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

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

When your front axles are chromoly part time is better for the axles.
 

Dave 2000

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When your front axles are chromoly part time is better for the axles.

Again you are not comparing eggs with eggs, why not make the entire front end from something like a Titanium kind of metal (no metal skills here), but you still won't get any improvement in fuel consumption...........well you might, your wallet would be a lot lighter. It could also be argued you bought the wrong vehicle in the fist place, buy the cheaper version with the OE P/T, put a big lift in and job done.

I think there is enough evidence against the conversion from FT to PT in the typical street vehicle, although you will often find those that have done money on the same for the 'pub talk' kind of view, tend to have trouble admitting the cost versus advantages are pretty much zero....no wait they are zero....er no, got that wrong again, doing the conversion leaves you in deficit.

But despite all the evidence people will never listen.

Now where is the 'Unwatch' button....oh there it is.....done!


Regards

Dave
 
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SNLC

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Worth adding to this that the front and rear prop shafts are also different lengths, so you need to swap them over too.
True as the part-time and full-time transfer cases are different lengths. I thought the front shaft is the same though - just the back one is different (?) because the full-time one has the viscous coupling section which the part-time one doesn't. Could be wrong.
 

SmokingRocks

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You will see about 1-2 mpg increase when road tripping a 2wd cruiser vs a full time 4wd version.

I’m talking 2 tanks of gas back to back (500 miles) of strictly highway driving. Idk bout you guys but an extra 25-50 miles per tank is a benefit on long road trips.

Plus, if you’re running over 2” of lift you’ll need a double cardan driveshaft to get rid of vibrations (and even with a DC it’s not perfect I can tell you that). double Cardan driveshafts aren’t cheap, so the cost of part timing instead of double cardaning becomes more intriguing. And I’m not even talking about how setting an axle up for a DC driveshaft negatively affects your caster angle, requiring even more serious modifications to correct.

Those who talk about how the handling is worse in 2wd than 4wd really need to get some high performance driver training. Nearly any vehicle driving the front wheels (either as FWD or 4wd) always has worse dynamics than one that just drives the rears. If you think otherwise then you need some seat time in good RWD vehicles. The 80 in 2wd feels much more connected to the road, I don’t have torque steer through the wheel, it’s overall more natural.

So yea there are benefits to part timing
 
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You will see about 1-2 mpg increase when road tripping a 2wd cruiser vs a full time 4wd version.

I think you might be right. I can't say for sure because my 1st cruiser was a 91 and my current 97 already had part time when I bought it. But my 97 just got 16.3 mpg on my last trip to Bryce Canyon. This trip was about 400 miles of highway driving with max speeds of 70.

Around town I average about 11 - 12 mpg's so I am always surprised to get up into the 16's on these longer highway trips.
 

SmokingRocks

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Yea it's kinda surprising but anything more than 5-10% city driving and it seems as though the percentage of highway driving isn't enough to balance out the gains.

If you have lower speed highways (55mph-65mph) you'll see better numbers than if you are blowing through Utah at 80.
 
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Yea it's kinda surprising but anything more than 5-10% city driving and it seems as though the percentage of highway driving isn't enough to balance out the gains.

If you have lower speed highways (55mph-65mph) you'll see better numbers than if you are blowing through Utah at 80.

Yep my last trip was almost all 55-65mph highways and high speed dirt, very little interstate. The 55-65 mph roads are where the cruiser really shines for road trips.
 

mudgudgeon

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Yea it's kinda surprising but anything more than 5-10% city driving and it seems as though the percentage of highway driving isn't enough to balance out the gains.

If you have lower speed highways (55mph-65mph) you'll see better numbers than if you are blowing through Utah at 80.

Months of daily driving burning 120-180 litres per week, traveling basically the same journey, before and after doesn't agree with your "2 tanks back to back" analysis
 

Dave 2000

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You will see about 1-2 mpg increase when road tripping a 2wd cruiser vs a full time 4wd version.

I’m talking 2 tanks of gas back to back (500 miles) of strictly highway driving. Idk bout you guys but an extra 25-50 miles per tank is a benefit on long road trips.

Plus, if you’re running over 2” of lift you’ll need a double cardan driveshaft to get rid of vibrations (and even with a DC it’s not perfect I can tell you that). double Cardan driveshafts aren’t cheap, so the cost of part timing instead of double cardaning becomes more intriguing. And I’m not even talking about how setting an axle up for a DC driveshaft negatively affects your caster angle, requiring even more serious modifications to correct.

Those who talk about how the handling is worse in 2wd than 4wd really need to get some high performance driver training. Nearly any vehicle driving the front wheels (either as FWD or 4wd) always has worse dynamics than one that just drives the rears. If you think otherwise then you need some seat time in good RWD vehicles. The 80 in 2wd feels much more connected to the road, I don’t have torque steer through the wheel, it’s overall more natural.

So yea there are benefits to part timing

I did 'Unwatch' but it not seem to happen, so I will try again after answering this post.

I am guessing that most if not all on this area of the forum do not full time off road, I include myself in this sentence. I am also unsure of how many actually enter into competitions to really prove their vehicles worth, check out my Avatar, that is my Discovery taking 1st place in an off road competition sponsored by Land Rover here in Spain many years ago, It was an all comers event, completely illegal vehicles for road use were being pulled off trailers and being entered. Me, I drove in won the competition, I would then jet wash the car off and pop up to the airport and collect a friend or family. That car had everything you could either buy/make or fit to a vehicle for off road use, we are talking no expense spared here.......and the answer is no, I did not consider changing the drive train configuration, diffs were changed for strength along with pegging and ARB lockers, stronger driveshafts all round along with stronger flanges, blah blah..... More iron around it than a tank you name it and it had it, even dislocation cones allowing the springs to leave the body mounting pads. So a true off roading vehicle, at the time it was my only vehicle and given the resources available I still did not convert it to 2wd, why? Because it is complete bo**ocks to do so. I only list the above paragraph to point out I am not talking out of my hat, and I am certainly no dreamer and perhaps more importantly not a 'follower'.

Facts:

I have driven a lifted 80 and it is less stable on the tarmac at speed, in particular in the event of an avoidance maneuver, if you want to argue that go and try it first, if you survive then you were purely lucky, if you try it shows you have no idea about the meaning of centre of gravity and were stupid to try anyway.

Re those who talk about handling being worse.......... Your kidding right? The 4wd is the only way to go from a handling and more neutral vehicle behaviour, of course all those that go off road racing use 4 x 4 full time regardless of marque Land Cruiser, Land Rover, Porsche and so on, of course they could be wrong? Remember the Audi Quarto wiping all before them in World Rally Cross? Please assure me it was absolutely nothing to do with the 4wd system, despite it being used on both rally courses with mixed soil and tarmac stages....nope nothing to do with being 4wd ...no way!

Re getting some performance training..................are we talking about the same vehicle here, this is the 80 forum right, it's a Land Cruiser FFS! Sure if your young and like to do some 'drifting' in your 2 ton PT Land Cruiser go for it, I mean the speeds you can get up to going around a corner with the 'tail out' should be quite high....well until you roll it over, no wait....driving like that will ruin the potential of another 1 or perhaps 2 MPG!

More connected to the road? Well with your two rear wheels pushing you straight on at the next bend whilst it is pissing down with rain while the two front ones are trying to steer fighting against the push of the rears, well not quite the same as two pushing at the rear and the two at the front being pulled around the bend (that would be the one with the big tree in front of you), you see 4wd wins all the time, so nope not really getting that 'connected feeling'. I'm guessing anyone who is coming up with excuses to have a PT kit fitted has already done it, and now are looking for reasons to justify the outlay, or returning to the 'pub talk' point of view?

@SmokingRocks Not aiming this directly at you mate, it is just that your post seems to have more reasons to not take away the surefooted grip and stability of 4wd than it does to make the conversion to PT, I have not looked at your profile/signature but wondered if you have made the conversion?

Having owned and driven cars for 53 years come August, and then spent most of that time driving pretty much every marque on the road as a full time mechanic with my own business, I can assure that your and anyone else's reasons to convert from permanent 4wd to to PT simply do not cut it and never will.

Regards

Dave.
 

SmokingRocks

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Dave,

I've been in 2wd for the past half a year via drive shaft out until I have time to get the PT swap in. I've got other projects in front of it including rebuilding a 1fz-fe from someone else, rebuilding my E30's clutch, painting it, selling it to buy an S52 swapped E30 touring, selling my audi A7 blah blah blah.

I am a racing instructor and have been racing Porsches for over a decade, my own of which was a 996 C4S. For those of you who don't know the 4 means 4-wheel drive, and YES they DO NOT handle as well ON THE STREET as their 2wd counterpart, but you are talking about in the dirt mainly when you are referencing 4wd not the street where I would begin to agree with you.

And your "Push pull" thing is not something we teach ever, because it's not a true representation of what's happening (and this isn't the place to debate that PM me if you want more), what we teach is the physics at play, mainly weight transfer and contact patch. 4WD almost ALWAYS tends to understeer sooner and have more of a numb feeling when pushed at the limit than their 2wd counterparts, whether that be high-speed cornering or conditions-based lack of grip. And it does this because of weight transfer and contact patch. Seriously go watch the last 10 years of top gear and see how often this is brought up, they had so much to say about audi's numbness and understeery nature for years specifically because of their 4wd system and weight over the nose.

You shouldn't be accelerating through dicy corners in terrible conditions in an 80 series whether its 2wd or 4wd, and then when you take the acceleration aspect away they are the same. THey have the same number of tires rotating at the same speed around the same corner, at that point there's no tires 'fighting each other' its all down to weight transfer, contact patch and how you the driver deals with those variables.

So I continue to respectfully disagree with you.

Now in an LC that's lifted 4"+ you need to buy a DC driveshaft, and rotate your pinion angle forward which DECREASES your caster which makes your overall highway driving more unstable and dangerous. To fix this you need to CLOCK YOUR AXLE which involves some serious modifications that many will never do. OR you could PT swap and leave your caster in a safe limit and run the OEM front driveshaft.

Stick to whatever you want, just understand (or don't, I don't really care) that there ARE reasons to make a PT swap.
 
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SmokingRocks

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Months of daily driving burning 120-180 litres per week, traveling basically the same journey, before and after doesn't agree with your "2 tanks back to back" analysis

Well seems like some of us have seen a bump in economy and others have not, which pins back to the OP's questions that a PT swap should not be looked at as a viable option to increase fuel economy. If you get 1 extra mpg then hooray but don't expect it.
 
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My 80 is converted to 2WD and now I'm towing a OTG trailer. The 80 is running 315s and 4:88s and even with the trailer in tow I still see 45-50 more miles per tank on flat roads of course. Trailer and Rig feel pretty solid on the road to me.
80s trailer.jpeg
 
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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.
Lol I actually have driven my 80 with the rear shaft off (using the front only) for a while about 5 yrs ago when original rear diff centre went bad and had no option but to run as a front wheel drive 80 series for about a month. Works fine. No CDL bs on mine - just lock it in 4wd high with front hubs engaged and off she goes with zero drive connection to the rear diff flange. Not recommended for long term as 80's are not engineered to operate as front wheel drive.
 

mudgudgeon

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Lol I actually have driven my 80 with the rear shaft off (using the front only) for a while about 5 yrs ago when original rear diff centre went bad and had no option but to run as a front wheel drive 80 series for about a month. Works fine. No CDL bs on mine - just lock it in 4wd high with front hubs engaged and off she goes with zero drive connection to the rear diff flange. Not recommended for long term as 80's are not engineered to operate as front wheel drive.
Yup, been there, done that too
 
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I drove my 91 with and for 5 years and I have been driving my 97 with part time for 2 years. I can tell zero difference in the handling between the two rigs on pavement. They are both slow and cumbersome.

Offroad the part time rig is easier to drift and a little funner to mob in.

Just blew a front inner axle seal tuesday evening. I can still daily drive my rig until I get parts and get it fixed because the rig is part time and nothing in the front end will move when I am commuting to work for the next few days.

Another win for the part time kit.
 

mudgudgeon

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I drove my 91 with and for 5 years and I have been driving my 97 with part time for 2 years. I can tell zero difference in the handling between the two rigs on pavement. They are both slow and cumbersome.

Offroad the part time rig is easier to drift and a little funner to mob in.

Just blew a front inner axle seal tuesday evening. I can still daily drive my rig until I get parts and get it fixed because the rig is part time and nothing in the front end will move when I am commuting to work for the next few days.

Another win for the part time kit.

Get your hands on a tuned up turbo diesel version that is anything but a slouch, push it along some mountain roads, then it becomes apparent there's definite difference in handling.

I miss my hdj80 :steer:
 

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