Before I rip this thing apart.....

[WayneR]

just wanted a second opinion on something but pretty sure I know what answer is.

I recently did some fron end work on my 96 Disco. Upon completeing I had a vibration in the fron end. I am pretty sure its the front drive shaft, so I pull it out and go to take it for a spin with no front drive shaft (2wd rear) and nothing. No gears work, forward or reverse. I make sure the truck is in high gear, then I try low and nothing.
I put the truck in gear and I have my neighbour confirm the front output flage is spinning, however the rear drive shaft isn't.
I then proceed to jack up the rear of the truck and check the back differential. The tires spin when I crank the axle shaft by hand, however the axle shaft won't spin when the truck is in gear.....fawked transfer case???

so if it is a transfer case, will that of an 95 auto work in a 96 manual?

thanks,
Wayne

[Greg S]

Did you lock the centre diff? Otherwise your front flange will turn but not the rear one, exactly as described.

[WayneR]

Yes i did lock the centre diff, i tried it in high & low range with no results.

[Greg S]

Then your centre diff lock isn't locking. From what I hear, it isn't too uncommon for the shaft to stick from lack of use and not engage. Some one other than me might be able to tell you how to free it up. (Regular use will keep it free once you have it working.)

[Bill E.]

I second everything Greg has said. Don't waste your time tearing anything apart. Your center diff is not locked! It absolutely needs to be locked for any forward propulsion.

[WayneR]

if it is in gear, should i be able to turn the output shafts in both direction?

[WayneR]

Its definatley in gear. I put the front driveshaft in & can move the truck. I am sure it is the transfercase, unless land rover has some AWD thing that I am not familiar with, this is the first AWD transfercase I 've dealt with.

[discojonny]

you should get under the truck and make sure the linkage to your diff. lock is working properly. you can turn the actuator on the TC to be sure it is moving all the way. The linkage can get stiff and not engage the diff lock properly.

[WayneR]

so what you're saying is it is possible that only the front gear is engaging?

[discojonny]

no. if the diff lock is not engaging properly the power will go through the diff to the path of least resistance. ie, the front driveshaft. If the DL is engaged both front and rear driveshafts must turn together. this is how it must be to get motion with a driveshaft disconnected.

[WayneR]

so I am clear on this..... my diff lock may not be engaging properly however there is enough power going through to the front drive shaft to power the vechicle to 50km?
I tried moving the actuator, it is very stiff and I can't move it underneath the truck but it seems to shift well inside the cabin of the truck

[discojonny]

the shifter may be moving but not actuating the TC all the way. This is the most likely scenario. You should check the shaft going into your TC is moving all the way. The diff. is the same as in an axle. The power wil go to the path of least resistance. ie. the one without the driveshaft. just like a "left tire fire" burnout on a rearwheel drive car. when you lock the diff. the power goes equally to the front and rear driveshafts ie. they are locked together. speed is irrelevant. your diff.lock my be broken but it is usually the shifter linkage not fully actuating the TC.get under there and use a cresent wrench or slip joint pliers to move the DL linkage. Get someone to move the shifter while you are under there to see how it all moves(or doesn't).

[WayneR]

I appreciate the help. I will report back....fingers crossed.

[WayneR]

uh, I guess i should check the gearbox fluid level too then eh?

[WayneR]

boy am I glad I posted here before I started pulling out that gearbox. Actuator was stuck as you suspected. worked it loose & now shifts freely and my truck will drive with out front d shaft in. Many thanks guys.

[WayneR]

ok, so why is it that the diff lock must be engaged for the rear drive shaft to spin? aren't disco's AWD?

[rezdiver]

normally the center diff in the tcase works just like your diff in your front and rear axle. it is an open diff and power will get transmitted from the motor to the path of less resistance. if the front shaft is off or the front tires are slipping the truck will not move. if the resistance is close or the same at each wheel then the power is split equally between the two wheels.

just like if you have rear wheel drive with an open diff and one wheel spins then you are not going anywhere.

when you lock the transfer case you have basically locked the front and rear driveshafts together. so they have to spin at the same rate and cannot slip.

realistically with the transfer case locked you are only in two wheel drive if you lose traction, one wheel in the front and one wheel in the back and without lockers those wheels can spin out leaving you stuck. try it on some ice.

rover seems to gain its 4wd capability from axle articulation where by design it will allow as much tire contact as possible to allow the 4wd design to work properly by reducing traction loss and allowing power to be transferred to all the wheels on the ground as required.

you also probably have traction control where the braking system pulses the wheel that is spiining and slipping, this pulsing will allow resistance to be added to the wheel that is spinning which allows the axle differential to transfer power back to the wheel that has traction.