Changing over to a part time 4WD and fuel economy. (1 Viewer)

[Dave 2000]

You need weight on the steering for 'feel', my version has variable rate steering, super light when parking and getting heavier as speed increases, either way the point has been proven that conversions to PT are pointless.

Regards

Dave

 

[leonard_nemoy]

either way the point has been proven that conversions to PT are pointless.

If they are pointless why did toyota sell them part time in half the world?

My rig was set up for serious crawling at 1 point. Slee 6" and 37's etc. Now I am running a 3" lift and 35's. I don't have to worry about ruining my nitro axles in the front or deal with front end vibes because the rig is set up part time. Definitely not pointless.

It would be pointless on a rig with only a small lift that doesn't see a lot of offroad.

 

[Dave 2000]

Mainly because they were cheaper and more accessible to those who might not be able to afford them?

Re 'My rig was up for serious crawling' Perhaps because Toyota they did not sell them like that? As I said it is pointless unless for serious off roading, and not even related to on highway use.

Re 'It would be pointless on a rig'. Spot on, and what I said going back a couple of posts.


Regards

Dave

 

[Kernal]

IME comparing a 2WD FZJ80 and AWD model the advantages of 2WD (CDL locked, front DS out) are steering feel/handling, a bit less front driveline rumble, and less wear on some components. The 2WD 80 feels a tad easier/quicker to manuever. I use both 80's interchangeably and the difference is not that much that it causes me to drive either vehicle differently (on dry pavement).

FWIW

 

[WarDamnEagle]

My Middle East 80s are all part time 4WD. I am nevertheless looking at installing locking hubs to reduce front end wear and tear. Likely I will put in the hubs on each next time they have a serious front end service.

I have never seen a part time 80 in the Middle East. Assume you meant full time?

 

[mudgudgeon]

I think

I enjoy the lighter steering you get with hubs unlocked.

I personally think it only makes a difference when under power, you get some torque steer.
The flip side of that is in all wheel drive, you can use that torque steer to drive the front around a corner a lot harder than in rear wheel drive.

I've played with this on open highway where you have a long consistent bend. Hold the steering steady, accelerate hard and the turn radius of the vehicle tightens up, it'll steer harder into the bend with no additional steering input. Back of the throttle, and it'll run wide in the turn.

Had my son do this when he was learning to drive

 

[mudgudgeon]

I use both 80's interchangeably and the difference is not that much that it causes me to drive either vehicle differently (on dry pavement).

I think the need for different driving technique is debatable.
In ordinary driving where you are not pushing the vehicle, and on good, dry pavement, there's not a lot of difference.

Push the car harder, or bring adverse road conditions into the mix, then the advantages of 4WD/AWD start to become more apparent.

I've personally had a situation where the AWD 80 enabled me to avoid a collision on a wet road at speeds that without 4WD almost certainly would have resulted in a fatality to the driver that fücked up by pulling blindly across the lanes of traffic traveling 50mph, downhill in the wet, then stopping dead on my lane.
I'll never forget the look of horror on that ladies face when she realised she was about to die. A lesser vehicle, and lesser driver, and she was dead for certain. For this reason alone, I would keep full time 4WD unless it was a built trail rig

 

[DivByZero]

I agree with a lot of the comments here. I'm a bit of a hoon at times, and I like the fact I can basically "drift" my 80. It's fun being able to lock the rear and slide on dirt. That said, I need to remember to lock my hubs when it rains, otherwise I can easily get wheel spin taking off on tarmac. I can't just leave it in 4wd though, I'd get wind up, so in wet weather you'll see me often sliding into 4wd when I stop at lights, then shifting back into 2wd when I'm up to speed. I've spun the car once around a bend on an unfamiliar road when I took it too fast in the wet at night. If I'd been in an full time 4wd model with a centre diff, that would not have happened. I'm also convinced fuel savings are so minute as to not be measurable.

The thing I like about the part time model is mechanical simplicity, and being able to minimise wear on the front drive train. That said, if there was a model that had a fully mechanical drive train with a lockable centre differential, IE, a lever transfer, to switch between 2WD, 4WD open centre, and 4WD locked centre, that'd be my personal pick. As it is, with my driving style and personal prefences, I prefer the part time model 80, although I know the full time model would be safer and handle better by default in any driving situation. I prefer reliable and easy to fix over that, same reason why I prefer a non-ABS model. I wouldn't ever do a conversion from full time to part time though.

 

[sunrk]

My 80 is diesel non turbo original motor 684 k km's and growing. Always been part-time 4wd. People try to paint fear into people's eyes to make them believe only a vehicle with drive to all four wheels is 'safe'.

You will get no better fuel ecomony. Lets get that one clear. You still have to deliver the same energy with drive to 2 or 4 wheels to get the same amount of mass to move. The transfer case with send it either one way (rear) or two ways (rear and front) and you'd be hard pressed to 'quantify' any changes in mechanical losses that can be easily measured.

Where you 'save' with part-time is the front driveline is rarely used so you 'lose' in another way as wear on the rear driveline is more. That's a long-term maintenance trade-off.

80's are big high vehicles - they have a high roll centre. So it's up to the driver - not the vehicle - to be aware of limitations.

 

[Squeegee]

But much, much easier than pulling the rear drive shaft, rear transfer case extension housing, and back cover of the transfer case to install the part time kit in the first place. I'm just saying that the arguable convenience in solving a theoretical trail breakdown is not worth giving up the nice handling and operation of Toyota's "full-time 4wd" system.

But yes, if you want to 1) preserve the front end components, or 2) avoid unsolvable front end vibes, then part time is the way to go.

It’s all compromises, but frankly, if the 80 didn’t come with it, I wouldn’t have put in the effort or money towards doing it

 

[sunrk]

HF1A is the part-time 4wd transfer case if a person wants to do it properly. I've never driven a full-time 4wd 80.

 

[gummycarbs]

You will get no better fuel ecomony. Lets get that one clear. You still have to deliver the same energy with drive to 2 or 4 wheels to get the same amount of mass to move. The transfer case with send it either one way (rear) or two ways (rear and front) and you'd be hard pressed to 'quantify' any changes in mechanical losses that can be easily measured.

I disagree with this. Technically.

I don't think you'll see any noticeable improvement when driving around town, since you're consuming so much energy bringing a 5k - 6k pound vehicle up to speed repeatedly.

In long highway driving, you'll see an improvement. You're cutting out the energy losses of the entire front half of the drivetrain. The only losses you're left with are from the wheel bearings and seals. With the standard US-market setup, you're spinning two u-joints, at least three bearings in the differential, the differential gears themselves, plus churning that Birfield butter and balls. Plus the front output of the transfer case. That's got to be at least something like a 5 - 10% efficiency loss.

Drivetrain losses (efficiency) – x-engineer.org

Introduction on how to calculate drivetrain (driveline) losses and their impact on the overall efficiency of the vehicle

x-engineer.org

That said, if you're concerned about highway mileage, then you're probably in the wrong vehicle. Unless you're somewhere like Australia, where enthusiasts regularly drive very long distances on dry, paved roads just to begin their off-road adventure.

So, again, there are some very specific benefits to a part-time conversion, but chances are that if you're reading this they don't apply to you.

If a part time conversion saves you a 10% energy loss, and if the part time kit costs you $350, then at $5 per gallon it will take 700 gallons to break even. If gas were $3/gal (approximate 2018 peak), it would take 1,167 gallons to break even.

 

[Dave 2000]

As usual there is always debate and so what is better and what is not just with regards to subject matter in this thread. Often people throw in stuff to bolster their opinion, and one thing I have seen on this thread is about additional wear on the mechanical side of the 4WD. When I bought mine circa 12 years ago I gave the front end a full overall mainly because the front swivels were leaking and the ABS would often trigger for no reason when coming to a stop. At this point the 80 was 15 years old, and the service history does not mention from this one owner car (but two on the log book for another reason), the prompting of the axle service was the brass bush in the front spindle housing. The CV had some weird wear patterns as well when stripped down, at the time I did not envisage going back into competitions as per the use of the Land Rover due to a shoulder injury. My point being I purchased a Joe soap CV, nothing special and it is still in there 10 years and around 100,000 miles later! I have not counted the last 20 months as Covid did stop a lot of use as have (and continue to do so) the last eight months due to surgery. But it is fair to say the wear on the front part of the transmission in 4WD is negligible if any. The UJ's are all original, the drivers side (RHD) still has the OE CV, all driveshafts are OE as is the differential, the axle to shaft seals on one side were replaced twice the second change just a few miles after the CV change due to a leak but that's it, and whilst the 80 has not been in any competitions when I could drive she spent a shed load of time off road most weekends fully loaded with camping gear and the additional wear over ten years? So with regards to wear @284,450 miles and approaching 26 years old, I will let you know when I find some.

In a nutshell, wear is not a valid argument when discussing the pros and cons between FT or PT transmissions.

Regards

Dave

 

[mudgudgeon]

In long highway driving, you'll see an improvement.

Not experience driving a full-time 80 with front shaft out, and hub flanges off, so residential identical to part time model.

Over 6 months of daily driving, 120-150 miles daily, 3/4 highway, 1/4 City, and using a fuel tracking app before and during that period.
No measurable difference.

 

[mudgudgeon]

In a nutshell, wear is not a valid argument when discussing the pros and cons between FT or PT transmissions.

I think the biggest wear item is the hub flanges on early models

 

[Dave 2000]

I think the biggest wear item is the hub flanges on early models

Agreed, they were thinner than the later versions, but the wear probably accelerated when off roading, given the effort applied to them on tarmac being shared via the rear wheels.

Dave

 

[White Stripe]

13mpg is pretty good. If you put a wideband gauge in the exhaust you can dial in the afm for better air fuel ratios while accelerating. Typically toyota runs a bit rich for that.

 

[TonyP]

I think the biggest wear item is the hub flanges on early models

Spending $800 to reduce (potential) wear on a $70 part. Land Cruiser logic.

 

[DivByZero]

HF1A is the part-time 4wd transfer case if a person wants to do it properly. I've never driven a full-time 4wd 80.

Worth adding to this that the front and rear prop shafts are also different lengths, so you need to swap them over too.

 

[mudgudgeon]

Land Cruiser logic

Oxymoron right there!!