Mopar Action On-line – Tech Questions


Tech Question

Lowell Grasse, Didsbury, AB, 1970, Plymouth, Satellite, 340

How Hard is it to put in an automatic tranmission withoverdrive from a newer pick-up? I have 4:10 rear end, and a 4th gear wouldbe nice.

We’ve covered this swap a few times over the years. Basically, the A-518 isa smallblock 727 with an overdrive grafted on. Early versions (1989 toaround 1991-’92) used non-lockup converters that are 100% interchangeablewith your stock 340 unit. The shift linkage, KD linkage, speedo cable,output spline, etc., are also the same.

Avoid the weak A-500 (based on the A-904.) The pans are the same shape astheir 3-speed cousins and can be used for identification

You’ll need to shorten the driveshaft and do some fabricating to get it toclear the transmission and torsion-bar crossmember. The stock Dodge truckmount is very tall, some extra room can be gained by using a biscuit-typeCamaro or Mustang mount.

Somewhere around 1997 they went to electronic governors, you’ll never getone of those to shift. Look for one with only the usual 3-pin backup-lampand neutral safety connector and a two-pin shift connector. Simply apply 12volts to the 2-pin connector and – voila! overdrive. Turn it off, normal3-speed TorqueFlite.

One other consderation not to be overlooked: even though the cooler fitingare in the same place as you old 727, they are bigger (for 3/8″ hardline).You MUST change your lines, and the cooler in the bottom tank of theradiator, to 3/8″ stuff, or the trans will cook!

Great swap! One was in my daily driver 340 W-2 Duster for 7 years. It alsohad 4.10:1 cogs, flip the switch and – bingo – 2.85!



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