Jeep Cherokee Talk banner

1 - 4 of 4 Posts

50 Posts
Discussion Starter #1
This gear install write up is from a couple of years ago, and it's on the HP44 that ended up in my 88 XJ. This is the same procedure as a HP30 gear install so I hope it's helpfull.

I've started with removing the carrier bearing caps and i'm just checking to see how tight the carrier is in the housing. Hopefully it won't easily come out. If it did, that would mean there's not enough carrier bearing preload. I have a wrench on one of the ring gear bolts and I'm rotating the flange to see if the carrier will push out.

It doesn't and that's good.

I want to have to use the case spreader and hopefully spread it somewhere between .015" and .020" before that carrier will come out.

I measure that with a dial indicator and set it to "0" before I start spreading the case

I spread it to about .018" before I was able to get the carrier to move with just a little bit of force. That's good, it means the shims that are on that carrier were just right for carrier bearing preload, and I will use the same thickness on the new carrier when I install it. That will make a real good starting point.

Once the carriers out I see something interesting, the oil slinger is damaged. I suspect either when someone installed gears before, that plate was bent or gouged, and it caught the ring gear and got mangled. Either that or some pretty big debris got in there and caused the damage.

I guess it could of had a loose pinion nut or bad bearing at one time to.

Once the pinion and races are out, it's important to keep track of what shims were in place and all the slingers and their position. The shims often get damaged when knocking everything out, I'll just measure the thickness of each and replace it with the new ones from the kit.

Now I can start pressing on some bearings and I'll need to know the thickness of the shims that are currently installed.

I don't really have to pull the pinion bearing off, all I really need to do is mic the oil slinger thickness, and install a new one that is the same. If it wasn't mangled, i'd reuse the current one.

But I went ahead and pulled the bearing, just to have the slinger to hang on the wall or something

Master kits don't always come with all the slingers, and this Motive Power one doesn't have that slinger in it.

But I keep all the left over shims from previous installs, and I had one.

It is .025" thick and matches the old one. Now I can press the new bearing on.

Now I pull both carrier bearings

And I keep track of the shims that were under each bearing, they are not damaged at all, so I will just reuse them.

50 Posts
Discussion Starter #2
I'll go ahead and install the pinion and carrier so I can run the pattern and check to see if the pinion depth is good.

First the shim and the stepped slinger. That new shim is .005" thick, same as the old one that came out.

Then I can pound in the inner race, I've also already installed the new axle seals.

Then I knock in the new outer pinion race as well

Then I lube the two pinion bearings and install the pinion, I am leaving out the pinion preload shims and the pinion seal, I carefully tighten the pinion nut until I can feel resistance when turning the pinion, that resistance should be close to the pinion bearing preload spec of 14 to 19 in lbs. I also use an old pinion nut that I have ground off the locking part of the nut. That way I won't damage any threads as new locking pinion nuts sometimes will do.

I've pressed the carrier bearings on to the new Detroit locker, with the same shims under each, that were on the old carrier.

By the way you can't always use a flat plate against a bearing like i'm doing, sometimes the cage will be damaged, but these inner races set higher then the cage on these bearings, so it's o/k here.

Then I can lube those bearings up. Spread the case again (I backed off the spreader as I always do whenever I don't need it spread).

And then slid the carrier into the housing, I make sure that there is at least some backlash or play between the ring gear and pinion gear as the carrier gets bolted in. In this case I can tell that the backlash is too tight by feel, so I know I'll have to make some shim changes, but as long as there is a little play, I know I won't damage the gears.

With the case still spread, I only tighten the carrier cap bolts a little more than hand tight, then I release the tension from the case spreader, still making sure I have some backlash, then I torque the cap bolts to spec and I can run the pattern now.

The pattern is what tells me if I have the depth of the pinion correct.

Here the coast side is a little deep but not too bad.

The drive side I am happy with, it's a little bit deep, I suppose the perfect pattern is right in the middle, but the inner area is the strongest part of the gear and I actually prefer the pattern to be a little deep

If I were wanting the pattern not to be as deep, I would change the shim that is between the inner pinion bearing race and the housing from the current .005" to .004" or maybe .003", and then run the pattern again.

50 Posts
Discussion Starter #3
Now that I know the pinion depth is good, I can now set the pinion bearing preload. So out comes the carrier and the pinion gear, and now I can install the shims you see below. There are 2 - .025" shims and 1 - .001" shim, same as what was on the old pinion. And I will install just these parts, leaving out the pinion seal and still using an old pinion nut.

I tighten down the pinion nut checking the turning resistance of the pinion as I go.

If it starts to get too tight before the pinion nut is all the way tight, I will need to stop and add more shims, I don't want to damage the bearings by over tightening.

If there was slop or the pinion turns real easily by hand, I will need to remove shims.

To get it just right, the turning resistance needs to be measured with an inch lb. torque wrench and the spec is 14 to 19 inch lbs.

The first time I did not get hardly any turning resistance when the nut was tight, so I took the pinion back out and removed 1 of the .025" shims, and I installed a .020" shim.

Here's where you need some patience when installing gears. I know i'm gonna mess with this awhile and I also know that the carrier shims are gonna need some changes.

So after that last shim change, I am reading about 20 inch lbs. and the nut is not all the way tight, so I'm gonna have to add a shim. It's close though, so I'm just gonna add a .001" shim.

After adding a .001" shim, I set the blue needle to 0 and then turned the pinion, and blue needle moved to the max resistance I had, sort of like a tattle tale tach. I got to about 13 inch lbs.

So now I have a descision to make, if I put back the .001 shim I am above the spec. for the pinion bearings, and If leave it out I am slightly below the spec.

Sometimes you can swap around shims to get different readings, for instance using 2 - .010" shims in place of a .020" shim, will sometimes take up more space than a single .020" will. I need to remove less then .001" though, I tried two combinations before I was happy, first a .010" and a .005" and 4 - .001" shims, that was too loose, worse then before.

So then I used a .010" a .005" and 2 - .001" and then it was good, 18 inch lbs.

Don't ask me why combining several smaller shims adds more than a single shim will, but it does.

It probably would have been fine to leave it at 13, and if I had to chose, I would want it a little loose, instead of too tight.

Now I can pull the yoke off one last time and drive in the pinion seal. And then install the yoke for the last time and I will now use the new pinion nut.

By the way the old inner pinion race fits the seal just right and makes a good tool to drive in the seal without damaging it.

Now I can just put the carrier back in the housing for the last time and this diff. is ready for the trails!!
1 - 4 of 4 Posts