In 1977 and
1978 there was a late model 3 speed overdrive transmission made for intermediate
passenger cars, light duty pickup trucks and vans. This transmission
looks just like an early Toploader, but it is not a performance transmission
The tag numbers
we know about are:
casting numbers on the main case or tailhousing start with D7DR
for 1977 model.
Some of the main cases have an ORION cast on the drivers
side. The gear teeth are cut very thin and the ratios are almost
the same as an early
3 speed with .85 or so overdrive in 4th.
At first glance
it looks just like the real thing.
Toploader in front, overdrive in rear
Here is a view
from the front, you will notice there are only 4 bellhousing bolt holes
instead of 8 on a true Toploader.
Toploader on right, overdrive
When you look
inside you will see a little tiny gear where third gear would normally
be. This is actually fourth gear in the 3 speed overdrive transmission.
Toploader on left, overdrive
When you look
at the shifter mounting holes on the tailhousing you will see that there
is no way this tailhousing will work in an early application. The speedometer
pickup is also on the wrong side.
Toploader in front,
overdrive in rear
On the passenger's
side of the main case you will notice a bulge or rib; this is to clear
the large OD gear on the cluster.
Toploader on top, overdrive