Backlash concerns

[Adrian D]

8000km from my ARB install, I needed a dial gauge for a different project and thought about measuring the backlash.

My friend who has helped me with the install has been in the Jeep business for a long time and it's not his first gear setup, however, he does it by hand, not with a dial gauge (I know, I should've bought one when I installed the lockers, such is life, you're free to flame me for it ).

The diffs have been fine, no noise, no extra heat, even following a 1200km drive. I've played in ravines and ditches where I had traction only on one front or rear wheel, even had the incident where the rear case flexed in reverse enough to cause the ARB to leak.

When replacing the diff covers about 1000km ago everything looked fine both fluid-wise and gear-wise.

Just to get it off my head, I assume the diffs would've failed by now had the backlash been out of spec, right?

[Qster]

They would be pretty noisy if it was wrong [emoji1745]

Sent from my SM-G970F using Tapatalk

[Adrian D]

I imagine they would be if it's too tight, but what about too loose?

I imagine they would lose strength, especially in reverse when the deflection is higher.

[Classic Boy]

Excessive backlash usually causes a driveline clunk from drive to lift off overrun, insufficient backlash can cause excessive heat, gear wear, and often a tight spot when turned by hand. As you appear to have none of these symptoms it’s probably ok.

[Classic Boy]

Originally Posted by Adrian D

I imagine they would be if it's too tight, but what about too loose?

I imagine they would lose strength, especially in reverse when the deflection is higher.

When the gear teeth are deeply meshed there is more tooth contract area so likely stronger. But there is a limit as the gears expand when the oil warms and so too little backlash can lead to binding.

[Adrian D]

Originally Posted by Classic Boy

Excessive backlash usually causes a driveline clunk from drive to lift off overrun, insufficient backlash can cause excessive heat, gear wear, and often a tight spot when turned by hand. As you appear to have none of these symptoms it’s probably ok.

Cheers!
I tried rocking the car going from drive to overrun on several occasions, no noises.

Originally Posted by Classic Boy

When the gear teeth are deeply meshed there is more tooth contract area so likely stronger. But there is a limit as the gears expand when the oil warms and so too little backlash can lead to binding.

By too loose I was thinking of too much backlash, that should move the ring gear away from the pinion, so less contact, right?

In hindsight, I really should've just bought a dial gauge before the install

[Classic Boy]

In my experience most final drive gears are set between 0.005” to 0.009” backlash irrespective of make, I find 0.006” backlash is normally adequate on most axles I have built.
Usually grabbing the input pinion and rocking it back and forward with the transmission in neutral on an assembled and installed rear axle can give a realistic feel of backlash. A small clearance is normal but you shouldn’t be able to make it clunk by hand.
The WG has a aluminum diff housing which is likely to expand faster than the steel gears and likely if all things are equal to slightly enlarge backlash clearance in use.