AOD or T5

[canadian_ranchero]

ford changed the rear planetary lube in mid 1988.89 to 91[mid 88] aod's are better to use than the early ones.i have a 4r70w in my wagon,seems to work really well   

[gasman826]

The AOD I built was a '89 unit with the most upgrades; best lubrication, 1-2 accumulator eliminated.  Of the three AODs that I disassembled for spare parts, all overdrive bands had failed (from heat cracks to completely smoked).  Two of them had failures in the forward sun gear bushings.  The bushings had spun likely due to lack of lubrication.  Both of these units were pre '89.  By upgrading to the 4R70 gear set, both problem areas are addressed.  As with ALL automatic transmissions, heat is the enemy.  Add coolers!   The bigger the better.  I have always saved AC condensers to use as transmission coolers.  The only down side to too big of cooler is that the fluid does NOT get warm enough to do its job.  Always route the fluid through the radiator to insure minimum temperature is maintained.  If not or sever use applications, use a gauge.