1985 Chevy Van clanks when initially started

1985 Chevy G20 Van - Clanking sound at startup
305 Engine
Automatic Trans.

Over the past few months if vehicle is not run for more than a
a day I was getting a repetitive clanking sound for the first 10
to 15 seconds that the engine was started. It sounded like it
was coming from the rear of engine or maybe the exhaust pipes.

I recently discovered my automatic transmission fluid was down
about 2 to 3 quarts. Last time I checked it was about 8 moths ago.
After refilling it, the clanking sound at startup has decreased
dramatically but it still clanks a couple of times when initially
stating the engine if the vehicle has not been run for a day or so.
Once the vehicle is in use and I restart it, there is no clanking
sound.

I'm also noticing a slight vibration when driving that seems to
be related to the drive train. I can feel the vibration in the
whole vehicle and in the gas peddle. Vibration is worse when
going uphill.

What do you think is the problem?

Am I doing more damage by driving with this slight vibration?
In other words, how urgent is it that I get this fixed?

---pete---

This could be a tough one to diagnose, but here goes. Check your motor mounts and transmission mount. Just for the heck of it, see if the exhaust is hitting anywhere too. Make sure that your starter, transmission to the block bolts and torque converter are all tight.

A loose converter will clunk, but for a short time and would be consistent regardless of how long it sits. If it was that low on fluid, filling it up could lessen the noise. My $$ is on a loose torque converter.

Bob

A loose converter will clunk, but for a short time and would be consistent regardless of how long it sits. If it was that low on fluid, filling it up could lessen the noise. My $$ is on a loose torque converter.


That makes good sense, Bob.
Perhaps the torque converter makes more noise when fluid is
low because it's off balance partially filled and this condition is
much worse when the fluid level is very low.

A loose torque converter could also account for the vibration
I'm experiencing.

I'll open the cover under the torque converter and look for
loose or missing bolts.

Thanks.
I'll let you know what I find in the next day or so.

---pete---

Check for a cracked flex plate as well, just thought of that. Once you pull off the inspection pan you'll get a better idea.

Bob

maybe there's a cowpie stuck on your driveshaft

Hey Bob,
You were right!
I removed the dust pan to the torque converter and found 2 of
the 3 bolts loose. I tightened the bolts and all is back to normal.
No more vibration or clanking. I'm very happy.

Thanks for the advice.

---pete---

Alrighty, one in a row for me. Glad it was something simple, but keep an eye on it. The flexplate holes and/or bolts may have some wear compromising their holding power. A little loctite on the threads might be all it needs if it happens again.

Bob

Alrighty, one in a row for me. Glad it was something simple, but keep an eye on it. The flexplate holes and/or bolts may have some wear compromising their holding power. A little loctite on the threads might be all it needs if it happens again.

I can't keep my eye on it so easy, but I'll keep my ear on it. :)
If it lossens again, I'll hear that clanking sound and I'll take that
as a sign that the bolts are streteched and no longer have the
holding power needed. I'll then go buy some brand new bolts
from the dealer.

Thanks again!

---pete---

I had to fix the same thing on a1976 gm 3/4 ton. convertor nut and bolt fell right out into into the flywheel cover. i could just here a tinkel when i shut the truck off. a quick fix with no damage. factory screw up.