Thread: Driveline Backlash

What vehicle Phill?

You need to get unbderneath and see exactly where the play is.

Park the vehicle on the flat, with the handbrake off. First check each uni, and the driveshaft splined joints. Then check how much backlash each diff has.

A lot of backlash is normal.

Most comes from the dog clutch that selects high/low, and is multiplied by the ratio of the side to pinions gears in the centre diff.

The difference between the backlash front to the rear, is just coincidental - the position of the numerous parts at that point in time.

you don't get extra backlash overnight,
if something's amiss, it will show in the oil drains when you replace driveline fluids.
lots of backlash is normal.

i have an auto td5 d2. i also have what i consider a fair bit of backlash. i'm comparing to my ba falcon. when i back off the throttle and then get back on, in a regular way, i can feel the slack being picked up and then there's a bit of a jolt/soft thump. its enough to be felt as the driver, never had my passenger mention it, but she isnt car orientated. is this "alot of backlash is normal" applicable to d2's?

Hi Phil
My D2 is manual
I was real suprised on just how much backlash was there when the front shaft was out as yours was.SCARY as I was towing a fully loaded trailer at the time.Drove the 100km to Albany(on the way home from a camping trip) wasnt prepared to do the 300ks home on one shaft!!!!! Got it fixed and continused the trip home.
Once the shaft was re-installed normality returned!!!
Andrew

There is a lot of backlash, which is normal.

Assuming you have normal backlash between the gear teeth, the drive is transmitted through many pairs of gears - in the gearbox, plus the transfer case, plus the centre diff. They all accumulate by the time you get to the drive shafts. A lot more pairs of gears are involved than in a Falcon for example.

But as I said, most of the backlash is in the dog clutch for selecting low/high range. Unlike the syncromesh in a gearbox, the dog clutch needs the extra backlash (every second tooth is removed to make the space wider) otherwise getting the teeth to align so the clutch can engage would be like winning on a poker machine (designed so you loose).

Now if you get underneath and rotate one of the driveshaft to check backlash, then the drive shaft has to rotate twice that of the total backlash because of the gear reduction between the side gears and the pinions in the centre diff. Driving on the road, both front and rear driveshafts are rotating together and the centre diff does not have this affect.

It could be that you do have extra backlash in the gears due to wear. If bearings are worn, they allow the gears to separate further, increasing backlash - taper roller bearings seem to be worse when worn. The backlash between the bevel gears in the centre diff also increase rapidly if the thrust washer are worn.

If this has hapened so quick I would suspect the pin in rear diff is ready to depart. You say rear shaft has a lot more play than front Are you cruel to it off road? If its a CWP problem it would likely howl its arxx out at speed.