The # 712146 is the thicker seal. The # 2146 is the thinner seal.Again,they look identical,but arer different.The only problem is that you will most likely damage the bearing trying to get it off to change the seal.

The carrier bearings should have preload on them,so it should take some effort to get the carrier out.It should not fall-out,but you also should not need to pound it in with a huge hammer.

 

67 - 68 12 bolt olds came with SEALED bearings and will not have the seal on the axle shaft it is in the housing tube. End play is what the bearing gives...period.

The 69 -70 were NON sealed or internally oiled bearing axle system. The 2146 seal .465 will usually NOT be thick enough for the end play to be tight enough. The 71 2146 are .490 and should provide the correct squeeze against the retaining axle plate to keep the end play very minimal .005-.015 range.

If you have a Bower brand press on non sealed NON TAPERED bearing there will be some end play. If you have a tapered bearing usually later model and most new bearings the end play should be almost nil. The tapered bearing will need the correct squeeze and is critical to not eat it self down the road.

Have fun guys....It is a HOBBY WE ENJOY Jim

 

By the way, a 7.5" c clip axle is the perfect prybar to remove carriers to reshim.

 

OK...I swapped the shims.

I removed the caps and used a 2ft long prybar to gently free the carrier. I didn't 'pry' so much as lightly smack the bar with my hand a bunch of times. Once it popped up about 1/3 of the way I could lift it out.

I kept track of what side pieces came from.

The pass side shim was .263-ish-.264
The driver side was .252
A diff of .012

Dunno if it means anything but the .252 had 2 green lines and the .264 had 3 yellow lines (green = .x5x and yellow = .x6x ?? ) ??

So, if my math & understanding of the CSM is correct, swapping .012 should bring my lash down by .006. It was ~.011-.012...it should now be ~ .005-.006.

I reassembled everything with the shims swapped. Others are right. This is complicated dance. I put the pass (ex drivers) side shim in and kinda spooned the carrier up next to it. It was tough trying to keep the races on the bearings. I tried some grease to stick it all together, but it didn't help much.

Once pass. shim and carrier (& races) were in, I forced it toward the pass. side with my hands along with working the driver side race as far over as possible. I tried reinstalling the shim but it was really tough and I was afraid I'd break it. I lightly greased the shim, housing face, & race face. Then I tapped the carrier toward the pass side with very light hammer action.

I tapped the driver shim in using the main cap.....with very light blows. (And kept checking the cap for any marks - none). After about 1000 taps the shim was even with the race. I used an old dull chisel to drive it the last few .000th's

I put the caps on, but only to ~5 bs and then turned it thru ~ 10 full revs. It felt noticably 'stiffer'. Then I torqued all 4 cap bolts to 63lbs and spun it thru another 10 revs.

Backlash is now .0045-.0055 at various points.

Is this too tight?!?!? Will it loosen a bit with use ?

Now what !?

 

I think it is too tight? but the CSM is saying .005-.009? so your right at the Minimum?
HMMMM
you did put the chamfer side in towards the axle tubes right?

I can see what size shims I have left over, if other folks ( with more experience doing these things) think it is too tight, thing is these are not single shims you keep adding till you get the size you need.. but your welcome to them.

 

Ya...the CSM says .005-.009 minimum average so I'm very borderline....
I did put the shims in with the chamfer toward the tubes per the book.

I did notice a small blop of yellow paint on the pass side shim before I dissassembled. This jibes with the yellow blop on the pass side bearing cap so I think (before today) the shims were in their correct factory positions. I wonder if the rearend was built to .009-ish spec at the factory & 100,000 miles simply wore my gears down to where the backlash is now just a bit over spec.

Sounds like I need to replace the factory shims with custom shim-packs with the driver side being ~ .257 & pass side being .259....

Thanks for the offer Eddie, but don't the shim packs have like a 'master shim' and then smaller add-ons ? I'd think I'd need a whole pack/kit....

 

Yes I still have a master shim left plus spacer shims will get them out when I get home and tell you what I have left

 

Yes,you need to find something in between there,but your shims should equal the same together,so you can maintain the same preload.

 

Thanks...that's what I thought (but hoped against!)

My original shims are .264 & .252..total .516

Flipping them (moving .012 from one side to other) change my backlash from ~.011 to ~.005. A diff of .006....just like the CSM says (move 2x the desired backlash change).

Looks like I'll need .256 on driver's side and a .260 on pass. side That'll give me a total of .516 and should put backlash at right at a tight .009...

.258 on both sides would put me at ~.008 backlash...

What's the ideal backlash ? & any recomendations on shim kits ?

 

Yay ! Shim kit !
Thanks to Brian, I learned that the 31 spline units use bigger shims (same size as Chevy 12 bolt...300" OD/2.75" ID) than do the 28 spline ones.....thus saving another round of frustration.


Double Yay...$6/pack

With a little luck I'll have them in tonight/tomorrow......Stay tuned...

 

Finally got it all together....
I built up shim sets in .256 & .260. I C-clamped them together while building/checking so that my measurements were accurate.Did this and it seemed to help. I still had to tap in the 2nd set, but it was a bit easier (& I wasn't worrying about breaking the old iron ring..)
Installed and...

Voilą!...a nice .009 all the way around (checked 4 different points)
And the pattern still looks good...

..although we've now switched to Fabulous Fuschia...

So..I cleaned up the axles a bit (very lightly scrotchbrighted the seal area to remove any crusties/goo & make 'em perfectly smooth) and put it all together for a test fit...& to gaze upon it...


A huge thanks to Brian, Eddie, Jim, & others who helped out with advice & info...!!

 

Looks like you have a lot of good contact on the drive side.
The coast pattern is weird though. It shouldn't be going off the heel end of the gear.
Maybe the lipstick is throwing off my view a little.
Nice work. That rear looks sharp.