24 GEARS July 2005
T he 4L80E has been a prettystrong unit since 1991. Over
theyears weve built quite a few ofthese transmissions with no
problems, but every now and thenone comes back that slips in
reverse. All the forward shifts aregood.
The first thing we check is line pressure and line rise.This one
checks out good. Then we pull the transmission andtear it down, and
the only thing we find wrong is a burnt band.So what happened?
This could be a parts mismatch problem, because thereare two
types of rear bands for the 4L80E: The early band has a grooved
lining (figure 1). The late band has a smooth lining (figure
2).
Plus there are two types of band surface areas on the
reactioncarrier assembly.
The early reaction carrier assembly is grooved like theband
(figure 3).
The late reaction carrier assembly is smooth like the lateband.
(figure 4).
The early, grooved band can be used on either reactioncarrier
assembly, but the late, smooth band can only be usedon the late,
smooth surface reaction carrier
If you use a late band on an early reaction carrier,
yourelooking for trouble. It might work fine for a little while
withno load, but with any kind of load it will slip and be
back.
Now that we know which band goes with which reactioncarrier
assembly, this is were the problems starts. If you needto replace a
grooved band, youll need to replace the carrierassembly too,
because the only new band available is the late,smooth band.
by Mike BrownSTREET SMART
Figure 4: Rev Drum Smooth
Figure 3: Rev Drum Rough
Figure 2: Smooth BandFigure 1: Grooved Band
mike b stsmt.qxd 6/17/05 2:31 PM Page 24
