My new wood scroung truck

SpaceBus

Minister of Fire
Nov 18, 2018
4,342
Downeast Maine
center diff verses transfer case ?
Could you explain what you are saying?
Thanks
Most part time 4x4 vehicles have a transfer case that locks the front and rear wheel speeds when engaged. This is why it's not good to run on the street in 4x4 as it will cause binding. The advantage being that most transfer cases are two speed. Full time 4x4/AWD vehicles have a center differential that can allow the front and rear tires to turn at different speeds, much like a regular front or rear differential allowing the outside tire to turn faster than the inside tire around turns. Some vehicles, like Humvees, have a transfer case and center diff allowing for full time 4x4 and a low range. Other vehicles like the Mercedes G-Wagen get around this by having an extra low first gear and a locking center diff instead of the transfer case. My truck has both an extra low first and a two speed transfer case. Some older 4x4 vehicles have single speed transfer cases which is really more like an on-off switch for the front wheels.
 
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ABMax24

Feeling the Heat
Nice truck. I really like where Ford is heading with the new super-duty. Light aluminum body, 10 speed transmission, new 475hp power stroke, first diesel pickup to feature steel pistons.

GM is similar with the 450hp L5P Duramax and 10 speed Allison.

And then there's the poor Dodge (or Ram or Fiat or whatever they want to be called) boys that are still stuck with the 370hp Cummins or 400hp if you choose the high output Cummins with the 6 speed transmission. One day they'll get a real truck again, but they are still just matching the hp figure Ford had in 2012.
 

salecker

Minister of Fire
Aug 22, 2010
1,086
Northern Canada
Most part time 4x4 vehicles have a transfer case that locks the front and rear wheel speeds when engaged. This is why it's not good to run on the street in 4x4 as it will cause binding. The advantage being that most transfer cases are two speed. Full time 4x4/AWD vehicles have a center differential that can allow the front and rear tires to turn at different speeds, much like a regular front or rear differential allowing the outside tire to turn faster than the inside tire around turns. Some vehicles, like Humvees, have a transfer case and center diff allowing for full time 4x4 and a low range. Other vehicles like the Mercedes G-Wagen get around this by having an extra low first gear and a locking center diff instead of the transfer case. My truck has both an extra low first and a two speed transfer case. Some older 4x4 vehicles have single speed transfer cases which is really more like an on-off switch for the front wheels.
[/Q
I will have to respectfully disagree i have been working on vehicles all my life,and will disagree with you on your description.
There may be a few odd AWD cars that have that feature.But any trucks have a real transfer case,i had an AWD astro van which had the same transfer case as 4WD models,no extra differential.Never seen a transfer case that didn't have low and high range.As for the Humvee ,the plastic covered 5 cylinder is a glorified chick car
I run my trucks in 4WD on the highway and never have any binding issues.Up here we have winter where 4WD is actually required to drive on the highway.I have done 200 mile round trips in 4 high in all my trucks with zero issues,or longer trips.I have 1500 to 3500 GM's with push button or leaver shift transfercases,every year from the 80's to 2005 and they all have thousands of miles in 4WD steady in the winters with zero issues other than mileage drops a bit.
 

SpaceBus

Minister of Fire
Nov 18, 2018
4,342
Downeast Maine
A full time 4x4 vehicle must have a center differential or the front and rear wheels will turn at the same speed and cause binding around turns. This is a non-issue on dirt and gravel, but can cause catastrophic failure on pavement. Just like how driving around on the street with a welded differential will cause serious issues. Most trucks do not have center differentials because they use multi-speed transfer cases, like I stated originally and you mentioned again. Some trucks have a 4x4 "auto" function which will engage the front wheels when slip is detected, but the front wheels are not default engaged. There are some full time 4x4/AWD vehicles that do utilize a transfer case, but like I said there is a differential inside of it. Really it should be thought of as a two speed differential. Transfer cases tend to be more durable, but there are plenty of very strong center differentials.

You can absolutely drive in the snow with four wheel drive engaged without issues, since the snow allows for wheel slip when going around corners. I as well do this in the winter. However, it does not work on dry pavement. Even on wet pavement four wheel drive can cause binding.
 

johneh

Minister of Fire
Dec 19, 2009
2,867
Eastern Ontario
What a long-winded explanation of 4 Wheel Drive (4x4))
All-wheel drive (AWD)
4X4 shiftable transfer case 4L-N-4Hand pos 4h lock
AWL 4wheel all the time in devouring degrees controlled by slippage of wheels (ice-Snow)
All units have differentials front and rear ( so no cornering hop )
Only get front-wheel hop when transfer case locked
AWD electrolyte by a switch in most cases
4X4 by manual shift or electrical switch
In all cases, no one is using a system that is totally automatic ( general public)
Then again they may have changed after I left the trade
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,072
NE Ohio
There are some full time 4x4/AWD vehicles that do utilize a transfer case, but like I said there is a differential inside of it. Really it should be thought of as a two speed differential.
Make/model?
 

SpaceBus

Minister of Fire
Nov 18, 2018
4,342
Downeast Maine
Make/model?
Most folks call them Humvees, but the specific title is HMMWV.


This article goes on to explain the full time 4x4 system utilizes an open center differential that can be locked and also changed to a lower speed. Hence it really being a two speed locking center diff.

Another cool thing about Humvees and Mercedes Galendawagens are the portal hubs which allow for much greater ground clearance, at the expense of added noise and complexity. Apparently the new G-Class has a low range, but I don't think the military vehicles did.
 
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lsucet

Minister of Fire
May 14, 2015
1,629
San Ysidro, New Mexico
If a vehicle has front and rear differentials whatever is mounted behind the transmission is a transfer case. Regardless if it is single speed, two speed, full time or part time.
Newest vehicle, most SUVs, with a setup of engine and transmission side ways like front wheel drive vehicles, has a PTU ( Power Transfer Unit ) and a RDM ( Rear Drive Module ) the last one, at the same time it is a transfer case mounted at the end like a rear diff but it is controlled by a DTCM ( Drive Train Control Module ). It can be single speed or two speed also. Different manufactures possibly give different names but it is the same.
 

SpaceBus

Minister of Fire
Nov 18, 2018
4,342
Downeast Maine
What a long-winded explanation of 4 Wheel Drive (4x4))
All-wheel drive (AWD)
4X4 shiftable transfer case 4L-N-4Hand pos 4h lock
AWL 4wheel all the time in devouring degrees controlled by slippage of wheels (ice-Snow)
All units have differentials front and rear ( so no cornering hop )
Only get front-wheel hop when transfer case locked
AWD electrolyte by a switch in most cases
4X4 by manual shift or electrical switch
In all cases, no one is using a system that is totally automatic ( general public)
Then again they may have changed after I left the trade
There are some specialty vehicles that have really trick AWD systems with a true center diff, but yes most are electro and/or hydraulic without a true center diff. All Subarus have center diffs, but only the STI versions have a limited slip center diff (LSD in the front and rear as well) and also adjustable bias. Mitsubish Lancer Evolution models have a very robust AWD system with limited slip front and rear differentials, some later versions even had computer controlled differentials. These are street going rally cars, so not really the same as a truck. The whole reason I mentioned differentials in the firs place was the 1978 Ford with a full time 4x4 system, which would require a center differential which would be pretty rare I'd think for the 70's. In fact it is so rare to see a full time 4x4 system with a low range that the only other vehicle I can think of is the Humvee. Jeep introduced a fully mechanical automatic 4x4 system with the Grand Cherokee, but it only sent power to the front during wheel slip events. GM also had an automatic system on some Oldsmobile and Chevrolet models, but I don't know much about it. The AWD system in the turbo Syclone and Typhoon was a full time 4x4 system with a center diff, but no low range. I want to say the Safari and Astro vans had a very similar, if not the same, 4x4 system.
 

SpaceBus

Minister of Fire
Nov 18, 2018
4,342
Downeast Maine
If a vehicle has front and rear differentials whatever is mounted behind the transmission is a transfer case. Regardless if it is single speed, two speed, full time or part time.
Newest vehicle, most SUVs, with a setup of engine and transmission side ways like front wheel drive vehicles, has a PTU ( Power Transfer Unit ) and a RDM ( Rear Drive Module ) the last one, at the same time it is a transfer case mounted at the end like a rear diff but it is controlled by a DTCM ( Drive Train Control Module ). It can be single speed or two speed also. Different manufactures possibly give different names but it is the same.
Not all transfer cases have a differential, but all full time 4x4 transfer cases must have a center diff to avoid binding and hopping in turns on dry pavement. I also would not call the Subaru or Audi transaxles with center differentials a transfer case, despite having front and rear differentials. What makes it a transfer case is having a low range. Otherwise it is just a center differential. There used to be multi-speed differentials in production in dump trucks and other heavy duty vehicles, but they were not transfer cases mounted to differentials. Some transverse engine vehicles that are also AWD have a viscous coupling rather than a computer controlled system to shunt power to the rear. I think the old Honda CRVs are like this.

This is all super pedantic, I was just surprised to see a full time 4x4 system on a 78 Ford, I had no idea it was even an option.
 

EODMSgt

Feeling the Heat
Dec 11, 2018
280
White Mountain Region, NH
I think this line is what started this whole thing:
Don't see many American trucks, especially older ones, with a center diff vs a transfer case.
It made it sound as if you were saying older trucks didn't have transfer cases. Even HMMWVs had transfer cases (they had New Process 242 2-Speed Transfer Cases).

As for the differential inside a transfer case, Jeep was using one as far back as 1973 with the old vacuum-operated Quadra Tac systems.
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,072
NE Ohio
I don't think there are too many old school firewood haulin pickups out there with a center diff...our old F250 "highboy" (don't recall the exact year...mid 70's) was full time 4x4 w/ high/low (NP203 maybe?)
 

johneh

Minister of Fire
Dec 19, 2009
2,867
Eastern Ontario
I had a 76 Chev K20 full-time all-wheel drive
Lived in Alberta at the time full tank of fuel Calgary to Banff National park
Uphill all the way truck had a 10 1/2 ft. camper on (my home). Get behind a
transport going back to Calgary only took 1/4 tank of fuel. Loved that Truck
 

Isaac Carlson

Feeling the Heat
Nov 19, 2012
329
I'll stick with my old truck. A new one costs 3-4x as much as our house.
My old one will carry as much as you can stack on it and still gets 16-20 mpg.
Take care of that beauty.
 
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lsucet

Minister of Fire
May 14, 2015
1,629
San Ysidro, New Mexico
Not all transfer cases have a differential, but all full time 4x4 transfer cases must have a center diff to avoid binding and hopping in turns on dry pavement. I also would not call the Subaru or Audi transaxles with center differentials a transfer case, despite having front and rear differentials. What makes it a transfer case is having a low range. Otherwise it is just a center differential. There used to be multi-speed differentials in production in dump trucks and other heavy duty vehicles, but they were not transfer cases mounted to differentials. Some transverse engine vehicles that are also AWD have a viscous coupling rather than a computer controlled system to shunt power to the rear. I think the old Honda CRVs are like this.

This is all super pedantic, I was just surprised to see a full time 4x4 system on a 78 Ford, I had no idea it was even an option.
All what I am saying is that it is a transfer case regardless. They are transfer case and center differential transfer case. It is just about they distribute and transfer between front and rear axles but they are transfer cases.
 

salecker

Minister of Fire
Aug 22, 2010
1,086
Northern Canada
Not all transfer cases have a differential, but all full time 4x4 transfer cases must have a center diff to avoid binding and hopping in turns on dry pavement.
Sorry i will still respectfully disagree with you because what you are saying doesn't jive with what i have seen and worked on myself.Exact same transfer case in a AWD astro van as an S10 4X4. I drive my 3500 4x4 in 4WD on dry pavement loaded without issues.It's a safety thing,with a huge load on it if i need to panic stop in 2WD the front tires will lose traction therefore losing steering,which is basically losing control of the truck and customers stuff.
With all the idiots driving these days if the things you thought were true the shops would be full of trucks needing transfercases and they would be lined up around the block.
Up here you rarely see a 2WD truck,period.
Lots of idiots driving in my town,everyone has 4x4 trucks no transfer-case issues around here.
 

ABMax24

Feeling the Heat
Sorry i will still respectfully disagree with you because what you are saying doesn't jive with what i have seen and worked on myself.Exact same transfer case in a AWD astro van as an S10 4X4. I drive my 3500 4x4 in 4WD on dry pavement loaded without issues.It's a safety thing,with a huge load on it if i need to panic stop in 2WD the front tires will lose traction therefore losing steering,which is basically losing control of the truck and customers stuff.
With all the idiots driving these days if the things you thought were true the shops would be full of trucks needing transfercases and they would be lined up around the block.
Up here you rarely see a 2WD truck,period.
Lots of idiots driving in my town,everyone has 4x4 trucks no transfer-case issues around here.
You are the exception if you drive around on dry pavement in 4wd. If only you're front tires skid you best have both your brakes and ABS systems looked at. No one I know drives around in 4wd except when it's actually needed. But that's also why so many new trucks have an auto 4wd mode, for those that don't know when to select it, to prevent them from burning out transfer cases, cv axles, and u-joints. Even a very small mismatch in circumference of a single tire puts a constant and significant load on every part of the drive train just driving down the highway.

So many people use 4wd as a crutch to replace lack of driving skill. I can take my pickup loaded up with sleds on our icy snow covered mountain logging road that would make most cringe when dry in the summer, 4wd gets engaged only for a short 5 km section, the rest of the 168km is done in 2wd.
 
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MTASH

Member
Dec 24, 2018
108
Montana
I don't think there are too many old school firewood haulin pickups out there with a center diff...our old F250 "highboy" (don't recall the exact year...mid 70's) was full time 4x4 w/ high/low (NP203 maybe?)
Yes, New Process 203 full time transfer case. Ford, Chevy and Dodge all had this as an option in the 1970's trucks. They are not super common and many were converted to part time due to fuel mileage and tire wear concerns.

Shift pattern was 4L Lock, 4L, N, 4H, 4H Lock. The 4L and 4H Lock positions locked the differential inside the transfer case.

The more common application in Ford pickups was a NP205 (or Dana 24 depending on model) part time transfer case with selectable front hubs. Ford also ran a single speed Dana 21 transfer case in some models.
 

SpaceBus

Minister of Fire
Nov 18, 2018
4,342
Downeast Maine
You are the exception if you drive around on dry pavement in 4wd. If only you're front tires skid you best have both your brakes and ABS systems looked at. No one I know drives around in 4wd except when it's actually needed. But that's also why so many new trucks have an auto 4wd mode, for those that don't know when to select it, to prevent them from burning out transfer cases, cv axles, and u-joints. Even a very small mismatch in circumference of a single tire puts a constant and significant load on every part of the drive train just driving down the highway.

So many people use 4wd as a crutch to replace lack of driving skill. I can take my pickup loaded up with sleds on our icy snow covered mountain logging road that would make most cringe when dry in the summer, 4wd gets engaged only for a short 5 km section, the rest of the 168km is done in 2wd.
Indeed
 

SpaceBus

Minister of Fire
Nov 18, 2018
4,342
Downeast Maine
Yes, New Process 203 full time transfer case. Ford, Chevy and Dodge all had this as an option in the 1970's trucks. They are not super common and many were converted to part time due to fuel mileage and tire wear concerns.

Shift pattern was 4L Lock, 4L, N, 4H, 4H Lock. The 4L and 4H Lock positions locked the differential inside the transfer case.

The more common application in Ford pickups was a NP205 (or Dana 24 depending on model) part time transfer case with selectable front hubs. Ford also ran a single speed Dana 21 transfer case in some models.
I always preferred manual hubs until I moved someplace cold. I've not in my lifetime (admittedly not that long and started after the 70's) seen a real full time 4x4 American pickup truck with low range, just the "automatic" systems. The GMC/Chevy Turbo S-10/15 chassis and the later AWD Silverado and Trailblazer SS being notable exceptions.
 

salecker

Minister of Fire
Aug 22, 2010
1,086
Northern Canada
You are the exception if you drive around on dry pavement in 4wd. If only you're front tires skid you best have both your brakes and ABS systems looked at. No one I know drives around in 4wd except when it's actually needed. But that's also why so many new trucks have an auto 4wd mode, for those that don't know when to select it, to prevent them from burning out transfer cases, cv axles, and u-joints. Even a very small mismatch in circumference of a single tire puts a constant and significant load on every part of the drive train just driving down the highway.

So many people use 4wd as a crutch to replace lack of driving skill. I can take my pickup loaded up with sleds on our icy snow covered mountain logging road that would make most cringe when dry in the summer, 4wd gets engaged only for a short 5 km section, the rest of the 168km is done in 2wd.
Don't worry i have been driving on shitty roads all my life.
I only use 4WD when i need it,no Auto 4WD needed.
I have never had an issue with a transfercase,maybe because i drive GM products.
When you have a big load on and your front tires are barley touching and you have ABS without 4WD on good roads you will probaly stop OK but on slipery roads you will just keep trucking because the ABS will not allow you to use your brakes effectively.But without ABS and in 4WD braking is fine and no steering loss.
Now you have to remeber i live/work in a remote area. I am the only tow service in a 100 miles each direction. So if there is a brokedown rig or an accident i am the one who has to deal with the stuff.No calling backup with a bigger truck once i am there.
So 25 years of doing this at my business,plus the years before working construction and mining on crappy roads most of you would be afraid of in 4WD,don't worry about me i have got this covered up here.
 
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salecker

Minister of Fire
Aug 22, 2010
1,086
Northern Canada
I always preferred manual hubs until I moved someplace cold. I've not in my lifetime (admittedly not that long and started after the 70's) seen a real full time 4x4 American pickup truck with low range, just the "automatic" systems. The GMC/Chevy Turbo S-10/15 chassis and the later AWD Silverado and Trailblazer SS being notable exceptions.
Gm had one in the mid to late 70's ,solid hubs fulltime case with high and low.Still have a case sitting in my yard.Didn't last long in the market,they were pigs on fuel without the locking hubs