The 1999-2000 truck extended crank flange engines used a flat flexplate, but because the crank flange is extended 0.400 inch, this flat design places the starter ring gear in exactly the same position as the flush flange, concave design. The most common design used with flush crankshaft flanges is concave exactly 0.400 inch. This creates essentially two different LS flexplates. The 4L80E, however, does use a much larger torque converter and mounting pattern, as we’ll see. Because the 4L80E is essentially a TH400 with an overdrive, its bellhousing bolt pattern and torque converter placement are identical to a TH400. This became a Chevrolet part number for the production use of a 4L80E automatic behind LS engines in selected heavy-duty applications. So, when bolting an older transmission like a Powerglide, TH350, TH400, 2004-R, or early 700-R4 to an LS engine, there will be a 0.400-inch gap between the flexplate and the torque converter.Ĭhevrolet’s simple solution for this was a steel spacer placed between the crankshaft flange and a flat LS flexplate. The LS family of engines (with one exception that we will detail) places the crank flange flush with the bellhousing mounting surface. The traditional Gen I small- and big-block Chevy crankshaft arrangement extends the crankshaft flange 0.400 inch beyond the bellhousing face. Let’s start this swap tale with some basics. So, don’t go out and buy one and expect to bolt it behind even an LS3. While Chevrolet Performance carries the 8L90E in its catalog, unless this trans is used in conjunction with a Gen V (LT1 or LT4) engine and controller, the 8L90E is currently incompatible with all previous generation engines. This story will focus on the most affordable opportunities with the electronically-controlled four-speed automatics, like the 4L60E thru 4L75E, and touch on the 4L80/85E. A two-speed Powerglide seems almost archaic now with the growth of GM six-, eight- and now 10-speed automatics, like what’s behind the 2017 ZL1 Camaro. Transmissions are undergoing radical change these days. While most stories only deal with swapping behind LS engines, we’ve expanded that into covering the details on how to swap transmissions between all the generations of Chevy engines. As with all interchange stories, a successful swap is dictated by handling all the fine points. The current favorite son seems to be the 700-R4/4L60E four-speed automatic, but there are also places where a TH400 might be the best solution for a 1,500-hp, blown LS engine, or a simple 200-R4 fits best behind a 5.3L LS daily driver. Everybody has a different take on the best automatic to use, which means there’s a huge world of opportunity for interchanging transmissions with Chevy engines. Bolt any bowtie automatic to any Chevy engine – if you know the tricksįor street cars, it’s all about overdrive these days. With a simple twist of a few wrenches, you can either bolt a ’90s 4L60E behind a Gen I small-block, as we’re doing here, or you can run an older non-electronic trans behind a 21st Century LS engine. Thank the Chevrolet gods for interchangeability.
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