescope
No inspection hole unfortunately. But I’m going to try to narrow down exact location.
 
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So when I pulled the bearing caps doing quick recon I Looked at the lowers and figured if they were ok the uppers likely were too. While checking the thrust tolerances I peeked at the uppers. Hmmmmm.

So far 3 & 4 look like this. Going after the others now. What’s the consensus on how bad these look for 4000mi?

CA69DD95-D265-40A8-AE70-73CDE00A5A5F.jpeg


E54D99A4-7A7E-4952-ACAC-A18AF20E24EA.jpeg



All plastigauged in spec on installation so I’m not sure how I got here.
 

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