Well I’ve had this bang for awhile, usually under putting foot down, but often I get nothing, sometimes for days no noiise.
many here gave great advice, took it into a good mechanic, it’s the rear diff, sigh.
to give you an idea the truck cost 7k nz a rebuilt diff 3500, a second hand one 1500 ish.
a lot of cash,
If I shop around for a used unit, will one off a d1 fit a d2 ?, is it worth looking for one that’s had lockers fitted ?

 

wait until something else goes like a engine lol
discos are money pits, period.

 

A D1 diff will not work on a D2. If you off-road I would look for a used unit that has lockers installed or even a built third member from Lucky8 that has lockers and new gears and that would cut down on install labor time significantly. I would check to see if the rubber disc is intact between rear driveshaft and diff and confirm it's not cracked before blindly buying new diffs.

 

Thanks, I’ll track down a diff specialist see what they think

 

Took it out today gave it hell, hard acceleration on straights and corners all good from standing start as well.
‘even 50 kph then foot down no noise, but if I’m going any speed take foot off the gas let the revs drop then hit the gas it bangs.
‘my passenger says it sounds like the middle of the car, I’m thinking gearbox or transfer case, I might book it in for a trans gearbox flush sigh

 

If it's an automatic, don't flush the transmission. That often causes more problems than it solves.
Did you check the condition of the rotoflex (rubber doughnut) just forward of the rear differential? What about your engine and transmission mounts? Is there excessive play in the driveshaft if you remove it from the diff?

 

@wheelspin drop the rear drive shaft, engage the CDL go for a drive around the block. If the noise vanishes it is either the driveshaft, rubber isolator or diff.

If the noise stays try the same with the front shaft, also check your engine and transmission mounts.

But honestly sounds like a drive shaft issue to me, we used to get that all the time on rear wheel drive cars when the u-joints were shot, thump on shifts or RPM changes,usually on downshifts

 

Thanks I looked under neath the front driveshaft looks newer, it’s an interesting project for sure, mine doesn’t have a cdl, something else to add to my list lol

 

Swing arm bushings? Decel with engine braking would torque the axle one way, then when you're back on the gas it goes the other way.

I agree with others, don't flush the trans. Drain and refill with a new filter if you choose, but your symptoms sound like something after the trans.

 

Yep check the u-joints in your driveshafts