RR Diff Lock - why keep under 25mph ?

4x2 PreRunner here. My question has to do with engaging the RR Diff Lock button.

With the rear elocker engaged, i do notice improved traction on takeoff when the pavement is wet and slippery or on incline trails with loose gravel.

Almost everything that I've read, it says to not go over 15-25mph with the elocker engaged or else damage will occur. Why is that?

I understand the unusual steering feel when driving with the diff locked. The skipping, etc...and understand it can be unpredictable if the driver is not aware or ready.

We're having massive amounts of rain (for N. Calif) and i think it would be helpful to have the added traction and felt correct about that when I've played around with it.

So if I do lock the rear diff and do mixed around at 35-45mph for an extended period, i dont see how I'm going to damage the rear end/3rd. Can someone more knowledgeable than me explain what trouble I may be inducing?

My truck is supercharged (330HP) and my throttle tip-in is pretty sensitive. I know I can dial it back on HP Tuners and a few other things to help not break traction so easily in wet/rain, but wanted to know if my solution is right at my fingertips (RR diff lock button).

 

Is the inherent weak point with the elocker motor/actuator itself?

 

4x4 here with the anytime locker mod. I can tell you from my experience no damage has occurred (yet) up to about 50-60 mph

I try to slow down quite a bit and make sure Im traveling roughly in a straight line before engaging or disengaging.

That being said I mostly use the anytime locker mod to F around in the snow or dirt in 2Hi (makes it very easy to turn around on tight snowy/ice roads instead of a million point turn). Not sure Id want to drive around on the street with it locked, might actually make things worse. Besides its just rain, cant be that slick can it? Maybe time for new tires if thats the case

 

If you're spinning your tires in the rain, maybe you're trying to drive too fast for conditions...?

 

Is it a manual trans? If so start in 2nd gear. Some auto trans do 2nd gear start when manually put into 2.

 

I doubt you are gonna break anything as long as you don’t get too much load on the diff with lots of traction. My sas’d 2nd gen had a welded rear diff and I would drive it on the street all the time. It was a little 4banger tho, fighting for dear life pushing 37s around.
I’d say the warning is there just so toyota could cover their ass and didn’t have to warranty a bunch of diffs if people decided to do a bunch of donuts with locked diffs

In your case it would be similar to running 4 wheel drive, but you will have less safety margin since if you are in 4x4 and are gonna bind up your drive train the most likely thing to break would be a cv axle. With just the rear being locked I’m not sure if it’s gonna be a ring gear or axle shaft or what. Also just be careful in turns until you get used to how it handles with both rears spinning at the same rate.

tldr: shouldn’t break anything just be mindful of your throttle in turns, your rear tires won’t be able to spin at different rates so its just going to handle weird. It also may piss off traction control so you may want to disable that

 

The context of my question was straight off the line drivability. I'm not trying to do a burnie at 45mph.

On a wet pavement/road, from a standstill/stoplight, with the elocker not engaged, i need to be careful or else i can hear the RR tire break traction and ill back off the throttle, etc.. Anytime under 25mph, i can get it to spin the tire with a small stab of the throttle, etc...

Same conditions, but with the elcoker engaged, its planted....no tire spin, traction loss.

I understand high HP + rwd, i understand hard compound = XT/MT tires, i understand I can play with tire pressure, more weight in the back, and even soften ny suspension.... I'm not as well versed with the technical stuff and slow speed crawl, grippiness + mechanical or electronic traction inducing stuff.

But my question has to do with is there really an inherent weak point or component with the elocker or the 8" rear thst puts it under unnecessary or terminal stress when the elcoker is engaged and I'm at a constant 35-45mph or faster.. (because the Toyota manual says death is imminent). Jk

So is it like what @Murphinator said which is toyota doing their due diligence and CYAing themselves. Which is fine...

I think I'm driving safer in my current conditions with the elocker engaged almost full time. Just want to know if my thinking is flawed. I'm trying to drive safer on slippery roads....not trying to faster safely.

 

I understand the masses thst will scream "just drive slower" or "get another vehicle". I can do that and have it at my disposal... but I like driving my truck and it's the most expendable if I'm involved in a wreck.

 

Just understand that with the back locked when you do break them both loose youre going to be sideways in an instant

As I mentioned above I have not had any issues with mine to date. Seem to recall there was a thread a while back that had a detailed disassembly of the 2nd gen locker and it seemed like a simple and robust design

 

By no means am I saying I'm driving in severe weather. And I also humbly agree that California severe weather is a whimper compared to Maine or anywhere else in the country.

 

Have you tried to go up i80 lately? Doner summit is pretty crazy.

 

Not this past weekend (storm) but yes, I was on the 80 the last storm over ski week (feb 23-26). It sucked balls due to the conditions... but relatively safe knowing i had non-EV AWD and also cables if called upon by Caltrans. Wipers got destoyed, visibility was nil and whiteout.

As a 40yr resident of the Bay Area...what we are experiencing is very rare. Snow level dropping super low on Mt Hamilton. Snow on highway 17 at Summit. Snow in the tri-valley, etc...But i think the guys in the New England states experience blizzard chaos every winter.

 

It could be due to the added heat from the electromagnet. I know if you leave it on for a long time the oil will start to get pretty hot. Not sure if it would get hot enough to break down though.

Harrop also does not recommend leaving their ELocker locked above 30km/h (18mph) but that is due to stability concerns.

"Differential engagement should not be maintained at high speeds (greater than 30 km/h). A locked differential at higher speeds can cause undesirable vehicle behaviour or loss of vehicle control."
- https://www.harrop.com.au/shop/system/download/A5Elocker Install Guide216_LoRes.pdf

 

Makes sense to me! Super helpful

I need to read that detailed breakdown of the elocker and see if it unlocks my cluelessness.

 

This. Taking off from a stop, yeah the locker will provide more traction and assist you. When driving around corners, your tires are travelling different distances and this is where open differentials come into play. With the rear diff locked around corners, you're forcing the truck to break traction to some degree. That's not what you want in slippery road conditions.

When I was on a fire road and wanted to get a little rowdy and slide the ass end around in 2wd, it was loads easier with the rear locked versus unlocked.

If you're having trouble pulling away from a stop without breaking traction then I would look at changing other things, like type of tire, tire pressure, weight in the rear, etc. Those things you mentioned above.

 

2nd Gen trucks dont use that system. They use a geared actuator much like the t-case and ADD. Once the system is engaged nothing is actively energized.

(As a side note on 3rd gens Ive read the PWM duty cycle drops off considerably once the locker is engaged. Likely to prevent anything getting hot)

 

Us 2 Gen guys have a smaller and “weaker” differential. It’s not the speed, it’s your ability to “quickly” maneuver the truck at speeds greater than 25 mph.

Just remember, when locked you are putting more strain rear axle to what ever direction you are turning. The “faster” you put the strain on that axle, the more chances you risk breaking something.

In short. Be careful, don’t use it on high traction terrain (when turning) and have fun.

 

Elocker diff is weaker than non e locker. Depending on what you plan to do with the truck I would get an non elocker diff with a lsd.

 

There is no inherent weak point. It is a cya issue and completely due to the effect on handling.

No electromagnet in his locker, but even so the heat generated is of zero concern.

Harrop plays the same cya game as Toyota. Handling is different, people may not understand how to deal with it.

Faster with locked diff is actually less strain than low speed. Why? One, at high speed the torque you can deliver to the wheels is smaller. Two, the higher your speed the less tight of a turn you can make so there's less bind from differential speeds to relieve. Third, relieving bind is easier for the tires at speed, similar to how steering effort and bind is much higher sitting still than moving.

What will get you at speed is slipping a wheel and then having it grab a load of traction and getting extreme shock loads.