Transmission trouble!

[ryans69chevy]

How do you tell if a transmission is going out? I have a 4 speed manual tranny in a 69 c10 and today when I was driving to college I got about 25 miles and this massive grinding noise started coming. I was going about 63 mph in 4th gear and I grabbed the shifter and tried to move it a lil bit to see if I could mess up the gears or see if it would help and it didn't really do much. The noise would come and go.

After I slowed down and got into 3rd gear going about 15 mph the grinding didn't come back. And then coming home it did the same after about 25 miles...

It felt different than my pilot bearing going out. So I'm confident that it's not that. I replaced that dec 09 along with a new clutch. I've changed the fluid in the tranny once or twice, so I've taken pretty good care of the tranny and I also don't race it or rev up a bunch before I shift so I don't think it's under that much stress. Unless going 70mph and the tach shows 5k was too much for it. I have a 307 with the 4 speed and 3:08's in the back.

Is there anything I can check, or are the hints that I gave a dead giveaway that it is the tranny?

[Wrenchbender Ret]

Check the carrier brg on the drive shaft. Its not likely the trans noise would come & go like that.

[ryans69chevy]

Isn't that the bearing that holds the two piece driveshaft together? and it bolts onto the frame in the middle between the two shafts? If it is that's also what I replaced two years ago. You think it would go bad that soon? What would I look for on the carrier bearing?

[oldgold70c10]

Originally Posted by ryans69chevy

You think it would go bad that soon? What would I look for on the carrier bearing?

Yes, they will. It is kind of hit or miss on them. I've had one only last 1-1/2 years, another been there over 3 years now.

[MARKDTN]

You may also want to check your rear end. In my '83 K20 it broke a tooth off the pinion gear and it only made noise when it got to 4th gear (700R4). Thought it was the transmission, but it wasn't.

[ryans69chevy]

Hmmm...That's strange that they don't last that long... Why is that? When I inspect it what should I be looking for?

And I'll check my rear end if the carrier bearing looks good. It just seems strange that it only does it every so often...And only after awhile of driving.

[Wrenchbender Ret]

Yes that is the carrier brg. It has been called other things but its the same part. If it spins freely without any noise & the rubber is good it is OK.
I just dicovered we have a spelling check on here. I won't have to show my ignorance.

[ryans69chevy]

Ha! I didn't even realize that we had that! I've sometimes caught myself "googling" a word to see if I had it spelt right before I would post haha!

Anyways, does anyone have any ideas of what else to check?

[ChevLoRay]

I can guarantee you that when the rubber goes bad, or if the bracket breaks loose from the chassis, you'll have some noise! The center bearing (U-joint) starts flopping as the driveshaft rotates and it is "noticeable"....

4-speed shifters are notoriously-good hand rests. But, that creates a problem with the synchronizers wearing. If that was the case, you'd probably find that the transmission pops out of gear when you let off on the gas.

[ryans69chevy]

The rubber looked good too! Like I said, I replaced this carrier bearing about sept of 09 so it's not that old.

And yeah, I've heard of a couple peoples trannys having trouble from them resting their hands on the shifter all the time. So I've learned from their mistakes and rarely rest my hand on the shifter for more than a couple min.

[rcbildr]

I had a similar situation with the SM-465 I had in my Burb which had similar symptoms...at about 60 mph I would get a bad bearing/grinding noise from the trans. The Bellhousing to transmission bolts were loose which caused the pocket bearing that supports the input and output shaft of the trans to go bad. The shop had to replace those parts, put all new bearing in the trans, replace the pilot bearing, and I had to find another bellhousing.