Rear Limited-Slip Differential?

I was curious and found mentions on the net of torsen/True-Trac/helical LSDs going into the rears of 3rd and 4th gens, a Tacoma but not any 5th gen that I could see.

I'd guess between traction control, a rear locker and the Limited's full-time 4WD it would be pretty niche and most appealing to SR5/TRD Sport models. I was thinking it'd be nice to have in wet pavement conditions.

Has it ever happened? Does such an aftermarket fitment exist?

 

I am curious about this as well. Although I haven't heard of the option for the 5th Gen 4R.

When I purchased my 4Runner I was worried that the open diffs meant it's less capable in certain conditions. When I experienced how well the traction control system and stability control systems work my mind was put to ease. The rig detects and reacts to slip very quickly and sends power where it needs to be. The only time the lack of an LSD comes up is when I come to a stop and hold the traction control button for a few seconds. This disables traction control and stability control. With these systems deactivated the 4R is pretty helpless in low traction/ 2-hi scenarios. The rear right wheel just spins like crazy.

Coming from the sports car world clutch style or VLSD's do wear out and need to be rebuilt every once in a while. Maybe since the 4R is such a long lasting vehicle Toyota wanted to remove the need for this? Plus Toyota's TC and SCS work so well it may be a redundant system.

Another thing to consider is ATRAC and MTS would in theory work against an LSD. So that's probably another reason they kept the diff open.

This is all just conjecture of course. An interesting topic for sure.

 

" The only time the lack of an LSD comes up is when I come to a stop and hold the traction control button for a few seconds. This disables traction control and stability control." - why would I do it ?

 

Why would you disable traction and stability control?
Because

 

Come to think of it maybe MTS and ATRAC would benefit from an LSD?

This is just speculation after all.

 

Traction/stability control and it not being very popular when it was around definitely means no factory LSD in most non-performance vehicles from the factory. IIRC the RAV4, Highlander, RX, Celica? at some point had a torsen rear option up to around 20 years ago.

I don’t think one would improve MTS or ATRAC much directly but I think it might result in less clatter by keeping power going to both sides more evenly before either intervenes and help out in 2H and 4H where traction control is less aggressive.

 

Update: Asked 4 Wheel Parts while I was there if any rear LSD’s, according to them or at least out of what they sell, exist for our fitment and the answer is no, just various lockers.

 

Fun fact: the McLaren P1 hypercar uses an open diff because utilizing the brakes and electronics was more efficient than adding the extra weight of a limited slip.

 

I think the 2wd 5 gen gets a LSD.

 

It's a brake actuated simulated LSD I think, not a traditional LSD like clutchpack or helical gear set up.

 

It’s an open diff. I believe there is a mechanical LSD option out there.

 

Same with the Dodge Caliber SRT-4!

 

The 8.2" is an oddball size yeah. I don't see any mechanical LSD options for it on ECGS' website.

Meanwhile all the McLarens other than the P1, including the more hardcore Senna, have mechanical LSD available as an aftermarket upgrade: https://www.m-engineering.us/products/mclaren-lsd-differential?variant=37417714679976

 

Ok, I might have been thinking of the older 4R/Tacomas before the introduction of electronic traction aids.

 

Another fun fact, rear torsen LSDs were an uncommon option on the RAV4, Highlander, RX before traction/stability control showed up!

 

I had a CJ with a limited slip once.

It caused a clutch issue to suddenly become a driveshaft and axle issue.

That was fun.

 

Proper LSD is very expensive mechanical part and it is only slightly better than modern brake-based simulated LSD. Mechanical LSD only makes sense in applications where you don't want to apply brakes because doing so reduces maximum acceleration and/or reduces grip available for cornering, such as track-focused RWD performance car. LSD also has lower maximum torque it can take when compared to open diff, so there are some cases where it can't be used.