limited steering/turning radius while in 4wheel low? (1 Viewer)

[wantatlc]

so, what exactly mechanically is going on when you swtich into 4wd low, lock up the front hubs which causes the steering radius to be limted and a bit tougher.

I notice when I get into trails that require 4wd low, I sometimes have to do 3 point turns on 180 switch backs to get through them becuase the steering becomes limited when hubs locked and in low, what is the actual reason for this?

Is this an after market Saginaw power steering limitation in my FJ or standard issue for all power steering.

 

[peesalot]

is you havin a front locker ?

 

[Trollhole]

I'm going to say this is standard on all 4wd's with our setup. Going around any corner makes one tire try to spin faster than the other. Though a 4wheel drive with traction wants both tires to spin at the same speed. What you get is binding. This should be sthe same in 4 lo and 4 hi. Though your are probably going slower thus more ability for more traction and the ability to feel it tug.

Or it wants to take the path of least resistance which is straight. Taking the resistance will get rid of bad turning angles. A locker just makes it worse.

If you had longfields or newfields I'd tell you to try it on pavement and see the difference traction make. BUt with stock birfs and big wheel you could easily break a birf.

 

[wantatlc]

is you havin a front locker ?

no sir, rear only from PO.

 

[Pin_Head]

It is normal operation that is exacerbated by having one or more lockers. It wouldn't be a problem if the transfer case had a center differential, like FZJ80s.

In a turn, the front and rear tires and the inside and outside tires are turning at different speeds. All the tires have different turning radii, so there is a difference in the speed of the ring gears in the front and rear. The transfer case is locked, so it forces one axle to turn faster than the tires want to. The situation is made worse by a locker in either end and is worse when you have two. Because of the locker, the inside tire cannot slow down as it would with an open diff, so this makes the F-R speed mismatch worse.

 

[wantatlc]

thanks pin_head, that splains it perfectly. now I understand the mechanics at work and know it is not a limitation of an afte market PS setup.

 

[honk]

I usually figure that if that's happening I've got enough traction to take it out of 4 wheel drive. It's one of the times that having 2 low is good.

 

[wantatlc]

I usually figure that if that's happening I've got enough traction to take it out of 4 wheel drive. It's one of the times that having 2 low is good.

so

H2
|
H4 - L4

sorry if dumb question, but to use H4 low, do you have to have the front hubs turned and locked in? I really only ever use H2 (daily driving setup) and L4 (off road setup for the trails I drive), but never seem to use H4.... do I turn the front hubs to engage H4 or only when shifted into L4?

 

[Ian Rogers]

looks like this

H2 - L2
| |
H4 - L4

you gust cut the gate also try a search for 2 low mod

 

[wantatlc]

wow - never even knew this 'mod' was even possible. do not know why I would need it as I do not even used H4 as it is (but maybe I should be and do not even know it as I find my rig can power through must stuff I drive in H2, and when not, I just go right to L4)..... but still want to know if I need front hub locked for H4 usage?

 

[solidfrontaxle]

Your hubs lock your wheel to the axle so the front tires get traction, so 4Hi with hubs unlocked is 2HI with your front driveshaft and axles turning. I use 4HI alot when in snow to keep from putting too much torque on my tires and spinning out. Also I use it when drving around town in the snow. The nice thing about 4hi is you can engage it when going fast (if your hubs are locked).

 

[honk]

Yeah, solidfrontaxle is right and the FJ40 came with the hubs locked all the time so you would just go from 2H to 4H with the lever or dash control. Dealers added locking hubs as an option.

But 2L is something that's locked out by the plate under the floor at the lever. They didn't want it used, or felt it wasn't something Americans wanted. Maybe they thought it would confuse us all . (it actually can put a lot of torque to the rear axle and cause breakage if not used carefully). It's a good thing for when you need low gearing for climbing or for engine braking but don't have the tire slippage that lets four wheel drive work well, and you can get it by either removing that plate lockout guide or grinding it so that the shifter can get the low range without four wheel drive engaged.

There have been a bunch of threads about this, some recent ones have pictures of how to deal with the plate. Might even be in Poser's great FAQ section above!

 

[PabloCruise]

2 Lo Mod

 

[legion]

Why would you ever want L2?

 

[Mickldo]

Why would you ever want L2?

L2 is handy to help eliminate unwanted three point turns on tight tracks and also useful when towing heavy loads. If you need to do a hillstart on a high traction surface eg;boat ramp. you can start in 1st L2 then double shuffle into H2. Also handy when reversing a trailer it slows everything down without excessive clutch slippage.

 

[PabloCruise]

Why would you ever want L2?

2 Lo and a rear locker and you don't need 4WD as much...

 

[wantatlc]

2 Lo Mod

Pablo -

thanks for the tip on this mod....

I still need 1 question answered people seem to keep bypassing in my thread....

when you go to H4... must you have the front hubs turned and locked to engage H4... or is that only needed when using L4?

 

[PabloCruise]

If you want all 4 wheels to receive power, you must have hubs locked.

Otherwise, putting t-case lever into 4 Hi (or Lo) will simple spin front drive shaft, which will spin your front axle and birfs, everything out to the hubs. So you will be powering your drivetrain all the way out to, but excluding, your front wheels.

Many folks will drive around in the snow in 2 Hi, but lock their hubs, so they can shift on the fly into 4 Hi.

Are we good now?

 

[peesalot]

correction Pablo , If you want all 4 tires to get power you must be in 4wd and have true lockers front and rear.

 

[wantatlc]

If you want all 4 wheels to receive power, you must have hubs locked.

Otherwise, putting t-case lever into 4 Hi (or Lo) will simple spin front drive shaft, which will spin your front axle and birfs, everything out to the hubs. So you will be powering your drivetrain all the way out to, but excluding, your front wheels.

Many folks will drive around in the snow in 2 Hi, but lock their hubs, so they can shift on the fly into 4 Hi.

Are we good now?

Ummm... I think so, but to be clear (and forget about the L2 mod for this stock setup understaning):

-you drive around in H2 daily
-and you could lock the front hubs in H2 and get a benefit in certain conditions?

-you could drive in H4 without hubs locked and it is better than H2 in certain conditions?
-and/or you could drive in H4 with hubs locked in and it is even better

-you could drive in L4 without hubs locked and it is better than H2 with locked hubs?
-and/or you could drive in H4 with hubs locked in and it is best for true 4x4 situations


I am just trying to understand all the possible combinations as I thought all there was was H2 then down to H4 and hubs must be locked or it was pointless and then over to L4 and hubs must also be locked or it is pointless. I assumed if you ever get out of H2, front hubs had to be turned and locked or the H4 and L4 were not truly engaged?