I have have measured my stock shims will I need to worry about setting the carrier preload wrong? How does everyone here do it? The service manual is pretty vague.

 

put one shim on one side of the carrier, install the cap, find a shim that is a tight fit to place on teh other side, coax it in, tap it lightly with a hammer if you must, install that cap and when you tighten the second cap down it will draw the shim / shims into place

 

How much interference should there be beyond having the shims just slide in? I have heard differing amounts, .004", .008", etc.

 

i dunno... i just find one thats tough to get in and force it, Ive only done a hand full of rears... look at the write up in the stickys there is a lot of info there

 

I know mine was tight as hell from the factory when I rebuilt it. I measured the shims as you did and put back the same total number as the factory cast shims.

BUT........I'm about to go back into mine because it's making noise although I think it's the torsen making the noise. I'll repost on how the carrier bearings look when I get in there. I remember from technical school (go Wyotech!) there is supposed to be .004 to .008 in carrier bearing preload though.

 

every time i checked the width of a shim on my caliper it came up 0.002 to 0.0005 different anyway... go Mitutoyo!!

 

I have found the stickies good for everything except carrier preload. Most people pack in the original shim total thickness and its fine. GM's manual is pathetic at describing this one area.

The table for preload measurement is as follows:

• Measurement of torque drag on pinion with only the pinion mounted. Different value for new or old bearings, and a seal is to be in place.
• Then a total torque drag with the carrier added in as measured at the pinion nut (the one you are turning)

Unfortunately the manual gives no clue as to the oversizing of the shim pack despite the fact that that used to be the way they used to spec it out, I guess they switched to this method of total pinion drag.

 

ahhhh, its really not that critical... (watch what happens to this post now that i said that) you just have to have some difficulty getting the second shim or sims in, there has to be some interference, you will figure it out when you try it, you should be able to tap it in pretty far with a small hammer and let the cap draw it in teh rest of teh way. IF you find the shim went in too easy, its too thin, if you have to beat teh **** out of it to get it 1/2 way in its too thick, but it dont matter anyway because you will probably have to take it out again once you see the pattern your getting, unless your lucky and get it the first shot

 

Found this in a quick Google search

Step #7 - GM rear cover style housings use shims on the outside, between bearing cup and housing, adjusting backlash and carrier bearing pre-load If starting with a bare housing, or you are installing a spool or different carrier, before you mount the ring gear, establish equal shim pack on each side of carrier and enough to create a drag when you slide it in and out of the housing by hand. Keep in mind you should keep the thickest shim next to the bearing cup. With a little loctite on the threads of the rings gear bolt, mount gear to carrier or spool. After adjusting shim pack to get proper backlash and once you have established your pattern, remove carrier and pinion. Now is the time to install crush collar and pinion seal. NOTE" Always use loctite on the pinion nut. If you do not have a rear end housing spreader, you will have to work at installing the carrier once you add more shim to pre-load the carrier bearings. As a rule of thumb all carrier bearings will require .010 pre-load After adding .005 to each side of the shim pack, coat surfaces of the shims with axle bearing grease to hold them in the housing, make sure the cups stay straight. Using a plastic or brass hammer, gently pound on bearing cups side to side until carrier has seated in housing. Again, it is important that you keep the cups straight during this operation. A spreader is almost necessary for all Dana Model rear ends. Torque caps to proper torque value.

from here...

http://www.coastdriveline.com/htmlfo...oninstall.html

This is another pretty informative link..

http://www.chevyhiperformance.com/te..._gear_install/

 

Actually... it is somewhat critical... as it is a major part of the backlash equation.

It is always in ones best interest to purchase a "supershim" kit when building up your parts list.

You dont really need a case spreader unless your dealing with D60, 70 and 80 series differentials.

The three things you need to pay attention to are...

"Backlash." Definition: The amount by which a tooth space exceeds the thickness of an engaging tooth. Think of it as... play between the mating teeth of gears or how tightly the ring and pinion gears mesh together.

How Measured... Measured as the free movement of the ring-gear with pinion held steady, in thousandths of an inch, using a dial indicator on the ring-gear. In other words, you’re measuring how much you can rotate the ring-gear before it engages the pinion teeth – this is the space between these teeth is known as “backlash.”

It is adjusted via... the carrier shims. Adding shims on the ring-gear side of the carrier moves the ring-gear closer to the pinion, causing the teeth to mesh more closely, decreasing the amount the ring-gear can rock without turning the pinion, and therefore decreasing the backlash. Adding shims on the non ring-gear side moves the ring-gear away from the pinion, increasing backlash.

Note that... carrier shims added to one side must be subtracted from the other, and vice versa, to maintain a consistent carrier pre-load.

Also note... Backlash changes about 0.0035” for every 0.010” the carrier is moved. The purpose of having backlash (i.e. the reason gears aren’t set-up tight, with no play) is to prevent the gears from jamming together. Lack of backlash may cause noise, overloading, overheating, or seizing and failure of the gears or bearings.

"Pinion-bearing preload." Its definition: Bearing preload is a measure of the rolling resistance in a bearing or “bearing stiffness”. As a cone is pressed against its cup, the point or line of contact between the roller and cup becomes larger, friction increases and preload is said to be higher. Correct bearing preload is a trade-off between bearing stiffness and the wear resulting from the preloading.

Think of it as... how tightly the pinion-bearing cones are pressed into their cups and consequently how stiff they are to rotate.

How it is measured... an inch-pound torque wrench is used on the pinion nut to measure the torque required to rotate the installed pinion.

It is adjusted via... outer pinion shims placed between the face of the outer pinion-bearing cone and the shoulder on the pinion shaft. Adding shims causes the pinion-bearings to be spaced away from their cups, reducing pre-load and vice-versa. Add shims to reduce pre-load and remove shims to increase preload.

Note... pinion preload is normally specified without the carrier or axle shafts installed, with the yoke installed and pinion nut torqued to spec but with no pinion oil seal installed. An installed carrier can add 2-4 in-lbs and a new oil seal adds approx. 3 in-lbs. Too little preload diminishes load-bearing capacity as the load-bearing surfaces between rollers and cup are decreased. Too much preload increases friction, resulting in excessive noise, heat, and rapid wear.

Next is "Carrier-bearing preload." Which is defined alot like pinion bearing pre-load. Its definition can be summed up like the pinion-bearing preload instructions above.

Think of it as... how tightly the carrier-bearing cones are pressed into their cups and consequently how stiff they are to rotate. Also controls how tightly the carrier is held in the housing.

How it is measured... its not really possible to measure directly.

It is adjusted via... adding or subtracting an equal amount of carrier-bearing shims to both sides of the carrier. Ideally, total carrier shim stack (sum of both sides) should be approx. 0.015” larger than the available space, and a case spreader should be used. However, a case spreader is not critical, and a good approximation of carrier-bearing preload can be made by ensuring the carrier can only be installed with a few good blows from a dead-blow hammer.
Note: If carrier preload is too little, carrier will move away from pinion under load (squirm or deflect), increasing backlash. This could lead to insufficient gear tooth contact, resulting in chipping/breaking of gear teeth.

 

i think im sending my next rear to las vegas

 

That how-to write-up is pretty good. Tapping in the shims with the carrier installed is a big no-no, and is sometimes impossible. A good rule of thumb for carrier bearing preload is to both setup backlash correctly and an additional 10 in/lbs of TTT (torque to turn) over the pinion bearing preload.

For example: If you have 28 in/lbs TTT for the pinion bearing preload, 38 in/lbs TTT for the pinion and installed carrier is ideal. This all assumes lubed bearings, as dry bearings skew the numbers. New or old bearings, an additional 10 in/lbs is what you're looking for.

 

I am interested as to why is it a big no-no and how should they be installed? The service manual does actually tell you to drive them in with a hammer, but not to re-use the factory iron shims since they are most likely going to break. They also use a curved tool to spread the load on the shims.

 

Used "thick" shims are often very brittle and will break when hit. They can also gall the metal creating incorrect preload. Thin shims can't be hit as they'll just bend.

The preferred method, as described in the how-to several posts above:

Apply grease to the shims and place them in the rear housing, allowing the grease to stick them to housing. Hold the carrier and races with both hands, slightly angling the races towards the front centerline of the car. Loosely install the carrier and hold with one hand, as you hit the races with a brass hammer/punch alternating towards the front of the car, then towards the carrier, to drive in the carrier and seat the races. Once the carrier is drawn in more than half way and going in evenly with the races properly seated, carefully draw the carrier in completely with the caps.

 

I didnt know adding pre-load shims can effect backlash...??? I always set my back lash and get it all right with set up bearings, then add .003" shims on both sides. Shouldnt really move the carrier one way or the other which is what would need to happen to change backlash...

I always used .003" for preload. Unless when installing the carrier it feels tight going in. Sometimes Ill add them, sometimes I wont. By the way this is on dana 30, dana 44, ford 8.8 axles... Never really messed with a corp. GM axle... But when I install the carrier, I like to have to hit it with a rubber mallet pretty hard to get it in. If it falls right in, or seats after one whack of the mallet, Ill add the .003 shims. If it takes quite a few blows, but goes in smoothly, I leave the shims out.

As far as "hammering" the shims in... Well I dont have a ton of experience with that. Because most of the axles I work on have the shims seated between the bearing and the carrier. So all you have to keep together is the bearing race. On the ford 8.8 however, there is a large machined shim on both sides of the carrier. No little shims from the factory. Just these cast spacers. Ive shattered one of those before while trying to tap it in with a hammer. So I always lay those in first, then drop the carrier and bearing races straight down.

Im not saying this is right!!! Im just saying how I usually do it. And Ive never had a problem with any of my axles or other peoples axles that Ive done. No whining, no gear failure, no pre-mature bearing failure...

Ill be taking apart my Strange 12-bolt to do some bearing replacements here soon...so I guess Ill get my first taste at GM axle engineering...

Justin