Technical Acceptable 9" rear end gear pattern........opinons please.

Rogga, I'm no expert but something just came to mind. You have 3:50 gears. Is the tooth count 42 and 12 ? If so that's a gear set that is what is known as timed. You see 3 will divide into 12 and 42 with answer of 4 and 14 which also is 3.5 when divided. Look for timing marks on your gears and while you do that I try to find a picture of what I'm talking about. It's a long shot on a non lapped gears set but all avenues must be explored.

 

This photo's are from Squirrel another member here that helped me on a set up question.

 

You may try moving the pinion in a bet

 

Hi Johnny!
If I remember right it was 35 and 10 , and could not find any marks on it.
Thanks ! // Roger .

PS. Any thoughts about Lucas Oil in it?

 

I have some used gears laying around these are 3:25 with 39 and 12 tooth, and a 2:75 with 44 and 16, these gears are marked and these are original Ford gears.

 

You mean thinner shims on pinion cartridge?
I started with .023" and working Down to .011" and stopped there when I was happy with the pattern......... I dont know why I didn't go lower and test it too.
If I must take it apart Again I'm gonna test it.
Thanks! //Roger .

 

Hi. Johnny.
I did some math here and my gears should be marked. I divided with 5 and got 7 and 2.
But I could't find any marks.......... :-/

 

Yes looking at the pattern it is wiping off the edge of the ring gear.

 

Take a careful look at each tooth after you clean it up. It only takes one small nick or burr to make it whine in the car. Good Luck

 

We tried.

 

Did your backlash change? It was .008? Did you check it after your test drive? Did you check your pinion preload to see if it has changed? It was 15inch lbs? I'm asking because one or the other of those has changed, if you know which has changed then you'll know what to adjust.
If the backlash changed and your preload is the same then your carrier has shifted; if the preload has changed then the pinion has moved (assuming they both didn't move, being a hot rod it is a possibility).
Did you clean the backside of the ringgear? The metaltreatment process can leave a residue, gear mfgrs reccommend getting a perfectly flat (like a big piece of glass) suface and fasten some 600grit (I think) sandpaper to slide the back mounting surface of the gear to true it up and remove that residue.

 

Rogga, here's an interesting read I found. http://www.fordmuscleforums.com/all-ford-techboard/565561-9-inch-gear-timing.html

 

Hi!
The backlash was the same, I took the pinion apart for inspection and put it togehter again, I was not able to measured the preload again ( inch/lbs torque wrench was borrowed at the first set up). I figured out now there was an issue with the first set up, when setting preload with adjustable spacer I did 125ft/lbs on nut and the final assembly 155ft/lbs plus the seal, that was now too much preload I think, did some experiment and add 0.004" shim .
This setup is now in car and under break-in period, let's see what happen........

Yes, I sanded the surface on backside of ringgear, and the run-out was 0.0011" ( 0.025mm).

Thanks // Roger.

 

Hi!
Interesting reading!
If I was buying gears today it would be 3:55 , just for eliminate some kind of trouble.
Thanks! //Roger .

 

I think I torque the pinion to over 200ft lbs - I made a 4' long bar to hold the yoke and use an extension on the breaker bar - probably over 250lb pounds. Torqueing that nut won't affect pinion preload once it is shimmed proper, your job is to make sure that nothing can shift. And you really have to get after it. Doing rears is as much brawn as brain, nothing delicate about them.
I also use loctite on the pinion nut.
Let us know how you do, this has become a very good thread and we'd like to see a happy ending.