I am ignorant about 4WD...

[Rineheitzgabot]

...but, I do not understand a few things about it:

1. What do locking hubs do (mechanically, how do they work/operate?)?
2. Why do we use them?
3. Will 4WD operate if they are not locked? If not, what happens?
4. What would happen if we left them locked all the time (whether in 2WD or 4WD) ?
5. Does driving in 4WD necessitate leaving overdrive off (or kept in low range)?

Thanks for your input.

[SafeAirOne]

...but, I do not understand a few things about it:

1. What do locking hubs do (mechanically, how do they work/operate?)?

A They mechanically connect or disconnect the front (usually) axle shafts to the front wheel hubs.



...2. Why do we use them?

A To prevent the wheels from spinning the axles, differential, prop shaft and transfer case when you're NOT using 4 wheel drive. Saves wear and tear (debate to follow, i'm sure) on the front driveline and saves fuel because the truck isn't having to spend the energy to turn all that stuff.



...3. Will 4WD operate if they are not locked? If not, what happens?

A Well, 4wd will still trun all the above stuff, but without being mechanically engaged to the front wheel drive hubs, it all be for nothing. The driveline will turn, but force will not be sent to the front wheels without the locking hubs engaged.



...4. What would happen if we left them locked all the time (whether in 2WD or 4WD) ?


A It would be just like driving a rover without locking hubs.



...5. Does driving in 4WD necessitate leaving overdrive off (or kept in low range)?

Don't know about that one. Someone else does, I'm sure.

[Leslie]

Mark's got one-through-four, so I'll stab at five....

The overdrive is basically an external 5th gear, for reducing the RPMs. Mechanically, I think it will function regardless of the transfer case (I could be wrong on this, but, I could be wrong, that part is a guess); however, I would suggest that you wouldn't want to bother engaging the overdrive if in 4wd... if you're in 4wd, you are probably traveling at lower speeds, within the 'stock' Rover's ranges....

I would suggest to only use the overdrive in 2wd on highway cruising, and leave it alone otherwise. (However, you don't want to go w/o using it, either... you want to regularly engage it for lubrication.)

[Rineheitzgabot]

Thank you both for that information.

Am I correct in saying that the harm in leaving the hubs locked all the time would be:

1. Fuel costs from all of the friction caused by more machinery being operated up front.
2. Wear and tear on said machinery.

Thanks again.

[Leslie]

The idea behind the hubs is to save wear and tear and fuel costs.


However, there are those who state that the system doesn't have adequate lubrication when constantly left unlocked.

I personally, leave mine locked most of the time, then unlock them if I'm going to make a road-trip. Then, lock them back.

FWIW......

[Apis Mellifera]

The steering is also lighter with the hubs unlocked. This is more noticable when the steering is at full lock and you're on high traction surfaces like asphalt.

[scott]

as i understand it with hubs unlocked and transfer case ingaged you will still put power to the front wheels but what you don't have is resistance at the front wheel when decending and using low rpms to control speed (engine braking). am i wrong?

[Apis Mellifera]

I R&R the gearbox in my SIII on Saturday. Test driving it with the floors and tunnel out, I was able to watch the driveshafts. With the hubs unlocked and the TC in 2H, the front driveshaft doesn't move at all. In 4H and 4L and the hubs unlocked, the front driveshaft rotates, but the front doesn't pull. Likewise when in 2WD and the hubs locked. In 4H and 4L and the hubs locked, only then is 4WD engaged and only then would the front provide resistance for hill descention.

Even in 2WD, with the hubs locked, the truck lurched turning at full lock. With the hubs unlocked, it turned easily.

[Rineheitzgabot]

I R&R the gearbox in my SIII on Saturday. Test driving it with the floors and tunnel out, I was able to watch the driveshafts. With the hubs unlocked and the TC in 2H, the front driveshaft doesn't move at all. In 4H and 4L and the hubs unlocked, the front driveshaft rotates, but the front doesn't pull. Likewise when in 2WD and the hubs locked. In 4H and 4L and the hubs locked, only then is 4WD engaged and only then would the front provide resistance for hill descention.

Even in 2WD, with the hubs locked, the truck lurched turning at full lock. With the hubs unlocked, it turned easily.

Honey Bee--

How lucky I am that you spent your Saturday the way you did. You basically answered all my questions with your account of what happens with the drive train in all those situations.

Thanks.

[Firemanshort]

FWIW - Overdrive and 4x4...

My Stage One has a full time 4-wheel drive system (similiar to Range Rover drive train). I also have an O/D installed (similair to the Fairy Series model). I drive down the highway with the O/D shifted in - no problem.

Note: my drive train has a center differential that the SERIES does not - so pay attention to what the boys said above - leave the O/D off when you are 4-wheelin' at low speeds.

[bmohan55]

Dunno about leavig the O/D off while wheeling at low speeds. I had a great oppertunity to go from 1st (low range) to 1st O/D (low range) while leaving a mud-hole and climbing a steep bank. I think it kept my momemtum up better than the steeper first to second shift. Of course I got out of O/D as soon as I topped the hill.

Probably not I good idea to use it too often in low but I think there are times when it give you the perfect range.

Of course what do I know as I've only had my SIII for 3 weeks!

[jimsshuman]

matt
please, please, please tell me the g/b is working good.

[Tim Smith]

I always thought that overdrive in low range would be a big no no. Simply due to all the torque. :confused:

[Apis Mellifera]

Michael:

It works a treat! Much better than the old one. I discovered the mystery clunk was from the rear output shaft on the TC, which was about ready to fall out. I think a bearing died because the output shaft nut was tight, but the brake drum/flange/shaft were flopping around and when I removed the driveshaft, gear oil poured out. The entire gearbox was encapsulated with oil so all the seals were blown. It had more oil on the outside than inside. I pressure washed the one I bought from you and replaced all the seals and gaskets and it actually looked pretty good afterward. The swap took all day, but in it went and it seems to work fine. It was perfect weather too and I didn't even hurt myself. Usually endevors such as these require blood letting.

Although the Toro OD looks OK, I decided to use my old Fairey and save the Toro for a spare. Thanks again.


On the subject of ODs and 4WD, I have the original install manual and it says to use the OD as you would a gearbox. It doesn't warn not to use in low range or low gears. In an MGB, OD damage can occure if you reverse with it engaged (sprag clutch), but the Rover is all gear driven so I don't think harm would come however it's used. That said, I wouldn't use mine in anything but 2WD on the highway just for sake of ease - shifting etc. The torque comes from the gearing downstream of the OD so I think it would be fine in low range.

[jimsshuman]

(sorry to use someone else's thread for personal business, but i'm done now)