Another 8 3/4 how’s my pattern?

[chrgdrt]

This is my first attempt at rebuilding an 8 3/4, 489 case using crush sleeve eliminater, new Richmond 3.91 gear set and reworked cone style sure-grip.
First hit looks to me like the pinion is a bit too deep. .038 under the bearing and backlash set at .007.

 

[Illahe]

This is my first attempt at rebuilding an 8 3/4, 489 case using crush sleeve eliminater, new Richmond 3.91 gear set and reworked cone style sure-grip.
First hit looks to me like the pinion is a bit too deep. .038 under the bearing and backlash set at .007.

View attachment 1716461200

View attachment 1716461201Is your pinion gear set to the spec etched in the gear? Looks too dep as you've stated. Do you have an inner pinion bearing that's slip fit to mock the depth up? Honing the press fit out of a spare inner pinion bearing works. Patience is the key...

 

[chrgdrt]

Yes the depth was set using the Ratech setting tool but there was some variation in the fit of the tool
Click here forPinion Setting Tool Diagram

 

[Illahe]

Yes the depth was set using the Ratech setting tool but there was some variation in the fit of the tool
Click here forPinion Setting Tool Diagram

I use a straight edge across the cap saddles and a magnet on the pinion gear with a dial caliper measuring the depth off the straight edge. Its not the best, but gets me within .003" and then I pattern from there.

 

[RustyRatRod]

Just remember the numbers on the pinion gear are a guide to get you close, not the end all be all. So many people think that's right where they need to be. It's not. You get close first and then zoom in with the pattern. The pattern IS the end all be all. Here is how mine turned out. Notice how dead center of the teeth my contact patch is. That's what you're looking for. If I was doing yours, I'd remove .010" from the pinion shim pack and back it our just a little. That'll probably get it dead on.

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

 

[George Jets]

Hats off to you for giving it a go, soon you will be "Expert".


* * * * *

 

[ValiantRacing]

I gave up the pinon depth tool years ago, the calculation would be so far off, when you go and check the pattern, i had Tom from Toms Diff, said checking the depth was a waste of time, and only go off the pattern only.

 

[RustyRatRod]

I gave up the pinon depth tool years ago, the calculation would be so far off, when you go and check the pattern, i had Tom from Toms Diff, said checking the depth was a waste of time, and only go off the pattern only.

He's right, essentially. I use the tool and checking depth, but only to "get in the ballpark". Sometimes the ballpark is pretty big. LOL

 

[Garrett Ellison]

A precision ground parallel across the cap flanges and a depth mic makes quicker work of setting the initial recommended pinion depth compared to most pinion depth tools. But yeah, pattern is the last word.

 

[RustyRatRod]

I've had a FEW come out dead nuts on using the checking distance on the end of the pinion gear. I think the reason for discrepancies is how the end of the pinion gears are machined or finished. For "whatever" that's worth. lol

 

[Garrett Ellison]

I’ve only seen a few short videos of the process of lapping gears in together, but the numbers stamped in the pinion for depth are a “best guesstimate” based on a set housing dimension number given to the person who is running the gearset in together on the machine. When you think about the margin for error housing to housing, we’re usually pretty fortunate the numbers come in as close as they do most times.

 

[chrgdrt]

Second hit, took out .011 out of pinion, back lash @ .007-.008.
Pinion depth on drive side looks better, a little shallow on coast and backlash needs to tighten up a bit.

 

[Garrett Ellison]

You're really close, just a couple of thousandths or so too much shim.

 

[john-9]

you are going in the wrong direction as far as shim changes ,, first try was closer to being good ,, make your shim changes in 0.003 increments up or down ,, scroll down on this page and read postings under -- check my tooth pattern -- your backlash is ok

 

[Daves69]

Yes the depth was set using the Ratech setting tool but there was some variation in the fit of the tool
Click here forPinion Setting Tool Diagram

Some trial and error is not unusual with a tool you've never used before IMO.

The old shop setup tool has a learning curve as well....

 

[Garrett Ellison]

you are going in the wrong direction as far as shim changes ,, first try was closer to being good ,, make your shim changes in 0.003 increments up or down ,, scroll down on this page and read postings under -- check my tooth pattern -- your backlash is ok.

Taking shims out of the pinion will move the pattern out closer to the edge of the ring gear and seat the pinion deeper into the bevel of the gear. I try to set backlash to the tight side of spec as well. The goal is to ensure maximum available tooth contact. That’s where the gears are lapped together at.

 

[RustyRatRod]

Taking shims out of the pinion will move the pattern out closer to the edge of the ring gear and seat the pinion deeper into the bevel of the gear. I try to set backlash to the tight side of spec as well. The goal is to ensure maximum available tooth contact. That’s where the gears are lapped together at.

I've told this story multiple times, but it's 100% true. I have a friend who lives about 50 miles away who is a retired drag racer/mechanic/tow truck driver, ect., ect, ect. He's in his 80s now. But for the over SIXTY years he drag raced, he set all his own gears up and always set backlash to zero and let it "wear in" any backlash. lol He never had a failure. He said the exact same thing you just did. That it gave the biggest contact area for the gear pattern.

 

[Garrett Ellison]

I've told this story multiple times, but it's 100% true. I have a friend who lives about 50 miles away who is a retired drag racer/mechanic/tow truck driver, ect., ect, ect. He's in his 80s now. But for the over SIXTY years he drag raced, he set all his own gears up and always set backlash to zero and let it "wear in" any backlash. lol He never had a failure. He said the exact same thing you just did. That it gave the biggest contact area for the gear pattern.

Now that's interesting! I'm guessing he "preloaded the ring gear against the pinion to very tight" and then moved the opposite adjuster in to just loose to preload the carrier bearings and thereby pre-stress the case in the direction of load. I'd be cringing at the thought of trying highway trip that with the oil clearance running that tight but I imagine it's great with a set of high nickel drag gears getting beat on with big shock loads...

 

[oldkimmer]

Second hit, took out .011 out of pinion, back lash @ .007-.008.
Pinion depth on drive side looks better, a little shallow on coast and backlash needs to tighten up a bit.

View attachment 1716462004

View attachment 1716462005

Like John-9 said u went the wrong way. U need to put the 11 back in as well as about .006 is my guess.