Difference between 4wd and awd?

Hi all, this may seem like a silly question as I know the difference on modern cars. But I know some Hiaces are full time 4WD and some are AWD. Is there any difference for these, or is the term just being used interchangeably? And is there any difference between the full time 4WD and the ones that you must engage 4WD. I am wanting to pickup a Hiace that can do moderate to light off roading so I want to make sure I know the differences, if there even is one. Thanks!

Hello.

I think the terms are rather sloppily used and there are probably country differences, too. My van has ‘4WD’ stickers all over it but I’d call it a ‘4x4’ as it’s part-time. I think full time 4WD is the same as AWD. Here’s my understanding:

Part-time 4x4 / 4WD.
This is the system I have so I know this better. Open front diff. Open or limited-slip rear diff (LSD). Normally driven in 2WD to the rear only. Front hubs (typically AISIN) normally are freewheeling so front drive shafts, front diff and front prop shaft not turning.

To engage, first step is to lock front hubs so front drive shafts, front diff and front prop shaft now turning but not driven. 4WD is selected and unselected within the transfer box by vacuum actuator and switch is on the dash. This should only be done when away from solid tarmac as there is no centre differential on part-time vehicles. Once in 4WD a low range can also be selected (via a lever next to the gear selector) acting in the transfer box. Low range can only really be selected when in 4WD. Reverse steps are to re-engage high, deselect 4WD, then sets hubs to freewheeling to reduce drag / wear on front drive components, especially on the highway.

Advice is to occasionally engage front hubs to turn front drive components to mix oils and flex CV boots and joints. It’s also worth occasionally selecting 4WD for similar reasons but if this has to be done on tarmac, it’s better just to do this in a fairly straight line. With front hubs engaged 2 to 4WD can be selected or disengaged ‘at speed’. Don’t know exact value but as actuation is electronic and vacuum it’ll only do so when the box ‘is happy’. If the transmission is ‘bound up’ (tightness between front and rear) it can be necessary to stop and sometimes reverse a short distance while steering side to side to remove the bound state, but this isn’t usually a problem / issue. Engaging low range should be done when stopped or moving very slowly at most.

Good traction and drive but limited if a front wheel is off the ground (dab of brakes helps). Same for rear, but here LSD helps a lot. If opposite wheels are off the ground then these two wheels will spin freely unless brakes dabbed or LSD. Reasonable economy on road as only rear wheels are driven and front drive can be fully disengaged. LSD can help with on road traction, too.

Ok to drive in snow in 4WD (on tarmac). If snow chains are fitted then should be put on all four wheels.

This system is the same as fitted to fifth gen (of the same era) Hilux and basically any 4WD vehicle fitted with lockable front hubs. Might be easier to look up.

Full time 4WD / AWD.
I don’t have this system so happy to be corrected. Open front diff. Open or limited-slip rear diff (LSD). All wheels, both diffs and both prop shafts driven all the time and I think there is a centre differential to accommodate slip between the front and rear (for turning etc). There might be a centre differential lock, but I don’t know. If so, it’ll help. I think these vehicles have a transfer box that will engage a low ratio. If so, same capability and caveats as above are likely for use.

Full time 4WD / AWD gives better traction on the road than a 4WD driven in 2WD as some drive is always at the front wheels. AWD is just as limited off road as part time 4WD if any wheel slips. If the slip is at the front then engaging the centre diff lock (if fitted) helps a bit as if forces both prop shafts to turn the same rate (just like a 4WD), but with an open front diff the front wheel will spin. Effective drive will only be to the rear, but this is the same for a 4WD vehicle with a front wheel off the ground. Same for rear, but here LSD helps a lot. Again, If opposite wheels are off the ground then two wheels will spin freely unless brakes dabbed or LSD.

AWD has similar economy on the road to a 4WD if the front hubs on the latter are engaged, but the permanent AWD generates more losses and worse economy compared to a 4WD driven in full 2WD mode.

If snow chains are fitted then should be put on all four wheels.

This system is the same as fitted to later Hilux and similar to Land Cruiser Series 80. Similar to LandRover Defender etc. Might be easier to look up.

HTH!

p.s.  Happy to be corrected.

https://toyota-club.net/files/faq/04-02-20_faq_4wd-2_eng.htm

The above link provides some info on Toyota drive systems.

Different manufacturers provide different configuration and capabilities. In general I believe that the AWD label is applied to vehicles that operate nearly all the time as front wheel drive, but can send power to the rear wheels for brief periods when extra traction is required. E.g. getting in and out of a ski area parking lot.

4WD drive vehicles can send power to all wheels continuously.

Within the 4WD realm there are degrees. The most "off road" capable rigs have the ability to "lock" all three differentals and drive all four wheels equally. This is useful on snow, loose dirt , mud, etc. But causes problems driving on pavement.

I’ve not seen the ‘toyota-club’ site. Thanks for sharing.

My understanding is AWD uses a center differential to split power between front/rear axles, while 4WD uses a transfer case.

Hi all.
Different Toyota hiaces have different all-wheel drive options.
Full-time & part-time. you can change the transfer case and install lock s on the front hubs .

LH119V wrote:

Full time 4WD / AWD.
I don’t have this system so happy to be corrected. Open front diff. Open or limited-slip rear diff (LSD). All wheels, both diffs and both prop shafts driven all the time and I think there is a centre differential to accommodate slip between the front and rear (for turning etc). There might be a centre differential lock, but I don’t know. If so, it’ll help. I think these vehicles have a transfer box that will engage a low ratio. If so, same capability and caveats as above are likely for use.

Full time 4WD / AWD gives better traction on the road than a 4WD driven in 2WD as some drive is always at the front wheels. AWD is just as limited off road as part time 4WD if any wheel slips. If the slip is at the front then engaging the centre diff lock (if fitted) helps a bit as if forces both prop shafts to turn the same rate (just like a 4WD), but with an open front diff the front wheel will spin. Effective drive will only be to the rear, but this is the same for a 4WD vehicle with a front wheel off the ground. Same for rear, but here LSD helps a lot. Again, If opposite wheels are off the ground then two wheels will spin freely unless brakes dabbed or LSD.

AWD has similar economy on the road to a 4WD if the front hubs on the latter are engaged, but the permanent AWD generates more losses and worse economy compared to a 4WD driven in full 2WD mode.

If snow chains are fitted then should be put on all four wheels.

This system is the same as fitted to later Hilux and similar to Land Cruiser Series 80. Similar to LandRover Defender etc. Might be easier to look up.

HTH!

p.s.  Happy to be corrected.

Don’t think you’re quite right on the Super Custom Full Time 4WD system (let’s call it AWD).

But I’m also happy to be corrected but this comes from 18 years of ownership and deep dives into the full service manuals for the Auto boxes.

Pretty certain there is no LSD option on the AWD. Never seen one in my country orbin Japan and no one here, when challenged to post their chassis plate showing LSD code for rear diff plus Auto trans on a Full time 4WD van, has done so.

The center diff has a viscous coupling and planetary gearset that through the magic of geometry and physics sends torque to the axle with most grip. Spin a rear wheel and the front axle gets the torque, spin a front wheel and the rears get grip. Only time a rear LSD would benefit is when one rear wheel was the only one of 4 to have any grip.

Never seen a center diff lock on the Super Custom.

No, AWD is not the same system as fitted to Landcruiser. Those came with optional auto boxes that had transfer case and low range.

The fundamental difference in daily use between the 4WD & AWD systems is 4WD cannot be driven in 4WD on sealed roads. You will likely break the transfer case (probably the chain). In my years and experience of both, for general use and especially towing, the AWD is superior.
I regularly towed loaded trailers and an excavator. Never got stuck, even on soaking wet grass on wet clay.

DJPOWER wrote:

Hi all.
Different Toyota hiaces have different all-wheel drive options.
Full-time & part-time.  you can change the transfer case and install lock s on the front hubs .

Have you done the swap? If so what parts did you use?

I intend to convert my 1996 KZH-106W at some point and have done a little digging in the parts catalog. It seems first generation 4runner/Surf or T100 parts should work. I believe the hubs will bolt right up. The transfer case I'm less sure about. I know it uses the same housing, so it should bolt on, but I haven't dug deeper than that. I need to verify that the shafts have the same lengths and spline counts.

Hi_ace to everyone. I have kzh106, part-time. I installed a transfer case from a Toyota townace. The transfer case is also suitable from Toyota hiace LH107. Hubs are also suitable from townace, 4runner, surf. All parts fit without alterations, you just need to connect vacuum tubes to the transfer case and install solenoids to turn on all-wheel drive. Fuel consumption becomes significantly less if all-wheel drive is not engaged.

Ganbatte wrote:

Pete_nz wrote:

Pretty certain there is no LSD option on the AWD. Never seen one in my country orbin Japan and no one here, when challenged to post their chassis plate showing LSD code for rear diff plus Auto trans on a Full time 4WD van, has done so.

Yep!

Does this have a low ratio?

Does it have a centre diff lock?

I know little about the full time 4WD setups.

Thanks

Ganbatte wrote:

DJPOWER wrote:

Hi all.
Different Toyota hiaces have different all-wheel drive options.
Full-time & part-time.  you can change the transfer case and install lock s on the front hubs .

Have you done the swap?  If so what parts did you use?

I intend to convert my 1996 KZH-106W at some point and have done a little digging in the parts catalog.  It seems first generation 4runner/Surf or T100 parts should work.  I believe the hubs will bolt right up.  The transfer case I'm less sure about.  I know it uses the same housing, so it should bolt on, but I haven't dug deeper than that.  I need to verify that the shafts have the same lengths and spline counts.

Hello.

I first thought you were trying to convert a 2WD to a 4WD, which is not an easy thing to do. The front lower arms on the 2WD are completely different to the 4WD and significant modification to the chassis would be needed for this.

Having had a quick check I now see that the ‘KZH106W-MRPGT’ is a full time 4WD so I presume you are looking to convert this to a part time 4WD.

If so, I think this is doable (infinitely more so than converting a 2WD to 4WD) but will take some time, effort and cost. It’ll be a while before you recoup the cost of somewhat better fuel efficiency but I think there are also other compromises to consider.

Please do take a good read through my comments above on the way the part time 4WD usually works.

My initial thoughts:

I think converting the front hub parts plus bearings etc (to the lockable AISIN ones) should be fairly straightforward.

I think the brakes should be fine, but this needs checking as replacing more bits here will get pricey. To check this, set up a page in Amayama with your van and another with a similar aged part time 4WD and check for comparisons. This might take a bit of doing as the part time variants did tend to be withdrawn before your van was made. The steering knuckle parts are also key I think and will relate to the brakes in terms of offsets.

The inner ends of the part time drive shafts are flanged to the differential, so a part time drive shaft should bolt straight to the differential. This is if you cannot modify the drive shafts that you have. I have most of the front of my van apart including front hubs and drive shafts so ask away.

As others have said the transfer replacement / modification will be key. On the part time (as above) this is both actuated and deactivated by vacuum, which is electronically triggered. You’ll need the switch, wiring and vacuum actuation assembly (box). This can still be bought new but the solenoids are now discontinued so you’ll need to get the whole thing as a second hand part or make something. You’ll also need to plumb the vacuum ‘box’ from wherever the vacuum on you van is generated. On mine this is from the pump on the alternator so there’s a double hose that runs from under the seat (open end) to the ‘box’ then back forwards to the rest of the vacuum system. Again the EPC is your friend. If you head over to my ‘show us yours’ page you can see some pictures showing the diagnostics for the part time 4WD electronic and vacuum actuator. The box just maintains ~400mm Hg equiv at idle to maintain the system in 2 or 4WD. There is also a picture of my gearbox (M/T) and transfer.

If you replace the transfer with a normal part-time variant then you will lose the ability to run in 4WD on normal roads as the part time type does not have a centre differential. I personally think this is a bit of a step backwards so I’d try to see if there is a transfer box that retains the centre diff (allowing you to run in 4WD on the road), but which can also disconnect to be just 2WD. This might be available from other Toyotas (see RandyOakley’s post above as this might be helpful of scour the wider Toyota world. You just want to disconnect the front take-off.

Failing this, a normal part time transfer will allow you to run in 2WD on the road and 4WD on gravel, snow etc. I’m going to stick my neck out here and say that all Hiace part time transfer boxes have high (1:1) and low (1:2.566 in my case) ratios. As above this is selected by a lever and cable. The lever (and bracketry) is still available (see EPC) but the cable is discontinued. The TownAce H/L cable is still available but it’s not the same part. I’ve no idea if it’s compatible, but if you want a low range then I think this needs consideration. If you really don’t need low range then this might be another reason for not swapping in a ‘typical’ Hiace part time transfer box but getting something else from something else that might retain the centre diff and road 4WD for occasional (winter?) use.

A different transfer box might mean you need new prop shafts, if it changes the relevant differences.

If you do head down this route it might be useful to make a new post and also be useful to see the progress in a ‘show us yours’ section.

HTH!!