All wheel drive???

Big Ugly · **Joined:** Fri Sep 25, 2009 12:13 am **Posts:** 52

tjkj2002 wrote:

geordi wrote:

My only question about that situation was that if I had a single locker, on the rear differential... Would it have forced the front to behave as well, or would I need a lock for both differentials.

F/R lockers are needed to make all 4 wheels turn no matter what.Just adding a rear locker will help but make exploding the front diff more likely offroad and you raise a front wheel.

TJKJ2002 - why would you be more likely to explode the front diff by adding a locker to the rear? Will I have that issue when I add the detroit truetrac limited slip to the rear?

tjkj2002 · **Posted:** Mon Feb 08, 2010 10:05 pm

Big Ugly wrote:

tjkj2002 wrote:

geordi wrote:

My only question about that situation was that if I had a single locker, on the rear differential... Would it have forced the front to behave as well, or would I need a lock for both differentials.

F/R lockers are needed to make all 4 wheels turn no matter what.Just adding a rear locker will help but make exploding the front diff more likely offroad and you raise a front wheel.

TJKJ2002 - why would you be more likely to explode the front diff by adding a locker to the rear? Will I have that issue when I add the detroit truetrac limited slip to the rear?

If your open/open and you lift a front tire you will most likely stop all forward travel(not always but most times),thus needing to back up and try another route.With a rear locker and open front end if you raise a front tire you will still move forward which leaves that one front wheel that is in the air spinning like mad and when it comes down------BANG,which is how most front D30A's have been exploded.With a locker F/R all 4 wheels will be turning at the same speed to matter how many are in the air,thus not creating that "shock load" that likes to make that D30A pinion walk.

Goglio704 · **Posted:** Mon Feb 08, 2010 11:17 pm

It sounds to me like a person would be better off locking the front first, but it seems nobody does that.

tjkj2002 · **Posted:** Tue Feb 09, 2010 12:08 am

Goglio704 wrote:

It sounds to me like a person would be better off locking the front first, but it seems nobody does that.

I'm a strong believer of locking the front 1st if you can only afford 1 at a time,though everyone else thinks I'm stupid but there is sound reasons for it.Heck most Wrangler experts will say lock the front diff before locking a D35.

geordi · **Posted:** Tue Feb 09, 2010 12:43 am

When you explain it that way, it makes a LOT of sense tho. Thanks for that, now I understand what is going on, and how it could be wrecked.

What are our options for locking add-ons? Is it only limited-slip clutches, or is an actual electro-mechanical system available without changing the entire differential?

tjkj2002 · **Posted:** Tue Feb 09, 2010 2:09 am

geordi wrote:

When you explain it that way, it makes a LOT of sense tho. Thanks for that, now I understand what is going on, and how it could be wrecked.

What are our options for locking add-ons? Is it only limited-slip clutches, or is an actual electro-mechanical system available without changing the entire differential?

For the front you are pretty much limited to the DTT(LSD) or the ARB air locker,you do not want a auto locker in the D30A.The rear 8.25 you have many options but the best are the Detroit locker(auto locker) and the ARB(selectable locker).

geordi · **Posted:** Tue Feb 09, 2010 3:25 am

Air lockers sound like something I would be interested in... Until I just looked up the price. As my Norwegian ancestors would say... Uf-Da!

They certainly know what they want for those things. I think my CRD will have to be happy with open differentials for a while, and I'll just have to use a winch on myself if I get stuck somewhere.

flman · **Posted:** Tue Feb 09, 2010 7:39 am

I thought part time meant front wheels were not propelled unless the rear wheels slipped, and full time is when all 4 wheels are propelled at the same time? I notice alot of you are saying, full time is safer on dry pavement then part time??

flman · **Posted:** Tue Feb 09, 2010 8:29 am

So I read the OM, and yes, part time is not really part time? What the hell kind of terminology is that? Any ways the last 4wd diesel vehicle I owned that had a 2 year production run also had PT and FT. It was the infamous Polaris Diesel. PT = power to front wheels only on rear wheel spin, FT = power to all 4 wheels.

Good thing I read this post.

Rich · **Posted:** Tue Feb 09, 2010 1:27 pm

flman wrote:

So I read the OM, and yes, part time is not really part time? What the hell kind of terminology is that? Any ways the last 4wd diesel vehicle I owned that had a 2 year production run also had PT and FT. It was the infamous Polaris Diesel. PT = power to front wheels only on rear wheel spin, FT = power to all 4 wheels.

Good thing I read this post.

PT/FT refer to the torque bias in the transfer case... the "type" of 4wd. These designations were around long before our transfer case was thought of.

Part-Time (Command-Trac) - Uses a system akin to what we all think of as a traditional 4wd. A big chain directly connecting the front output to input and rear output within the transfer case. This system is designed to aid the vehicle in low traction situations (sand, gravel, loose dirt, snow, ice, etc) and give traction by sending power to both front and rear axles. It is the oldest, simplest, and one of the most reliable variation of multi-function transfer cases (2wd/4wd).

Full-Time (Quadra-Trac) - Uses a system akin to trucks with a traditional Full-time 4wd system, or something like a modern AWD passenger car. These systems are constantly sending power to front and rear outputs without driver input. This allows front and rear outputs to spin at different rates with the addition of a limited slip coupling. Like a traditional LSD, this coupling "locks" the front and rear outputs together if one is beyond the allowable slip rate, like if the rear looses traction. During normal driving on high traction surfaces the front and rear axles will naturally spin at different rates at different times, using the limited slip coupling damage to the drive train is prevented.

We have the choice of both systems in our transfer case. (Selec-Trac). Although the transfer case is slightly weaker than the Command-Trac units, they are still a decent unit. The option of using either a PT or FT torque bias allows us to have 4wd better suited for variations in traction surfaces.

flman · **Posted:** Tue Feb 09, 2010 5:07 pm

Rich wrote:

PT/FT refer to the torque bias in the transfer case... the "type" of 4wd. These designations were around long before our transfer case was thought of.

Part-Time (Command-Trac) - Uses a system akin to what we all think of as a traditional 4wd. A big chain directly connecting the front output to input and rear output within the transfer case. This system is designed to aid the vehicle in low traction situations (sand, gravel, loose dirt, snow, ice, etc) and give traction by sending power to both front and rear axles. It is the oldest, simplest, and one of the most reliable variation of multi-function transfer cases (2wd/4wd).

Full-Time (Quadra-Trac) - Uses a system akin to trucks with a traditional Full-time 4wd system, or something like a modern AWD passenger car. These systems are constantly sending power to front and rear outputs without driver input. This allows front and rear outputs to spin at different rates with the addition of a limited slip coupling. Like a traditional LSD, this coupling "locks" the front and rear outputs together if one is beyond the allowable slip rate, like if the rear looses traction. During normal driving on high traction surfaces the front and rear axles will naturally spin at different rates at different times, using the limited slip coupling damage to the drive train is prevented.

We have the choice of both systems in our transfer case. (Selec-Trac). Although the transfer case is slightly weaker than the Command-Trac units, they are still a decent unit. The option of using either a PT or FT torque bias allows us to have 4wd better suited for variations in traction surfaces.

Good to know, but just give me some front locking hubs, and I would be alot happier.

dieseldoesit · **Posted:** Tue Feb 09, 2010 6:11 pm

tjkj2002 wrote:

If your open/open and you lift a front tire you will most likely stop all forward travel(not always but most times),thus needing to back up and try another route.With a rear locker and open front end if you raise a front tire you will still move forward which leaves that one front wheel that is in the air spinning like mad and when it comes down------BANG,which is how most front D30A's have been exploded.With a locker F/R all 4 wheels will be turning at the same speed to matter how many are in the air,thus not creating that "shock load" that likes to make that D30A pinion walk.

It will only be spinning as fast as the rear tires are spinning right? I mean, the driveshafts are locked.

The reason for lockers in the back first is for directional stability. In slick conditions, you nail the gas, and the rear end breaks loose, yet you can still be in control. You do that with a locker in the front, and you loose any ability to steer. Note, I am not talking rock crawling here... more like slick roads.

I knew a guy who what a full size blazer for plowing. He had lockers front and rear on it. He said if you were going in a corner with a bunch of snow, and you punched it, you would immediately spin out of control. He stopped plowing with that vehicle.

The needs for trail riding and rock crawling are much different then for driving on slick roads.

Goglio704 · **Posted:** Tue Feb 09, 2010 6:24 pm

With a locker in the rear, an open diff in the front, and the transfer case in part time (front and rear driveshafts locked together), a lone front tire in the air will spin a lot faster than the rear tires because of the amplification in the front differential.

CRD Joe · **Posted:** Tue Feb 09, 2010 6:30 pm

tjkj2002 wrote:

Goglio704 wrote:

It sounds to me like a person would be better off locking the front first, but it seems nobody does that.

I'm a strong believer of locking the front 1st if you can only afford 1 at a time,though everyone else thinks I'm stupid but there is sound reasons for it.Heck most Wrangler experts will say lock the front diff before locking a D35.

I was wheeling Fordyce Creek in California climbing the fourth winch hill when I blew my rear R&P. I had a locked front end ONLY! The truck was USELESS! I couldnt go anywhere or do anything. I had to be pulled off the trail and onto a logging road. My point is that a locked front end is NOTHING compared to a locked rear end. Ive built five rigs with front and rear ARB's. Ive used Lock-Rights and Detroits as well. Ive wheeled the Rubicon, Fordyce Creek, Moab, the Hammers and all over Washington State. If you have the oppurtunity to lock up one end make it the rear end! A locked rear end will often get you more places than four wheel drive open.

dieseldoesit · **Posted:** Tue Feb 09, 2010 6:55 pm

Goglio704 wrote:

a lone front tire in the air will spin a lot faster than the rear tires because of the amplification in the front differential.

amplification? I thought it was just straight gearing?

tjkj2002 · **Posted:** Tue Feb 09, 2010 7:22 pm

dieseldoesit wrote:

Goglio704 wrote:

a lone front tire in the air will spin a lot faster than the rear tires because of the amplification in the front differential.

amplification? I thought it was just straight gearing?

The one wheel in the air will spin 3.73 times faster then those on the ground,if you still have the stock gearing.

Quote:

I was wheeling Fordyce Creek in California climbing the fourth winch hill when I blew my rear R&P. I had a locked front end ONLY! The truck was USELESS! I couldnt go anywhere or do anything. I had to be pulled off the trail and onto a logging road. My point is that a locked front end is NOTHING compared to a locked rear end. Ive built five rigs with front and rear ARB's. Ive used Lock-Rights and Detroits as well. Ive wheeled the Rubicon, Fordyce Creek, Moab, the Hammers and all over Washington State. If you have the oppurtunity to lock up one end make it the rear end! A locked rear end will often get you more places than four wheel drive open.

I have had the complete opposite,I blew a front CV and with only the rear locked it was useless as bringing a knife to a nuke fight on the rocks.If you play in more mud having a locked only front will be 100% better then a rear only locked 4wd.

DarbyWalters · **Posted:** Tue Feb 09, 2010 8:56 pm

A DTT front and rear would work great offroad...but it will definitely (the front DTT) make the steering feel very heavy on road in FULL TIME 4WD.

CRD Joe · **Posted:** Wed Feb 10, 2010 7:34 pm

tjkj2002 wrote:

dieseldoesit wrote:

Goglio704 wrote:

a lone front tire in the air will spin a lot faster than the rear tires because of the amplification in the front differential.

amplification? I thought it was just straight gearing?

The one wheel in the air will spin 3.73 times faster then those on the ground,if you still have the stock gearing.

Quote:

I was wheeling Fordyce Creek in California climbing the fourth winch hill when I blew my rear R&P. I had a locked front end ONLY! The truck was USELESS! I couldnt go anywhere or do anything. I had to be pulled off the trail and onto a logging road. My point is that a locked front end is NOTHING compared to a locked rear end. Ive built five rigs with front and rear ARB's. Ive used Lock-Rights and Detroits as well. Ive wheeled the Rubicon, Fordyce Creek, Moab, the Hammers and all over Washington State. If you have the oppurtunity to lock up one end make it the rear end! A locked rear end will often get you more places than four wheel drive open.

I have had the complete opposite,I blew a front CV and with only the rear locked it was useless as bringing a knife to a nuke fight on the rocks.If you play in more mud having a locked only front will be 100% better then a rear only locked 4wd.

TK, that doesnt make any sense. Physics are physics. Then the vehicle moves forward the weight shifts to the rear, thereby taking weight from the front wheels and reducing their traction capabilities. I had 35" boggers, a fuel injected engine a 145 to 1 low range and a front ARB and the truck wouldnt go anywhere on dry rock!!!

flman · **Posted:** Wed Feb 10, 2010 7:38 pm

Today when I was testing my Mexican :SOMBRERO:

tires in the snow, I was playing with the 4wd. It make sense now, FT is all the time, and PT is only for extreme situations. I guess what I read in the Polaris Diesel OM stuck?

tjkj2002 · **Posted:** Wed Feb 10, 2010 9:45 pm

CRD Joe wrote:

TK, that doesnt make any sense. Physics are physics. Then the vehicle moves forward the weight shifts to the rear, thereby taking weight from the front wheels and reducing their traction capabilities. I had 35" boggers, a fuel injected engine a 145 to 1 low range and a front ARB and the truck wouldnt go anywhere on dry rock!!!

I was going down hill,all the weight being transferred to the front.Also guess you don't have the ability to do front digs,the rear axle is totally disconnected for those(need twin sticks,aka Atlas).

All wheel drive???

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