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Speedway Tech Talk - LS Flexplates


If you want to run that old school TH350, TH400, or 700R4 behind an LS motor, you will need a couple parts to make it work.

If you have a junkyard 4.8, 5.3, or 6.0L LS, take a look and see what style of flexplate you have. Most of the 5.3's came with a concave style flexplate. You can tell because the center of the plate will protrude towards the motor. If you have this plate, all you need is P/N 57518346. This sleeve slides onto the nose of the torque converter and helps align the unit into the flexplate.

If you have a 6.0 LS, the flexplate will be completely flat. If you have this plate, you will want to purchase the following items:

  • 35512563532
  • 12563533
  • 57518346

The flexplate spacer will need to be installed between the engine and the flex plate.

If your motor came with a bent or broken flex plate or you just want something new, Speedway Motors carries a kit from TCI that has everything for you; P/N 282399753. This kit gets you the 6.0L style flexplate, the sleeve, and the flexplate to crankshaft bolts.This flexplate is built .35” thicker and so you do not need an adapter plate like item 35512563532. This adapter is built in!

If you want a new 5.3L style plate you will want to order P/N 57534610 and the adapter sleeve, P/N 57518346. Using these 2 items will get your transmission bolted up to the motor.

Using these combinations of parts from Speedway Motors will hopefully help you make that LS install a lot easier.

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