Reading the tea leaves (or is it starting a fight) about ring gear patterns..

[Miranthis]

I got my 8.75 center section set up. I set the pinion gear shims with the jig; it called for 2.770 and I got it to 2.7695 depth. Then set the preload per the Dr. Diff specs. Then buttoned up the pinion, seal and all, and set the backlash right on 0.007, in the sweet spot called f for. Torqued the caps and such and this is my first pattern...

The various folks I have been reading on the net lead me to believe that his is pretty well centered heal to toe, but too much to the crown side of the drive teeth (2nd pic). Same on the coast side (1st pic). As I understand it, moving the pattern to the root a bit to get the 'football' or 'cheeseburger' patterns means ADDING shim to the pinion gear (Back to step ONE), correct?

Putting on my asbestos jacket, I turn to you all and ask, what would you do with this pattern??

 

[RustyRatRod]

I very VERY rarely pay attention to what the coast side is doing. You can drive yourself batty doing that. I get the drive side lookin right and let it ride. That said, IMO, you COULD go just a HAIR deeper on the pinion depth......maybe another .010" shim. But I'm not sure I'd yank it back apart for that. I might.

 

[RustyRatRod]

And just so you know that I have set gears up in the past, here's my latest set. This is something I've done a LOT of.

Thread 'Gear Pattern'

Oct 18, 2023

This is the Ford 9" I have going in Vixen. @Garrett Ellison and I have talked it over and we feel pretty good about this gear pattern. What do yall think? Sorry it's not 100% in focus, but you get the idea.

• RustyRatRod
• Replies: 13
• Forum: Transmission and Drivetrain Tech

 

[Miranthis]

I am gonna check it in two more places on the ring and see if the pattern is the same. If it is, I will call it good. The car is probably 10-12 months out from needing this, so I can mull it over. I know my next closest shim stack put me at 2.7715 (as opposed to 2.7695 that is in it now) and the printed spec on the pinion is 2.770.

 

[RustyRatRod]

I am gonna check it in two more places on the ring and see if the pattern is the same. If it is, I will call it good. The car is probably 10-12 months out from needing this, so I can mull it over. I know my next closest shim stack put me at 2.7715 (as opposed to 2.7695 that is in it now) and the printed spec on the pinion is 2.770.

Well, just remember, that number they give you is a guide to get you close on the pattern. The pattern is the end all be all. I don't remember ever setting one at the given number and being happy enough with the pattern to leave it. Yours does look pretty good though.

 

[George Jets]

Your's looks good the way it is now, nice pattern.

Final test is to put it in the car, fill with gear lube and friction modifier additive then take it out and drive it around the block.

The heat test, feeling it by hand will tell you a lot.

If you feel the housing is warm to touch you are probably good to go. If you feel the housing is "Hot" then the gears are too tight.

It is said a 500 mile break in is good, and then change the fluid again. (Easier said than done with the 8 3/4)

Driving figure 8s in a large shopping mall parking lot is good for breaking in the Sure-Grip Clutches too.


☆☆☆☆☆

 

[Desoto291hemi]

Run it,,,you will never know anything is off any .
It’s not black magic,,,it’s just a ring and pinion .
If your readings are truly correct,,,it will work fine .

Tommy

 

[john-9]

i would try to improve on the pattern ,, if the patterns shown are at the checking distance 2.770 i would have added 0.003 to the shim you have and check the pattern again . on the 8-3/4 with too much toe (pattern towards inside of the ring gear ) you take shim out ,, to much heel ( pattern towards outside of the ring gear ) add shim . make your shim changes in 0.003 increments . as stated above the checking distance is a start but final say is the gear pattern. pattern should look like this pic.

 

[Miranthis]

Ok, mover the pattern to the root a bit and it is more roundish. But, now the pattern is out on the heel a bit

. I adjusted backlash to 0.006. Ideas?

 

[Miranthis]

Ok, to compare, this was my initial pattern with 0.0315 of shim and backlash at 0.007

Seemed a bit too much on the crown as opposed to the root. I had available shim stack combinations of 0.0330 and 0.0340 so went with the 0.034 (original shim from the previous ring gear) that added 0.0025. The backlash was at 0.006. This pattern resulted:

Opinions? I even going to zero backlash did not center the pattern left to right, but the crown/root looks better, I think.

I am all out of pinion shim combos from my Doctor Diff kit.

 

[Miranthis]

Somebody gonna tell me I had drive and coast sides reversed? chat gpt and Gemini lied to me. . Here is the drive side after the 0.0330 shim, back to middle of the available stacks. Backlash 0.007

 

[RustyRatRod]

Somebody gonna tell me I had drive and coast sides reversed? chat gpt and Gemini lied to me. . Here is the drive side after the 0.0330 shim, back to middle of the available stacks. Backlash 0.007View attachment 1716462996

I believe I would run that.

 

[john-9]

yes much improved drive pattern ,, when you get the drive pattern right the coast will be ok as well ,, that's the type of drive pattern i shoot for in my in my differential builds as shown in my previous post ,, run it ,, now as long as you have the pinion bearing preload set correctly ( 8-15 in/lbs with used bearings 20-25 in/lbs for new bearings ) and backlash at 0.007 - 0.009 you should be good to go.