Adapts a Gen III LS engine to a TH350, 700R4, 200-4R, 4L60 or Powerglide by correcting the flexplate bolt pattern and crank spacing for a non-LS converter.
Putting a junkyard 5.3, a 6.0 or an LS1 in front of the TH350, 700R4 or Powerglide you already own is one of the cheapest ways to build a reliable street car, but the two were never designed to meet. The LS crank flange sits farther back from the bellhousing face than a small-block Chevy's did, and the factory LS flexplate has the wrong bolt pattern for an early GM converter. This kit is the fix: a 168-tooth adapter flexplate (575-34610), a crank sleeve adapter (575-18346), six LS flexplate bolts and a converter bolt kit, so the converter you already have pilots into the crank and bolts up without machining.
An early GM automatic expects the crank to hold the converter snout at a set depth and expects a flexplate drilled for a small-block or big-block converter. Bolt it to a stock LS and the converter nose does not reach the crank pilot, so it is unsupported, and the lugs do not line up with the flexplate holes. The included sleeve fills the gap at the crank so the converter is centered and engaged at the right depth. GM's own spacer for this swap is listed as setting converter spacing and engagement depth to prevent pump damage, and this sleeve does the same job. The flexplate then puts the right bolt circle in front of the converter. It is drilled for both 10.75 in and 11.066 in patterns, made from 4 mm cold-rolled steel with a double-welded ring gear, and cut to work with the stock LS starter.
Confirm three things. First, the engine: this kit covers 1997-2007 Gen III LS1 and LS6 engines, the LS2 through 2009, and the 4.8, 5.3 and 6.0 truck engines with six-bolt cranks. Gen IV engines with the later eight-bolt crank flange are not covered. Second, the 6.0: some 1999-2000 LQ4 engines built for the 4L80E have a longer crank flange and run a flat flexplate, so this dished plate and sleeve are the wrong parts for them. Third, the converter: measure its bolt circle so you know which flexplate holes you will use. If you are keeping an electronically controlled transmission, wiring is the next problem; our LS 4L60E standalone harness covers that side, and if you would rather adapt at the converter snout, compare the ICT Billet converter hub adapter.
The transmissions named on this kit are the TH350, 700R4, 200-4R, 4L60 and Powerglide, in the versions that were originally built to sit behind a non-LS engine such as a small-block or big-block Chevy. A 4L60E taken from a factory LS truck or Camaro already has an LS-length converter and does not need this kit. If you are not sure what you have, send us the transmission's origin and the converter's bolt circle and we will tell you before it ships. For 4L60-family parts and upgrades for the transmission behind your swap, see the 4L60E parts page.
Install the crank sleeve first, then the flexplate with the six supplied M11 x 1.5 twelve-point bolts, torqued in a cross pattern to the LS service specification. Seat the converter fully into the pump, so it drops through all its engagement steps, before you hang the transmission. With the bellhousing bolted up, there should be a small gap between the converter pads and the flexplate; pull the converter forward to meet the plate rather than drawing it in with the bolts. Many builders use OEM-grade converter bolts with thread locker on final assembly. A high-mileage transmission that is about to see LS power is a good candidate for a shift kit and fresh frictions; our 4L60E common problems guide explains why the 3-4 clutch is the first thing to fail behind a stronger engine.
| Flexplate | 168-tooth, one-piece forged steel, 4mm cold-rolled |
| Fits engines | 1997-2007 LS1/LS6 (LS2 to 2009); 4.8/5.3/6.0 L33, L59, LM4, LM7, LQ4, LQ9, LR4 |
| Adapts to | TH350, 700R4, 200-4R, 4L60, Powerglide (non-LS applications) |
| Converter bolt patterns | 10.75 in and 11.066 in |
| Starter | Works with the factory LS starter |
| Flexplate bolts | 6x M11 x 1.5, 12-point, 200,000 psi |
| Included | Flexplate 575-34610, crank sleeve 575-18346, converter bolt kit |
| Does not fit | 1999-2000 LQ4 6.0 built behind a 4L80E (tall crank flange needs a flat plate) |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Gen III LS1 and LS6 from 1997-2007, the LS2 through 2009, and the 4.8, 5.3 and 6.0 truck engines including the L33, L59, LM4, LM7, LQ4, LQ9 and LR4. It is not for Gen IV engines with the eight-bolt crank, or 1999-2000 LQ4 engines that came with a flat flexplate behind a 4L80E.
No. The 575-18346 crank sleeve adapter is included, so the converter pilots into the crank at the correct depth without buying a separate spacer.
Yes. The 168-tooth ring gear is cut to work with the factory LS starter.
It is drilled for both 10.75 in and 11.066 in bolt circles, which covers the common early GM converters used on the TH350, 700R4, 200-4R, 4L60 and Powerglide. Measure yours before ordering.
No. A 4L60E that came behind an LS engine already has the matching converter and uses the factory LS flexplate. This kit is for transmissions that were originally built for a small-block or big-block Chevy.
