SkinnyG's 1977 Chevy Silverado

My best in the summer was 12mpg(US).  Worst in winter was 8 I think. Looking forward to see if there is any improvement when I'm on less choke.

Hey.  Guess which vehicle blew a collector gasket.  THIS one, I'll try the copper silicone stuff.  It's easy to get to.

Sealed up and holding.  Hoo ray.

Also, the new shorter tires sure make the truck lower.  I am more afraid of the lower control arms now.  

And the used set of flowtech headers I put in originally are pretty garbage headers. Hopefully they make the duration of ownership....

I love the sound headers make when they fly into the recycle pile.

Most of them are garbage with flanges too thin. The only ones I've had good luck with have been from Banks or Gibson.

Our Beaumont customer supplied a set of Hooker Blackheart headers that seem decent. Time will tell.

SkinnyG said:

Sealed up and holding.  Hoo ray.

Also, the new shorter tires sure make the truck lower.  I am more afraid of the lower control arms now.  

You have more clearance than I do. 

If I were building one again, I would forego the dropped spindles, and just pancake the front crossmember.  This would get the a-arms off the ground and above the wheel lip.

I still want to lower the front another half inch.....

Gave a demo in Mechanics on using an older Snap-On engine scope on wheels. 

Running the secondary patterns, everything looked really consistent, all around 15,000V.

Ran the cylinder balance test, and I had about four cylinders where the idle rpm went UP when deactivated.  Odd.  Kind of like that one co-worker who drags the team down.

Surely the engine isn't having issues???

Today I put a couple kids on doing a compression test and put in new plugs.  I haven't changed plugs in 3 years. Plugs (copper) looked good, and only slightly worn. Compression was 180psi all across the board.

Maybe it's a machine issue, and not my motor.

I might try the test again, but not do it automated.  See what happens.

Interestingly, there are now three exit wounds in the 12-bolt cover.

Apparently a ring gear bolt worked its way out, and was jettisoned from the diff cover, draining all the oil out, taking out the gears and some bearings.

Yay.

So now, $1700 lighter, I have a new and installed set of gears and bearings, and a BAD ASS vibration from the back of the truck.

Yay.

But, I have a nice new chrome cover.

Yay.

so, new center section in old drum-to-drum assembly, including old axles and axle bearings?

The axle had everything new something like 4 years ago. Everything.

I was able to get driveline vibration down to a very narrow speed band at 50mph.

I have found that over-tightening the U-Bolts at the axle cause a nasty vibration, and these were pretty tight. I re-tightened them less and will give it a go today. The vibration I have now is acceleration, cruise, AND deceleration.

The other challenge to my understanding is pinion angle.  I -get- that the pinion should match the angle of the transmission so they cancel themselves out. And I get that leafs need to be a bit less angle on the pinion to counter axle rotation. Except that this is significantly lowered.

Currently, the trans is down 5°. The driveshaft is down 1.8°. The pinion is down (nose up) 1.9°. This gives an operating angle at the trans of 3.2° and an operating angle at the diff of 3.7°. These operating angles are good, although the pinion is pointing the oppsoite way. This had vibration only at 50mph.

My old Nissan Hardbody worked awesome with the pinion dropped 3° and the carrier raised 1" back when it was lowered. That goes against proper pinion angle theory.

Way back, with no shims in the back, the trans was down 5°, the driveshaft was 0°, and the pinion was up 1°. Operating angle at the front was 5°, Operating angle at the back 1°. It had NASTY vibrations everywhere.

ANYWAY, when I picked up the truck, they said it had a nasty vibration. I even turned around twice to take it back it was so bad, but I wasn't going to make it back before they closed. I'm taking it back today.  It was NOT that bad when I dropped it off.

Whenever I've had bad driveline vibes like that, it was due to an unbalanced driveshaft.  One time it completely shattered the tailshaft housing on a C6 (Ford).  Swapping driveshafts made it go away.  

loose lug nuts?

AngryCorvair said:

loose lug nuts?

What'd you call me?? 

volvoclearinghouse said:

AngryCorvair said:

loose lug nuts?

What'd you call me?? 

sorry, i didn't mean to put a dampener on things.

These round-eye squares are some of my favorite trucks.

I'm always on the lookout for a crew cab dually, but those are rarer than hens teeth!

In reply to SkinnyG :

For what its worth, you are lucky that is what happened. On my tundra, one of the bolts backed out and locked up the rear for a second or two at 50+mph before shearing out and freeing up again. Fortunately there was no one around to hit at the time but it put the fear in real quick.

Did you check the bearing caps on the diff when you reinstalled everything? 12 bolts aren't known for having great caps. I run a single mark williams enterprises forged cap on mine with a moser bearing support diff cover.

Sean

Everything looked good when I put it all together years ago. I KNOW I used locktite red on all the ring gear bolts, and I am CONFIDENT I torqued them ALL. And yet.....

I didn't put this one back together. I paid the man. I figured I screwed up the install way back when, because I could hear a faint whistling from the diff at some speeds.  Exciting to find the new gearset does the same thing. 

Yay.

And yeah, having the rear lock would be an E-Ticket level of pucker right there. E-ticket - am I that old? Wow.

You lost me on E-ticket, so...Yeah 

I had an old 6 cylinder square body once, daily driver. 10 bolt rear. One day moseying on down the highway I hear a "ca-THUNKA!" from the rear end and managed to hit a nearby off-ramp quickly. The truck ground to a halt about 2/3 of the way up and wouldn't move at all. Some guy in an Astro van managed to shove me up and out of the way, and the wrecker had a helluva time removing the truck to a shop. 

GM rear ends suck. Mrs. VCH's Camaro has a tenner, and it has about 1/8 turn of slop in it. Just waiting for it to grenade so I can stick in something beefier. 

Dropped the truck off yesterday morning to have them chase the vibration.  I've chased it for years; it's defeating me.  And it's not like it's the first squarebody with a flip kit.

Waiting to hear back.

Meanwhile, I'm dailying the Super 7.

In reply to AngryCorvair :

*ehem!*

Back on task, gentlemen.....

Truck shop called, they found the driveshaft off by .050" (odd, since they re-trued it winter before last in chasing vibration for me), but they're having a tough time truing it better. They're likely going to re-tube the driveshaft.

Perhaps it is, indeed, the driveshaft was a piece of poo even "as built" 5+ years ago?

We'll find out.

In reply to SkinnyG :

Potentially good if infuriating news.  It'll be great if this is *THE* fix, but man what a bummer to have gone through all this to find it.

In reply to SkinnyG :

What do they mean "off by 0.050"?  Driveshaft is a solid hunk of metal, don't see how/why it would change.  My theory on why the one in our car that started vibrating suddenly was it threw a balance weight.  Or got impacted by something.