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Tips to Keep Your T5 Alive! |
by Chris Herzog
After having D&D Performance of Wixom, MI rebuild one of my transmissions
this past off season, I inquired about some of the typical failure causes
for T-5 transmissions. The top 3 were:
-
Using the wrong lubricant - they were pretty adamant about running an ATF
based lubricant (unless you're running one of the older GM, non-world class
units specifically spec'd for gear lube)
-
Excessive end play - they recommended pulling the trans after it's first
post-rebuild race to check/reset end play. It's not unusual for the
trans to have have .005" of end play after the first race. After
resetting the end play after the first race, pull the trans every 3 or
4 races and keep checking and correcting the end play.
-
Misalignment between the transmission and the engine. This is checked
by measuring the alignment of the bell housing surfaces when the bell housing
is bolted to the engine. Misalignments can put significant side loads on
the transmission's internals and lead to a very rapid failure. In
some cases, you'll even put a side load into the crank which can even cause
the rear connecting rods to fail.
I felt that I had the first two items covered but wanted to checkout
the bell housing alignment while large parts of my Mustang were apart this
past winter. It looked simple enough and I already had a dial indicator,
I figured I'd give it a shot. I tried to call Rotunda (the folks
that make the special service tools for Ford) and was told the bell housing
alignment fixture had been discontinued with no replacement. More
than a little bummed, I decided to take a look into building a tool myself
since it seemed pretty straightforward.
There are only two important measurements to check on your bell housing:
you want to make sure the face of the bell housing where the transmission
bolts is perpendicular to the crankshaft and you want to make sure the
center bore in the bell housing that aligns the transmission input shaft
with the crank is concentric with the crankshaft. At first, I was
concerned about how to accurately pickup the crankshaft center line for
the second measurement. After thinking for a bit, it's obvious that
you don't need to align your tool with the actual crankshaft centerline
but you merely have to have a solid surface to make sure the dial indicator
doesn't move around. The key is that in all cases, what you're trying
for is a relative measurement.
From the description and drawings in the Ford shop manual, I was able
to make a tool that allowed me to make all of the measurements I needed
out of metal I already laying around the garage. Some photos of the
tool are enclosed (beware, that's a 15" ruler in the picture, overall the
tool is about 12" long!).
The tool consists of two parts, an "inner" and "outer" half.
It is designed to bolt to the clutch release arms after the bell housing
(and all of the things it normally covers like clutch, flywheel, etc.)
are bolted to the engine. The "inner" shaft has a large washer welded
to the end of it. The sides of the washer have been cut of parallel
to each other (a 2.25" OD washer fit my Ford's clutch just right) - this
allows the inner part to be inserted inside the clutch cover once the clutch
cover is mounted to the flywheel. You'll probably need to do a little
fitting to adapt it to your setup but it's no big deal.
The "outer" half is a tube with a washer welded to the end which slides
over the threaded rod of the inner piece. Once you tighten down a
nut on the end of the tube, the entire assembly clamps onto the clutch
release arms and becomes quite rigid. I used a 3" OD washer for my
tool.
The only other thing required is a tab to hold your dial indicator.
Weld this tab to the outer tube at whatever distance works out best for
your dial indicator. It's best to do this last after you've bolted
the inner and outer halves to the clutch cover and can see how deep your
bell housing is.
There are two measurements that need to be made using this fixture.
The first measures the run out of the rear face of the bell housing.
For this measurement, you need the make sure the bell housing and block
mating surfaces are clean and free of burrs (as well as the surfaces of
any parts that go between them) and install the bell housing (be sure to
torque the bolts to spec). Mount your dial indicator in the fixture
so the actuating arm is roughly parallel to the crank centerline and zero
your indicator. Move your crank through one full revolution and record
the maximum and minimum readings. The range between these readings
is the total run out for the bell housing face.
The second measurement measures concentricity with the crank.
Mount your dial indicator in such a way that the actuating arm is perpendicular
to the crankshaft and it's touching the side of the transmission locating
hole in the bell housing (you might find it easier to attach two separate
tabs to your fixture to handle your specific indicator; you can also make
your life much easier with a side reading dial indicator). Zero the
indicator and run the crank through one full revolution. The difference
between these readings is the total out of concentricity of your bell housing.
Ford recommends that the face of the bell housing be no more than .010"
out of parallel when measured in this way. The maximum out of concentricity
value is .015". Check your shop manual for specific values if you're
running a Camaro or Firebird.
Ford recommends replacing the bell housing if either of the run out
values exceed factory spec. But don't worry, depending on how far
off you are, there are ways to correct it.
If the rear face of the bell housing isn't parallel, you can have the
rear face of the bell housing milled to bring it into true with the front
(this assumes the rear of the block is perpendicular to the crank which
is a pretty safe bet). Be sure to take off the minimal amount needed
since this will allow the transmission to sit closer to the engine.
You can easily take off 10 thousandths with no problem - just don't take
a 200 thousandths cut off of the bell housing and expect things to be OK.
If the bell housing isn't concentric, you can purchase misalignment
dowels that have a built in offset to allow the bell housing to be offset
to bring it into alignment. Lakewood sells them as will your local
dealer's parts counter in most cases. Be sure to keep checking your
alignment and whenever possible, check the alignment after the bell housing
has been installed for the last time (this might require checking it in
the car if you can't install your motor with the bell housing attached).
Hopefully these tips will keep a few more T-5 transmissions alive!
Chris Herzog
Chicago, IL
zog@stg.com