Glittery diff oil
Thread Starter
Pro
Joined: Nov 2017
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From: Belgium
Glittery diff oil
Hi guys, accidentally drained the oil when changing the spring bolts..
The oil was very glittery, although it has literally done 4 miles since the oil was changed..
It's not magnetic, what could cause this? Crush sleeve breaking down?
There is a slight up and down movement on the side yokes, don't know if that's normal. Side yokes have 40 thou endplay, break away of the unit is around 80 Nm atm iirc.
any pointers?(He asks while looking at rebuild kits)
cheers
The oil was very glittery, although it has literally done 4 miles since the oil was changed..
It's not magnetic, what could cause this? Crush sleeve breaking down?
There is a slight up and down movement on the side yokes, don't know if that's normal. Side yokes have 40 thou endplay, break away of the unit is around 80 Nm atm iirc.
any pointers?(He asks while looking at rebuild kits)
cheers
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lets go back one second, how do you accidentally drain the oil when changing the spring bolts and why is the cover no longer on the case? Was this rear in the car?
Last edited by MelWff; Dec 25, 2018 at 05:03 PM.
Tech Contributor
Joined: Aug 1999
Posts: 15,175
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From: Connecticut, USA
Crush sleeves don't break down. They are steel sleeves that are compressed under heavy load and keep preload on the bearings. I can't tell anything by looking at the oil picture there may be some metal in it or not. The ends of the axles appear good, there are sharp chamfers on each one. Looks like the axles are pushed in and there is a gap between the snap ring and side gear.
It appears to be an otherwise stock diff- rough posi castings, spring pack, etc. If it was quiet, you are not pushing the car hard, install the new cover and install it in the car and go. Use the correct length bolts of course.
Be careful buying parts, not all kits are the same. Do your homework.
It appears to be an otherwise stock diff- rough posi castings, spring pack, etc. If it was quiet, you are not pushing the car hard, install the new cover and install it in the car and go. Use the correct length bolts of course.
Be careful buying parts, not all kits are the same. Do your homework.
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Thread Starter
Pro
Joined: Nov 2017
Posts: 587
Likes: 49
From: Belgium
Crush sleeves don't break down. They are steel sleeves that are compressed under heavy load and keep preload on the bearings. I can't tell anything by looking at the oil picture there may be some metal in it or not. The ends of the axles appear good, there are sharp chamfers on each one. Looks like the axles are pushed in and there is a gap between the snap ring and side gear.
It appears to be an otherwise stock diff- rough posi castings, spring pack, etc. If it was quiet, you are not pushing the car hard, install the new cover and install it in the car and go. Use the correct length bolts of course.
Be careful buying parts, not all kits are the same. Do your homework.
It appears to be an otherwise stock diff- rough posi castings, spring pack, etc. If it was quiet, you are not pushing the car hard, install the new cover and install it in the car and go. Use the correct length bolts of course.
Be careful buying parts, not all kits are the same. Do your homework.
Do you know if the light up and down movement on the side yokes is normal?
maybe best to replace the clutches?
Tech Contributor
Joined: Aug 1999
Posts: 15,175
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From: Connecticut, USA
040" endplay for a rebuilt diff is absolutely lousy, for a stock built diff with miles on it then it's about right. There should not be a lot of lateral play in the axle/bearing. If there is, then the Torrington bearings may be bad.
I never use synthetic gear oil. Plain old 90 or 85-140 gear oil with GM additive is all you need. You pay more for oil you don't need. The clutches are not going to burn up, without the additive they would chatter. That appears to be a 70's posi so it would have the weak snowflake clutches unless they hav been replaced in the past, Do NOT use fiber coasted clutches as they will wear.The stock posi set up is pretty sloppy and more them likely a lot of the axle endplay is from the posi setup.
I never use synthetic gear oil. Plain old 90 or 85-140 gear oil with GM additive is all you need. You pay more for oil you don't need. The clutches are not going to burn up, without the additive they would chatter. That appears to be a 70's posi so it would have the weak snowflake clutches unless they hav been replaced in the past, Do NOT use fiber coasted clutches as they will wear.The stock posi set up is pretty sloppy and more them likely a lot of the axle endplay is from the posi setup.
Thread Starter
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From: Belgium
Its not a rebuilt diff although it seems Like it has the older style clutches.
with the side yokes in that shape, where can the play come from, only from worn clutches or am I wrong?
There is not a lot of lateral play, but you can see it none the less, difficult to say how much without my dti
with the side yokes in that shape, where can the play come from, only from worn clutches or am I wrong?
There is not a lot of lateral play, but you can see it none the less, difficult to say how much without my dti
Tech Contributor
Joined: Aug 1999
Posts: 15,175
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From: Connecticut, USA
Sounds like you have a stock diff with common axle endplay of 040" and a broken cover. As mentioned you can bolt on a new cover and drive it. Otherwise you might as well correctly rebuild it.
Axle endplay comes from 3 areas
1- worn soft faced axles
2- posi setup
3- posi case cross shaft holes worn
Axle endplay comes from 3 areas
1- worn soft faced axles
2- posi setup
3- posi case cross shaft holes worn
Thread Starter
Pro
Joined: Nov 2017
Posts: 587
Likes: 49
From: Belgium
Sounds like you have a stock diff with common axle endplay of 040" and a broken cover. As mentioned you can bolt on a new cover and drive it. Otherwise you might as well correctly rebuild it.
Axle endplay comes from 3 areas
1- worn soft faced axles
2- posi setup
3- posi case cross shaft holes worn
Axle endplay comes from 3 areas
1- worn soft faced axles
2- posi setup
3- posi case cross shaft holes worn
Do you know the stock thickness of the posi clutches by any chance?
mine measure all at 67-68 thou, snowflake clutches sadly
thanks
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,987
From: Connecticut, USA
068-069" so you have little wear on them and most don't realize they don't wear like a fiber flywheel clutch. They can be reused if you want but they are weaker. Solid steels are the best and available. If you build it stock make sure the lash is 002", Tuning is a better option but more time consuming and you have to balance it correctly or it will not work correct. Measure your axle face to snap ring should be 190-200 if original GM, could be anywhere between 170-185 with the quality of axles sold today -new or used. If you have 185-200 and had 040 endplay then the problem was with the posi setup- unless you found the case holes enlongated.
Thread Starter
Pro
Joined: Nov 2017
Posts: 587
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From: Belgium
068-069" so you have little wear on them and most don't realize they don't wear like a fiber flywheel clutch. They can be reused if you want but they are weaker. Solid steels are the best and available. If you build it stock make sure the lash is 002", Tuning is a better option but more time consuming and you have to balance it correctly or it will not work correct. Measure your axle face to snap ring should be 190-200 if original GM, could be anywhere between 170-185 with the quality of axles sold today -new or used. If you have 185-200 and had 040 endplay then the problem was with the posi setup- unless you found the case holes enlongated.
I'll be running around 300-350 hp, dreaming of a burnout but probably will never do one . Don't want to ruin the expensive tyres here(200$ a piece).
So snowflake clutches might be okay, but I d rather swap to solid clutches. Any preferred retailers? I see them aviable at zip for example, but don't know if ill be paying the corvette tax on those and if they can be got cheaper/better quality at other retailers.
Axles look like theyre at 191 now, so im getting away lucky 😅
And again, a big thanks
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,987
From: Connecticut, USA
For your application I would
1- Use only new Timkens
2- ARP RG bolts
3-Use Socket heads in the caps and make sure they are fit for 001" rock
4- Fully polish the posi case, use the 1017 spiders in the case. Mark the position of them as they came out.
5- Correctly tune the posi- balanced and no lash
6- Use solid steel clutches
7- Check the hardness of the axle faces, harden if under 50Rc.
8- Set the pattern and lash
Built to these spec's it will hold up to 350hp a long time for your intended use. For added insurance : If you have access to someone who can cryo treat parts that take the polished posi, spiders, axles, and R&P for a batch treatment. You always treat after the polishing is done, not before.
1- Use only new Timkens
2- ARP RG bolts
3-Use Socket heads in the caps and make sure they are fit for 001" rock
4- Fully polish the posi case, use the 1017 spiders in the case. Mark the position of them as they came out.
5- Correctly tune the posi- balanced and no lash
6- Use solid steel clutches
7- Check the hardness of the axle faces, harden if under 50Rc.
8- Set the pattern and lash
Built to these spec's it will hold up to 350hp a long time for your intended use. For added insurance : If you have access to someone who can cryo treat parts that take the polished posi, spiders, axles, and R&P for a batch treatment. You always treat after the polishing is done, not before.
Thread Starter
Pro
Joined: Nov 2017
Posts: 587
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From: Belgium
Many thanks, this diff will be a lot better now!
Will these fit our stock posi units?
https://www.vividracing.com/82858875-inch-clutch-kit-12p12t-eaton-posi-plate-steel-nitro-gear-and-axle-p-151885693.html
Will these fit our stock posi units?
https://www.vividracing.com/82858875-inch-clutch-kit-12p12t-eaton-posi-plate-steel-nitro-gear-and-axle-p-151885693.html