Friction modifier for eBay Eaton posi

[theraymondguy]

I have just finished installing an eBay Eaton style posi in my third gen Firebird. The posi moans / drags when turning, I’ve confirmed my installation and believe (hope) this is caused by my choice of friction modifier.

My testing has been limited to a loop in my neighbourhood. I did idle the car with the wheels elevated with 80W90 and FM before trying it on the street. I’ve rebuilt and repaired several open diffs in the past, and I’m (very) satisfied with the carrier installation.

My next most affordable option is Castrol ls 80w90.

Has anyone installed one of these units? What worked for you?

 

[Deleted member 89374]

Congratulations on successfully installing the Eaton style posi in your third-gen Firebird. It's a fantastic upgrade, providing a great performance boost. And I totally understand your concern. While it's not uncommon to experience some initial noise or drag after installation, we definitely want to get to the bottom of it.

There could indeed be a connection between the noise and the choice of your friction modifier. Some differentials are quite picky about what you put in them, and not all friction modifiers behave the same in all types of posi units. Hence, it might be beneficial to try a different type.

You mentioned considering Castrol LS 80w90, which is indeed a good choice. Castrol is known for producing reliable lubricants, and the LS 80w90 has been tested in a wide range of applications with positive feedback. Moreover, it's worth mentioning that many aftermarket posi units are actually shipped with Eaton's own friction modifier. So, if you continue to experience problems, you might also consider trying Eaton's product to see if it makes a difference.

You mentioned that you've broken the differential in by idling with the wheels off the ground, which is indeed a good practice, as it allows the gears to mesh and distribute the lubricant without any load. However, did you give it a good drive after the initial break-in? Usually, it's advised to drive about 15-20 miles, while avoiding hard acceleration and tight turns during this time. This can help ensure the gears have meshed properly and the differential has a chance to settle into its new environment.

If you've done all of this and the differential continues to moan or drag, it may be worth taking a second look at the installation. It might seem tedious, but it could be something as simple as a slightly misaligned gear that's causing the noise.

Lastly, remember that these things can take a bit of time to smooth out as everything seats and wears in together. So, give it some time and see if it settles in. If it doesn't, keep troubleshooting with the advice above.

Keep us posted on your progress. The community here is always ready to assist. We're all learning together!

Good luck and happy driving!

 

[bullwinkle]

If that's the gear type Eaton posi, I don't think they're supposed to have friction modifier(?) The one in my F-450 in my sig doesn't require it, just plain old GL5 gear oil.

 

[theraymondguy]

Th

Congratulations on successfully installing the Eaton style posi in your third-gen Firebird. It's a fantastic upgrade, providing a great performance boost. And I totally understand your concern. While it's not uncommon to experience some initial noise or drag after installation, we definitely want to get to the bottom of it.

There could indeed be a connection between the noise and the choice of your friction modifier. Some differentials are quite picky about what you put in them, and not all friction modifiers behave the same in all types of posi units. Hence, it might be beneficial to try a different type.

You mentioned considering Castrol LS 80w90, which is indeed a good choice. Castrol is known for producing reliable lubricants, and the LS 80w90 has been tested in a wide range of applications with positive feedback. Moreover, it's worth mentioning that many aftermarket posi units are actually shipped with Eaton's own friction modifier. So, if you continue to experience problems, you might also consider trying Eaton's product to see if it makes a difference.

You mentioned that you've broken the differential in by idling with the wheels off the ground, which is indeed a good practice, as it allows the gears to mesh and distribute the lubricant without any load. However, did you give it a good drive after the initial break-in? Usually, it's advised to drive about 15-20 miles, while avoiding hard acceleration and tight turns during this time. This can help ensure the gears have meshed properly and the differential has a chance to settle into its new environment.

If you've done all of this and the differential continues to moan or drag, it may be worth taking a second look at the installation. It might seem tedious, but it could be something as simple as a slightly misaligned gear that's causing the noise.

Lastly, remember that these things can take a bit of time to smooth out as everything seats and wears in together. So, give it some time and see if it settles in. If it doesn't, keep troubleshooting with the advice above.

Keep us posted on your progress. The community here is always ready to assist. We're all learning together!

Good luck and happy drivin

I’ve only run the car in my neighbourhood, not even a 1/3 mile.

 

[Greasymechtech]

For a clutch type posi, need to find an empty park lot and do a bunch of figure eights, and left and right roundabouts.
If that doesn't help, then use more FM.

FM should be dosed as needed, within reason. Don't assume that preblended gear oil has enough.

Limited Slip Supplement - Lubegard

www.lubegard.com

 

[theraymondguy]

For a clutch type posi, need to find an empty park lot and do a bunch of figure eights, and left and right roundabouts.
If that doesn't help, then use more FM.

FM should be dosed as needed, within reason. Don't assume that preblended gear oil has enough.

Limited Slip Supplement - Lubegard

www.lubegard.com

It isn’t chattering, but moaning - does it require this figure 8 exercise to “break in”?

I’ve added 5 oz of fm to 2 quarts of oil.

 

[Greasymechtech]

What type of diff? Specifics please, like PN!
What choice of FM? brand/pn/sizebottle?
What PN of the gear oil?

Add some detail to this thread if you want a realistic answer.

All clutch/cone diffs, whether new, rebuilt, or a during a SIMPLE drain refill maintenance, require a figure 8 run.

 

[theraymondguy]

What type of diff? Specifics please, like PN!
What choice of FM? brand/pn/sizebottle?
What PN of the gear oil?

Add some detail to this thread if you want a realistic answer.

All clutch/cone diffs, whether new, rebuilt, or a during a SIMPLE drain refill maintenance, require a figure 8 run.

It’s a white box (china) eBay plate style posi, styled after eatons’ 19663-010.

I’m using shell spirax 80w90, generic friction modifier from CRC

CRC® Trans-X® Posi Trac® Limited Slip Gear Oil Additive, 7 Fl Oz

Limited-slip differentials (or LSD) are used in many vehicles to allow different wheel speeds, transferring more torque to one wheel when it is slipping. This technology provides better traction on slippery surfaces. Over time, the components of the differential can wear and cause a chattering...

www.crcindustries.com

 

[skyactiv]

 

[skyactiv]

Edit I removed bad info

 

[theraymondguy]

It came assembled. I did not disassemble it and soak the clutches and reassemble it. I can see the benefit but can’t see it being standard practice either.

 

[theraymondguy]

What type of diff? Specifics please, like PN!
What choice of FM? brand/pn/sizebottle?
What PN of the gear oil?

Add some detail to this thread if you want a realistic answer.

All clutch/cone diffs, whether new, rebuilt, or a during a SIMPLE drain refill maintenance, require a figure 8 run.

Thanks for your replies Greasy I’ll put some miles on it and put some time into figure 8s in a local parking lots and report back.

 

[theraymondguy]

I couldn’t bring myself to put miles in the car making noise like that without at least trying to change something. I did more reading and repeatedly found that Ford friction modifier received great praise for all disc clutch type differentials, it’s also quite affordable.

After draining the fluid, adding new mixed well with 6 Oz of Ford FM, I backed the car down the driveway, it groaned once to the right and once to the left as rolled out… and has been absolutely quiet since. It is literally night and day better. Absolutely 100% recommend

Ford CM19546A1 Friction Modifier for China / off shore plate style clutch Posi.​

I also highly recommend mixing it in a parking lot far from your house and leaving the waste behind, my god what a stench.