87 740 wagon loud thud/knock when accelerating

  • Thread starter Thread starter g13
  • Start date Start date
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g13

hey,
about 50% of the time when i accelerate (and usually during heavy
acceleration from complete stop in 1st gear), i hear and feel a heavy
knock or thud coming from the rear (differential, maybe?). it feels like
as if a heavy object like a bowling ball rolled back due to the
momentum and hit the back of the trunk.
any ideas?
g13
 
g13 said:
hey,
about 50% of the time when i accelerate (and usually during heavy
acceleration from complete stop in 1st gear), i hear and feel a heavy
knock or thud coming from the rear (differential, maybe?). it feels like
as if a heavy object like a bowling ball rolled back due to the momentum
and hit the back of the trunk.
any ideas?
g13
Click to expand...

The center support on the drive line is weak, let's the drive line hit the
exhaust pipe. At least that's what happened with our 2000 XC 70. Had to
replace the drive line, couldn't get the center neoprene mount separately,
according to our technician.

Dale
 
Dale_Peterson said:
The center support on the drive line is weak, let's the drive line hit the
exhaust pipe. At least that's what happened with our 2000 XC 70. Had to
replace the drive line, couldn't get the center neoprene mount separately,
according to our technician.
Click to expand...

The 740 has a more robust drive train (since it has lasted nearly 20
years in this case), but then all the modern Volvos are made from rubber
bands and matchsticks. I don't know what I buy if my 940 becomes
uneconomical to repair (hopefully it will last until the oil runs out
and I'll convert it to electric).

Anyway, its probably a loose bush at the rear, holds some arm in place,
something is colliding under rotation. Support the car on axle stands
or ramps and take a pry bar underneath and leaver each bush to check for
excess play.
 
g13 said:
hey,
about 50% of the time when i accelerate (and usually during heavy
acceleration from complete stop in 1st gear), i hear and feel a heavy
knock or thud coming from the rear (differential, maybe?). it feels like
as if a heavy object like a bowling ball rolled back due to the
momentum and hit the back of the trunk.
any ideas?
g13
Click to expand...
I HAD THIS WTH MY WIFES CAR A GEARBOX MOUNT WAS WORN OUT REPLACE IT
MARKING WHICH WAY IT GOES IN .I didnt and had to put it back in right
side up oy voy a dumb goy !
 
Have you checked that there isn't a bowling ball in the trunk?
 
John said:
I HAD THIS WTH MY WIFES CAR A GEARBOX MOUNT WAS WORN OUT REPLACE IT
MARKING WHICH WAY IT GOES IN .I didnt and had to put it back in right
side up oy voy a dumb goy !
Click to expand...
Please tell us which on it is as I believe its the gear box mount to the
frame and I have two 740 turbos .
 
John said:
Please tell us which on it is as I believe its the gear box mount to the
frame and I have two 740 turbos .
Click to expand...
SORRY THAT DIDN'T MAKE MUCH SENSE CANT BELIEVE I WROTE IT, BUT TRY OUT
THE MOUNTS ON THE GEAR BOX ANYWAY !
 
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