How to replace GMC/Chevy alternator bearings ??
Norman Weiler
My 1996 GMC Sierra 350, 5.7l, 5-speed 4x4 has the alternator bearing
whine at 56,000 miles. The dealer parts dept says they can supply a
rebuilt for $220 - no bearings available for the do-it-yourselfer.
Searching back, I've seen other Deja posters say that they just
replaced the bearings for $15 to $20. They make it sound easy. I'd
like to try that, but I've never been inside an automotive alternator
before, so here are my concerns...
1. Can I even get the bearings, and from whom?
2. What's inside the alternator? Will small parts under tension shoot
all over the place when I open her up?
3. If 1 and 2 above are not a problem, will I need a special tool
(bearing, gear puller) to extract the old bearings?
4. Any gaskets involved?
5. What else will I need to know?
6. Is there an on-line, step-by-step for this?
7. My alt is the 100-amp.
Thanks for your help.
Norm in NJ
the fly
>
> Hi,
>
> My 1996 GMC Sierra 350, 5.7l, 5-speed 4x4 has the alternator bearing
> whine at 56,000 miles. The dealer parts dept says they can supply a
> rebuilt for $220 - no bearings available for the do-it-yourselfer.
> Searching back, I've seen other Deja posters say that they just
> replaced the bearings for $15 to $20. They make it sound easy. I'd
> like to try that, but I've never been inside an automotive alternator
> before, so here are my concerns...
>
> 1. Can I even get the bearings, and from whom?
Should be available from your local auto parts store.
> 2. What's inside the alternator? Will small parts under tension shoot
> all over the place when I open her up?
The brushes (electrical contacts for the rotor field
winding) will leave their holder when the rotor is
withdrawn. Small springs which keep tension on the
brushes can come out, but don't usually take off
uncontrollably.
> 3. If 1 and 2 above are not a problem, will I need a special tool
> (bearing, gear puller) to extract the old bearings?
You'll need a means of removing the pulley from the
exposed end of the shaft. On some later alternators the
pulley is a shrink fit on the shaft, and is not designed
to be removed. If this is the case, seek out a local
electrical rebuilder and have him do the job for you.
I've had alternators rebuilt (bearings & brushes
replaced, diodes and stator insulation tested) for about
$40-$50.
If the pulley can be removed by means of a large nut on
the end of the shaft, you can do it yourself fairly
easily. You'll need something to use as a press (an
arbor press or a large vise will do fine). Sockets of
appropriate size can be used both to support the end
frame of the alternator, and as arbors with which to
press bearings in and out. DON'T use a hammer to try to
drive the bearings. Press them slowly and accurately.
> 4. Any gaskets involved?
There might be a dust-cover gasket under a sheet metal
cover outside the drive-end bearing. It's normally
reusable.
> 5. What else will I need to know?
Mark the two end frames before disassembly, so that
they go back together in the same relative positions.
When separating the halves of the alternator body, keep
the stator winding with the NON-drive end frame. Its
wire ends are connected to the diode bridge which is
mounted in this end frame. Some are removable with nuts
or screws, and some are soldered to the diode bridge.
You don't want to rip loose the ends of the stator.
Protect the wire coils of the stator while things are
apart. What look like bare copper wires are in fact
insulated with a coating. If you bang them around, the
insulation can be damaged, and you may end up with a
shorted stator winding.
For re-assembly, the brushes must be held down against
their springs in their sockets, to clear the rotor as it
goes back into place. This is often done by means of a
wire (straightened paper clip?) inserted through
openings in the brush holder. The wire is withdrawn
after the rotor is in place and the case halves are
screwed together.
> 6. Is there an on-line, step-by-step for this?
I don't know; it's worth a search.
Rex Burkheimer
only the bearing that was making noise. It's usually the rear bearing that
fails on those later units, according to the guy that fixed mine.. They can
do the rear one without pulling the drive end. Cost me less than $100, and
that was 200K miles ago.
--
Rex Burkheimer
Parts Plus Marketing Director WM Automotive Whse., Fort Worth TX
Give a man a fire and he will be warm for a day, but set
him on fire and he will be warm for the rest of his life.
"Norman Weiler" <nwe...@nac.net> wrote in message
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