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Discussion Starter · #1 ·
Recently broke the spider gears in my rear using the trans brake for the first time and am in process of installing a new ring/pinion/spool/c clip eliminators/bearings/etc. This time I intend to do it myself, but I am a rear axle virgin - never done it before. I have some questions about something I noticed on the carrier bearings.

Originally had the complete thing built for me - was not expensive rear - $1400 IIRC. It's originally a 2002 8.65 ring gear rear housing out of a 2WD Blazer Extreme with a new Eaton clutch type posi and 30 spline stock axles. Howled pretty good at 45-50 mph cruise from the first 300 feet of use. I removed the cover and looked at pattern on the gears and seemed like a large percentage of the tooth was covered with the pattern and the pattern extended all the way to the outside edge of the ring gear teeth. It did seem centered but a very large contact pattern. Also I had found that the left axle was bent slightly and wobbled. Took it back out and transported it myself back to the builder, who reportedly replaced the ring/pinion as well as the axle. Installed again and same howl was present. Since then I've primarily use the vehicle for racing a few seasons - so the noise has been a nuisance, but little more. Now I have everything in pieces for repair and I noticed what I think is a funny wear pattern on the carrier bearing races and I don't know what to make of it - if it might be a problem with the case or what?

Funny thing is that the width of the pattern is not consistent. it narrows and then gets wider twice in the circumference of the race. Any comments or advice?


 

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Check the bearing bore diameter. Put the caps on the housing and tighten the bolts. Measure the bore diameter perpendicular to the parting line. Both sides should be the same size and should be within about .002 to .003 of the OD of the bearing race. Chances are the person who built it got the bearing caps swapped and it was crushing this bearing race. The caps must be installed on the correct side of the housing and they must be in the correct position. There are tabs that stick out on one side of the caps. This tab must be pointed to the outside of the housing. Most of the time the bearing bore is a little too large. Many times I will use a large flat file and remove just enough material from the mating surface so that the bore is the same size as the bearing race. You must be very careful not to remove material on an angle or you might have more problems.

If you are drag racing then I recommend replacing the bolts with ARP studs. Don't use cheap gears or other cheap parts. Take your time and get the pattern and bearing preload just right. Those S truck housings have small 2 5/8 inch diameter axle tubes, so a LPW Ultimate cover with the housing brace would be a very good idea. https://www.lpwracing.com/Ultimate_GM/Ultimate_GM.html
 

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Discussion Starter · #3 ·
Check the bearing bore diameter. Put the caps on the housing and tighten the bolts. Measure the bore diameter perpendicular to the parting line. Both sides should be the same size and should be within about .002 to .003 of the OD of the bearing race. Chances are the person who built it got the bearing caps swapped and it was crushing this bearing race.

The caps must be installed on the correct side of the housing and they must be in the correct position. There are tabs that stick out on one side of the caps. This tab must be pointed to the outside of the housing. Most of the time the bearing bore is a little too large. Many times I will use a large flat file and remove just enough material from the mating surface so that the bore is the same size as the bearing race.

If you are drag racing then I recommend replacing the bolts with ARP studs and use a T/A Performance cover with the preload bolts. Don't use cheap gears or other cheap parts. Take your time and get the pattern and bearing preload just right.
Thank you. I intend to be particular. Honestly I am wondering if the bearing caps are original. I can see a bit of rust on the housing at a parting line at one spot, but nothing on the cap itself. I see that Strange offers aluminum caps and they say they are made to cut some off the mating surface to get the bore diameter right. So it seems that the important thing is the bore diameter perpendicular to the parting line?? Would you say that having the bore diameter exactly the same size as the bearing race would be the target, with ± 0.002 to 0.003 acceptable (I think that's what you said before, just confirming)?
 

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I had a 8.5 housing from a '96 Impala that was machined wrong. The bearing caps didn't even touch the housing when the bearings were installed and the bolts were tightened. I had to fit another set of caps to the housing so that I could use it. It's not common, but it does happen. I think I would use steel caps if I was going to replace them. Mark Williams, Strange and Tom's Differentials have steel caps that can be fitted to the housing. Most of the time you will want to use a mill to fit them, and very careful measurements must be made so that just the right amount of material is removed. Some of these caps are designed to be used with 1/2 inch bolts, so be careful of what you get. I would aim for the same size as the bearing, or maybe .0005 smaller. Too small might crush the race and too loose might let the race spin in the housing.
 

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Discussion Starter · #5 ·
I had a 8.5 housing from a '96 Impala that was machined wrong. The bearing caps didn't even touch the housing when the bearings were installed and the bolts were tightened. I had to fit another set of caps to the housing so that I could use it. It's not common, but it does happen. I think I would use steel caps if I was going to replace them. Mark Williams, Strange and Tom's Differentials have steel caps that can be fitted to the housing. Most of the time you will want to use a mill to fit them, and very careful measurements must be made so that just the right amount of material is removed. Some of these caps are designed to be used with 1/2 inch bolts, so be careful of what you get. I would aim for the same size as the bearing, or maybe .0005 smaller. Too small might crush the race and too loose might let the race spin in the housing.
Thanks! I've got some measuring to do. At least there is a way to fix if it's screwed up and that is comforting.
 

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That race doesnt look too unusual, the races are not flat when new, they have a convex arc to them so they wear into the rollers a little.
I see at least one rear a month with the caps on the wrong side, check that first, even if they are marked people manage to mark them wrong.
Were the axle bearings replaced?
 

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Discussion Starter · #7 ·
That race doesnt look too unusual, the races are not flat when new, they have a convex arc to them so they wear into the rollers a little.
I see at least one rear a month with the caps on the wrong side, check that first, even if they are marked people manage to mark them wrong.
Were the axle bearings replaced?
As I understood it, everything was supposed to be new (not axles themselves) - but I don't know for fact the axle bearings were new. Axle surfaces the bearings ride on still look good. But I'm going to C-clip eliminators for stock 1.400" surface axles with this repair. Why do you ask?

Just got back in from doing some preliminary functional checking on the carrier bearing cap size. Put a .0015 feeler gauge between the race and the cap and then tightened the cap bolts. You could feel there was just a little something in there as you snugged the bolts the last 1/16 turn or so (compared to tightening with nothing there) and the feeler gauge was definitely trapped. So I think the cap size seems virtually the same size as the race. Both caps were the same in this respect. Do you think I should take the axle housing somewhere to have it measured with an inside mike. Maybe I'm making much ado about nothing?
 

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Was the howling related to the throttle or was if just a function of road speed?

Throttle related means differential or pinion bearings, or gears. A steady noise independent of throttle application is often wheel bearing related. Is the pinion still installed? If so, it should feel perfectly smooth when rotated, there should be not notchiness or roughness.
 

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If you have a question about a bearing then now is the time to inspect it and be certain that nothing is wrong.
 

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Discussion Starter · #10 · (Edited)
Was the howling related to the throttle or was if just a function of road speed?

Throttle related means differential or pinion bearings, or gears. A steady noise independent of throttle application is often wheel bearing related. Is the pinion still installed? If so, it should feel perfectly smooth when rotated, there should be not notchiness or roughness.
Howling was throttle related. Nothing when decelerating. Only when steady or accelerating 45-60 mph. Quieter at faster speeds. Pinion is out now but it turned smoothly on it's bearings.

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Discussion Starter · #11 ·
If you have a question about a bearing then now is the time to inspect it and be certain that nothing is wrong.
Planning a lot of new parts here. Spool, ring and pinion, all 4 bearings, c clip eliminators. Just trying to make sure all will turn out as expected with no howling. Plan on using another two modified new bearings to do pinion setup and then pressing on the final ones.

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The infamous sing from 40-60 is a function of the gears and you cant really fix it. This is the issue I deal with daily. About 5-10% of the gears I install have that sing, sometimes it can be really loud with what I would call bad gears.
Ford 9 gears are a battle nowadays, in every ratio.
The GM 8.5/8.6 is usually not a problem but I have had noisy ones.
You can get a factory gear set from American Axle if you're using a factory ratio, that is, those have the best chance of being guaranteed quiet.

Also, you are running this thing hard and launching it, check the runout on the diff where the ring gear bolts up.
 

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Discussion Starter · #13 · (Edited)
Thanks guys, Please tell me if this makes sense.

I'll have the new bearings pressed onto the new spool. Then without the ring gear I'll install the spool/new races in the housing, finding the correct number of shims to give some preload - and check run out of the ring gear mounting surface - then remove it. Is there a way to test the preload on the carrier bearings this way? How tight should the spool turn without any gears present.

I plan to start with a couple of new bearings and races where the ID of the bearings have been ground out enough to slip on/off the pinion. I don't have the pinion depth tool, so intend to begin with same shims that was previously on the other pinion (should be somewhere around 0.025"-0.030"). Set pinion preload to 25 in.lbs with no crush sleeve or spacer. Install spool and ring gear with same carrier bearing shims as original and check backlash. Set backlash to 0.008 (yes I have a dial indicator) by adding or subtracting appropriate shims to different sides. Then check pattern on a few teeth.

Depending on pattern, add or subtract pinion shims to move pattern towards heel or toe - set pinion bearing preload again to 25 in.lbs, set backlash again to 0.008, and recheck pattern. Repeat as necessary until I have a good drive pattern centered from heel to toe and appropriate coast pattern on other side of tooth..

Install new bearings on pinion and adjust pinion preload to 25 in.lbs using a spacer and shims.

Finally, if pattern is towards the inside or outside edge - adjust backlash to try to correct it as much as possible, as long as backlash remains between 0.006-0.010". Manufacturer's backlash spec on my (new) ring/pinion is 0.008" - 0.010", but could I go just slightly tighter if there is a need in order to get a good pattern? Don't think looser than 0.010" would probably be good when drag racing?

I did already buy the Strange LPW Ultimate Cover just by chance. Got a good deal on it at Jegs ($139.00 with the $20 off). Probably not going to do the axle tube kit for my 400 rwh in the S10, but the cover seemed quality and that is what attracted me to it.

Finally, should I be inspecting the backlash again at the end of the season? Keep an eye on gear or bearing wear that might cause too much clearance?

thanks in advance.
 

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Thanks guys, Please tell me if this makes sense.

I'll have the new bearings pressed onto the new spool. Then without the ring gear I'll install the spool/new races in the housing, finding the correct number of shims to give some preload - and check run out of the ring gear mounting surface - then remove it. Is there a way to test the preload on the carrier bearings this way? How tight should the spool turn without any gears present.
The best way that I know of to set the preload on the differential bearings is to put the shims in as tight as you can get them without damaging the shims or the housing while tapping them in. There is no good way that I know of to measure preload on these bearings. As for the pinion bearings, I usually go 19 to 21 inch pounds of preload on these, but 25 should be fine too.

As for the pattern, don't get hung up on heel and toe. Look at the pattern from root to face and adjust the pinion depth by this. Be ready to disassemble everything and change the pinion shim if the pattern changes when you install the bearings that will be run in the rear end. It's common for the pinion depth to change when switching from set up bearings to the real bearings. This is why I never use set up bearings. If you don't have a press then set up bearings save a lot of time. I wouldn't set the backlash tighter than the manufacturer's specs. Also, break in the gears the best that you can before putting a lot of power to the gears. You want the teeth to wear smooth before putting a lot of pressure on them.
 

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Discussion Starter · #20 · (Edited)
You mentioned a spool, I have had new name brand spools with as much as .040 runout on the ring gear mounting face.
Thanks! Guy that pressed bearings on my spool for me last night also told me I should check this, but on the surface of the ring gear itself. I suppose that way you are checking both at the same time. He also helped me make the setup pinion bearing using my old one, and had a list of starting shim specs for different rears. His document said 0.037" as a typical starting place for pinion shims. 0.038" was under the bearing on my old pinion. He has the ultra fancy pinion depth tool as he does a lot of rears, but I don't feel I can ask to borrow it. We're friendly, but not friends and he does race car fabrication in his own small shop as his source of income. I never ask or expect to borrow tools that people make their living with, but then again I wouldn't turn them down if offered. He did offered to mentor me on the install if I had any trouble or questions.
 
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