Rarely when I go to start my 66 L-79 she will crunch. This Spring it happened again so I pulled the starter and found the ring gear issue. Pulled her apart last week and I am in the middle of the replace/rebuild portion of the program, Muncie, clutch, shifter assembly, obviously the flywheel ( for what they cost I am ok replacing the flywheel rather than resurfacing and swapping ring gears, remember I'm a novice and scare easily), all of it.
I would think the origin of this was/is the starter. Looking like only 20% of the tooth thickness was damaged it seems like the pinion did not fully engage before it started spinning, just speculation on my part. Thing is I can have it rebuilt, put a new solenoid and pinion on it, but would there be any other explanation. Obviously do not want to do this again.
I have what looks to be an original or original type starter, big, heavy, black casing. Can post a picture of it if that would help.
Thanks in advance.

 

After MANY years of engaging the starter, those damaged teeth are not completely uncommon.
If the starter was working fine, but you had that aggriveting crunch noise, I'd replace the starter drive (commonly referred to as the bendix)-------------------ESPECIALLY if it is the original starter.
Then I would flip the ring gear over on the flywheel------------------------TOOOOOOOOOOOOOOOO EASY! I've done it on several flywheels that had worn teeth like yours. Again, ESPECIALLY if it is the original flywheel.

To flip the ring gear over, you only need a soft metal drift/tool (brass, alum, etc) and a good hammer and your wife's oven.
Place the engine side of the flywheel on the workbench and slowly work your way around the ring gear with a drift and the hammer.
Once the ring gear is off, THOROUGHLY clean the ring gear and flywheel mating surfaces.
Heat your wife's oven to the max (most go to 500deg) and place the ring gear in the oven for AT LEAST 30min.
Have the flywheel placed with the ring gear side up.
Carefully, and quickly, remove the ring gear from the oven and place it on the flywheel. It may or may not fall all the way onto the flywheel. If it does not go on all the way, use the drift and hammer to quicly tap it on all the way.
You now have a FREE new starter ring gear on your flywheel that should last as long as it did before.

 

DZ is indeed the expert. If you want to assure a easy fit, put the flywheel in the freezer and let it stay overnight or at least a few hours. Then heat the ring gear as DZ said, and they will go together with no interference. I personally don't have the courage to put the ring gear in the wife's oven while she is home, so I use a propane or oxy-acet torch. I have a beer refrigerator that is in the garage and she never checks it at night.

 

Actually I just PM'd DZ, he has been working with me. If I were to try this I would think I would first have to see if the flywheel can be re-surfaced. Is there a thickness spec I can measure?
Thanks

 

As a suggestion--mark the ring gear and flywheel before dis-assembly--tray to align the marks when reassembling--if balanced--should stay in balance
If no freezer, have used dry ice in the past--24 hours for flywheel--heated ring gear in oven couple hours--dropped in place and lots of noise-- !!

 

When you put the starter back on, check the clearance between the starter pinion and the ring gear. You should be able to stick a paper clip wire (about.025 inch) between the crest of the pinion teeth and valley of the ring gear teeth. Shim the starter between the starter nose and the engine block if you don't have enough clearance. The shims are available at most parts stores. I can't tell you how many old Chevys I hear starting up at cars n coffee gatherings and the starters sound like....its almost a grinding sound. its a quick and easy check and may save you a repeat performance of chewing the ring geat.

 

I can defiantly check that and will shim accordingly, thanks. Is there not also some critical distance between the starter and the flywheel? The two bolts that hold it to the block were shoulder bolts (one long, one short) so I would think that distance is not adjustable but not sure.

 

As the starter goes up or down that distance changes because the flywheel is round.

 

No, I get that. I was referring to a horizontal measurement.

 

The horizontal position is set by the holes in the block and the shoulder bolts. There is no critical dimension for the horizontal position either forward or back nor side to side. The correct clearance between the starter drive pinion teeth and the ring gear teeth is set by shimming the starter down to increase clearance. Before you put it all back together, check the bushings in the rear cover of the starter and the starter nose cone. Don't know how old the starter is, but they are cheap and eliminate the slop of the drive pinion gear moving around.

 

Agreed that the front to back position of the starter isn't critical. Also agreed that the bushing in the starter nose and the other one in the motor cover can wear to the point that the armature is loose in the starter case. Sometimes makes for some strange bendix engagement problems. Opinions on this last point are mixed, but the factory didn't often put in things that just aren't needed. Is the bracket that hangs the motor end of the starter on the block in place? That bracket is better in place than not. Interesting that many rebuilt starters don't have a threaded stud for the upper starter nose/case/cover bolt, which is where the bracket attaches to the starter case.

If it wasn't clear from my earlier post, you'll need to check the pinion to ring gear tooth clearance with the bell housing removed. You might also consider either removing the solenoid so you can extend the pinion by hand to measure the tooth clearance, or disconnecting the motor power terminal from the terminal on the solenoid. That way the motor won't turn when you energize the solenoid. If you do it that way, be sure the ignition is disconnected from power so there's no possibility of the engine kicking itself over while you're under there.

 

 

I will follow your recommended procedures although I will need to wait for the new flywheel/clutch combo to arrive, few weeks.
Buns, way to go with yet another excellent diagram, thank you.
Several have mentioned a support bracket for the starter. Mine had no such bracket, just the two bolts. assuming it is important I'll look at my AIM and see what it is and try to find one.

 

Readily available from all the vendors.

 

CORRECT, get one and put it on!

 

Tom Austin may have one he can send me but I have found them online. Will also pick up or make the solenoid heat shield that's missing. Thanks all.

 

All, I believe my solution for this, will be what MelWff suggested, (below pic)
I haven't had a chance to get back out to the garage, hopefully will soon..