OBS chevy truck 1989

[sick620]

I have a 1989 chevy truck 4.3 2wd 5speed long bed. It is my datsun support vehicle. It has low mileage 120k Runs and drives great, except for input shaft bearing noise that the transmission is making. At idle it makes noise press in the clutch it goes away (opposite of a bad throw-out bearing symptom) I feel pretty confident that if just the input shaft bearing was replaced it would be a good transmission. Shifts and drives great. Transmission is the 5lm60. Do you think this is an easy diy job splitting the tranny, swapping bearing, and putting back together? Trying to get away with not buying a new transmission and just servicing this one myself. I barely have money for the Datsun projects last thing I want to do is put money into a chevy 😉. I ask on ratsun because you guys know your shit, can't find a single chevy forum or video where someone has tackled this job. 

[datzenmike]

Is it significantly quieter in 4th gear when driving? Fourth is the only gear where no power is being transmitted through the counter bearing.

[sick620]

It’s pretty quiet in all the gears but no I think it’s about the same. Loud only while idling in neutral with foot off clutch. 

[datsunfreak]

FWIW, still sounds like it could be a throwout bearing to me...

[Wildcat Walker]

Have the exact same truck, but with 250,000 miles. It's more than likely the throw-out bearing. You can pull and change this in a few hours. Might was well slap a clutch kit in it and have the flywheel surfaced. For lubricant, ND-30 is what I run, keeps things quiet, can be stiff on cold mornings. Cheers! 

[datzenmike]

On 2/10/2023 at 11:43 AM, sick620 said:

It’s pretty quiet in all the gears but no I think it’s about the same. Loud only while idling in neutral with foot off clutch. 

 

1 hour ago, datsunfreak said:

FWIW, still sounds like it could be a throwout bearing to me...

 

50 minutes ago, Wildcat Walker said:

Have the exact same truck, but with 250,000 miles. It's more than likely the throw-out bearing. You can pull and change this in a few hours. Might was well slap a clutch kit in it and have the flywheel surfaced. For lubricant, ND-30 is what I run, keeps things quiet, can be stiff on cold mornings. Cheers! 

 

 

Then the clutch is not in use, foot off of it, the throw out bearing is not under any load and not spinning, so not going to be making any noise. When the pedal is being depressed or held down or being let up, the bearing is under load and spinning.

 

This is true of the pilot bushing in the end of the crankshaft also. When idling with the clutch pedal up, the crankshaft and the input (main shaft) of the transmission are locked together. When the clutch is disengaged the flywheel is spinning but the transmission is not and there may be the possibility of some noise.

[Wildcat Walker]

46 minutes ago, datzenmike said:

 

 

 

 

Then the clutch is not in use, foot off of it, the throw out bearing is not under any load and not spinning, so not going to be making any noise. When the pedal is being depressed or held down or being let up, the bearing is under load and spinning.

 

This is true of the pilot bushing in the end of the crankshaft also. When idling with the clutch pedal up, the crankshaft and the input (main shaft) of the transmission are locked together. When the clutch is disengaged the flywheel is spinning but the transmission is not and there may be the possibility of some noise.

Good catch Mike. 

 

You might give these guys a call. Their website is crap. But they WILL have what you need. 

 

Whatever It Takes (wittrans.com)

 

If it were me, I would run it till it quits. These transmissions are not the quietest even when new. The ND-30 makes them run quieter. I had a 2004 with a 5 speed and it sounded horrible when it was brand new. Something about the gear shifter design transmits noise into the cab. 

 

 

 

[flyerdan]

If it's just making a little noise and not grinding or rumbling like failure is imminent, you might try adding some moly gear additive.  That stuff plates one molecule thick and will quiet down bearings that are a little rough, and keep them from getting worse.  Only do that if the front seal is good though, because if it gets in the clutch it will start slipping right away.

[datzenmike]

The very front bottom of the front case below the flywheel has a small drain hole.

[datsunfreak]

22 hours ago, datzenmike said:

Then the clutch is not in use, foot off of it, the throw out bearing is not under any load and not spinning, so not going to be making any noise. When the pedal is being depressed or held down or being let up, the bearing is under load and spinning.

 

I've seen multiple vehicles where a slight amount of slack in the bearing (usually due to lack of grease) causes the noise. Clutch pedal down, slack is taken up and it gets quiet. Clutch pedal up, slack is reintroduced and the bearing rattles and squeaks. 

 

Even with the clutch pedal up, the bearing may still spin if it's in close enough contact to the pressue plate, especially common with a hydraulic clutch.