Im about to install the CDL with 7pin mod and was wondering if this will allow use of the diff locks in high range? if so what about Toyota's "5mph" limit while locked?
Locked diffs in high range?
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Locking the center, regardless of transfer range, "arms" the diffs and they will lock, provided the vehicle is traveling under 5 mph. The diffs will not unlock if the vehicle speed exceeds 5mph, they will stay locked until they are switched off or the center is unlocked.
The reason that engagement is prohibited above 5mph is to prevent the vehicle from making sudden unpredictable movements when the diff(s) lock.
The same holds true for the top recommended speed. You can drive as fast as you dare.
The reason that engagement is prohibited above 5mph is to prevent the vehicle from making sudden unpredictable movements when the diff(s) lock.
The same holds true for the top recommended speed. You can drive as fast as you dare.
Locked diffs are a bad idea on high traction surfaces at any speed. At highway speeds I imagine it'd be downright dangerous.
Locked Rear or Front diffs are a bad idea at higher speeds on low traction surfaces too. Even when plowing off-road through heavy snow at ~20MPH you can get sideways in a hurry, and with the front locked you can't steer very well.
-B-
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Low speeds are best, and it's a good idea to play with them a bit in a snowy parking lot to understand the magnitude of accidental direction changes they can cause. Far better than listening to advice is the sudden feeling of an uncontrollable veer to put it indelibly on the ol' bean.
DougM
DougM
So, the low speed limit locked is because of driver's safety and not mechanical limits?
That's very good news...
Can you confirm that I can spin the axles with the stock lockers engaged at high rpm and it won't grenade on me? Basically, the situation is a long sand dune climb, where you have room for a long run-up to gain momentum - so you scream along the flat and then start the climb, and hopefully reach the top.
The steering wheel stays straight throughout, even if you reverse down.
AFAIK, the danger with driving on locked diffs is turning and/or accelerating on a turn.
That's very good news...
Can you confirm that I can spin the axles with the stock lockers engaged at high rpm and it won't grenade on me? Basically, the situation is a long sand dune climb, where you have room for a long run-up to gain momentum - so you scream along the flat and then start the climb, and hopefully reach the top.
The steering wheel stays straight throughout, even if you reverse down.
AFAIK, the danger with driving on locked diffs is turning and/or accelerating on a turn.
I have pulled sand hills at ~25 MPH (wheel speed) with both ends locked, WOT, in low range, motor trying to crawl out through the radiator with ~8 lbs boost and the methanol pumping at 14GPH. The diffs are still attached and functioning.
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Yes, if I read you correctly when you say "spinning the axles...engaged at high rpm" you simply mean "operate" as in the axle is merely spinning at high rpm - right? High rpm like operating it on the freeway compared to low rpm as in operating at walking speed. There would be no detrimental effect on the locked diffs simply driving quickly.
However it is worth noting that as you operate faster, forces that might be dissipated by tire slippage - say a turn - will ramp up correspondingly faster and perhaps too fast for the tires to slip. This force is called axle windup and is merely the twisting effect on a locked axle that comes from turning - a tire must slip. So, higher speed operation is not without added possibilities.
But no - simply operating the locked axles at higher rpm/vehicle speed of itself will not cause harm. It's worth noting that in high range, the engine torque is denied the doubling of the low range and actually reduces the ability to place stress on the diff in some ways.
You mention reversing. That is a danger with the diff is that you are placing pressure on the 'coast' side of the front diff's gears. This side is ramped and cannot handle nearly the amount of force that the gearset can when the normal gear faces are engaged as when moving forward. Locking the diff in this circumstance may help reduce peak forces by eliminating wheel spin, or if done on a high traction surface may put far more force on it if on a high traction surface. Best advice is try not to use the skinny pedal heavily in reverse and low range. If circumstances force you as an assisting vehicle to pull against a tow rope in reverse, use a bit of vehicle momentum and corresponding less gas pedal.
HTH, I've had poor luck in sand with my 80 though I do not have correct tires for this surface by a long shot.
DougM
However it is worth noting that as you operate faster, forces that might be dissipated by tire slippage - say a turn - will ramp up correspondingly faster and perhaps too fast for the tires to slip. This force is called axle windup and is merely the twisting effect on a locked axle that comes from turning - a tire must slip. So, higher speed operation is not without added possibilities.
But no - simply operating the locked axles at higher rpm/vehicle speed of itself will not cause harm. It's worth noting that in high range, the engine torque is denied the doubling of the low range and actually reduces the ability to place stress on the diff in some ways.
You mention reversing. That is a danger with the diff is that you are placing pressure on the 'coast' side of the front diff's gears. This side is ramped and cannot handle nearly the amount of force that the gearset can when the normal gear faces are engaged as when moving forward. Locking the diff in this circumstance may help reduce peak forces by eliminating wheel spin, or if done on a high traction surface may put far more force on it if on a high traction surface. Best advice is try not to use the skinny pedal heavily in reverse and low range. If circumstances force you as an assisting vehicle to pull against a tow rope in reverse, use a bit of vehicle momentum and corresponding less gas pedal.
HTH, I've had poor luck in sand with my 80 though I do not have correct tires for this surface by a long shot.
DougM
Thanks, guys - good to know.
Axle wind-up won't be a problem as the wheels simply release the built-up stress when they spin on sand.
In fact, since they spin so much, correct tires is key. The LC-80 does very well on sand, despite the long wheelbase (which makes it hard to crest dunes easily, you need to drag the chassis over), but also because of its hefty weight you really need the right tires or you sink and have to fight through the sand instead of staying on top. Wide and soft, non-aggressive tread, down to 10psi (less if possible).
I don't have an owner's manual - what's the correct procedure for shifting into LO, and engaging factory lockers?
Axle wind-up won't be a problem as the wheels simply release the built-up stress when they spin on sand.
In fact, since they spin so much, correct tires is key. The LC-80 does very well on sand, despite the long wheelbase (which makes it hard to crest dunes easily, you need to drag the chassis over), but also because of its hefty weight you really need the right tires or you sink and have to fight through the sand instead of staying on top. Wide and soft, non-aggressive tread, down to 10psi (less if possible).
I don't have an owner's manual - what's the correct procedure for shifting into LO, and engaging factory lockers?
That's easy. Shift the transmission to Neutral (N), then shift the transfercase to LO, you will see the center diff lock light on the dash, then you can shift your RR/FR locking diffs. With three locked up, you should see three diff lock lights on the dash.
OK, thanks. The locker lights on the dash, when they flash it means "engaging" and when it's on solid it means "engaged", right? I got my rear one that doesn't stop flashing - meaning it doesn't engage, yes?
Can I engage 4WD at any speed?
Can I shift HI to LO when in P or only in N?
Can I engage 4WD at any speed?
Can I shift HI to LO when in P or only in N?
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Correct, the rear collar only has 5 teeth, so takes more wheel slip to lock. When you operate the switch, does the actuator motor run?
Don't know mine is full time 4x4?
It's possible on flat ground, park holds the truck in place with a lock in the trans applying load to the tranfer gears, making shifting difficult or impossible, so neutral is best.
You can shift from high to low in either N or D. I've done it 'on the fly' a lot, but try to keep the shifting below 25 mph.
Ok, um--- now that I think about that I did that in my 60 a lot, not the 80. Can anyone confirm that you can do the H to L while moving in D on an 80?
Ok, um--- now that I think about that I did that in my 60 a lot, not the 80. Can anyone confirm that you can do the H to L while moving in D on an 80?
Thanks for taking the time to respond - I'm kind of in the middle of nowhere so I can say how great it is to have a link to you guys, kind of a connection to sanity... can you imagine that!!! My connection to sanity is to a bunch of off-road crazies!!!!!! 
I'll check.
Mine is part-time, with auto front hubs. A button on the dash marked 4HI engages the front driveshaft and a 4WD light comes on the dash. It seems to do this smoothly at speed, say 50kph.
OK, thanks. In N on the transmission lever, when I shift into 4LO with the t-case shifter, I get a grinding sound as it engages, then it works fine. Do you normally have to lift or depress the t-case shifter from N to LO?
I just got the truck, so I'm still at early stages of deciding what needs attention and how to go about it.
I'll check.
Mine is part-time, with auto front hubs. A button on the dash marked 4HI engages the front driveshaft and a 4WD light comes on the dash. It seems to do this smoothly at speed, say 50kph.
OK, thanks. In N on the transmission lever, when I shift into 4LO with the t-case shifter, I get a grinding sound as it engages, then it works fine. Do you normally have to lift or depress the t-case shifter from N to LO?
I just got the truck, so I'm still at early stages of deciding what needs attention and how to go about it.
Could be, though it sounds like it's coming straight from under the shifter, not from the wheels.
It's like this: as I move the t-case shifter down from N, as it reaches LO, just as it starts to engage, it fights back for a second, sending out a strong vibration and an accompanying grinding sound that makes you grimace and swear... and then it slips in, and it's all systems go.
I think it has to do with the gear-box, like it thinks it's not really in Neutral. In fact, sometimes the gearbox shifter is in N but there's no green light over the N symbol on the dash.
So that's where I'm thinking to start looking... any advice? Sounds like a good starting point?
It's like this: as I move the t-case shifter down from N, as it reaches LO, just as it starts to engage, it fights back for a second, sending out a strong vibration and an accompanying grinding sound that makes you grimace and swear... and then it slips in, and it's all systems go.
I think it has to do with the gear-box, like it thinks it's not really in Neutral. In fact, sometimes the gearbox shifter is in N but there's no green light over the N symbol on the dash.
So that's where I'm thinking to start looking... any advice? Sounds like a good starting point?
Try it in P and see if it still grinds.
This may be a good procedure for you:
1 Engage 4hi (light comes on?)
2 Stop and shift to P
3 Move t-case to L
4 Engage lockers if desired
5 Place trans in forward gear and go.
I think that you may have to go back or forth a little to get the lockers to engage sometimes.
Dave
This may be a good procedure for you:
1 Engage 4hi (light comes on?)
2 Stop and shift to P
3 Move t-case to L
4 Engage lockers if desired
5 Place trans in forward gear and go.
I think that you may have to go back or forth a little to get the lockers to engage sometimes.
Dave
Also, when I'm shifting into 4L, I like to stop on a slight decline, shift the TC into neutral, and let it roll just a little bit, then put it in 4L. I think it gets rid of any stored energy in the driveline, and there's never any grinding.