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Discussion Starter · #1 ·
Hi all, so I have a well loved 79 pickup, 2wd shortbed base.

I had what we believed to be the throwout bearing go several months ago, it went from perfectly fine to terrible sound basically overnight. Found another trans, swapped with new t/o bearings and has ran great for months, no issues. But on the way home from church last night I heard what sounds like the same dreaded sound come back suddenly, though it seems hard to believe it could fail that quickly though I'm sure it can. Otherwise maybe input bearing?

Here is a video of sound.


It is present when truck is in neutral and disappears when clutch is engaged, seems to not be present in 1st/4th or at least not much compared to the sound of 2nd/4th.

To my understanding I can see how it can be the throwout bearing again, but I'm curious if you all think there is other culprits since its such a fresh swap? Funny it went from totally fine to terrible in a day.


Other information, may or not be relevant, has a strong vibration from only 50-60mph we can't seem to solve at home, (tires are new, just aligned too, driveshaft not bent as far as we can tell and Ujoints pretty new) and I've noticed the clutch is starting to get crunchy and less pleasant, holds pressure but does not feel good, I do think either the master/slave is going slowly, and I hear there is a adjustable fork on the slave end that can cause issues?



Appreciate any insight. I love this truck and the sound causes grief, as you all know well.
 

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I've never heard a release bearing make that much racket but if the sound goes away then that does point to the bearing. What brand did you use? For the vibration it could be driveshaft this happened to me I took it to a shop to have it balanced. I think the weight fell off although I never knew for sure.

Adjustable fork? Not sure on that. How are the shocks? If you've ever seen a car driving down the road with bad shocks the tire bounces like crazy.
 

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It is present when truck is in neutral and disappears when clutch is engaged, seems to not be present in 1st/4th or at least not much compared to the sound of 2nd/4th.
This is a very confusing description. Not trying to be jerk, but can we be clear about the symptoms?

Present when the truck is in neutral and disappears when the clutch is engaged? Do you mean the sound is present only when the clutch pedal is pushed in? If so, there's no power to the gearbox input. That mean (a) it's not a transmission bearing. If also means (b) that the gear you're in has no bearing on it.

Part (b) is what I don't understand. Why are you talking about noises in the various gears when the clutch is in and there's no power to the gearbox?

Just want to be clear on the symptoms so we can give you the best advice.
 

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Discussion Starter · #4 ·
thank you and for sure you are right that was poorly worded. my apologies.

the noise is present and loud when the truck is in neutral, sitting. thats what the video is from, I started it in neutral and got out of the car.

if I get into the cab and push on the clutch it goes away.


as far as part b: it also does make the same noise though not as loud when I am driving and in 1st and 3rd gear on the road.
 

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the noise is present and loud when the truck is in neutral, sitting. thats what the video is from, I started it in neutral and got out of the car. if I get into the cab and push on the clutch it goes away.
I think I understand. As a point of nomenclature, my understanding is that a clutch is "engaged" when the pedal is out and the clutch is transferring power to the transmission. If I have this backwards, I'm sure some kind soul will correct me.

My understanding is that the throw-out bearing only bears load when the clutch is in. therefore, I think we can rule that out. Your noise is present only when the throw-out is *not* under load.

It does sound like a bad input or countershaft bearing in the transmission is a likely suspect. You'll want to rule out the possibility that it's just a loose something-or-other vibrating. It would be a shame to rebuild the tranny and find it was a loose license plate making your noise.

I'm actually in the process of doing the bearings and synchros in my W50 transmission. It's not as hard as it sounds, and kind of fun. What kind of tranny do you have?
 

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Discussion Starter · #6 ·
thanks for your help wekadog.

What you are saying makes sense.

I did get under there this morning and feel around, its absolutely a mechanical grinding type of thing rather than a vibration. Although I know what you mean because we replaced the last driveshaft we had a shake/vibraiton so bad I lost my blue plates on the freeway :( which was a shame because they matched the truck too.

I'm wondering maybe we just got a bad set of replacement bearings when we put the last trans in. We had our friend mechanic do it because its a little out of the scope of our garage, me and pops do the less back hurting jobs. I'm assuming he swapped input/counter because why not but perhaps they were cheap.

re:transmission, it's just a four speed, I looked around for a 5 but was harder to source at the time and didn't want to overcomplicate since it ran great with the 4. Would be nice though :) I bet that is a fun rebuild.
 

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I'm wondering maybe we just got a bad set of replacement bearings when we put the last trans in. We had our friend mechanic do it . . .


Well, if you put in new bearings recently, that casts things in a different light. It's hard to imagine bearings so cheap they wouldn't last 100K miles. You do have oil in the gearbox, right?


There are other things that can go wrong inside the gearbox. You would need to get advice from a better expert than me, but something like excessive end play on a shaft comes to mind. I suspect even an expert will tell you that once you narrow the problem down to the gearbox, the only way forward is to open it up and see what the problem is.
 
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