No power to rear wheels without CDL on (1 Viewer)

[Kylebsaz1]

Hi everyone,
This is my first post so bear with me. This weekend I put a new 3rd member in my 1991 Land cruiser and kept the drive shaft off because I need to match the rear gearing to the new front gearing. As I was trying to leave I had no power to the rear wheels like it was in neutral. The only reason I got it home was because I engaged the Center Diff Lock and it drove with no noise or problems. Anyone know if that's normal or what the problem may be? Ask me any questions I will try and answer them the best I can

 

[mct75]

You have an all-wheel-drive vehicle and without the front driveshaft installed the center differential will just spin the front output flange.

This behavior is entirely normal.

 

[Jgrauman]

You don't have a driveshaft and the wheels don't have power? Pretty normal operation. .. Have to lock the CD for the front to move.

 

[Kylebsaz1]

Yeah I understand that obviously without a front drive shaft the front wheels will not have power. I just don't entirely understand why the rear wheels would be affected. Is that due to the center differential? Just a note I got this land cruiser about 2 months ago I am still learning how it all works

 

[george_tlc]

^ yes.

The vehicle is AWD in its 'road/highway' mode, so there must be a differential action to prevent windup of the drivetrain. Hence the center differential. Unlocked it will provide all the drive to the least resistance path - which in your case is the rear output and so you don't move (no prop shaft).

The later model 80's have a viscous coupler that can provide a 'little' drive to the rear - but it is NOT a good idea to run it that way since it will overheat quickly, it is intended only to 'smooth' the center differential operation.

Locking the center diff ensures front/rear prop shafts both turn together, so then you can move.

cheers,
george.

 

[Kylebsaz1]

^ yes.

The vehicle is AWD in its 'road/highway' mode, so there must be a differential action to prevent windup of the drivetrain. Hence the center differential. Unlocked it will provide all the drive to the least resistance path - which in your case is the rear output and so you don't move (no prop shaft).

The later model 80's have a viscous coupler that can provide a 'little' drive to the rear - but it is NOT a good idea to run it that way since it will overheat quickly, it is intended only to 'smooth' the center differential operation.

Locking the center diff ensures front/rear prop shafts both turn together, so then you can move.

cheers,
george.

Thankyou George that's good to know and great explanation

 

[Dragos80]

In an open differential situation power will always go the the wheels with less resistance.
In your case this is the front wheels.
It's as if you are off road, open diffs, and get stuck with some wheels spinning but the car is not going anywhere.
The wheels spinning without traction will get all the power and those "stuck" will get no power.

In your case the front wheels have no resistance and get all the power and the rear are "stuck" and get no power.

The CDL will connect the front and rear to work at the same rate regardless of the slip/stuck situation.

 

[Kylebsaz1]

Perfect thank you all for clearing that up for me makes a lot more sense now!
@Dragos80 @george_tlc @mct75