12 Tooth Pinion Howl

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Model T Ford Forum: Forum 2013: 12 Tooth Pinion Howl
Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa - Poulsbo, Washington on Friday, August 30, 2013 - 09:42 pm:

I recently changed the gear ratio in my Ruckstell to a 12 tooth pinion and a 40 tooth ring gear. This gives a 3.33:1 gear ratio and I like the performance in my 16 Touring.

My problem is that is howls excessively. It has howled from the beginning.
I have about 1500 miles on it and there is no change.
I am using 75/145 synthetic gear oil.
The 12 tooth pinion is new (from Chaffins)
The ring gear is a 40 tooth (Ruckstell stamped) gear and looked to be new old stock. It had no discernible wear.

I have since removed the rear end and tore it down. Here is what I found.

The ring and pinion clearance is about 0.018 ( I set it up to 0.010)
The pinion has developed burrs at the leading and trailing tooth tips (see sketch). I have since filed them off.
No other defects were found.



The tooth geometry of the ring and pinion seems to be different.
The pinion teeth are more rounded compared to the ring gear teeth.
Look at the photo below. Both ring gears are 40 tooth stepped Ruckstell ring gears.
Notice that the tooth geometry on the bottom one is considerably more straight then the other.
The one in my rear end is like that.

Could this gear geometry mismatch be the cause of the howl?

Has anyone put in a 12 tooth pinion successfully?

Thanks in advance for your input.

Be_Zero_Be


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Friday, August 30, 2013 - 09:51 pm:

Bob
I thought it was supposed to be used with a 39 tooth crown. I have one but have not installed it yet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa - Poulsbo, Washington on Friday, August 30, 2013 - 09:56 pm:

Chaffins says it can be used with both.

Be_Zero_Be


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Friday, August 30, 2013 - 11:00 pm:

Why don't you blue the pinion teeth and see what the contact pattern looks and feels like.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Saturday, August 31, 2013 - 12:53 am:

The top gear is an involute profile and the bottom gear is straight cut. What does the pinion gear look like. They shouldn't be mixed. The straight cut gear teeth need more clearance or they wipe the tops of the gear teeth (as you experienced). This would cause the howling. If the pinion has an involute profile then it or the ring gear has what's called a positive variation. Probably caused by tooling being worn or the cut was too shallow. This leaves too much material at the top of the tooth form. In either case, the clearance would need to increase to compensate for tooth profile variance.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Saturday, August 31, 2013 - 02:03 pm:

The bottom gear is also cut to an involute profile and appears straight cut. Gears require involute profile on both teeth so they roll in and out of contact, rather than slide.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa - Poulsbo, Washington on Saturday, August 31, 2013 - 03:31 pm:

Ken & Ted,

Thanks for the information. I am going to change the ring gear to the one on the top in the picture above. I will post the results when I see how it works.

Best Regards,
Be_Zero_Be


Top of pagePrevious messageNext messageBottom of page Link to this message  By Glen Chaffin on Monday, September 02, 2013 - 02:45 pm:

Bob, I just noticed your post. Sorry In didn't respond sooner. Do not use the ring gear on top. It is worn out. The teeth have excessive wear and that is why they are rounded. It should look like the gear on the bottom. When you installed the 12 tooth pinion did you recheck the clearance? You cannot just change the gear and expect the clearance to be correct. We have over 500 12 tooth pinion gears in use with no problems. Yes, they can be used with both the original Ruckstell 40 tooth gear and the reproduction 39 tooth gear. In my experience the gears will only howl if they have insufficient clearance. This will also cause excessive wear. Could you post pictures of the gears that were howling? Gears will usually not howl if they have excessive clearance but will wear faster just like they do with insufficient clearance. My guess would be that you changed the gear and did nor recheck the clearance. You should have had no noise with 18 thousands clearance.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Glen Chaffin on Thursday, September 19, 2013 - 04:54 pm:

Bob, Did you recheck the pinion clearance after installing the 12 tooth pinion?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa - Poulsbo, Washington on Thursday, September 19, 2013 - 11:37 pm:

Glen,
I am going to initiate a Do-Over and take out the worn ring gear that I put in and go back to the original ring gear that I had. I think my problem all along was too little clearance. I will start it this weekend and post the results after I get it back in. Thanks for caring.

Be_Zero_Be


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