Front Drive shaft spinning in 2 wheel drive

[tyron]

Hi guys,


Had my 4wd actuator replaced in an insurance claim and now my auto lokka with lock up when in 2 wheel drive.

If I remove the front drive shaft it's fine, as a test I put some electrical tape from the drive shaft plate on the transfer case to the chassis and went for a drive, it didn't snap but it's stretched it right out.

Any ideas on how to fix this? Can an actuator incorrectly installed cause this?

Appreciate any help.

 

[Old.Tony]

The front axle and drive shaft turn over all the time on D40s, there are no unlockable hubs. Front-rear axle separation is achieved by the gearing in the transfer case.

I wouldn't have thought that would trigger the locker though.

 

[tyron]

I'm talking about the drive shaft from the transfer case to the front diff.

 

[Old.Tony]

Yep. If you move the car forward, because the front hubs are not unlockable (always engaged), the front axles will turn, the front diff will turn and so will that drive shaft.

 

[tyron]

Sorry, just read you mentioned the drive shaft too.

So the plate on the transfer case shouldn't spin in 2wd should it?

 

[tyron]

If I remove the drive shaft I have no issue with the lokka.

 

[Old.Tony]

It can, there's nothing preventing it from spinning. It won't be driven by the engine until the gears mesh inside the transfer case, but it'll still turn - moved by the motion of the front wheels.

I just don't expect that sort of motion to engage the locker - surely the designers took the always-moving drive train into consideration!

 

[tyron]

It never used to have an issue until the actuator was installed.. I would have thought with the drive shaft removed it shouldn't spin at all especially not enough to stretch the electrical tape.

 

[Old.Tony]

Ok I think I see what you're getting at.

If you remove the front drive shaft, in 2WD there is still some motion in the front plate of the transfer case.

I wonder if too heavy an oil might have been used in the transfer case. There's a pawl that engages the toothed gear that the transfer chain is on. The input shaft to this mechanism is the drive from the gearbox, which also drives the rear axle, but until that pawl moves and engages the gear, the chain SHOULD stay stationary. A heavy oil could cause some of the rotational energy to be passed to the gear anyway.

If I recall, transfer case fluid is auto trans fluid (which is fairly thin). Is there a chance someone used gearbox oil in yours?

 

[tyron]

Definitely a chance, mechanic was pretty useless.. I'll definitely try new oil

 

[tyron]

Well I just dropped the oil and chucked the same oil I had in before the actuator was replaced.. Still happen though.

 

[tyron]

It's also worth noting it only happens when I turn right.. And as a part of the insurance job the entire engine was replaced.

I've swapped the side the cv joints are on and it still only happens turning rights..

 

[Old.Tony]

When you're turning to the right, there are different forces acting on the front differential than when going straight or turning left, because the right-hand front wheel is driving around a smaller circle than the left-hand front wheel. When turning left, the same thing happens, but the diff may react differently. Being an open diff, something in the diff has to turn if one input is turning (consider both axles and the drive shafts as inputs for the moment). If you turn the left axle forward and hold the drive shaft still, the right axle rotates backwards. If you hold the left axle still and rotate the drive shaft, the right axle turns.

In a right-hand turn, the left front wheel is turning faster than the right, and maybe there's something in the locker arrangement that is taking this movement and assuming that power is being applied. As far as I am aware, auto lockers engage when the input shaft starts turning, but I did think that it would need to have some force behind it to engage the locker. Could the auto locker engaging mechanism be stuck, sticking or otherwise slightly out of place? In a left hand turn, the right front wheel turns faster and the drive shaft should rotate in the "reverse" direction.