LS Swap Flexplate Adapter Kit for TH350 Transmission

This adapter kit lets you bolt a Gen III LS engine to an early GM automatic that was never built for it. The 168-tooth adapter flexplate (part 575-34610) is a one-piece forged steel unit made from 4mm cold-rolled stock, about 0.035 in thicker than a factory plate, with a double-welded ring gear so it holds together behind a high-RPM LS. It is cut to work with the stock LS starter, so you are not buying extra parts to finish the swap.

It fits 1997-2007 GM Gen III LS1 and LS6 engines (up to 2009 for the LS2) plus the 4.8, 5.3 and 6.0 truck engines, including the L33, L59, LM4, LM7, LQ4, LQ9 and LR4. It adapts any of those to a TH350, 700R4, 200-4R, 4L60 or Powerglide that originally sat behind a non-LS engine such as a small-block or big-block Chevy. The flexplate is drilled for both the 10.75 in and 11.066 in torque converter bolt patterns, so it clears the common early-GM converters.

Here is the problem it solves: an LS crankshaft sits farther back than an old small-block, and the converter bolt circle is different, so a factory LS flexplate will not line up a non-LS transmission's converter. This kit corrects the crank-to-converter spacing with the included sleeve adapter (575-18346) and puts the right bolt pattern out front, so the converter pilots and bolts up without machining the case or the crank.

In the box: the 575-34610 adapter flexplate, six M11 x 1.5 twelve-point LS flexplate bolts rated at 200,000 psi, the 575-18346 crank sleeve adapter, and a torque converter bolt kit (7/16-20). One caution before you order: some 1999-2000 LQ4 6.0 engines that came behind a 4L80E use a taller crank flange and need a flat flexplate, so this curved adapter will not suit those builds. Torque the flexplate bolts in a cross pattern to the LS specification, and many builders run OEM-grade converter bolts on final assembly. Ships from the USA.