8 3/4 gear setup

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I wonder what it would measure, torqued down with the old crush sleeve in it.
Also make sure that inner race is seated in the case all the way.
 
Jadaharabi said:
Are you ready for my idea?
Take a pushrod or straight edge an mount it catty-cornered across the cap area.
It would be underneath the cap on one side of the carrier and the other would be underneath the cap on the other side of carrier so that the straight edge is above the back of the pinion.
Then take a caliper and measure from the back of the pinion to the bottom side of the pushrod or flat Edge.
Then you would add Shims in order to bring it up to that number that is scribed in the back of the pinion.
This is how aftermarket gears are set up. OEM not so much.
Anyway it won't hurt to try it.
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I had that same idea, but then I discovered the dead center of the carrier bearing bore, isnt exactly at the parting line of the cap. Your results may vary
 
SGBARRACUDA said:
With this tool. I have the same tool as in this video. If you ever plan to do it again, invest in this tool.
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Another tool (Miller) that seems to work pretty good. Call around to some rent-all outfits. Maybe they just happen to have it available..……
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Really, all this to set up a 489 once? Ill check my **** again. If were only looking for centerline of the ring gear to reference the pinion depth, Ill find it with some high school geometry. Job one is to mic the height of the caps to see if they are centerline with the diameter.
 
This will be a picture of the two caps off of a 489 housing against each other. You will notice they form a perfect circle. Which tells us that the other side of this is the housing must also form a perfect half circle so whoever comes up with this that the Caps are not cut in the center is full of crap.


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I also took measurements around the circle to make sure it was a circle. The only way these caps would work if they were not split at the center of the hole would be if one side was u-shaped.
 
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My measurement from the top of the inner pinion race that's the side closest to me to the bottom of the pushrod is 4.764. You can use that as kind of a reference to see if your race is hammered all the way in.
The bottom of the pushrod is in parallel with the center of the carrier or spool.
 
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Looking at the picture you would think that I was measuring from the top of that push rod which is not the bottom of the pushrod where the Centerline of the carrier is.
But what I did was calibrate the thickness of the pushrod at zero then I measured from the top to give me my measurement.
 
pishta said:
Really, all this to set up a 489 once?...….
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Actually, no, not "all" that is used setup a 489. I believe that kit handles 7-1/4", 8-1/4", 8-3/4", Dana 60, and includes a pinion race install tool.
 
sounds good, ill check it and tell you what I find to top of race. then Ill measure the thickness of the pinion gear to see if something is hinky there. Almost seems that the race is not completely in or the gear itself is 'thick' as I see no way to increase the distance from centerline to pinion top without any shims installed.
 
Daves69 said:
Actually, no, not "all" that is used setup a 489. I believe that kit handles 7-1/4", 8-1/4", 8-3/4", Dana 60, and includes a pinion race install tool.
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Not "all that" as in the kits equipment, but all the specialty tools to measure one thing.
 
pishta said:
Not "all that" as in the kits equipment, but all the specialty tools to measure one thing.
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I was shown the pushrod method back in 1975 when I was just out of the Army in El Paso Texas, working at the speed shop called The Pro Shop.
1 pushrod an a vermier caliper and you're in business.
My disclaimer this does not usually work on OEM gears because they don't have that pinion measurement etched into the back of them. Then you just have to go to swaping shims until you get the right set-up. There is a method to the swapping of the shims also but you don't need to know that at this time.
 
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The Pinion depth tool comes with info on most common rear ends that tells you the factory pinion depth for stock gears which is a good starting point. Any job you do is easier and better in the end when you use the correct tools.
 
Update: I looked at the pinion and how it was seated in the race and the darn thing was hung up on the bottom (yoke hanging down) by a shim (?) between the oil seal and the front bearing! The pinion threads were hanging the pinion up off the setup bearing by just a hair, that would explain the slightly rough turning of the pinion that I felt. After figuring that out (I popped the oil seal off and ditched the old bearing and some shim looking thing on top of the small bearing by the yoke) the pinion sat down and spun like a skateboard wheel. I placed the pushrod across the carrier and measured but I could not get a repeatable measurement due to the round nature of the pushrod and the swinging angle of the caliper depth probe. I needed a square beam across so I could get a 90 degree reference for the caliper to pinion measurement. I found a perfect fit from half of a tube flaring press. Its .550 square, straight, flat and fit between the caps. With this setup I measured the bare pinion (without any shims) to be 2.787 deep repeatably. So now I am confident that I only need a .020 shim under the pinion to bring it up to the spec'd 2.767 scribed on the pinion face. Makes much more sense than the old 2.607 measurement that I got when it was not fully seated in the race. First pic is 'spanner' over caps to provide a centerline reference, second pic is bonus of using a square stock over a pushrod as you can get a 90 degree reference for your caliper so you can get a repeatable X/Y axis caliper depth probe angle.
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Bearings are cheap. Buy a new one and hone it for a slip fit.
 
pishta said:
Update: I looked at the pinion and how it was seated in the race and the darn thing was hung up on the bottom (yoke hanging down) by a shim (?) between the oil seal and the front bearing! The pinion threads were hanging the pinion up off the setup bearing by just a hair, that would explain the slightly rough turning of the pinion that I felt. After figuring that out (I popped the oil seal off and ditched the old bearing and some shim looking thing on top of the small bearing by the yoke) the pinion sat down and spun like a skateboard wheel. I placed the pushrod across the carrier and measured but I could not get a repeatable measurement due to the round nature of the pushrod and the swinging angle of the caliper depth probe. I needed a square beam across so I could get a 90 degree reference for the caliper to pinion measurement. I found a perfect fit from half of a tube flaring press. Its .550 square, straight, flat and fit between the caps. With this setup I measured the bare pinion (without any shims) to be 2.787 deep repeatably. So now I am confident that I only need a .020 shim under the pinion to bring it up to the spec'd 2.767 scribed on the pinion face. Makes much more sense than the old 2.607 measurement that I got when it was not fully seated in the race. First pic is 'spanner' over caps to provide a centerline reference, second pic is bonus of using a square stock over a pushrod as you can get a 90 degree reference for your caliper so you
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Now your cooking with gas.
Good now you should be able to get it together.
 
Jadaharabi said:
Now your cooking with gas.
Good now you should be able to get it together.
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Great help all! :thumbsup:

OK here are some Yukon gear torque specs for the record. They also recommend that you set the backlash slightly under spec on gear side and then tighten the opposite adjuster to see if it opens up, if it forces backlash past spec, relax and go back and tighten gear side a little and repeat. This should set carrier bearing preload (no spec given) as well as backlash. Then proceed with getting adjusters as tight as possible with equal turns on both sides. Seems no one has an adjuster torque spec as this doesn't use a torque wrench interface, unless someone makes a crows foot adapter for an adjuster?
----------------pinion P/L (new-------used)----B Lash in thou---ring gear--cap torque--adjusters---pinion
8-3/4” ’89’ . . . . . . . . . . .14"-19" ... ..6-9" . . . . .6-10 . . . . . . .55' . . . . . .90'..........TIGHT.....210' min

TIGHT is as tight as possible with a 10-12" spanner once backlash has been set, tightening both equally so as not to disturb final backlash.

They also mention that as long as the drive side pattern is centered from root to top land under load, the coast side pattern is not critical as long as the back lash is to spec. It's the nature of the gear cut, not an adjustment.
 
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I hit the wrong button OK here we go I agree with U Rusty I read this quite a few times about Honing a bearing so I tried it with a Wheel cylinder Which is all I had at the time didn't work Real well so I bought an 80 grit ball home from mcmaster Carr I think it was about 20 bucks made real quick work of it worked real nice also made this yesterday since I'm doing the same thing only on A 741 case need to set up my gears Also. Thanks for the thread guys this is gonna help me a lot this weekend.
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Man I like that jig you made........but I have a suggestion......and no offense meant, I think it's great. But as you assemble that case, it's going to get really heavy. Those vise jaws may let you down holding that piece of round pipe stock. Why not take it out and weld a piece if say 6" x 2" 1/4" flat plate on the end? That would give the vise a better bite.

Just a suggestion. Your feet may thank you.
 
RustyRatRod said:
Man I like that jig you made........but I have a suggestion......and no offense meant, I think it's great. But as you assemble that case, it's going to get really heavy. Those vise jaws may let you down holding that piece of round pipe stock. Why not take it out and weld a piece if say 6" x 2" 1/4" flat plate on the end? That would give the vise a better bite.

Just a suggestion. Your feet may thank you.
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Copy that rusty we did think about That but opted to machine 2 flats on the end of the round bar that is clamped in the vice I think what I will do is make those 2 flats the whole length of the vice and give me a lot more strength. we were able to put a lot of weight on it and it didn't budge so I think will be all right but thanks for the suggestion
 
Mysons68dart said:
Copy that rusty we did think about That but opted to machine 2 flats on the end of the round bar that is clamped in the vice I think what I will do is make those 2 flats the whole length of the vice and give me a lot more strength. we were able to put a lot of weight on it and it didn't budge so I think will be all right but thanks for the suggestion
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Well keep it in the back of your mind.......cause it it decides to move, it's gonna do it all at once.
 
RustyRatRod said:
Well keep it in the back of your mind.......cause it it decides to move, it's gonna do it all at once.
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Well rusty believe it or not i think # 1 priority is safety My son made this for me yesterday when I was out and thought the flats would be enough to hold it but I think you're right
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so hows this. We can both sleep easier tonight lol.
 
Jadaharabi said:
This will be a picture of the two caps off of a 489 housing against each other. You will notice they form a perfect circle. Which tells us that the other side of this is the housing must also form a perfect half circle so whoever comes up with this that the Caps are not cut in the center is full of crap.


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I also took measurements around the circle to make sure it was a circle. The only way these caps would work if they were not split at the center of the hole would be if one side was u-shaped.
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I can tell u that maybe 1/3 of the diffs I do has the caps cut in the Center of the circle. I have been doing diffs for 40 years. The proper tools are by far the best and the fastest to use. The old school way was to install the pinion with the factory shim and see what kind of a pattern u got. Then u guessed what shim u would need. When I first started doing diffs I could not beg, borrow or steal the arbour set up. Kim
 
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