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Possible issue with starter eating ring gears (72 340 - 727 Combo)

plymouthman72

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Hi Everyone,

I am having a heck of a time with my starter eating ring gears on my 727 torque converter. I will try and explain it as best I can and hopefully someone has had experience with this before.

I started the car up for the first time not to long ago and got it running on its own. I have gotten it through a couple of heat cycles and while the timing is not perfect, it is very close. When I started it the first time, I was using the original converter with a brand new mini starter. I did run the battery down a couple of times but what it sounds like is that the starter goes through a couple of revolutions and then just slams to a stop. I am not sure that is what is happening but that's what it sounds like. I figured it was possibly a bad starter and or I got too excited and tried to start the car to fast and ground the teeth off. Truthfully I needed the proper torque converter for my set up so I was not upset.

So now I buy a brand new Hughes toque converter and another brand new mini starter (summit brand this time) and installed them. I get the car started and I am super excited thinking I am about to move on down the road to finish the interior. Then I tried to start it in the cold this last weekend and it took a while to get it started but did. I went to start it again and 3 revolutions in the, I get the same loud cracking sound and sure enough I broke teeth off my new torque converter. Summit warrantied the converter but not the starter and once I got everything back in the car yesterday, it almost happened again but luckily I didn't break teeth.

At this point I am at a complete loss. I don't think you can shim 727 starter (at least it didn't come with any) and I don't know what would cause it to do something like that.

Something that I did notice is that when I was using the bump starter vs key, the starter sounded much stronger and turned much harder then when I was using the key. Could a bump starter cause and issue like that?

Here are things about the car and items I checked
- 416 stroker motor with 10:1 compression
- Doug's Headers which is the reason for mini starter
- Engine runs and runs well. No smoking and it idles. Does not like to start cold
- No overheating
- Battery - Interstate Mega Tron Series 24 - 800 cca
- Bench tested both of the starters I have and both pop and spin as they should without hanging up. That is why I am not sure if it is the starter or not.
- I am taking back my summit brand starter to summit today and letting them know what happened to see if they will exchange it for a new one.

Sorry to be so long winded, I am just trying to be as descriptive as possible and I greatly appreciate any help you all are willing to provide. I am to the point I want to get rid of the car and just take my losses and so frustrated.
 
If the dentist can't fix it there is an alignment problem.Everything MUST be inspected and measured for proper engagement or your problem is the result.:thumbsup:
 
Out of curiosity, is there a difference in the number of teeth on the ring gear, origional converter vs replacement converter? The exact tooth count is important between the two meshing parts. Likewise, is there a difference in the numbet of teeth on the starter pinion gear between the two starters? Contact angle of the different gear mesh parts (ring gear and starter pinion) may be effecting the problem as the contact angle will result in rapid wear and possible breakage. Excessive diametral clearance usually results in a noisy gear mesh and is not usually adjustable thru shims as the GM starter is. The uniform hardness of the converter's ring gear is also a factor...too hard may result in breakage due to shock load at innitial engagement. Just speculating....
BOB RENTON
 
Out of curiosity, is there a difference in the number of teeth on the ring gear, origional converter vs replacement converter? The exact tooth count is important between the two meshing parts. Likewise, is there a difference in the numbet of teeth on the starter pinion gear between the two starters? Contact angle of the different gear mesh parts (ring gear and starter pinion) may be effecting the problem as the contact angle will result in rapid wear and possible breakage. Excessive diametral clearance usually results in a noisy gear mesh and is not usually adjustable thru shims as the GM starter is. The uniform hardness of the converter's ring gear is also a factor...too hard may result in breakage due to shock load at innitial engagement. Just speculating....
BOB RENTON

Thank you for the response. Unfortunately, I threw away my old converter once I got my new one installed so I would not be able to check the converter itself. I will check both of the starters when I get home tonight. I was and still am thinking it could be the contact angle but when I first install it, it sounds normal and doesn't sound noisy. What is weird is that it still turns the engine over just as it should for one or 2 revolutions then I get the snapping sound almost as if the starter tries to reverse or something. It's hard to describe the sound honestly. I will likely tow the car somewhere to have a pro sort it out for me. I just don't have the knowledge and am just guessing at this point so it's best to let the professionals handle. I'm just a guy in a garage messing crap up at this point. hahaha
 
Was the block align honed or bored when you built it
Is this the original transmission as the guide for the nose of the starter is in it
 
Was the block align honed or bored when you built it
Is this the original transmission as the guide for the nose of the starter is in it

It was bored out to .030 over when I got to clean out the cylinders. It's been a couple of years since I had the block worked on but I do not think I had the block align honed. I hope the problem does not run that deep.
 
Was the block align honed or bored when you built it
Is this the original transmission as the guide for the nose of the starter is in it
IMO..
IF the block was align honed, how would this change the starter pinion/ring gear relationship? Crankshaft horizontal centerline would not change and any differences would be adjusted when the bearings were installed (bearing shell OD). True, the starter mounts in the transmission housing or the bell housing and the centerline relationships are maintained thru the locating dowel pins. Starter depth of mesh or engagement is fixed. Starter install dimension is adjusted by any shims to control any axial changes. I believe the ring gear on the converter's OD is replacable and is shrink fitted on the converter and tack welded to the converter's shell. Perhaps the replacement converter's ring gear was not installed square to the centetline?? causing an mesh alignment issue in operation. Just my opinion of course.
BOB RENTON
 
With align hone when you take .005 off cap you move the crank up about half of that
Align bore you can just take from cap
 
Sounds to me like it could be an ignition issue. Timing wrong, pickup wired backward, firing order incorrect? Do you have any issue cranking it with the coil wire removed or distributor lead disconnected? If it cranks ok disconnected it shouldn't be alignment. There is a fair amount of clearance between the starter pinion and the converter ring gear. No way a few thousandths during align hone is going to make difference. It did have both dowels in the back of the block to align the trans case, correct? They weren't pushed in too far? If so the trans could be out of line with the crank. But the dowel issue would be the only possible cause. What ignition box and distributor does it have?
Doug
 
Sounds to me like it could be an ignition issue. Timing wrong, pickup wired backward, firing order incorrect? Do you have any issue cranking it with the coil wire removed or distributor lead disconnected? If it cranks ok disconnected it shouldn't be alignment. There is a fair amount of clearance between the starter pinion and the converter ring gear. No way a few thousandths during align hone is going to make difference. It did have both dowels in the back of the block to align the trans case, correct? They weren't pushed in too far? If so the trans could be out of line with the crank. But the dowel issue would be the only possible cause. What ignition box and distributor does it have?
Doug

Hi Doug, I didn't even think to try without the coil plugged in. That is a great idea and I will try that tonight when I get home. I just need to put the starter back in. I have been afraid to try it again for fear of breaking another tq converter but that would tell me if its timing causing the issue. I am hoping it is something as simple as the timing (I did triple check the wiring order) and that can fix the issue. I did talk to several of the Mopar guys at summit and the shop I plan on taking it to and they are thinking it is likely something to do with the timing since it does start and doesn't happen right away. With open headers, it's hard to really hear anything but I do know that my timing is not perfect but it does idle on its own once its warmed up.

*edit - I do have both dowel pins and it lined up with no issues.
 
Look at the condition of the starter seat before re installing your starter too. I don't have the info on the number of teeth for ring gear/starter combos but I would double check this. You can pull all of the spark plugs before trying it next time to reduce any strain on it and listen for binding. I know on a big block, you can look up into the bell housing and see the starter bendix. Don't know about the small block. Good luck!

20200211_194251.jpg
 
Not all mini starters use the nose seat pictured above. No issues with them.
Doug
 
Not all mini starters use the nose seat pictured above. No issues with them.
Doug

Wouldn't hurt to check it for damage or deformities. Might keep the starter from seating flat on the bell housing, causing binding.
 
Look at the condition of the starter seat before re installing your starter too. I don't have the info on the number of teeth for ring gear/starter combos but I would double check this. You can pull all of the spark plugs before trying it next time to reduce any strain on it and listen for binding. I know on a big block, you can look up into the bell housing and see the starter bendix. Don't know about the small block. Good luck!

View attachment 908169

Good call, I got home late last night and did not have a chance to install it so there is still time to check it. I do remember looking at it before I put it in this last time and it looked fine but I didn't inspect closely. I probably won't do much before I take it in because I have lost all confidence in my ability to work on it and do not want to break another expensive converter.

Out of all this I would like to give a shout out to Summit Racing, I told them exactly what I told you guys and they warrantied it without question. I even told them that it was very possibly my fault but they said teeth should not break off a new tq converter like that with a new starter and gave me a new one. They did not warranty the starter however because they said it was likely still good.
 
When you described the starting noise and that it would crank then click my post was the 1st thing that came to mind.

My battery is brand new but I suppose it's possible it's bad as well or maybe I drained it to much killing it. I will take it in and have it tested too. I would love for it to be something as simple as that.

This is a dumb question but can trying to start you car with a low battery kill the starter?
 
Update on the project! I did not know this but I had the stud on the wrong side and that was causing an alignment issue. They corrected it and have not had any issues since.

Sometimes it just takes a second set of eyes that knows what they are doing and small things like this can be fixed.
 
Update on the project! I did not know this but I had the stud on the wrong side and that was causing an alignment issue. They corrected it and have not had any issues since.

Sometimes it just takes a second set of eyes that knows what they are doing and small things like this can be fixed.
Thank you for following up! This thread may help someone in the future.
 
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