D40 Front Diff issue?

[dejmacro]

Picked up a D40 recently that needs a touch up.

One item that has been scratching my head is the 4x engagement/disengagement. Looking into it there are more than one type of ratios used.

When engaged in 4x4, the rear wheels are dragging, and, to disengage 4x4 is a practice in patience. Rocking back and forward - checking neutral on the way. Eventually it allows return to 2x4.

I'm wondering if the front diff was replaced, or internals changed somewhere. Or the selector mechanism is bad. Seen lots about the 4x Electro mechanical engagement problems mentioned around the place.

Anyone dealt with this sort of problem/s and could point me to something I can check to isolate the problem. I want to rule out the front/rear diff first.

Thanks

 

[Old.Tony]

I would have thought if the front/rear diff ratios were out it'd bind up really quickly - it's bad enough if you put new tyres on the front with oldies on on the rear!

The 4WD select mechanism is a servo that rotates a shaft through 270 degrees. The first 90 degrees engages a pair of pawls to bring the front transmission into gear with the rear. The pawls may have burrs or bends (almost unheard of). The second step is a 180 degree rotation to change the gear ratio in the transfer case from 1:1 to 2.6:1. The gears may have damage and/or the selector may have damage or debris inhibiting its movement (again, almost unheard of).

The usual schtick is a binding of the front-rear axles, usually caused by a turn of the vehicle. The usual fix is to simply drive forward (after selecting 2HI) and change direction a few times until it lets go - eventually the tension on the drive train eases and the servo is able to pull the pawls back out - usually.

If it is really problematic then the only option is to open the transfer case and take a squiz.

 

[landmannnn]

I would have thought if the front/rear diff ratios were out it'd bind up really quickly - it's bad enough if you put new tyres on the front with oldies on on the rear!

The 4WD select mechanism is a servo that rotates a shaft through 270 degrees. The first 90 degrees engages a pair of pawls to bring the front transmission into gear with the rear. The pawls may have burrs or bends (almost unheard of). The second step is a 180 degree rotation to change the gear ratio in the transfer case from 1:1 to 2.6:1. The gears may have damage and/or the selector may have damage or debris inhibiting its movement (again, almost unheard of).

The usual schtick is a binding of the front-rear axles, usually caused by a turn of the vehicle. The usual fix is to simply drive forward (after selecting 2HI) and change direction a few times until it lets go - eventually the tension on the drive train eases and the servo is able to pull the pawls back out - usually.

If it is really problematic then the only option is to open the transfer case and take a squiz.

If you are using 4wd on sealed or reasonably high grip surfaces the transmission windup and subsequent fiddling between 2 and 4 wd are perfectly normal.

The D40 was US designed so no thoughts of a centre diff.

Easy to double check diff ratios. Jack up a wheel, rotate the wheel by hand exactly one revolution of the propshaft/tailshaft. The two ratios normally available are 3.63 and 3.69, so you will need some chalk and a tape measure to tell the difference.