SFI 29.1 chromoly flexplate with a 153-tooth ring gear for internal balance small block Chevy engines running a TH350, Powerglide or 700R4.
Building a small block Chevy with a TH350 or Powerglide, or replacing a plate that cracked behind a stall converter? PRW part 1835002 is the 153-tooth, small-diameter version of the PRW Sportsman Series SFI 29.1 flexplate, for internally balanced 1957-1985 two-piece rear main engines. It is the plate many 700R4 swaps end up needing too, since the tooth count follows the starter and bellhousing rather than the transmission name.
All torque from the crank reaches the converter through this plate, and the starter turns the engine through its ring gear. The factory part is thin stamped steel with the ring gear spot welded on. Add more power, a looser converter, or a hard launch, and the stress concentrates around the crank bolt circle until the plate cracks, or the welds let go and the ring gear walks. PRW's version uses cold-rolled chromoly 0.035 inch thicker than stock with a forged one-piece ring gear double welded to the center, finished in gold iridite against rust, and certified to SFI 29.1 for tech inspection.
Remove the inspection cover, bar the engine over, and inspect every bolt hole, converter pad and ring gear tooth with a light. Then count the teeth on the old ring gear. The 153-tooth and 168-tooth plates are different diameters and each needs its own starter mounting. Putting the wrong count in is the classic cause of a fresh install that grinds or will not crank. If the noise turns out to be a whine that follows engine speed in every gear, the pump is a better suspect; see our 700R4 pump failure guide.
PRW lists the 1835002 for Chevrolet small blocks with the two-piece rear main seal and an internally balanced crank, 1957-1985, along with the 90-degree Chevy V6, and names the TH350 and Powerglide as the transmissions. It has a 153-tooth ring gear, neutral balance, and is drilled for the GM three-bolt 10.75 inch and 9.75 inch converter patterns. A 700R4 behind a small block can use it when the starter and bellhousing are set up for the 153-tooth gear; if your old plate is 168-tooth, order the PRW 1835001 168-tooth plate instead. One-piece rear main 1986-and-later engines and externally balanced 400s need a different plate. Not sure? Send the engine, transmission and tooth count, or browse our TH350 parts and 700R4 parts.
If the transmission is coming out anyway, a 700R4 overhaul kit and a correctly set Lokar TV cable handle the two jobs most swaps skip. Our 700R4 common problems guide explains why.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Count the teeth on the plate you are replacing and order the same number. The two sizes are different diameters, and the starter mounting must match the count.
Yes. PRW lists the 1835002 for the TH350 and Powerglide behind internally balanced 1957-1985 small block Chevy engines.
Yes, if your 700R4 installation uses the 153-tooth gear and matching starter. If the old plate is 168-tooth, use the PRW 1835001 instead.
No. 1986-and-later small blocks use the one-piece rear main seal crank flange and need a different plate.
PRW drills it for the GM three-bolt 10.75 inch and 9.75 inch converter patterns.
