Installing a Trac Lok or Eaton Truetrac for a Super 8 (8.8)

[SALEEN961]

I installed a Ford Trac-lok limited slip in my semi-float 9.75" rear differential to replace my factory e-locker. I'm very happy with the outcome and I would definitely do this upgrade again because I often find myself in situations where I couldn't use the e-locker or 4HI, but I still wanted more traction than an open differential provided.

I used the factory trac-lok differential carrier for a 2014 F150 and carrier bearings ordered by VIN for my 2021. After adding in the cost of fluids and everything else, I was able to complete the whole swap for under $300 back in 2021. Even without wholesale pricing, this job could easily be completed for less than $700 for those looking to tackle it themselves, but I would expect to pay a shop about $1300 for the whole job if they supply the parts. I was able to reuse my factory shims, but I always suggest having a shim kit on hand just in case you need it. In my case, the backlash and gear patterns were identical before and after the swap but you won't always get that lucky.

Limited Slip Carrier: 9L3Z-4026-F, $250.77
Bearing Cup: BL1Z-4222-A, MSRP $17.50 (2 needed)
Bearing: 7L1Z-4221-A, MSRP $33.17 (2 needed)
Ring Gear Bolts: F75Z-4216-AA MSRP $15.00 (2 packs of 6 needed)
LSD Friction Modifier: XL-3
Retaining Compound: Loctite Green 638
Gear Oil (3 quarts)
Diff Cover Gasket: HL3Z-4036-A (Optional)
Yukon Gear Carrier Shim Kit: SK-SSF9.75

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[amschind]

It's rare to wear out a LSD clutch assembly under normal usage. They don't start fully engaging until the spider gears try to spread apart when there's differential torque applied to the wheels. Typically works great for burnouts. Not quite sure if there's going to be anything but marginal difference when there's an active tractive system.

I know the active system in the MME w/ open diffs is damn fine engineering. Its torque vectoring which is handled entirely by the brakes is amazing. I don't throw the F150 around like I do the MME despite being a 5klb vehicle.

I may be biased because I have seen several. Getting stuck in a muddy field in West Texas because the "limited slip differential" in an old F150 was flinging mud 25 yards with one rear tire while the the other sat perfectly motionless is a powerful object lesson. My second truck had a factory locker in the rear, and chirped tires in corners like that was its job, though that clutch pack didn't wear out in the 4 years I had that truck. I am generally intolerant of wear items buried deep within a machine unless there is no practical alternative, and back in the 1990s there wasn't (E-lockers were still just an idea and although Torsens existed....they weren't common or easy to find). Today, we have lots of options, most of which work better than a friction plate LSD even when that LSD is functional.

If we have the choice of "maintenance which requires removal of the differential and spins wheels when you need it most" vs "fluid change maintenance and electric on-the-fly switching between open diff OR spool", it is very hard for ME* to pick the former. The biggest change for me was the realization that Torsens behave better than clutch pack LSDs even in front differentials. I put Eaton Torsens front and rear in my old Explorer, which used 4A instead 2H (i.e. there was no 2H without performing the "brown wire mod" to shut the solenoid off). It chirped the rear tires less than the old clutch pack LSD did (which the prior owner had already replaced once when it failed) even in hairpin turns, and I never noticed the front diff was no longer open. Same experience with my current F150: I have slightly more front end noise, but its really tough to tell if that's the diff or the just the AT tires that went on about the same time. In terms of driving, I have never heard any of the 4 tires chirp except when I engage the rear E-locker on a dirt road.

*For a street vehicle, where marginal traction (either via speed or snow/rain) is far more common than highly intermittent traction and working on the vehicle is expected, I can see how a clutch pack LSD would make sense. I drive a truck that's mostly on the highway and every so often in soft, East Texas clay mud. I need Michelin Touring tires that can magically turn into Boggers......the compromise being a set of KO2s. One tire with traction is actually common, and 4 wheel lockup and a recovery board is what fixes that. I went to look at a piece of property just after I got the truck with the Hankook "dry pavement only AT" tires on it, and drove into submerged grass just far enough to close the gate behind me. I had it in 4L and rear locked (didn't have the front Torsen yet) beforehand. Look around for a big, don't get eaten by a Timber Rattler, get in truck to back up and....spin all 4 wheels. I was lucky to find a piece of metal grate to shove under one rear tire, and that one tire got me out. A clutch pack LSD would've spun the rear tire without traction, which made me pretty grateful for the E-locker. My use case may not be representative for everyone, and is certainly different from folks who want high performance street trucks or an easier time in snowy/icy roads, but for dry pavement or zero traction mud, it's what works for me.

 

[TexasTruck]

All this talk about 9” has me feeling, uh… inadequate ? I see speedmaster makes a worm gear style 8.8 34 spline LSD for C clip axles.

@HammaMan What is MME?

If you have a mechanical LSD, will it play nice with the factory traction control? Or does traction control need to be disabled all the time?

 

[Snakebitten]

Mustang Mach-E

 

[EricR]

... because I often find myself in situations where I couldn't use the e-locker or 4HI, but I still wanted more traction than an open differential provided.
...

Please help me understand and maybe avoid a bad situation.

I am rather new to this 4x4 world and have an e-locker differential on my 2021 PB Lariat.

Please expound on situations where the the e-locker or 4H can't be used.

Wouldn't 4A or 2L cover most all of such scenarios?

Thanks!

 

[SALEEN961]

Please help me understand and maybe avoid a bad situation.

I am rather new to this 4x4 world and have an e-locker differential on my 2021 PB Lariat.

Please expound on situations where the the e-locker or 4H can't be used.

Wouldn't 4A or 2L cover most all of such scenarios?

Thanks!

With an e-locker you have to be careful to not engage it on high traction surfaces, especially if you are making tight turns. You also can't use it over 25mph unless you are in 4L or 4H with specific drive modes selected (Deep Snow/Sand, Mud/Ruts, and Rock Crawl). If you exceed the speed limit for the e-locker, it will automatically disengage which could cause an accident if you suddenly lose traction while climbing an icy hill.

In my area, the main roads always get plowed and salted, but side streets are often full of slush and snow and 10-20% grades are common. Transitioning from steep and very slippery roads to dry main roads is a challenge because I would need to use the e-locker or 4WD to get onto the main roads, but the high traction of the main roads immediately causes driveline binding as I leave the snow covered side streets.

For my use case, the best solution was to get rid of the factory e-locker and factory 2H/4H/4L transfer case. After installing a Trac-lok limited slip differential and a Raptor 4A TOD transfer case with mechanical locking 4H, I have tons of traction that is always there and I don't have to worry about road conditions at all. I spend 90% of my time driving around in 4A and if the roads are really bad, I can shift into 4H.

 

[Snakebitten]

Doesn't the Raptor have a different speed limit for the E locker? Beyond 25mph, I mean?

 

[SALEEN961]

Doesn't the Raptor have a different speed limit for the E locker? Beyond 25mph, I mean?

The Raptor has no speed limit for the e-locker in 4L. You also have no speed limit in the Baja and Off-Road drive modes when you are in 4H, and no speed limit in the Rock Crawl drive mode which shifts the truck into 4L.

If you are in 2H or the Normal, Slippery, Sport, or Tow/Haul drive mode in 4A or 4H, the e-locker is limited to 25mph.

 

[EricR]

With an e-locker you have to be careful to not engage it on high traction surfaces, especially if you are making tight turns. You also can't use it over 25mph unless you are in 4L or 4H with specific drive modes selected (Deep Snow/Sand, Mud/Ruts, and Rock Crawl). If you exceed the speed limit for the e-locker, it will automatically disengage which could cause an accident if you suddenly lose traction while climbing an icy hill.

In my area, the main roads always get plowed and salted, but side streets are often full of slush and snow and 10-20% grades are common. Transitioning from steep and very slippery roads to dry main roads is a challenge because I would need to use the e-locker or 4WD to get onto the main roads, but the high traction of the main roads immediately causes driveline binding as I leave the snow covered side streets.

For my use case, the best solution was to get rid of the factory e-locker and factory 2H/4H/4L transfer case. After installing a Trac-lok limited slip differential and a Raptor 4A TOD transfer case with mechanical locking 4H, I have tons of traction that is always there and I don't have to worry about road conditions at all. I spend 90% of my time driving around in 4A and if the roads are really bad, I can shift into 4H.

Perfect.

Much appreciated!

 

[5.0Screw22]

It sounds like he has an 8.8" rear open differential and wants something with better traction. I will add this one snippet: A clutch pack LS differential depends upon clutches which have to slide against one another every time you turn the truck. The clutch packs are wear items and will wear out. You must pull the differential out of the truck to replace the clutch packs; if you leave worn clutch packs in, you have an open differential which you must pay ALL of the labor cost of the original install to restore to full function.

A large part of the popularity of E-Lockers and Torsens is that they are simple and robust mechanical devices which don't have (planned) wear components. An automatic transmission will wear out eventually, but the expected maintenance is replacing the transmission fluid and filter vs a manual in which planned maintenance involves removing the transmission from the engine and replacing clutch packs. I think that's a good analogue for Torsen/E-locker vs clutch pack LSDs.

If there was a Torsen or TrueTrac available for the Super 8.8, that would be a far better option. I would not put the E-Locker in the same classification as far as functionality. Changing a clutch pack is no big deal on these rears. If you have done it on a 9" Ford, this is way easier! You do not even have to pull the carrier to swap a clutch pack on these rears. It's a beautiful thing. "ALL" the labor cost is just my 2-3 hours to do the job.

 

[5.0Screw22]

The Raptor has no speed limit for the e-locker in 4L. You also have no speed limit in the Baja and Off-Road drive modes when you are in 4H, and no speed limit in the Rock Crawl drive mode which shifts the truck into 4L.

If you are in 2H or the Normal, Slippery, Sport, or Tow/Haul drive mode in 4A or 4H, the e-locker is limited to 25mph.

I would have answered the same, but I was away for the weekend. ? Here is a page from the Ford owners manual that may be helpful as well.

One other thing... According the the owners manual, the Raptor is not much different than the other F150's. The deactivation point isn't any different in normal mode. Here is the Raptor E-Locker page:

For a lot of applications, the E-Locker is probably a better choice. There is not a one size fits all. It depends on how you use your truck. A supercharged, lowered truck with performance tires drives a little different than a lifted, off-road truck with large tires. I see it this way; with an E-Locker, I basically have an open rear end from anything above a 24mph rolling start. I want 2 wheels being driven, so a Traction Lock is a better choice for me. I am not trying to get out mud or off-road my truck.

 

[amschind]

If there was a Torsen or TrueTrac available for the Super 8.8, that would be a far better option. I would not put the E-Locker in the same classification as far as functionality. Changing a clutch pack is no big deal on these rears. If you have done it on a 9" Ford, this is way easier! You do not even have to pull the carrier to swap a clutch pack on these rears. It's a beautiful thing. "ALL" the labor cost is just my 2-3 hours to do the job.

That's useful info re: clutch pack exchange without pulling the carrier. Re: Torsens for the 8.8", I had one in my 2002 Explorer.

 

[HammaMan]

The Raptor has no speed limit for the e-locker in 4L. You also have no speed limit in the Baja and Off-Road drive modes when you are in 4H, and no speed limit in the Rock Crawl drive mode which shifts the truck into 4L.

If you are in 2H or the Normal, Slippery, Sport, or Tow/Haul drive mode in 4A or 4H, the e-locker is limited to 25mph.

So to confirm your experience with the factory system in slippery mode was that it was useless? This is really surprising to hear that ford went a completely different direction than other vehicles with open diffs. Both the bronco and mach-e systems don't even flinch when a wheel comes off of the ground with fully open diffs (though bronc has drive modes, MME has no drive modes, just full reactivity always).

Given the open diffs, any wheel losing traction is dealt with as fast as the computer sees a speed delta that shouldn't be there, which occurs with just a couple ticks of the exciter ring. There's no special traction computer; It's just regular old hardware. The only variant that gets a special anything is like the F150 w/ active / CCD shocks. I'm in the SE and our chances to play with icy roads are few and far between. The mach-e folks in the icy regions rave about its capabilities. I've only got to test its torque vectoring which is quite pronounced.

For 2 decades + we've seen companies making advertisements about traction control w/ torque vectoring. When I say that you've probably had a few come to mind. Yet when you test them you at best get a 'tick tick tick' of an ABS unit as it half-assedly grabs and releases a wheel's brake, an unimpressive clunky sounding attempt at best. My personal experience has typically been testing such functionality, particularly T.V. and walking away rather disappointed. I was quite surprised to see just how well / fast / quietly the system in the mach-e works. The brakes on the F150 have more than enough authority to allow it to work the same

Personally if I was going to bother with the rear end, it'd be torsen or keep the e-locker.

A few diffs tested (torsen knockoff, enhanced LSD, auto locker....


Mach-E w/ low power front motor (power is rear biased)

 

[5.0Screw22]

That's useful info re: clutch pack exchange without pulling the carrier. Re: Torsens for the 8.8", I had one in my 2002 Explorer.

Yes, there is a Torsen for the regular 8.8". I put one in the 8.8" rear in my old 97 Cobra Mustang. Unfortunately, they do not make one for Super 8.8" used in our trucks. It would be the way to go, if they made one for this application. I install a TrueTrac or a Torsen in many of my vehicles. I installed an Eaton TrueTrac in the 9" Nodular case in my 71 Mustang Mach I. Once you have one, you'll add one to everything. They are far superior to a Traction Lock LSD, but that's the only option available today.

 

[5.0Screw22]

I feel like I say this all the time on this forum, but it depends on how you use your vehicle. It seems a lot of people have formed their opinions based on how they use their vehicle. While some parts, or systems, or setups work well for some people, they do not work well for everyone. There is an aftermarket full of parts to accommodate those people. When Ford designs their systems, it is done with the majority of people in mind. Not everyone will like everything and there will be things that do not work for them. For me, the E-Locker and the traction control on this vehicle are terrible!

The E-Locker does nothing after 25mph. Ford states, "The electronic locking differential is for off-road use only and is not for use on dry pavement." So, it does nothing for the way I use my truck. The OP and I are doing this for a performance application. The E-Locker is not good for that purpose. I will add that, for me, the mandatory traction control function is also not good.

The traction control is great if you are driving around like a little old lady. The system is great for people who are not good at handling a vehicle in adverse conditions. I will say that if you are an experienced driver, there are many times when you could do a much better job than the system. On multiple occasions, I have had the system "perceive" wheel slippage (on a dry road) and it throttles the engine and applies the brakes (momentarily) while I am trying to pull out on a road with a 55 mph speed limit. The vehicle slows you down with a truck coming at you, because it doesn't want your tires to spin a little bit. It's OK that you will be drug for half a mile under the wheels of a semi, but god forbid that you lose a slight amount of traction!

I do not need a system to take over for me when I have things well under control. An experienced driver can manage a slight loss of traction using the throttle and the wheel. I understand that the average driver cannot. I don't need or want the vehicle to brake and throttle my engine. I understand that some people benefit from that. I have had that happen a couple of times with this truck when it was not needed or welcome.

The TCS in this 2022 truck is not as good as the one in my 2019 F150 Limited. I believe a large part of that deals with the front axle system. My Limited had the Raptor front differential. Saleen961, I suspect you have cured some of the things that I dislike by doing that Raptor differential transplant. ?

In the snow, I also shut off the traction control for most normal driving. It depends on the conditions. It works fine on plowed roads, but when it’s deep snow or a sloppy mix, it sucks. We see a couple hundred inches of snow most years, and I have been driving in snow and ice for over 40 years. A lot of those years were with only rear wheel drive. If I see a sloppy spot in an intersection, I will accelerate to push through it to avoid getting stuck. I will slip a little but I am in complete control of the vehicle. With traction control on, it will slow me down and possibly get the truck stuck. I do not consider that a helpful system.

There should be a way to disable this system entirely. I know you can disable it (partially) with the button, but it will still come back on if it thinks it needs to. The only way I have seen to disable entirely it is to unplug a wheel sensor. I have seen that a lot of the people with performance trucks seem to be doing that. There should be more control permitted to the user. Not everyone uses their truck the same way. Some of us do not benefit from these systems all of the time. Rant over!

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