C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Motor stuck

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Old Apr 4, 2026 | 09:11 PM
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Default Motor stuck

Hello everyone, I spun a bearing in my 89 6 sad. I found a 87 L98 and installed it. On Saturday I tried to start the motor, it ran on Monday. Started right up. Yesterday it wouldn’t crank fast enough to start. After checking the battery and starter I discovered I couldn’t hand rotate the motor. We packed it in for the day. The car is in neutral. But I can’t depress the clutch pedal.
Im thinking something in the clutch. I can’t get to the car until
Wednesday, I m on Guam in the Navy base. The auto hobby shop is closed until Wednesday.
I am hoping someone has a suggestion on how to troubleshoot this issue.
I am thinking I should pull the slave cylinder and see if I can rotate the motor. Thank you all

So a couple of days ago I made a spanner wrench to try and turn the engine at the harmonic balancer. It didn't work. I cut into the bell housing and looked in. It turns out the clutch fork is infront of the throw out bearing. So obviously the clutch will no work. What I don't understand is why the clutch is holding the transmission in and I can not rotate the motor. Any ideas? thank you

Joe

Last edited by jseremba; Apr 11, 2026 at 02:46 AM. Reason: update
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Old Apr 5, 2026 | 08:17 AM
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When you tried to hand rotate, were all 8 spark plugs removed ?
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Old Apr 5, 2026 | 10:56 AM
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Originally Posted by AGENT 86
When you tried to hand rotate, were all 8 spark plugs removed ?
This is the correct question. Without saying it Agent 86 is really asking if the engine is hydrolocked. If a cylinder is full of coolant no amount of force will compress it. Dan
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Old Apr 5, 2026 | 06:41 PM
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I pulled 4 of the plugs and checked the oil for water. I'm going to pull the other plugs. But, I'm pretty sure the engine is not hydrolocked. I am thinkingof pulling the transmission and seeing if the motor can be hand turned. Does anyone know the size and thread of the bolts that hold the transmission to the bell housing. I think it is 12 mm with 1.25 thread. Ty
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Old Apr 5, 2026 | 11:03 PM
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You need to find out why you can't depress the clutch pedal. This is a GLARING problem you need to track down. I would do that before pulling the trans so you can source the error with it all together. You say its in neutral will it roll with ease?

You said it started right up where you able to drive it?

Drain some of the oil? Is it milky or black?
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Old Apr 5, 2026 | 11:11 PM
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You are correct about the clutch pedal. I think the two are related. I did not drive the car but we were able to roll it easily.
I was just wondering.
Car in neutral wheels off the ground. If I rotate the wheels the drive shaft rotates. Does the transmission input shat rotate in the pilot bearing?
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Old Apr 5, 2026 | 11:14 PM
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Default motor stuck

You are correct about the clutch pedal. I think the two are related. I did not drive the car but we were able to roll it easily.
I was just wondering.
Car in neutral wheels off the ground. If I rotate the wheels the drive shaft rotates. Does the transmission input shat rotate in the pilot bearing?

There oil looks fine. We checked
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Old Apr 8, 2026 | 07:38 PM
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Originally Posted by jseremba
Car in neutral wheels off the ground. If I rotate the wheels the drive shaft rotates. Does the transmission input shat rotate in the pilot bearing?
If the transmission internal components are actually situated in the correct neutral position then no, the input shaft should not be rotating when the driveshaft rotates.
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