Okay, first, this El camino is the first old american car with a manual I've owned, so not much experience with them other than what I've experienced so far. When I drive my El Camino, in any gear, when I engage or disengage the clutch I can hear and feel a light 'clunk'. It doesn't happen in neutral, only when I'm engaging the clutch into gear or disengaging it from a gear, especially if it loads the drivetrain, like when I'm shifting while accelerating or down shifting using the gears and engine as a brake. When I replaced the transmission not long ago, I replaced the U-joints as well, so I don't think its the U-joints. The motor and transmission mounts seem solid as well. Is this my differential? Or is this normal for these old cars? It is only an 8.2 inch 10 bolt rear end, and with the way I drive it I wouldn't be surprised if it was the cause, but I'm not sure because I can feel it through my seat, and it almost sounds like its below the cab. Is there a way to test if it is the rear end having excessive gear lash or something?

Thanks for any info provided guys.

lee

Clutch plate is bad.
After time the lining starts to move on the plate itself. The rivits that hold it on start to loosen.
When you had the tranny out, sure would have been a GOOD time to replace the throw out bearing, clutch disc, pressure plate and re-face the flywheel!
Now you get to pull the tranny, AGAIN!
When ever you are that deep into a project like that is wise not to half-a** the job!

And do the Pilot bearing as well while your at it.

Would hot rodding, (not dropping the clutch, but definitely spirited driving), the car cause a clutch to go bad within ~800-900 miles? I did replace the whole clutch. New flywheel, new pilot bushing, new RAM clutch kit with disc, throwout bearing and pressure plate, hell I even replaced the clutch fork and pivot ball. I know I've been a bit hard on it, but damn, that's pretty fast for a clutch to crap out isn't it??

Couple of questions first. Was the replacement trans new? Did you have the clunk before you did all the work? Is the rear end open or posi?Are the splines on the yokes tight? How many miles on the diff.

You'll have to look up the specs for backlash on your ring and pinion. I would think between .010-.020.

The clunk on my 82 was reduced by replacing the carrier side and pinion (spider) gears.

Jack the rear up and manually turn the driveshaft back and forth to see if you can duplicate the noise.

I'm not familiar with the 66s. Does the trans. support have rubber isolators where it bolts to the frame? Could be some slop there. Rick

Hey hel. The transmission mount is a rubber type mount, though it was good when I put it in. I'm going to check the drivetrain for slop and see if any movement there is the cause after work today. The transmission is new, not rebuilt, but the diff might as well have been dragged from a field, I don't think it has a ton of miles on it since being put in this car, but it was originally out of a 64 chevelle, so no telling how many miles it had on it before it was put in this El Camino and I've definitely not been kind to it.

The clunk did exist before, but it was much worse sounding then, I thought I'd completely fixed it when I replaced all the rear bushings and control arms, since one of the bushings on the top of the differential housing was REALLY badly worn, pretty much just a shell at that time, and the whole differential was moving back and forth when I drove it. Either the sound I'm hearing now was just masked by that one, or it didn't entirely fix the problem, whatever it may be. It's not loud at all but I can feel it through the seat and floor. It almost hears and feels like the seat itself is loose, but the seat is tight and doesn't move when I push it around, so it isn't that. It's really bugging me! :mad:

P.S. Now that I've driven it again this morning, it is much more noticable when I'm accelerating or decelerating in gear, not when I'm engaging or disengaging the clutch. When I push the gas to accelerate from coasting in gear, it takes a noticeable bit of time from when I press the gas pedal until the car actually accelerates, and the clunk happens then, and again when I let off the gas to coast in gear. If it were the mounts, wouldn't this happen even when out of gear from the engine torquing over? That's why I'm suspecting the differential is having issues of some kind...

When I was talking about isolators I meant the mounts where the trans. support attaches to the frame. It would be almost directly under the seat.

I'm leaning towards the diff as the cause of the clunk.

Noises are one of the most difficult problems to diagnose. It's possible you may have body mount problems also. Rick

Might have found the issue. When the car has its parking brake on, the transmission out of gear, is the driveline supposed to be able to move? I can turn mine either direction a bit more than half in inch. Does this mean it's toast?

Not necessarily toast. Some play in the drive line is normal. When you get play from the trans,drive shaft and rear end it can accumulate to cause the clunk.



Pull the diff. cover and check the spiders. Rick

Might have found the issue. When the car has its parking brake on, the transmission out of gear, is the driveline supposed to be able to move? I can turn mine either direction a bit more than half in inch. Does this mean it's toast?

sounds like something isnt right in the rear end.

I figured the responders might like to know and hoped others would learn from my experience. I found out what is causing that 'clunk' I keep hearing when I drive my Elco. It's the drivers side motor mount and frame bracket. I couldn't see that it was the cause because it doesn't move until under a heavy load or being let off of a load and the wear spot it made from moving was on the firewall side, where it's hard to see. I used a dentists mirror to see the shiny bare metal left on the frame bracket when the motor mount moves up and down on it and scrapes it. I put some paint on it, took the elco for a spin and voila, it rubbed the paint off, showing the extent of the movement. I've got about 1/4 of movement due to the motor mount bolt having wallowed out the hole in the frame bracket for it, so I need new ones. Oh well, you live and learn! Thanks for the advice guys!