rocketraider

Bud has a 77 LeSabre Estate Wagon w/ 403 that is having to have it's 2nd flexplate in 10 years. It developed a knock that sounded just like a rod knock so he had it towed, and the mechanic found the "new" flexplate cracked almost out to the ring gear.

Car did this about ten years back and that one sounded just like a weak lifter.

Apparently all you can get now are Chinesium replacements. Anyone else having 403 flexplate issues?

joe_padavano

When I've had cracked flexplates, it was always due to misalignment problems between the block and trans case. In particular, I had one situation where the bolts has loosened up, causing the flexplate to, er, flex. That led to cracking. I'd get the shop to ensure the trans input shaft is concentric to the crank, and that the bellhousing bolts are properly torqued. Be sure that there isn't a problem with debris or burrs or casting flash on the bellhousing mating faces or dowel pins.

BillK

What Joe said and also make sure there isn't a lot of end play in the crankshaft. I would think that this would give other symptoms also but on a seldom drive car maybe not ? And make sure that you can pull the converter back from the flexplate 1/8" or so when it is unbolted.

oddball

Note that the 403 uses the typical later Olds pattern so you can also just look for a flexplate for any 350 or 455. There are a handful of aftermarket and SFI certified ones.
As mentioned, breaking two flexplates is really strange.

jackolds403

Do you know if there are compatible flywheel for the 403olds?
I will mount muncie on this engine, but need a right flywheel...

joe_padavano

As mentioned above, all 1968-1990 Olds motors take the same flywheel or flexplate. Any flywheel that fits a 350 or 455 also fits a 403.

jackolds403

Sounds good!

matt69olds

Koda

My money is on missing dowel pins.