1956 Bendix gear disintegrated

[seatramp]

Has anyone seen this before? went to start my 56 after about a moth or so and had to crank it a couple times to get gas to the carb.The third time I cranked it she kicked and I heard a bang. I instantly stopped trying to crank it, went and looked to see if anything visible might have caused it but didn't see anything so I tried start it again. I could hear the starter spin up but no crank. I tried it a couple more times with the same results so i figured the bendix gear hung up or some how stripped a couple teeth on the flywheel. Tried rotating the engine by hand with the same result so I figured the only way to be sure was pull the starter motor. I was realy surprised when I saw the gear. I have seen starter gears that were worn and would not engage but this was new to me. All the teeth were gone. Not just worn or broken, completely gone. I fished around in the starter opening and found one of the teeth laying inside but that was it. I pulled the access plates off the bell housing and found the majority of the pieces in the air outlet of the bell housing (early 56 with the air cooled tranny) but still missing some. I had a friend turn the engine by hand while I checked the flywheel and it looks ok (note to self: next time mark the tooth where you start, he didn't realize he went around twice 😁). It's possible they went down on the air intake side but I can't check all the way in there because of the screen. The gap at the bottom of the bell housing is large enough for any loose teeth to drop out so I'm thinking when I replace the gear I will leave the access holes open and crank the engine with the coil unplugged to see if the missing teeth show up.

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[Tom Alpers]

I would look at the broken parts and try to assess whether they all look like clean recent breaks or if some breaks look older then others. If I was to guess I'd say that when the engine "kicked" the starter kept trying to turn that Bendix gear against the ring gear and they all sheared off right then and there like a big bite of corn on the cob.

 

[seatramp]

I examined the pieces I have and they look like new breaks so what you suggest is the most likely scenario but I'm still missing a tooth (found one using an air hose to blow out the air intake through the screen) it's like having a puzzle with a missing piece, never sure what the whole picture is🤔. The new Bendix will be here Tuesday or Wednesday so until then there's nothing more to do.

 

[Frankie the Fink]

Yeah clearly an engagement problem and it doesn't take much wear to cause an issue...

I'd make very sure the ring gear teeth (all of them) are not hooked or worn badly.
Next that the mechanisms to engage/disengage the bendix are strong enough for the job...
If the gear only got into the flywheel a tiny bit and the engine started to lite off and the disengagement wasn't good or you didn't get off the ignition key quick enough - then 'bang'..

This little bit of wear on my GM flywheel was enough to cause issues:

 

[seatramp]

Yeah clearly an engagement problem and it doesn't take much wear to cause an issue...

I'd make very sure the ring gear teeth (all of them) are not hooked or worn badly.
Next that the mechanisms to engage/disengage the bendix are strong enough for the job...
If the gear only got into the flywheel a tiny bit and the engine started to lite off and the disengagement wasn't good or you didn't get off the ignition key quick enough - then 'bang'..

This little bit of wear on my GM flywheel was enough to cause issues:

Had teeth chip and cause disengagement but never destroyed the gear before, ring gear seems to be good.Guess I'll find out when the new gear gets here😱

 

[doug7740]

If the pins inside the Bendix drive are sticking, that would cause the Bendix not to retrace causing damage to the drive gear.









I have rebuilt a number of these Bendix drives, mainly because people do not know how to retract them. Here's how you do it.

doug7740
1955 Thunderbird Blue

 

[seatramp]

If the pins inside the Bendix drive are sticking, that would cause the Bendix not to retrace causing damage to the drive gear.

I didn't have a problem with the original bendix not retracting but, when installing the new one, while trying to compress the collar to insert the drift key it slipped and when i grabbed it, it fully extended locking it in place. Thanks to the procedure in the video it was a much easier fix than having to totally disassemble the whole thing and i thank you for posting it. After the first try I used a piece of masking tape to hold the pieces where they belonged until just before installing the starter. (hindsight is 20/20)
It is more difficult to compress the collar on the new style bendix. You must compress the collar far enough to move a retaining ring out of the way to insert the drift pin. Not having an extensive work shop and limited to mostly basic hand tools this is what i came up with. My fix for this was to place a short piece of pvc pipe, with a hole drilled on either side near the end, over the collar and compress the assembly using a small bar clamp until the ring was clear of the hole in the collar. Now, the new stylegear comes with a shorter pin than the original but using both pins partially insert one drift pin in each side of collar to hold the retaining ring in place, but not blocking the hole for the armature shaft, and remove the bar clamp. Now slide the assembly onto the armature shaft, align the hole in the shaft with the pins and drive the shorter pin into the shaft. Use a pair of pliers to remove the original pin from the collar, check the retaining ring is in place and you're ready to reinstall.
Wish I had thought to take pictures as i went but I was kinda flying by the seat of my pants ....again hindsight! But I thought somone might find it useful.