Happy Easter to all first.

The dealer had told me the rear end in my truck was shot including the power-lok. The total price for all parts through the dealer was about $1400. I got them, through good advice from here, from Randys Ring And Pinion. My cost was about $625 and it is just about everything in the rear diff with the exception of the axle shafts.

I have pulled the axle shafts and the "differential/power-lok?" The carrier bearings seemed sloppy and the gears inside seem to have a bit of play like the clutches in the power-lok are gone or severely worn. I plan on removing the bearings and shims to replace them and also taking the power lok apart and replacing all gears and clutches.

The ring and pinion gears look perfect with no wear at all. How do I diagnose these? Do I just replace them even though they look unworn?

For the power-lok, do I merely remove the existing shims behind the bearings and put those back if not worn? Then just verify the backlash? The imntructions mention having the shims correct for bearing pre-load on the carrier bearings and for backlash purposes. I uderstand how to determine the backlash but how do I determine the preload on these bearings? Is it assumed the preload was correct on the initial build so the same thickness shims will be OK? Do I have to worry about backlash if I am not changing the ring or pinion gears? Is the gear contact check enough to verify everthing?

Supposed to be in the mid 40's today so it is a great day for laying under the truck.

Thanks in advance

Charlie

 

You ask some pretty good questions. Here is what I would advise:

If you have a new set of ring and pinion gears, replace the old ones if there is evidence of any sharpness on the corners of the teeth. Run your finger along the edge of each gear tooth, right where it bevels over to the crown. If you feel any sharpness at all, replace the gear set. If there is no sharpness where the gear face meets the crown on each tooth, and there is no evidence of pitting or galling on gear faces themselves, you are good to go with the old ones. The OEM gear set should be good for well over 500,000 miles if kept serviced.

Regarding questions on the power-lock shims, I assume you actually mean the spool that carries the clutch pack and holds the ring gear. If so, your question is a bit confusing. The shims should be outside the carrier (the housing with the power-loc clutches and to which the ring gear bolts) on each end where they abutt the carrier bearings. If that is the shims you describe, then the answer to your questions is yes, and yes. However, what you do is reinstall the carrier and then do this drill to know which shims need to be added to or replaced (this is the most time consuming part of the procedure):

1. Expand the case spreader on the differential housing a maximum of .020" to get to the proper spread for installing the carrier and measuring end play in order to set up the preload.

2. Install the carrier and bearing cups, and then use a soft hammer and rotate the ring gear and tap the ring gear to assure a proper bearing seating.

3. Reinstall the bearing caps in their proper location, as noted by the reference marks you made when you disassembled the unit.

4. Finger tighten the bearing cap bolts, and remove the tension on the case spreader.

5. Tighten the carrier bearing cap screws (bolts) to 85 foot lbs.

6. Install your dial indicator assembly to the carrier, set to zero and then set the feeler against the back of the drive gear.

7. Rock the differential toward the dial indicator and read the gauge. Do this several times to be sure you get a reliable average.

8. To that reading you will add .015 to .020" and that is the exact shim size you now need to add to get the proper preload.

9. Install the needed change in the shim pack to the bearing opposite the the drive gear (facing the ring gear teeth and clear across the carrier is opposite side).

10. Button up the bearing cap again, and do another test with the dial indicator. If you get zero lash, you are now good to test the friction. If not, repeat the process until you have less than .002 inch play.

While you are adding shims, be sure your gear contacts remain good. If the ring gear starts pulling away from the pinion, go back and remove a thin shim from the side you have been working on and move it to opposite side.

It is always a good idea to use a dye such as Prussian Blue on the gear teeth and read the contact to be sure they are even and well meshed, but if the gear side does not change during the preload adjustment, do not worry about it.

Once there, you are ready to button it up, install conventional track-loc lube and break in the assembly. Do not switch to synthetic gear oil until you have at least 3,000 miles on the rebuilt unit. It now needs a bit of friction to seat the shims, and synthetic will prevent that.

When you reinstall the spool with the clutches and ring gear, the preload will be where it was from the factory.

If you run into a snag, shoot me a private message and I will respond.

Good luck.

 

The gears feel like new with no obvious wear at all and no pitting or galling.



That is the exact shims I was referring too.



I don't have a case spreader and the "spool" came out with no pressure on the sides at all. Is this a bad thing?



I assume this requires pulling the bearings off and pressing them back on each time?



Hopefully this will be the case and any additional shims will only be on that side. I got the dye from Randy's Ring and Pinion and will use it but you make a good point about if it is needed if only the opposite side from the ring gear is shimmed.

Thanks a bunch!! Got busy with Easter family things and didn't get a chance to get back to it today. Luckily I really don't need to use it right away. Have to wait for another dry day above 40 degrees, I guess.

 

As far as needing to pull the carrier bearings to insert the shims, the answer is yes. leave the axles out, pull the entire assembly, then insert the shim packs between the bearings and the spool. Then replace the assembly. You will be concentrating on the shim pack on the opposite side from the ring gear, once you reinstall the OEM shims on the other (ring gear) side and know it is back to normal.

The case spreader is normally needed to properly set up the case to accept the spool. This is necessary to acheive enough play to slide the assembly with properly spaced shims into place, as it will appear to be just a frog hair longer than the bearing bosses when properly shimmed. It really is not a full frog hair, just a half frog hair or about .015 of an inch too long for the bearing bosses when properly shimmed.

I have done it without a spreader, but to do so you will need to find a way to power the bearings back into their seats when the assembly is quite tight.

There is a way to do that, but you need to very lightly oil the bearing bosses with a thin oil like musical instrument oil, press the unit and bearings back in, and then place the caps over the bearings and use a brass hammer to rap them lightly as you torque the cap screws back into place. Then spin the unit over several times before you set up the dial indicator and measure for end play (preload) again. When you are done, there should be no free play and a slightly tight fit to the bearings.

A lot of this is by feel, and you should be able to feel everything snug up against the bearings, yet not be actually binding. The shim packs should just be snugly pressing against the bearings after the unit is properly set up and the caps torqued into place. The trick is to avoid over loading the preload, and yet having it just snug enough to avoid differential carrier drift away from the gear contact faces when under a torque load by the engine.

However, all said and done, if you rent a case spreader the setup will go like hot butter. Just remember to loosen the spreader before you use the dial indicator to find any endplay.

Do not get frustrated by a few tries, I sometimes have to do this more than once myself, and I have done more than I can count over the years.

Good luck, and have a Happy Easter.