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Old 10-28-2019, 01:12 AM   #21
ions82
 
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Default Re: Replacing differential bearings - pinion and carrier

I am amidst the wonderful process of installing new bearings in the rear of my 2004. Fun times!

Anyway, I noticed that the pinion bearing is a Koyo and the carriers Timken. Makes me wonder if someone has been inside of this thing at some point. It's a retired FedEx unit that has 333K. Once the axles were moved, the carrier just came right out with virtually no resistance. That also made me a little suspicious that someone had previously been in there. Each side only had one thick shim behind it. I found this odd as there really isn't much "fine tuning" to be done with only thick shims. The last rebuild kit I bought (for a Dana 70) came with an assortment of thin shims for tuning the gear mesh and bearing preload/interference. After pulling the carrier in and out a couple times, I got the backlash down to .005". Fortunately, the rebuild kit from EuroParts-SD (highly recommended) comes with a number of thin shims. I suspect that I will have to do a process of trial and error by pulling the carrier in and out to check backlash and mesh.

Bottom line, I would be very hesitant to trust anyone to "rebuild" a differential for me. It is a tedious process when doing it right. The other Dana 70 I looked at had something like .080" backlash. I think many people who "rebuild" a differential simply put new bearings in and call it good. Getting this one dialed in is going to be a headache, but, with proper care and maintenance, it should be good for another 300K.
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Old 10-31-2019, 03:17 AM   #22
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Default Re: Replacing differential bearings - pinion and carrier

FWIW, mine was stock almost for certain, and had never been dug into before. I only had one thick shim on either side as well of the carrier. Didn't have to mess with my backlash after bearing replacements. I did have to rubber mallet the carrier back in, but no too hard. The mismatched bearings are possibly an indicator though like you say, that someone scuba dove before you.

Similarly I only trust myself for this kind of work, even though I had never done it before ;)
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Old 11-02-2019, 06:43 PM   #23
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Default Re: Replacing differential bearings - pinion and carrier

I measured the width of the bearing seats to be 6.470". I put the carrier up on the granite inspection block and measured a total width of 6.469". I was hoping to set it up with a thousandth or two of interference, but it looks like it is what it is. The carrier bearings (Timken) actually looked pretty good, but the pinon bearings had a bit more wear (Koyo.). None of them felt "crunchy" once cleaned up.

There was plenty of metallic residue in the black sludge that was stuck in every nook and cranny. I'm curious about the health of the wheel bearings. I still need to give them a good cleaning. I'm going to use a power washer through the axle along with some Purple Power. I want to get as much of that metallic residue out as I can. Nasty stuff.
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Old 11-10-2019, 04:08 AM   #24
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Default Re: Replacing differential bearings - pinion and carrier

I'm about to start putting everything back in. I decided to do the wheel/axle bearings, too. So, I ordered those up and got everything sorted. I used Purple Power and my small electric pressure washer to get the axle housing as clean as possible (of all the nasty metallic residue.)

Anyway, going back through the thread, I didn't see any mention of checking backlash along with gear mesh. My rebuild kit came with pinion shims. I believe they go BEHIND the race of the larger pinion bearing. So, if any need to be added, that thing has to be hammered out again. My plan is to machine a dummy shim that I can use to pull the pinion into its race so I can check backlash before installing the driveshaft side bearing. As mentioned earlier in the post, that's the point of no return.

Also, a previous post mentioned a small shim that slides over the pinion and goes on before the crush sleeve. That one is only on 2004 and earlier units. For those, a shorter crush sleeve was employed. 2005 and later had no shim but just used a longer crush sleeve. The shim and shorter crush together are the same length as the longer crush. The shim is beveled on one side to clear a radius that is machined into the pinion shaft. So, the longer crush sleeve can't be used in place of the short+shim unless you machine a bevel into one side.
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Old 11-11-2019, 08:18 AM   #25
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Default Re: Replacing differential bearings - pinion and carrier

I finished all prep work for reinstallation. As I mentioned in my last post, I wanted to check backlash before installing the front pinion bearing (in the event that I would need to add shims behind the rear pinion bearing race.) So, I machined a bushing that would sit in place of the front bearing so I could tighten the pinion in place and check backlash. Worked like a charm.

Anyway, I now know that MB doesn't mess around when they build a differential. Everything I checked and measured came out right on the money. The measured backlash was .004-.005". Doesn't get much better than that for fresh bearings. Both of the carrier bearing shims were identical in thickness. I thought for sure there would be a difference in pinon depth with the new bearings. Everything seems perfect. Couldn't have asked for better results. The Dana 70 I did in the past was far more tedious than this one.

Also, the carrier measured out to .001" less than the distance between the bearing seats. However, once going back in, there was just the right amount of interference. I carefully tapped the carrier and shims in place and used the yokes to pull it in the rest of the way. I don't think a spreader would've been worth the trouble. Perhaps others' carriers were a bit more finicky, but this one was rather cooperative.

Also, I noticed that the new pinion bearings (Timken) had longer rollers than the ones being replaced (Koyo.) Obviously, this was inconsequential. Just caught my eye as I was closely inspecting everything as I went through it.

Last edited by ions82; 11-11-2019 at 08:20 AM.
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Old 11-15-2019, 02:44 PM   #26
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Default Re: Replacing differential bearings - pinion and carrier

Just a word of caution on the B/L since you are a bit on the tight side :
It should be a nominal 0,3 mm taken at three positions equally around the 360 circumference of ring gear (crown wheel) .
This ensures no binding loss of clearance and accounts for wear and slight run out that as occurred during previous service periods.
What preload have you set the carrier bearings to for curiosity sake, as that will affect the true B/L in service?
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Old 12-01-2019, 07:34 PM   #27
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Default Re: Replacing differential bearings - pinion and carrier

Thank you for the guide. I just completed this myself and all of the information here was very helpful.

For anyone else getting ready to change bearings there are some things that made this whole process a little easier for me. I am not the best writer so bear with me.

While removing the carrier I used pry bars with wood strips against the case to protect it. I leveraged against the bolts and with a small-medium amount of force the carrier came right out. Make sure you have some rags or wood under the ring gear to protect from damage when it pops out. As mentioned in this thread the right way of doing this as per the manual is to use a case spreader, I considered welding one up but decided against it due to time and risk of over spreading the case.

Pushing the pinion out required a considerable amount of force. I measured the threads to the case to ensure it was coming out. If I were doing this again I wouldn't be so worried about hitting it harder.

Removing the bearing races was taking forever with a punch so I used an air hammer with a brass set. Apply equal force around the race and it will pop right out. Also don't hit the pinion shim. Installing the bigger pinion race was a PIA, I eventually heated the case up with a heat gun, then oiled everything up and it drove right in. The smaller pinion race went in easy without heat. Both races were put in the freezer for 6 hours before installation. You will hear the difference in noise while hitting the race driver when everything is seated so wear some ear protection. Another way to know is when the hammer somewhat bounces back.

I heated all of the new bearings up and they slid right on without the use of the shop press this includes the smaller pinion bearing. The use of a nice heat gun really makes this whole process easier.

I used a parts washer to clean all of the removable components and I used 4 cans of brake parts cleaner coupled with a magnet to clean the differential housing and axle tubes. YMMV with the brake/parts cleaner and a magnet but it worked great for me.

It may be a good idea to change wheel bearings during this process. Its hard work yes but those wheel bearings are lubricated with differential fluid. The same fluid that was full of metal. When I was cleaning the axle tubes I found just as much metal as was in the case. At the very least clean and inspect the bearings.

Last tip I can think of is to check that case vent while you have everything apart.

Thanks again to everyone in this thread. Total cost for parts was $180 and 3 days labor @ 3 hours a day. Attached are some pictures of a tool I made to hold the pinion in place.
Attached Images
File Type: jpg IMG_20191130_155627.jpg (223.9 KB, 17 views)
File Type: jpg IMG_20191130_155620.jpg (203.8 KB, 16 views)
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