Starter turning but not the engine

T

Toadman

Junior Member
Running a built from scratch '39-'48 Mercury flathead in my '32 Roadster. Last year I started hearing a high-pitched squealing noise related to rpm and clutch pressure off & on. Thinking it was a bad throw-out bearing, I pulled the engine to replace it-lot of work for a 5 min. part replacement. Unfortunately, the noise continued after all that work. Just the other day I was getting a grinding noise when starting the engine (sounds like the starter is spinning) but engine did not turn over. I took out the starter, and it looks fine, no signs of breakage and Bendix spring is intact. A friend suggested that the ring gear may have disengaged from the flywheel. Although it still seems to be seated on the flywheel, I can get the ring gear to manually rotate without turning the engine which tells me it must have become disengaged.
As I proceed to tear things down again and pull the engine, is this fix as simple as tack welding the ring gear to the flywheel? Could this create a balance issued with the whole assembly? What if I ever needed to replace the ring gear?
 

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i would take some time to determine if the problem is really a detached ring gear. as it's highly unlikely that an owner could even start an engine with a detached ring gear. or that a ring gear, and the flywheel for that matter, could remain intact and not have been completely destroyed when they parted way. is suspect there's something else afoot. :) and in a nutshell, welding plays no part in the process of attachment, nor in the manner in which a ring gear remains attached to a flywheel.

in any event i've included a link to a video of how one might go about installing a ring gear DIY style. it's not how pros do it, but it might be useful. BTW pros (at least pros about forty years ago) use a torch, usually oxy-acetylene or something similar to heat the ring gear to red hot then either pound it on with a sledge or use a press. its called a thermal interference fit. one heats up the ring to red hot in order to expande the inside diameter a few thousands of an inch. just enough to pound the ring on to the room temperatore or colder flywheel. when everything cools, is is never coming off in one piece. :)

detachment is a destructive process for the ring gear, often involving a chisel and press or hammer. ring gears are very brittle as they need to be extremely hard. they are not that difficult to crack apart with a cold (my grandpa (b. 1894) called them "coal") chisels. good luck!

https://www.youtube.com/watch?v=_9ewsP7LByI

here's another link that might be useful.

https://forums.yesterdaystractors.com/threads/removing-a-ring-gear-from-flywheel.1630955/
 
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I have never fitted a new ring gear, however there are two things I do know.
Do not get it red hot!
It does have a correct orientation, chamfer on the teeth go to the rear.
Also! If the ring gear is loose on the flywheel, You will need to accurately measure the flywheel to ensure it is not undersize.
 
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I’ve installed close to 100 ring gears. I agree that you should not get them red hot. They only need to be hot enough to allow the new gear to thermally expand enough to clear the slight flange on the flywheel. A couple of pointers.
1). To remove the old ring gear, I always cut it with a hacksaw. The cut doesn't have to go all the way through. I then take a chisel and split the gear at the cut line. Make sure to check the flange for any dirt or rust and clean appropriately.
2). I put the new ring gear in my oven to get it just hot enough to clear the flange. (You will have to take the flywheel in your house or heat the gear with a torch in your shop). You can handle it with a pair of slip joint pliers.
3). As stated earlier, be conscious of the teeth chamfer orientation. Once the gear has reached the temperature necessary for enough expansion, it will fall right in place. Make sure it is seated correctly as it will cool quickly and I assure you, it will be attached.
 
Thanks Huey and others. To be clear, I'm working with a forged flywheel with 1,500 miles on it. The engine is not turning over or starting even though the starter is doing its job. I am able to spin the ring gear manually by prying it with a screwdriver through the starter connection hole. Even though it's still in position on the flywheel, I can't come to any other conclusion except that it has lost its bond with the flywheel. I've seen the how-to-remove and replace videos and appreciate the reference, but my dilemma is how to re-engage the ring gear to the flywheel since it has seemingly lost its friction fit.
 
If you weld it, I’d think that flywheel is a gonner if the ring gear ever needs replacement again. If it only has 1500 miles on it, it must be a new one. Can you contact the vendor about replacement?
 
if the flywheel is a custom flywheel and or some sort of performance item, then i think you've got your answer. the ring gear and the flywheel are the wrong size for one another. and either the flywheel or the ring gear or both will need to be replaced. the inside diameter of the gear and outside diameter of the flywheel must be compatible to make the thermal interference fit. it is critical and i know of no reasonable solution other than replacement.

BTW, i suppose using the word "red" may have been a slight exaggeration. i used it to express the fact that the ring gear needed to be heated to a very high temperature.

when observing the mechanic installing a ring gear on my flywheel he used an oxy-acetylene torch on the gear for over five minutes in order to get it hot enough. it was smoking and it was beginning to glow when he finally started pounding it on. IOW it needed more than a barbeque grill or an oven to get it hot enough. it's a precision fit. and when one begins pressing or pounding on it, it better by golly have been heated up enough to expand and get it on. as it cools rapidly and if it was not hot enough to expand enough to get it on all the way, well...there it will most likely play the starring role in a destructive removal. i'm sure people that do this sort of thing know enough to error on the "too hot" side. ha

so ya, as the previous commenter pointed out i would be on the horn with the manufacturer of either the ring gear or the flywheel and if they are the same, they need to be informed that they've most likely a quality control problem. which would not surprise me in the least these days.
 
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> I can't come to any other conclusion except that it has lost its bond with the flywheel.>


Prolly cracked. Lucky engine didn't start.:eek:
 
alchemy said:
If you weld it, I’d think that flywheel is a gonner if the ring gear ever needs replacement again. If it only has 1500 miles on it, it must be a new one. Can you contact the vendor about replacement?
Click to expand...

i agree...

1500 miles and a forged flywheel implies, IME, a new high performance boutique type of flywheel. it's often recommended to buy such flywheels and ring gears as a set and more often to have them prefitted by the manufacturer. if the ring gear and the flywheel were not manufactured by the same company, then it's not too surprising that the interference fit failed.

it's also a possibility that if the flywheel was purchased with the ring gear pre-installed (it's actually recommended on custom flywheels that that be done) that it was pinned and glued on. they do that now. and if that's the case...well... ha

BTW i used the word "red" to make it clear that the ring gear may need to be heated beyond the capabilities of a butane torch or oven. i was closely observing the mechanic install mine. and as the gear was laying on the flywheel he heated it and would occasionally tap it lightly to see how much clearance he had and only when it was starting glow that he decided it had expanded sufficiently to get it all the way on. which is a necessity in that one cannot get it partially on and then remove it to try again. it's an all-or-nothing type of job.

of course, there's nothing to prevent one from tack welding a ring gear on and chancing a balance issue or a clearance issue or a repeat of a disengagement issue. unfortunately, it could end up destroying the flywheel and ring gear and possibly the clutch and the transmission housing too.
 
Install some set screws between the flywheel and the ring gear, drill and tap a hole in the flywheel where the set screw can secure the ring gear in place. This method helps prevent the ring gear from slipping during operation.

 
Toadman said:
Running a built from scratch '39-'48 Mercury flathead in my '32 Roadster. Last year I started hearing a high-pitched squealing noise related to rpm and clutch pressure off & on. Thinking it was a bad throw-out bearing, I pulled the engine to replace it-lot of work for a 5 min. part replacement. Unfortunately, the noise continued after all that work. Just the other day I was getting a grinding noise when starting the engine (sounds like the starter is spinning) but engine did not turn over. I took out the starter, and it looks fine, no signs of breakage and Bendix spring is intact. A friend suggested that the ring gear may have disengaged from the flywheel. Although it still seems to be seated on the flywheel, I can get the ring gear to manually rotate without turning the engine which tells me it must have become disengaged.
As I proceed to tear things down again and pull the engine, is this fix as simple as tack welding the ring gear to the flywheel? Could this create a balance issued with the whole assembly? What if I ever needed to replace the ring gear?
Click to expand...
586940
 
I did a no-no in 1965 with my ‘50 Ford, the ring gear was slipping and so I push started the car and drove it around the corner to a farm store where they welded it. The welder said he put several beads equally spaced around the edge. I drove the car for at least for another year or two before I sold it, I didn’t have any vibration issues guess I got lucky.
 
Given this was a custom flywheel, the best bet is to send it back to RAM (who made it for us) and have them address the issue. I will check with the guy that I worked with at RAM and see if he is still there. He was the General Manager of the place - though this was during the COVID era.
 
One thought before pulling anything apart, mark the flywheel and ring gear, try the starter and see if things actually have moved.
 
If you bought it from a reputable dealer call them and see what they have to say, otherwise I would bite the bullet and buy another one. That would be much easier than trying to fit the ring gear back on only to have it happen again and leave you sitting out in the boondocks. just a thought from my addled brain. tom
 
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