Starter sticking put 3 rebuilt starters on blazer all done same thing when you crank it over the bendix keeps sticking in flywheel

Sounds like a bad bendix, replace the starter?

If your sure bench test was good and bend ex is not sticking, assuming it is your starter I would say your flywheel ring gear is missing or worn teeth. try rotating engine by hand a quarter revaluation and trying starter again.
Bendix Gear sticking

Not likely. More likely is that the starter, or the starter solenoid is bad.
This is the way it works. Turn key, car checks to see if all safety items are OK (in neutral or park, brake pedal depressed, etc), if OK then sends signal to starter solenoid to engage(it's basically just a magnetic switch), which allows the full power of the battery to turn the starter and engage the bendix, which engages the flywheel and turns the motor. If any of those things are bad, the car don't start. If it's the starter, the bendix will make a metallic click or thunk. If it's the bendix, the starter turns, but not he motor. If it's a fault in the electrical system, then no starter, and no bendix. If the battery is weak, the bendix may or may not click.
To repair;
1; starter can be rebuilt, including the bendix. moderately expensive if done by shop. Inexpensive if you can do it yourself. Warning - it's a PITA to get it out!
2; selenoid can be replaced. Usually inexpensive, except for shop charges. It sets on top of the starter.
3; If electrical; this can get expensive as it is labor intensive to track down the fault, even if the part is usually inexpensive.

Check timing belt first , check starter also .

The "Bendix" is the starter drive in the actual starter. When you crank the starter the bendix is driven forward into the flywheel. It sounds like the bendix spring is worn or week and it's not meshing with the flywheel. Instead it's grinding against it. If you're ambitious you can pull the starter, dismantle it and replace the bendix or option 2 replace entire starter w/new or rebuilt. Both will have new drive and save you a bunch of time.

Apply some white grease to the starter gear and turn the engine over without starting it, remove starter and check the gear mesh pattern to make sure starter is aligned right. You might need to shim the starter. The starters bendix drive might be sticking. Is it a brand new starter or a used or rebuilt starter?

The Bendix drive is bad in the starter. You can either rebuild it or just purchase a new rebuilt starter.
The Bendix drive is what pushes the starter gear into the flywheel the then it will turn the flywheel. When the Bendix drive goes bad the starter just spins/whirls.

Hello, I would make sure that your car is not one of those half year cars becuase two differn't starters may be offered for the same year of car. Also, I would check and see if your battery has enough CCA's to power your system. The only other thing is to turn your crankshaft with a breaker bar to turn your flywheel to possibly get a fresh area of teeth on it. If none of this fails it's as simple as just replacing the flywheel. If you did a bench test on the starter and the bendix engaged that is good. Buying parts from an Auto parts store does not gurantee the part is good and that the bendix engages the full distance to turn the flywheel. I would try to find a mechanic who rebuilds starters to make sure that the bendix is engaging fully. I hope this helps you!

Sounds like the bendix is stuck in the starter. When this happens, the starter energizes and turns, but the gear does not kick out to make contact with the flywheel. Have someone tap on the starter while cranking the engine.

engine crank thrusts worn and crank moved back enough to not engage ,with a manual the clutch would push it forewards.or the flex plate on the back of the torque converter damaged and broke in teh centre where bolts to the crank