The Stovebolt Site Forums The Shop Area Engine Shop RING GEAR 139 VS 168 TEETH

Hi.....my truck is a 1953 Chevy 1/2 ton with a 1955 235 engine and a 12 volt electrical system.

Just counted the flywheel teeth and there is 139. From what I read it should be 168 teeth for a 12 volt system.

Why does the flywheel count have anything to do with the electrical system ?

Does it positively have to be changed and if so, can just a a ring gear be purchased ?

Thanks in advance.......

Just keep the 6 volt starter and you'll be fine.

The change to a 12 volt electrical system was made mid-year 1955. If you've got a 55 1st. series engine it would have been manufactured with a 6 volt starter and a 139 tooth flywheel. The 55 2nd. series engine would have a 12 volt starter and a 168 tooth flywheel. The simple fix will be to install a 6 volt starter- - - -it will work just fine on 12 volts.

The reason the starter and flywheel must match is because the geometry between the flywheel teeth and the starter pinion gear has to match up. A 139 tooth flywheel with a 12 volt starter will be noisy, and will wear out quickly. Ditto for a 168 tooth flywheel and 6 volt starter.
Jerry

Sounds like I need to find out if I have a 6v or 12v starter.

How does one tell if the starter is not tagged with a label stating 6v or 12v ?

The ring gear is chewed up in one area. Are they readily available ?

The truck has not been started in many years.. maybe 7-10 years so I dont really know is this ring gear will be ok.

Thanks.....John

I

Hy zoegrant, measure the diameter of the starter armature shaft, I can check my starter shafts to confirm the measurements but I know the six volt armature shafts are larger in diameter than the twelve volt armature shafts, these are metric dimensions. That is the reason why we can't simply swap starter drives to get the voltage we want with the drive we want. Okay I measured the shafts, 12 volt starters have 12mm shafts and 6 volt starters have 14mm shafts, hope that helps.

If there is a metal tag on the starter, a 6V unit will have black paint. A 12V is red. Ditto on the shaft size difference, but I'm not at my shop right now to provide any measurements.
Jerry

As per Dads50 and Hotrod Lincoln's advice, I used a 6V starter powered by 12V for 15 or so years.

ok...I measured the shaft on my starter and it is 14 mm.
The color of the starter is black.
No tags to indicate what voltage the starter is.
So the 14mm wins out and tells me it is 6v and the ring gaer has 138 teeth so that too is 6 volt. So even tho the truck has been converted to 12v I do have a matching flywheel ring gear and starter so I think I am good.

I will be changing the ring gear to a new one as it is chewed up in one area.
I will use a 6v one with 138 teeth to keep the match of the stater and flywheel.

Thanks to all who came to my help..........

I have the same issue with my 55 First series. It has been converted to 12V, but the starter was originally 6V and the ring gear is 139 tooth - My ring gear is very worn and will need replacing soon. My new starter is grinding about every 5th start Thinking of doing the clutch at same time if needed since labor to get the flywheel replaced will make clutch replacement "free" labor wise. The shop who rebuilt my starter said it will work just fine on 12V but run fast. the Owner was a man in his 70's who knows this starter and these old Chevy's well. What I am concerned about is if the now 12V starter will chew through a new ring gear quickly as well, even though the number of teeth is correct

Finding a 6 Volt ring gear can be a project. But..the ring gear can be gently removed, flipped over and re-indexed and re- installed. I did this to mine. It takes a shop with patience and care but it can be done. Disconnect the battery. Work the linkage by hand. With the cover removed from the bottom of the bell housing you can see just how and when the bendix drive meets the flywheel ring teeth. If the bendix engages before the switch, Good. If the switch engages before the bendix, Bad. The link arm that pushes the switch can be modified with a bit of weld(switch never contacts) or a bit of filing(if the switch contacts before the bendix and ring) The contacts on the starter can be replaced, turned around, and cleaned with a file to get a good connection. Lots of things can be done to this system. The engine tends to stop in one position(just the nature of the beast) moving the ring gear to another spot can reposition those worn teeth out of the most common starting spot. Like putting a new one on without a new one..:)

As long as the starter pinion gets engaged fully before the motor starts turning, the teeth won't wear excessively even at the higher voltage. One sneaky trick is to turn the ring gear over rather than replacing it. Tap the ring gear off the flywheel with a block of hardwood and a BFH, heat it with a torch to expand it, and drop it back on with the undamaged side of the gear facing the starter. Tap it down snug and straight as it shrink-fits itself to the flywheel as it cools.

It looks like Steve and I were typing at the same time!
Jerry

If you have trouble finding the ring gear, try Northwest Transmission Parts. They may have the ring gear you need, or they can machine yours as they have a machine shop as well.

http://nwtparts.com/

A.R.