Should the big gear assembly in my diff slide back and forth?

[Thomas DeBusk]

Some of you have been following my rear axle thread with breathless excitement. There's more.

Just about to put it all back together today, I grabbed the big wheel (pinion?) and tried to move it. It slides back and forth a lot. Is this normal? Or are the bearings so worn out they're letting it move too much and that's what destroyed my axle bearings?

Is changing the diff bearings a professional job?

I have another axle with a good set of bearings, but a bad axle tube. Is swapping the tube a backyard mechanic type job?

Thomas

[Crazy_Jeepman]

The big gear is the Ring gear, or also called Crown gear. If you are able to move it side to side,that is very bad. If you have a spare axle it would be a good idea to swap it in, provided the gear ratio is the same. It would be easier to swap in the rear axle than it would be for you to change the gears. ;)

[Thomas DeBusk]

I want a second opinion.

[porkchop]

Yes it is very, very bad!!! Is that good for a second opinon :D .


I am going to be changing my gears in the next week. I would rather just change out the axle if it was possible to find one with 4.56 gears. What is bad with the axle tube on the other axle?

[Lugnut]

Wanna third opinion? It's very, very, very bad.

[jasonthomasfrance]

Hmm... If CJM says it's bad, I'm guessing... Ahh... It's bad...

Play is bad... Ah... very bad... :D

[Thomas DeBusk]

That's still the wrong (o)pinion.

Seriously, the crown gear slid back and forth about 3/32". I just took out the diff gears. They look great. The bearings on each side looked terrible. The races were galled really badly.

So that confirms the source of the problem. Diff gears wander around with a low rumble, take out axle seals.

I want to replace the diff bearings. I guess I'm just ignorant, but it looks like all I need to do is pull out the old bearings and put in some new ones. Ok, I suppose there must be some clearance issues, right? Or is that just for people who are changing gears also. And I did notice that the bearings are a press fit, so I know I'll have to get someone to press them off and on.

Incidentally, the shop that turned my drums yesterday for $8 apiece charged me $82 today to press on the new axle bearings. And I've already spent a small fortune on the axle bearings and other parts. So I'm not yet ready to abandon this axle. I'm going down with this ship.

P.S., when the axle went bad last August, the axle shaft wound up halfway out of the axle tube with the weight of the vehicle riding on it. There was a long piece of metal wrapped around the shaft. Don't think I want to trust the shaft or the tube.

[ February 09, 2002: Message edited by: Thomas DeBusk ]</p>

[Langdon]

It's important that the ring and pinion gears mesh properly so that should be checked when the bearings are changed. This is done by painting some gear teeth with marking compound and observing the pattern produced when the gears rotate. It is conceivable that with new bearings, and general gear wear that shims may be necessary to ensure proper set up...good luck :cool:

[jeepbob]

Simply put, if the ring and carrier asm slides back and forth it is very bad. This was your low rumble. If the bearings were galled up chances are the both the ring and pinion are shot. By the time you buy new r&p, bearings, and install kit and then pay to have it set up properly you would be much farther ahead to cut your losses and buy a used axle that has the right gear ratio. It sounds like you are suffering from either a lack of lube or a lot of water in the lube. My guess would be a lack of lube.
BTW if you have a D44 rear axle the shims go on before the bearings and the bearings are pressed on.

[ February 09, 2002: Message edited by: jeepbob ]</p>

[Thomas DeBusk]

Fact is, I actually HAVE a good used axle, sitting under a GW about 3 hours away. But I thought when I started I was just in for replacing the brake wheel cylinders. Now my parts-fetching vehicle (the Wag) is lying in pieces all over my driveway. So it looks like I'm in for either paying a fortune to rebuild this axle or buying another axle when I already have a good one. Or swapping out the gears in the original axle for these. Which could lead to a new set of wear problems. What a great set of options! Remind me again why I love these things so much?

By the way, how can you tell the gear ratio? That is, how many teeth should a 3.31 axle have on the ring gear?

Incidentally, this is an AMC 20 axle, not Dana 44.

Thomas

[porkchop]

Why do you love them so much? That is a question only the individual can answer. The way to tell the ratio is count the number of teeth on the ring gear and then count the teeth on the pinion and divide the ring gear with the pinion gear. So if you had 43 teeth on the ring and 13 on the pinion you would divide 43 by 13. You would get 3.30769. Which is 3.31.

[Thomas DeBusk]

Well, this site is one thing that makes them easier to love. So much great information, just for the asking.

Thanks,
Thomas

[Thomas DeBusk]

This axle will be a DANAMC 4420 by the time I'm done. I had a hard time finding replacement diff shims.

Nobody local had them, including Jeep dealer. Finally went in person to the dealer where a mechanic gave me two shims to try that were actually for a Dana 44. They are within thousandths of the correct diameter, and are just the right thickness.

I'm replacing shims because one of the old ones is scarred from spinning a little. The tapered rollers looked awful-lots of pitting.

Everything fits snug with the new diff bearings & shims, so I intend to put it all back together & see how it works. Backlash? What's that? Never heard of it, so it must not be important.

Seriously, local gearheads seem to think if I'm putting the same ring & pinion back in the same housing I should be OK if I'm not changing the shim thicknesses much. I'm about to find out. With a different kind of luck I hope to get it back together Thursday. Need it for towing & I want to go back to simple things like the TFI conversion & that bizarre electrical problem.

Thomas

[Thomas DeBusk]

Got the rear axle back together tonight I went out for a spin. The low rumble is gone, even up to 50 mph.

The ring gear assembly was very tight, but still spun once I got it in. I put the shims in first and then the bearings with the gear assembly. It looked like the shims were trying to distort while going in, but it looked right after I got it all in. I had to put the bearing caps on and use them to drive in the gear assembly.

I'm holding my breath to see if it self-destructs. And I only had 3 quarts of Mobil 1 gear oil to put in. I hope that's enough.

I'd like to use my Wag this weekend to go pick up a '52 Chrysler New Yorker. Nothing like a workout right away.

Thomas

[porkchop]

I would give it at least a 500 mile workin period before I towed anything. Just to make sure it was all together right. I would treat it as a new R&P install just to be on the safe side.

[andy d]

a 52 nyer! wow ! i had a 53 as car #2 ca 1964. got the hemi?

[Thomas DeBusk]

Got 4 hemis:

'52 Saratoga
'52 New Yorker (the new one)
'55 C300 red
'55 C300 white

Thomas

[Rogue]

the movement you're talking about if I understand you correctly IS THE BACKLASH and is adjusted with the shims, once you got your backlash into range, you check your pattern, and adjust pinion gear depth and ring gear back lash until the pattern is centered AND you're backlash is within tolerances much much patience required, bad pattern = premature failure

[Rande]

You might consider going to get that other axle before this one self-destructs. Putting a ring and pinion together without using a dial indicator to check the backlash and checking the pattern seems a might iffy to me. From your description, it seems you took a couple of shortcuts here.
You see, the back and forth movement of the ring gear, is constantly changing the depth of engagement with the pinion. This cannot have been good for either gear. I would be very suspicious of the gears in that axle.

[Thomas DeBusk]

OK, fetching the other axle is on my list of things to do.

In the meantime:

I replaced only one shim, but I did it with one of the same thickness. I'm sure someone's going to say the new bearings have variances that might have changed the backlash. Perhaps so. But with the ring gear moving back and forth 3/32", I think I've achieved a real improvement. The installation was very tight, so I won't be surprised if there is a premature failure, but if I lose this axle, I will only lose an already damaged set of gears. The original bearing rollers looked terrible. All badly pitted. It's a wonder it didn't bind up.

As for breaking it in slowly, too late. I picked up the New Yorker Sunday, towed it 100 miles over hilly topography, and delivered it today. The axle ran quiet. But the rear taillight fuse blew and I dropped plenty of oil. In other words, everything's fine.

Keep in mind, this axle is behind a 190,000-mile 360. I'm just trying to keep it on the road until I can get the fuel injected 360 completed and installed in my J10. Then the Wag can take a vacation.

Thomas

[ February 18, 2002: Message edited by: Thomas DeBusk ]</p>