growling sound?

66 c10, 3 speed on column. suddenly developed a growling sound while driving. seems to be worse at slow speeds 5-25 mph. above that it seems to get quieter or disappear completely. seemed to do this about a week ago in first gear only. lasted about a day, today started doing it all gears. any suggestions??? sounds a lot like a disk brake growl when the pads are worn out and its metal to metal

Most likely it's a bad u-joint. They can be louder in low gear due to increased torque on take off. Could be a bad bearing in the transmission, but not as likely unless the trans has been run dry or is really old. Depending on where it's coming from, it could also be a bad wheel bearing. They can really growl, but normally don't get better with increased speed.

It's less likely, but it could also be a bad bushing in the back of the crankshaft, or excessive wear or a dry surface on the pilot shaft. It could also be a bad throwout bearing, but that would normally only make noise when the clutch is depressed.

thanks for the info, i am leaning toward a bad u-joint or wheel bearing myself. one other thing a couple days ago before the noise started, the truck will kick itself out of 3rd gear when driving at 50-60 mph. has vibration in the gear shift. will a bad u-joint cause that kind of thing also?

It certainly can. If it's bad enough to cause that much vibration I'd stop driving it immediately and pull the driveshaft and check. Bad u-joints can run for a long time before eating themselves up, but they can get bad enough to break. With that much vibration at the transmission, it's likely the front joint (if in fact it is the u-joint). If that breaks it can drop the front of the driveshaft on the ground, and if this happens at speed - the driving experience can become very entertaining.

It's possible something has gone away inside the transmission, but not as likely unless it's really been abused. Normally if something goes bad in an old 3 speed manual, bits of the bad parts end up between the gears causing the gears to start howling long before anything breaks.

U-joints however are a wear item, and do have a service life. If one is bad, be sure to replace both (or all 3 depending on type of driveshaft) so you don't have to go through this again, "in the field".

Mark, turned out the growling sound was a very worn carrier bearing. pulled driveshaft and fixed that over the weekend, now however the kicking out of 3rd gear got much worse, it kicked out on me today and will not go back into 3rd. all other gears seem fine any thoughts? i am thinking something serious in the tranny like maybe a synchronizer or something.

According to the 1966 Motors Manual, the most likely causes of a 3 speed manual jumping out of gear include:

1. Linkage parts worn, bent, broken or out of adjustment.
2. Excessive end play caused by wear in shift forks, sliding gear fork grooves, thrust washers, mainshaft and countershaft bearings, or clutch pilot bushing.
3. Misalignment or excessive clearance between sliding gear and mainshaft.
4. Damaged synchronizer.

Per the 1960 Chevrolet Service Manual, the following issues should be considered specific to "slips out of high gear":

a. Transmission loose on clutch housing.
b. Dirt between transmission case and clutch housing.
c. Misalignment of transmission.
d. Clutch gear bearing retainer broken or loose.
e. Damaged mainshaft pilot bearing.
f. Shifter lock spring weak.
f. Clutch gear or second and third speed clutch improperly mated. (I'm not exactly sure what they mean by this).

If you're still using the factory column shift linkage, I'd start there looking for problems. These are famous for wearing so badly they won't control the transmission correctly. And it may not be worn, could be just loose parts. Should the problem be internal to the transmission, these old 3 speeds were about the easiest to rebuild. If you have decent mechanical skills you can replace the bearings, thrust washers and synchros yourself.

If it turns out there's damaged gears or parts inside, it may be easier and cheaper to replace the transmission with a guaranted rebuilt unit. Good luck, M.

thanks for all the info, i pulled the tranny last night and removed side cover. the 2nd-3rd shift fork was sheared off on one side. everything else appeared to be ok, synch rings were not broken (i thought they would be). found a tranny for less than $100 in salvage yard. think i am gonna buy that and put in temporary. then order a rebuild kit for mine, rebuild, clean and paint it and put back in the truck later just for the experience.