80/90 weight is the usual recommendation. If it's a posi, don't forget the posi additive.
transmission fluid
Any Dexron fluid will work fine.
75-140 synthetic
you have to drop the entire pan since there is no plug and you might as well change the filter and gasket while you have it off
it goes in the same tube where the dip stick is at. just dont over fill add a little at a time or it will leak
Synthetic 75w90
90 weight gear oil
You can use any SAE certified rear differential fluid in your 1970 Chevrolet. The 1970 Chevrolet differential fluid can be checked from the differential fluid check port.
It has a transaxle, there is no separate differential fluid.
gm syncromesh synthetic
Under the car on the upper side of the transmission, you will find a plug. Remove the plug and stick your finger in the hole. If you feel fluid, it is full. If not add the proper lube as stated in the owner's manual.
80 w90 gear oil front and rear!