10-bolt setup...final pattern check, posts #54 & #55 - 4/20/2008

[jonrpick]

I'm back at it, trying to set up the backlash on my 10-bolt.

I bought a "master install kit" which has shims, bearings & races, seals, etc... The shims that came in the kit measure out like so: there are four .100" shims, and several .020", .015" and .010" shims.

Ok... so, using the original shims, I am seeing about .013" of backlash, and it needs to be between .008" and .010" as I understand it. So I turned to my shims in the kit.

The stock shims measure out at .225" (left) and .255" (right). When using the supplied shims in the kit, do I measure them individually and add them up, or measure the entire shim pack/stack?

The reason I ask is...I get different measurements depending on which method I choose. Maybe it's because the new shims aren't perfectly flat, and will flatten out once installed??? Reason I ask is, I added them numerically rather than measuring the entire shim pack, and it's TIGHT. According to the guy in the axle rebuilding DVD I'm watching, after getting it all right, you should add a little shim to both sides (in equal amounts) to set the preload on the new carrier bearings.

Either way, the total amount of shim with the original ones was .480", and when added up, the new ones total .480" as well. I shimmed it .005" toward the pinion to decrease backlash, and now backlash is sitting at .007". The dude on the DVD says that's too tight. In fact, that guy actually was at .007" when he first set it up and he changed it.

Also... He had a pimp shim kit. His kit had shims as thin as .002". Do I need a better shim kit?

 

[readymix]

I have always had shims smaller than .010, and shoot for a BL of .008

Are you setting up a used gear set or a new one?

 

[Hogback Fabrication]

Usually the kit will include shims thinner than .010" but you will probably be able to get it withing spec with the shims you have.

I always measure each shim individually and add them up to determine the overall thickness. The shims will compress together when you tap the carrier back in. Make sure the shims are very clean (though based on your previous work on this diff I'm sure everything is spotless )

If .480" worth of shim came out, that's how much should go back in. There is a spec for carrier bearing preload (you measure it just like you measure pinion bearing preload) but I don't usually worry about it too much. When I am setting up gears I usually have the shims packs thin enough that I can just barely install/remove the carrier by hand and then add ~.003" total shims upon final assembly (which requires tapping the carrier in with a hammer).

If you wanted to run it as it is, .007" is probably fine. There are plenty of diffs that spec backlash as low as .005".

On the other end of the spectrum, the engineers that designed it would look at it as .009" +/- .001".

If I was setting up the gears I would change the shims and shoot for .009" backlash.

For people that care more about strength than longevity and noise, less backlash generally means more ring and pinion strength.

 

[jonrpick]

I have always had shims smaller than .010, and shoot for a BL of .008

Are you setting up a used gear set or a new one?

The gears are *slightly* used, like a few thousand miles (well under 10,000)

Usually the kit will include shims thinner than .010" but you will probably be able to get it withing spec with the shims you have.

I always measure each shim individually and add them up to determine the overall thickness. The shims will compress together when you tap the carrier back in. Make sure the shims are very clean (though based on your previous work on this diff I'm sure everything is spotless )

If .480" worth of shim came out, that's how much should go back in. There is a spec for carrier bearing preload (you measure it just like you measure pinion bearing preload) but I don't usually worry about it too much. When I am setting up gears I usually have the shims packs thin enough that I can just barely install/remove the carrier by hand and then add ~.003" total shims upon final assembly (which requires tapping the carrier in with a hammer).

If you wanted to run it as it is, .007" is probably fine. There are plenty of diffs that spec backlash as low as .005".

On the other end of the spectrum, the engineers that designed it would look at it as .009" +/- .001".

If I was setting up the gears I would change the shims and shoot for .009" backlash.

Problem is, because of the shims I have, I can adjust a MINIMUM of .005".

The shims I have now are like this:

Left
(2) .100" shims
(2) .015" shims
Total of .230" (was .225" originally)

Right
(2) .100" shims
(2) .020" shims
(1) .010" shim
Total of .250" (was .255" originally)

This all adds up to .480" total "shimmage"

 

[readymix]

.005 shim will not always equal a .005 change in the BL measurement.

Do you have the pinion depth set correctly, or just in the ballpark until you deal with the BL a little longer?

 

[Hogback Fabrication]

If you run it at .007" and have a good pattern the gears will probably live a long and quiet life. It all depends on how picky you want to be about it.

If I didn't have the shims to get the backlash from .007" to .009" I would probably just run it.

 

[jonrpick]

.005 shim will not always equal a .005 change in the BL measurement.

Yeah, I know... The fact that the two measurements are within few thousands of an inch is almost coincidental... I'm just saying that the smallest adjustment I can make to the carrier bearings is .005".[/quote]

Do you have the pinion depth set correctly, or just in the ballpark until you deal with the BL a little longer?

Ballpark... it's got new bearings with the original shim in there as a starting point.

 

[jonrpick]

If you run it at .007" and have a good pattern the gears will probably live a long a quiet life. It all depends on how picky you want to be about it.

If I didn't have the shims to get the backlash from .007" to .009" I would probably just run it.

Which is worse, slightly too loose or slightly too tight? The .007" is much closer than the .013" I started with.

Actually, going back to Readymix's comment... The dude on the DVD was at .007" and he shimmed it .002" toward the pinion, and got right at about .0085". In my mind I agree that .005" of shim shouldn't make .005" of difference in backlash, but actually, my .013" was probably between that and .012"... and if I'm at .007" BL now, then the .005" shim DID make almost exactly that much difference in backlash.

 

[readymix]

Set the BL to .007 and check the pattern. I doubt you will need to, but you may need to move the pinion, and I would verify that before you start playing games with the carrier shims.
After that is verified, then let the games begin. In a case like this you should be glad you don't have a D60....it would get ghey real quick.

 

[readymix]

It depends on where the pinion is sitting at. If you have the depth set correctly it will be close enough to a direct ratio.

 

[Hogback Fabrication]

Go ahead and take a pattern and see where you are at (feel free to post up pics).

If you aren't changing ratios the original pinion shim will almost certainly be the right one.

 

[jonrpick]

Interesting info:

"factory specs for recommended backlash in a 8.5 inch 10-bolt
are : between .005 - .009. Performance differential shops typically use .008 - .010 . I setup my last one at .007 - .008
using new gears and it has remained quiet for me."

http://answers.yahoo.com/question/index?qid=20070201141606AARSMpc&show=7

Granted, that's not an "official" source...

The guy on the DVD says between .008"-.010"...but I just watched that part again and he specifically says, "the manufacturer of the gears". So apparently that's for the gearset, per THAT manufacturer, not necessarily GM. Can anyone clarify? I just read on another forum that GM specs it to .006"-.010".

 

[jonrpick]

Set the BL to .007 and check the pattern. I doubt you will need to, but you may need to move the pinion, and I would verify that before you start playing games with the carrier shims.
After that is verified, then let the games begin. In a case like this you should be glad you don't have a D60....it would get ghey real quick.

It depends on where the pinion is sitting at. If you have the depth set correctly it will be close enough to a direct ratio.

Go ahead and take a pattern and see where you are at (feel free to post up pics).

If you aren't changing ratios the original shim will almost certainly be the right one.

Well, I'm gonna do it... Between posting I ran out and played around (made it worse... .003"!!! ) I'm getting fast at this... I'll put it together and run a pattern and take pics to post...

Be back in like 20 probably.

 

[readymix]

Here is what my book says.

Old gear style: .006 - .010
New gear style: .003 - .006

 

[Chevy305]

i really wouldn't worry about it. run it as is. If the gears blow up first drive out I'll buy you a new set... jk

 

[Hogback Fabrication]

Here is what my book says.

Old gear style: .006 - .010
New gear style: .003 - .006

Which book is this?

.006-.010" sounds right to me.

I've heard something about newer front ends needing some unique gear setup techniques (i.e. their patterns are different than most gears)

 

[readymix]

The IFS rigs are speced to .006 - .010 also. The only difference in setting up these gears is the clamshell case. Kinda like a Toy IFS front end....just a little bigger.

Book is from Yukon.

 

[jonrpick]

Well guys... I get out there, change it back to the way I THOUGHT it was... I'm at like .004".

Well, I'd shifted shims around earlier to experiment. Apparently, I knicked one of the big .100" shims, and the others don't appear to be consistent, even within the same shim... Taking the digital calipers around one single shim will give varying measurements +/- .002".

Since I may have damaged one, I'm gonna hold off tonight, and go to 4Wheel Parts tomorrow and get a shim kit (hopefully they'll actually have it in stock).

I'll update then...

 

[AddictedOffroad]

I set up a lot of gears. Whenever you set up a used set of gears, ignore the drive pattern. The coast pattern is more important than the drive pattern.

FWIW, I am going through a hell of a setup with my rear 12 bolt. The gears are GM legit 4.56s. But have a couple thousand miles on them. The previous owner had a "buddy" do the install. We'll he didn't crush the crush sleeve and the pinion had slop for and aft as well as in and out. It would roar when turning right.

Another issue was that the carrier bearings weren't shimmed correctly and were way too loose. You could literally move the carrier back and forth(left and right) at least 1/8" in either direction.

Anyway, the issue that I have found is that the gear pattern is so worked over, that I can't get a decent pattern on the coast side. Drive side looks fine, but the coast side is more important on used gears.

Also, spec for a 10 Bolt is as follows:

 

[jonrpick]

Ok... BL is back at .007". I'm aboot to run my first pattern. I got new shims today, but they're basically identical to the other set I have. The smallest movement I can theoretically make is .005", and that's only when using a .015" shim.

Also... when I add up the shim values in my head, the measured value always ends up much higher. The shims were so tight that I could barely get them in, and getting the carrier back out was *very* difficult. That doesn't seem right to me.

Anyway, the current setup was arrived at after stacking the shims and THEN measuring the ENTIRE stack. I was able to get the 2nd shim in next to the carrier with the same amount of effort as the original shims required. Only difference is that these are new bearings.

Does anyone think this will be a problem. If I need to add even more pre-load on the bearings, I'm not sure I'll be able to, unless I want to add .010" to each side, which seems excessive.

Worst case scenario, I had little faith in the Motive Gear shim kit from Advance Auto (they were the only ones who could get me shims TODAY), so I also ordered a real adjustable shim kit from 4Wheel Parts, should be here hopefully Friday or Saturday at the latest. It *should* have shims as thin as .002", so we'll see.

Thoughts?