Front Differential Rebuild, irregular clicking and clunking...Already

[marcello7x]

So this is my first post on here, I bought my SS in november and i started getting my first issue this past Tuesday. It sounds like clicking and clunking from the front end. Very irregular, so i ruled out CV, there was no play in the wheels so i didn't thing it was a wheel bearing. After some research found out how weak and often our front differentials tend to chew up bearings. My truck has 215k on it so i figured its probably time for a rebuild. With the long weekend coming, ordered a new ring and grear, and master bearing kit. Last night i pulled the diff, and tonight i took it apart. With the sound of the clunking i expected some carnage, but nothing!! Fluid was dark but fairly smooth with no real visible metal. Very little on the drain magnet as well.

The gears are showing some age, but nothing that would cause the noises i've been hearing. The only thing i did find, was that the carrier bearing races slid right out!!! There are some markings that indicate they have spun in the case, as well as some wear in the surface that meets the bearing. My only thought is those started spinning causing the clicking.

Someone chime in if they have experienced something similar. Should i go ahead and just rebuild everything? This is the first differential i have attempted to rebuild. I have rebuilt multiple Volkswagen trans-axles, but never "properly" with a proper machinist gauge or anything. BUT the last one i built has not had any issues over the past year.

My pictures are too big to upload as an attachment, so i put them in a gallery.

 

Side note, the sooner i get this done, the sooner i can do the fun stuff!!! I have my ported 799 heads and cam waiting to go in this weekend as well!

 

[Downeast Johnny]

When my front diff went the noise it put out was a distinct bearing rumble but no clicking, and by using a mechanics stethoscope I could tell that the noise was coming from the differential. How did you diagnose your noise?

 

Edit; It is pretty unusual to see no metal shavings on the magnet on the drain plug. I had obvious metal, (Although very minor and fine), on my drain plug within 500 miles of the rebuild and the fluid had a silver sheen to it.

 

It is very rare for these trucks to go 200,000 miles without the front diff having been rebuilt at least once. I am not the original owner but my trucks front diff went out at about 45,000 miles.

 

Did you get a vehicle history when you bought the truck?

 

I can't answer your question about the bearing races.

Edited February 13, 2015 by Downeast Johnny (see edit history)

[marcello7x]

There was very very little metal. But not as much as i expected. And yes it must have been rebuilt at some point.

 

 

I got my new bearings in, and the carrier races slide right in and out, does not need to be pressed in. They have been outside in the freezing cold all day, but i've never had something slide in that easy. I've read of people using some green locktite and hammering in a little tick in order to keep them in place.

 

At this point i'm going to go through the rest of the rebuild. Its out and i might as well..

[Downeast Johnny]

I would continue the rebuild too, if it was mine. I would not close the diff up until I found out for sure about those loose races. I've not rebuilt one of these myself but have replaced a lot of bearings and races and have never seen a race slide in or out easily without some other means of containing it.

 

Do you have a dial gauge to test the housing where the races sit for being out of round, Wear, and overall size?

 

Is the locktite impervious to oil? (The oil won't break it down?)

[marcello7x]

So i think found the issue. Something caused the locking tab on the driver side to loosen. I went to go measure depth on it for a starting point when i reassembled everything, and as i went to clean it it spun on me. I pulled the axle seal and saw it was bent up slightly.

 

I'm starting to believe that the spun race put added pressure on the locking tab and caused it to loosen. the clicking i heard must of have been the adjuster teeth hitting the locking tab.

 

I don't think im going to swap the gears at this point. I didn't realize the bearing kit i ordered did not include the shims. So i won't be able to set correct pinion depth. If i reuse the current pinion and gear, i should be able to reuse the shim and have correct depth since all the bearings were replaced with koyo bearing which i what i purchased by dumb luck.

 

OR

 

Leave the pinion bearing as is, since its in good condition still. figure out my loose race issue/replace carrier bearings and reset backlash and be done with it.

 

 

The part i am unsure of is how do people typically set pinion depth if the bearing has to be pressed on? IS there a safe way to pull a bearing to add or remove shims?

 

[marcello7x]

I think my options to "fix" the loose race issue would be to use a punch to knurl the housing a bit. That coupled with loctite 620 which is made for this specific issue.

 

Lastly worst case i can weld tiny tacks to the race and grind them down so they are very shallow then press it in with the above methods.

[Downeast Johnny]

I have a few old post's about the front diff bookmarked. They may give you some info, although you may have gotten beyond these stages of rebuild. I haven't found anything specifically about your loose races, yet, but will keep looking. I would worry about losing hardness in the races while tacking material to them, but that knowledge is beyond my experience in that sort of thing.

 

http://www.silveradoss.com/forums/topic/59887-front-differential-rebuild-instructions/

 

This guy sounds like he knows what he is talking about. Lot's of pictures and tips. He does talk about the possibility of the carrier bearings falling out easily, but doesn't explain what is supposed to hold them in.

 

http://www.truckmodcentral.com/forums/f168/rebuilding-gm-8-25-ifs-differential-**56k-beware-pic-heavy**-13813/

 

Best of luck to you, and keep us posted with your progress.

[marcello7x]

I was able to find the green bearing loctite at a CAP near me. Once i get my inch pounds torque wrench in i'll get back to it. In the meanwhile i pulled my heads and am ready for my cam swap. IF i could get my harmonic balance bolt off.

 

I tried every trick possible except wedging something in the flywheel for fear of breaking something and drilling out the center of the bolt. I just ordered a flywheel locking tool. Not an issue i anticipated since i don't normally drive automatics.

[Downeast Johnny]

Keep us posted on your progress.

[marcello7x]

So its all back together mostly. I used a hammer and a sheet rock screw to knurl where the bearing went along with that bearing loctite and its in there good now.

 

My only issue is re-installing the half shafts. I'm concerned for how hard to hit them with a hammer to get them back in. I gave it a few swings and no luck. So i backed off and left it unfinished while i finished out the heads and cam install. Maybe i just need a bigger hammer. Going to pick up a dead blow hammer and give that a try.

 

My push rod measuring tool comes in today, so i'll have the rods by Thursday[thanks to amazon prime!] By then i should have made some changes to my base tune to get the truck to atleast idle. My cam isn't too big, with only 3.5* of overlap so tuning should be easier than when i did a speed density tune for my 404ci.

 

One last thing, i didn't realize how F$#%$# hard it is to find nitrous[at a decent price] near Boston. I've never used it, so Im considering buying another 80cf tank and filling my own 10lbs when i need it.

[marcello7x]

Ok i'm a blatant idiot! So i couldn't figure out why i was hitting the half shafts with a 4lb dead blow hammer and couldn't get them into the carrier. For some reason i thought i was supposed to install the C clip on the shaft then put it in, not install the new c clip into the carrier!!!

 

I didn't really put any thought into it until last night when i went to reassemble the diff finally. then it just came to me and made so much sense. I must have just overlooked it due to being in a rush to get it back together quickly and focusing most of my time on back lash and pre-load.

 

I have still yet to drive the truck though, fabricating the new exhaust first. Then i can pull it out of the garage for some light driving and tuning.

[Aldofashow]

How much do you think It ended up costing for all the parts to rebuild the front diff and how much time did it take just wondering I need to do mine after winter before she starts giving me trouble everything else has already been gone through in the drivetrain it's the only thing left to refresh

[MatthewCarney]

Downeast Johnny, when you needed your front diff rebuilt @ 45K did it have an obvious humming noise over 50MPH speeds? I'm hearing that in mine and not quite sure what it is. I thought it may be just the front shaft's U joints. Got any opinions for me?

[Downeast Johnny]

Downeast Johnny, when you needed your front diff rebuilt @ 45K did it have an obvious humming noise over 50MPH speeds? I'm hearing that in mine and not quite sure what it is. I thought it may be just the front shaft's U joints. Got any opinions for me?

 

My front diff made an obvious bearing rumble starting above 40 MPH. From 40 on up the rumble was pretty constant. Maybe got a little louder going through a right hand curve.

 

I changed the front diff fluid to Mobil 1 as an experiment before having the diff rebuilt and that quieted it down noticeably, (Made it obvious that the diff was where the noise was coming from).

[marcello7x]

Costs actually weren't bad considering what i expected to spend. First 2 are from Jegs. Going to return them since i didn't end up replacing the gears.

 

Gear and marking compound:

1 1 683-G885411IFS GM 10BL 8.25 REV. R/P 4.1 173.99 173.99 1 1 555-612200 GEAR MARKING COMP-1/2 OZ 3.99 3.99

 

I didn't end up using either one of these, so they're getting returned.

 

Dial Indicator Set with On/Off Magnetic Base - $19.99 - http://www.amazon.com/gp/product/B001QXR2LA/ref=od_aui_detailpages00?ie=UTF8&psc=1 GearWrench 2955D Beam Torque Wrench - $47.99 - http://www.amazon.com/gp/product/B00004SQ3B/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1 USA Standard Gear (ZBKGM8.25IFS-B) Bearing Kit for GM 8.25" IFS Front Differential - $86.14 - http://www.amazon.com/gp/product/B00D61FG68/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

BackLash locks + C clips from dealer: ~$10 or so. I got extra locks just in case, they didn't have any extra C clips in stock.

 

Add in some MISC like 3-4 cans of brake clean, silicon sealant, harbor freight dead blow hammer and it came out to around $200.[Only because my gears were in good shape, otherwise ~$380]

 

Also i didn't replace the pinion bearing so i could avoid the trouble of figuring out pinion depth. It was in great shape, as were most of the bearings. But since i was in there and had the issue of the spun races i decided to replace the rest of the bearings that came with my kit.

 

One other thing to note[Feel free to bash here] I did no use the new crush spacer. I reused the old one. I could not get enough torque on the new one to actually crush it. Being my first rebuild on a diff i was worried about breaking something.