Rear differential upgrade - who's done it?

[The_Auto_Tech]

Getting ready to install my TBM rear brakes and the axles need to come out to remove the dust shields. I'm wondering if I should just upgrade the diff at this time, as I currently just have the regular open diff on the 8.8" rear in my 2WD XL truck. Not sure what gearing I want to run, but I assumed 3.55 would be plenty since I won't be running oversized tires. What have you guys done?

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[v8440]

I put a detroit locker in my dually. Works pretty well, though much more involved than simply pulling axles out. Since yours is currently an open rearend, I would put a so called "lunchbox locker" in there. Those don't require you to remove/re setup the ring and pinion gear when installing them. Of course, if you're going to re gear it then that doesn't matter.

 

[The_Auto_Tech]

I put a detroit locker in my dually. Works pretty well, though much more involved than simply pulling axles out. Since yours is currently an open rearend, I would put a so called "lunchbox locker" in there. Those don't require you to remove/re setup the ring and pinion gear when installing them. Of course, if you're going to re gear it then that doesn't matter.

That's what I was wondering if it was going to require setting the rear end back up if I wasn't changing gear sets. I've not yet done an aftermarket rear end, just stock setups.

 

[HammaMan]

Don't want a detroit back there. A proper LSD would probably be best for your use case. Really depends what's available for the 8.8. Various discussion on it previously. Better results using google to search this domain specifically.

 

[The_Auto_Tech]

Don't want a detroit back there. A proper LSD would probably be best for your use case. Really depends what's available for the 8.8. Various discussion on it previously. Better results using google to search this domain specifically.

Was leaning towards an Eaton TrueTrac, which is a helical gear style LSD. It seems to be the most popular choice anyways.

 

[HammaMan]

Was leaning towards an Eaton TrueTrac, which is a helical gear style LSD. It seems to be the most popular choice anyways.

I'd considered one for my front end quite heavily, don't use it enough to warrant it right now though. @SALEEN961 is a good brain to pick on the topic in general given his venture through diff swaps.

 

[The_Auto_Tech]

I'd considered one for my front end quite heavily, don't use it enough to warrant it right now though. @SALEEN961 is a good brain to pick on the topic in general given his venture through diff swaps.

Upside it seems though is that the Super 8.8, besides just changing to some sort of LSD, locker (besides the factory e-locker), etc. seems to need nothing to withstand some serious power and abuse. I had asked in another area about changing axles, c-clips, etc., but apparently there's just really been no issues at all with them, unless of course you're beating the tar out of it constantly at the track, in which case at some point it'll break something.

 

[FaaWrenchBndr]

TrueTrac would be my choice

 

[SALEEN961]

How much power are you planning on making? Will your truck be daily driven and rack up miles quickly? Will you drive this truck in the snow and rain or just on dry roads? Are you planning to drag race at all?

 

[Marcsrx]

I actually can't believe it's an open dif except the e locker. In 2024 on a truck. It has abs and therfore wheel speed sensors. Why didn't they integrate the locker to activate when slip detected. Such a bummer.

 

[The_Auto_Tech]

How much power are you planning on making? Will your truck be daily driven and rack up miles quickly? Will you drive this truck in the snow and rain or just on dry roads? Are you planning to drag race at all?

Daily driven, but probably only about 8000 miles a year maximum. Driven year round in the rain and snow. Yes, once the truck is built up a bit more it'll see some track use.

 

[SALEEN961]

Daily driven, but probably only about 8000 miles a year maximum. Driven year round in the rain and snow. Yes, once the truck is built up a bit more it'll see some track use.

At a certain power level, I think the added strength of a full aftermarket carrier like the Eaton TrueTrac or Yukon Duragrip is desirable, but I really Ford Traction-Lok carriers like the stock Mustang carrier that is commonly modified to fit in F150 Super 8.8" rear axles. Lots of people avoid clutch based limited slip differentials due to the added maintenance of needing to replace the clutches, but they should easily last 60K if not much longer.

The big thing that I like about clutch based limited slips is their predictability. With a Traction-Lok rear differential carrier, my truck always reacts in the same smooth and stable manner and this isn't always the case with Torsen differentials. With Torsen differentials you can occasionally feel them shift power from side to side, especially on low traction surfaces.

I have never run a rear Torsen differential in one of my vehicles, but I do have a Torsen front diff in my truck. With the stock open front diff my truck was always very stable during a WOT pull. With the Torsen front diff installed, I have noticed it shifting power from side to side in a fairly rapid manor during a WOT pull on a few occasions. Most of the time the Torsen will just pull in one direction or the other to minimize the speed difference between the wheels, but the pull is normally consistent and predictable.

If you decide to run a Traction-Lok rear differential, the biggest issue that I've personally seen is running the wrong gear oil or friction modifier. On my 2014 F150 everything was working great until until I used an aftermarket gear oil that "already contained friction modifiers for limited slips". After using that gear oil, I had to completely replace the clutches to fix the damage that was done. If you run a Traction-Lok, be sure to only use Motorcraft XL-3 friction modifier and either Motorcraft gear oil, Redline 75W90NS gear oil, or Redline 75W140NS gear oil. Redline NS gear oils contain no friction modifiers and have worked well in my 2014 and 2021 F150s.

 

[The_Auto_Tech]

I can definitely understand the reason why people would go with each setup. The clutch-type LSD's seem to be pretty popular for their predictability and operation, whereas the Torsen style LSD's are insanely durable and require no special fluids. I know a previous Foxbody I had was using an Eaton TruTrac and it was generally pretty predictable and insanely durable.

 

[OGKC]

I am a Jeep guy also and have been through most of the available options.
Here is my opinion. Open diff meh. We all know them and agree they exist. Much better options out there.
I had the factory ford 9.75 limited slip in my 2011 F150 ccsb 5.0 truck and loved it. It did everything I desired for my hunting truck in mud. Tow pig on wet dirt roads pulling my 8,000 lb travel trailer. Only minimal downside was adding limited slip lubricant to the diff on diff oil changes. Put 4.56 gears in that truck and loved it. All the power. At 14.5 mpg average. 285/75r17 tires. Even at the altitude in Denver it would light up the tires.it had 140,000 miles on the truck when I sold it and the clutches were still in good condition.
Current 2021ccsb eco3.5 has an e locker. Wish I had 4.10 gears in the truck. Has 3.55 gears. Running 285/65r20 tires and would like a touch more pickup.
Had an Eaton true track put in a Jeep riding on a ford 9”. It was good in the snow and ice. I wouldn’t say anything bad about it. They are definitely much better than a locker for general driving. It wasn’t great in mud or on tire lifting rocks. If you have any more questions just ask.

 

[The_Auto_Tech]

I am a Jeep guy also and have been through most of the available options.
Here is my opinion. Open diff meh. We all know them and agree they exist. Much better options out there.
I had the factory ford 9.75 limited slip in my 2011 F150 ccsb 5.0 truck and loved it. It did everything I desired for my hunting truck in mud. Tow pig on wet dirt roads pulling my 8,000 lb travel trailer. Only minimal downside was adding limited slip lubricant to the diff on diff oil changes. Put 4.56 gears in that truck and loved it. All the power. At 14.5 mpg average. 285/75r17 tires. Even at the altitude in Denver it would light up the tires.it had 140,000 miles on the truck when I sold it and the clutches were still in good condition.
Current 2021ccsb eco3.5 has an e locker. Wish I had 4.10 gears in the truck. Has 3.55 gears. Running 285/65r20 tires and would like a touch more pickup.
Had an Eaton true track put in a Jeep riding on a ford 9”. It was good in the snow and ice. I wouldn’t say anything bad about it. They are definitely much better than a locker for general driving. It wasn’t great in mud or on tire lifting rocks. If you have any more questions just ask.

This would be specifically in a street truck. I would never run a locker on a street vehicle unless it was very specifically for racing. That's why I'm planning for an LSD, and leaning towards the TruTrac.

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