I apologise in advance for any details I leave out (or putting too many in), but here goes.
The main highway in & out of town is a constant 5% gradient for 5 miles before it levels out. It's a big hill, and trucks have lost brakes and killed people before.
I have a square body Suburban with a tired, and stock (carb and headers only) 454 that I have punted up and down this stretch numerous times before, and it seems to be most comfortable at 45mph in direct gear @ 2000rpm. Water temp steady around 200*f, even in ambient temps of 100*f plus.
Yesterday, I had to make the trip for a friend's wedding; in a moderate 85*f day, BUT traffic had been horrible before the hill, so everything would have been heatsoaked from sitting still for 30min plus with the AC running.
So I'm pulling my usual 45mph@2000rpm when halfway up this hill I heard what I thought was a single pebble flick up and hit the floorpan, like a click. Only once. Then it happened again maybe 15-20 sec later, then once every 5-10 sec after that, with no loss of power.
I kept my speed thinking it was gravel on the road, but about a minute later heard a slightly louder click, still within the volume of a stone hitting floorpan. Only this time I felt it through the pedal and a very slight hesitation at the same time. Right back to normal after, and soft enough my wife didn't notice anything.
I pull over and pull out my IR temp gun as she idles fine. Oil pressure normal (30psi idle), water temp within limits (205*f read off the T-stat housing), trans temp 195*f (IR'd off the outlet line pre-cooler). The only thing off is that I have a thermocouple-washer style temp gauge under one of the torque converter cover bolts (just to monitor block temp I guess, and this peaked at 225*f (old high score was 210f, and it always climbs under load through radiation from the longtubes).
I idle it for about 2min, the 'block temp' dropped back to 205f, so I pull out and climb the rest of the hill at my usual 45mph with no issue. Everything back to normal, didn't happen again.
The ONLY difference yesterday was sitting in traffic prior to hitting the hill.
I've felt the telltale detonation can-of-marbles rattle before (in an old 998cc Mini, never in this truck), but this seemed like a single event. Can detonation happen once, then stop? Slight lean backfire maybe? Reading the plugs after my first highway pulls were pretty much spot on for color.
I'll admit I don't know what my timing is. :embarrass
So my question is what did I feel? :confused:
The main highway in & out of town is a constant 5% gradient for 5 miles before it levels out. It's a big hill, and trucks have lost brakes and killed people before.
I have a square body Suburban with a tired, and stock (carb and headers only) 454 that I have punted up and down this stretch numerous times before, and it seems to be most comfortable at 45mph in direct gear @ 2000rpm. Water temp steady around 200*f, even in ambient temps of 100*f plus.
Yesterday, I had to make the trip for a friend's wedding; in a moderate 85*f day, BUT traffic had been horrible before the hill, so everything would have been heatsoaked from sitting still for 30min plus with the AC running.
So I'm pulling my usual 45mph@2000rpm when halfway up this hill I heard what I thought was a single pebble flick up and hit the floorpan, like a click. Only once. Then it happened again maybe 15-20 sec later, then once every 5-10 sec after that, with no loss of power.
I kept my speed thinking it was gravel on the road, but about a minute later heard a slightly louder click, still within the volume of a stone hitting floorpan. Only this time I felt it through the pedal and a very slight hesitation at the same time. Right back to normal after, and soft enough my wife didn't notice anything.
I pull over and pull out my IR temp gun as she idles fine. Oil pressure normal (30psi idle), water temp within limits (205*f read off the T-stat housing), trans temp 195*f (IR'd off the outlet line pre-cooler). The only thing off is that I have a thermocouple-washer style temp gauge under one of the torque converter cover bolts (just to monitor block temp I guess, and this peaked at 225*f (old high score was 210f, and it always climbs under load through radiation from the longtubes).
I idle it for about 2min, the 'block temp' dropped back to 205f, so I pull out and climb the rest of the hill at my usual 45mph with no issue. Everything back to normal, didn't happen again.
The ONLY difference yesterday was sitting in traffic prior to hitting the hill.
I've felt the telltale detonation can-of-marbles rattle before (in an old 998cc Mini, never in this truck), but this seemed like a single event. Can detonation happen once, then stop? Slight lean backfire maybe? Reading the plugs after my first highway pulls were pretty much spot on for color.
I'll admit I don't know what my timing is. :embarrass
So my question is what did I feel? :confused:
