Oil gear backlash

[NoMoreCash]

I have scoured the old posts on the oil pump gears and backlash. The last one I read said that backlash didn't matter as the gears seal when they are driven. I understand this and think that the oil pressure is not greatly affected by the back lash because of this. But I am concerned with the back lash when it is larger than what is recommended, specifically for maintaining the prime of the pump. Wouldn't a larger gap be prone to losing the prime when the engine sits?
I have just redone my 9N engine and put it all together, started it up (sounded good) and had initial pressure of 30 pounds on a new gauge. When I turned it off, 30 min later it had no pressure when I tried to restart it. I had to prime the oil pump to get it to get pressure. Upon inspection of the oil pick up tube showed some movement, so I took off the nicely matched oil pan to inspect closer. I discover that the solder joint on the pick up tube had cracked, so that could be the main reason for the loss of prime, but upon closer inspection of the gears they have .024 inches of clearance for the backlash. So before I put it back together I am hoping that I can get some comfort in knowing that this much backlash is going to be okay and I won't have to have the oil pump pulled a second time to correct this. I did take the pickup tube and brazed the joint, it seems much more solid than before. Anything else I should consider, or do I just put it back together?

Thanks for your thoughts on this ahead of time.

 

[HFJ]

i have no clue on the backlash, but have u rotated the crank to be sure you're not going to hit the pickup now? it doesn't take much of a change from its original position to put it in harm's way.

 

[TheOldHokie]

(quoted from post at 01:44:52 03/13/20) I have scoured the old posts on the oil pump gears and backlash. The last one I read said that backlash didn't matter as the gears seal when they are driven. I understand this and think that the oil pressure is not greatly affected by the back lash because of this. But I am concerned with the back lash when it is larger than what is recommended, specifically for maintaining the prime of the pump. Wouldn't a larger gap be prone to losing the prime when the engine sits?
I have just redone my 9N engine and put it all together, started it up (sounded good) and had initial pressure of 30 pounds on a new gauge. When I turned it off, 30 min later it had no pressure when I tried to restart it. I had to prime the oil pump to get it to get pressure. Upon inspection of the oil pick up tube showed some movement, so I took off the nicely matched oil pan to inspect closer. I discover that the solder joint on the pick up tube had cracked, so that could be the main reason for the loss of prime, but upon closer inspection of the gears they have .024 inches of clearance for the backlash. So before I put it back together I am hoping that I can get some comfort in knowing that this much backlash is going to be okay and I won't have to have the oil pump pulled a second time to correct this. I did take the pickup tube and brazed the joint, it seems much more solid than before. Anything else I should consider, or do I just put it back together?

Thanks for your thoughts on this ahead of time.

Backlash is the running clearance between gear teeth in mesh. What are you measuring that gives you .024 backlash and how? That would be an awful lot of wear. Did you measure the face width of the new gears? That seems to be the most common issue.

TOH

 

[NoMoreCash]

Thanks for the quick response! When I had the engine apart and in the machine shop I ask him to replace the pump with new gears. I didn't measure the gears with a caliper but the gears now look new with no wear marks. When I rotate the Drive Gear it looks like it has about 1/16" of play before it engages with the idler oil gear which is .o625 inches if my new math is right. The backlash was then measured with a feeler gauge at .024. (I measured the face of one gear tooth to the back face of the other gear tooth) I am nervous about the gears after reading about how some of the "new" gears are poorly replicated. Because of this I ordered two new oil gears from YesterdaysTractors to have just in case. They arrived today, and upon close inspection the one idler gear that is currently installed seems to have more rounded corners on the teeth (the area that would ride against the landing area of the body) while then new ones received are more squared off at the corners. The installed also seem to be cut just a bit differently when you take the new gears and interlock them. The ones currently installed don't seem fit as deep into each other as the newer ones just received.
I hope this clears up some stuff. I am now thinking I should go ahead and replace the gears because of the rounding of the gears currently installed. The question I now have is how hard is it to remove the pressed gear from the shaft of the drive gear? And would I have to have new bushings installed or if they are close enough can I just pop them in? Again thanks for the insights.

 

[NoMoreCash]

I did get a measurement of the gear width, (face) and the gear currently in it measures 0.567. The new gears I just received measure 0.562. I believe these are within specks.

 

[NoMoreCash]

Thanks for the reminder. I turned over the crank and had atleast 1/2" of clearance from the tube. Hopefully it lines up with the oil screen in the bottom of the pan. I will be checking this too.

 

[TheOldHokie]

(quoted from post at 15:34:23 03/13/20) I did get a measurement of the gear width, (face) and the gear currently in it measures 0.567. The new gears I just received measure 0.562. I believe these are within specks.

If that is accurate the old gear is. 005 over. That is not within "specks" and should be rubbing/binding on the cover. What are you using to take measurements? Aso please explain how you got .024 backlash.

TOH

 

[TheOldHokie]

(quoted from post at 18:50:30 03/13/20)

(quoted from post at 15:34:23 03/13/20) I did get a measurement of the gear width, (face) and the gear currently in it measures 0.567. The new gears I just received measure 0.562. I believe these are within specks.

If that is accurate the old gear is. 005 over. That is not within "specks" and should be rubbing/binding on the cover. What are you using to take measurements? Aso please explain how you got .024 backlash.

TOH

Missed the other post. If you have .024 clearance measured with a feeler gauge between teeth the gears are junk. If the bushing was properly reamed you can swap gears with no problems. Visual impressions are worthless- you have to measure and accurately.

TOH

 

[NoMoreCash]

Thanks for the post! I guess I will take out the old gears and press on the new ones that I have to see if that makes a difference.

Thanks again!