When I am measured up and ready to preload the carrier, I had read that you do not shim both sides evenly due to it moving the ring toward the pinion, messing up the measurements. Is there some sort of rule of thumb like 75/25 ,ring side being the lesser? specs call for .015 preload which could move it quite a bit, compared to say a d35 that needs only .008 preload evenly dispersed. Any self proclaimed experts out there? :D

I have set up d30, d44 and d60 axles, and in all of them I only added 3 thou shims on each side of the carrier for preload upon the final assembly, just enough to hammer the carrier in place with a rubber mallet.

If you're talking about final assembly, you should add the same thickness shims to both sides, otherwise you might throw your backlash right out to lunch.

I think maybe you should do some more reading, because it sounds like you have carrier bearing preload and pinion bearing preload mixed up....

I know I don't have the preloads mixed up. The d30 calls for a housing expander to properly set the preload with the additional .015, which I have access to. It does look like, from what I have read on several forums and info I found on the net, people who set up their own diffs are far and few between and even those people don't really care if they are set up with the proper amount of side bearing preload

One - you don't need a diff spreader.

Two - carrier bearing preload isn't normally a set value, it's enough shims to have to slightly force the carrier back into the housing. i.e. once your backlash is set, add x amount of shims to have to lightly tap it into place.

If you search this site, there are a lot of gear set up threads that should help explain what you want to know.

Thanks for your help. I found the information I was looking for in factory service manual at the library:

Model 20 requires .004 shim to be added to each side after all other settings are made at zero preload (then recheck backlash/pattern). Dana 30 requires .015 to be added to the side facing the teeth of the ring gear (again after all other settings have been made, and again recheck backlash/pattern after preloading the bearings).

They say a spreader needs to be used, like the OTC 7071, made specifically for dana 30 and 70 due to the high amount of carrier preload required for those two axle types, , but You, among other people, have told me I should be able to tap it in. Wish me luck!

Oh, and I did a search on this sight, to no avail.

It doesn't make sense to add preload shims to only one side of the carrier especially that much shims (.015), your backlash will be screwed. The statement about the model 20 makes sense, now why would the dana 30 be any different?

If you are able to add .015 shims to your carrier when you preload it, I have to guess that it was too loose on the trial runs with dummy bearings, thus your backlash would have been off. On the other hand, if your preload is too tight, you will definitely need the spreader to get the carrier out of the housing and your bearings won't last that long.

That's why I posed the question, it doesn't make sense, but it's in the book.

See if this makes sense:

1. Press the differential bearings onto the case without shims (Fig. 14). The bearings must bottom on the case shoulder.

2. Place the cups on the differential bearings and install the assembly in the housing. Install the bearing caps and tighten the cap bolts just enough to keep the bearing caps in place.

3. Mount a dial indicator on the axle housing, with the indicator button against the ring gear (Fig. 15).


4. Pry the differential assembly away from the dial indicator, using a screw driver between the bearing cup and the case, and set the indicator at zero. Pry the differential assembly toward the indicator and note the indicator reading. This reading indicates the amount of shims needed behind the differential side bearings to take up the total clearance between the differential bearing cups and the case. Record this reading.
5. Remove the bearing caps and lift the differential assembly from the housing. Do not install shims under the differential hearings at this time. The total-clearance reading obtained in the above step must be integrated with a second reading to be obtained after the pinion has been installed and pinion depth has been adjusted. The two readings are used to calculate the shim thickness necessary to obtain proper differential bearing pre-load and ring gear back-lash, as well as end play adjustment.

Then after the pinion is set:

1. Refer to the reading taken in step 4 under Differential Bearing End Play Measurement Conventional and Limited-Slip Differentials. This reading (taken before the pinion was installed) represents the total clearance between the differential side bearing cups and the case.

2. Again install the differential assembly in the housing (this time with the pinion installed), and tighten the bearing caps lightly. Install the dial indicator with the button against the back face of the ring gear. Move the differential and ring gear assembly tight against the pinion gear and then set the dial indicator to zero. Move the differential and drive gear assembly toward the indicator, and note the reading.

3. This reading indicates the amount of shims necessary to take up the clearance between the bearing cup and the case at the ring gear side of the differential assembly. Subtract this reading from the previously recorded total reading to obtain the amount of shims necessary to take up the clearance between the bearing cup and the case at the pinion side of the differential. Increase this pinion-side shim pack by an additional 0.015 to 0.020 inch in order to provide correct bearing preload and backlash.

Holy Shyt! It makes sense now :shaking: they are doing the same damn thing preloading as any other axle. They are just getting the measurements while the ring gear is pressed tight against the pinion. That is why they are adding .015 to .020 to the pinion side bearing. to set the backlash and and set the preload all in one shot. Why, why?

So it would be similar to setting your lash up first, and then splitting the preload shims evenly at .007 to .01 on each side?

There's no need to press new bearings on and off during the set-up:

1) Grind the inside of old or previously used carrier bearings so you can install and remove them off the carrier by hand.

2) On the first pinion depth trial, add shims to both sides of the carrier equally until the carrier fits tight in the housing without having to hammer it in. Make sure there's no side to side play in the carrier once installed. Once you have the total number of shims figured out, measure your backlash and simply move the shims from side to side in order to arrive to the right backlash.

3) run a pattern and adjust pinion depth accordingly. Repeat backlash procedure as necessary until the pinion depth pattern is centered on the pinion teeth.

4) preload the pinion bearing...

5) once the pinion is completely installed, add 3 thou to each side of the carrier shims and press the real bearings in. This constitutes the carrier bearing preload.

Huh. Well, after installing my second ARB in a D30, the only place I've ever added carrier bearing preload was on the right (away from the ring gear) side. That's what ARB's manual says to do and every other thing I've read about the subject - hence the case spreader, although I have gotten away without one, using a 2x4 and a BFH. The new ARB design will not allow that. I haven't seen the addition of carrier preload with shims on the right move the backlash more than a thousandth.

my $0.02

Jay