Why are my tires spinning when off-road? (10 Viewers)

[runningdrew]

-deleted-

 

[runningdrew]

No real data to really know. From what I have seen, passed 120k with no R&R on the 8" seems to put it into a vulnerable state. Wheeling with nothing done to the diff when getting over 120k seems to put it in a critical state. This is all just "me thinking" based on watching 9 years of posts.

Is Diff maintenance (setting preload) something that is on a service schedule, that Lexus is performing and will show up on service history? Also can this diff maintenance be down while still installed in-place? A quick photos search shows all the diffs detached on a vice...

This is the knowledge I come here for.

 

[tlin]

8" rear carrier has towers on either side to establish and hold the preload. Those towers (due to design) flex under load, or over time with prolonged (mileage) use. Eventually it will back off preload to where it will allow the pinion gear and ring gear to not mesh properly and will start to wear, or even chip/fail. I had my first R&P fail on a gravel road. Second (nitro, locked) chipped in harsh offroad use. If you proactively maintain the preload in the rear (R&R) you can prevent the random failures, but in harsh use you can cause a major mismatch on preload and chip it regardless. If you "do nothing" it will eventually give out and fail with even light duty offroad use.

I'm assuming this covers the preload R&R you're referring to, correct?

+ @runningdrew since it sounds like he's also interested in better understanding this...

 

[Dharma Dude]

I put 4.56 gears in my old 8". Solid spacer. ARB. It failed. I saw the pattern and torque specs myself and they were perfect. I was on gold bar rim so I think I simply flexed the towers in the carrier so much it chipped the ring gear, but there it is. Light wheeling, light weight...I think preload and solid spacers are goodness. HEAVY? I would do something regardless.

How light is light? The GX is my spare car. I put 5K-7K on it per year, and maybe at most 1K of that is dirt. The hardest wheeling I have done is Death Valley.

So it sounds to me I should have preload checked regularly and solid spacers.

 

[little_joe]

That carrier bearing preload article is not the issue discussed here. But, it may be very relevant to the "issue" some have had as both carrier bearing preload and pinion backlash affect gear wear (or breakage).

The crush sleeve/preload thing is related to the actual pinion gear. Toyota uses crush sleeves to move the pinion gear in towards the ring gear. (Carrier bearing preload moves the carrier and ring gear side-to-side.) Installers gradually "crush" this sleeve by torquing the pinion flange nut (under the flange the driveshaft is bolted to) to set the gear pattern. If they crush it too much - which would have the pinion too far into the ring gear - they basically have to start over with a new crush sleeve. Shocks and jolts to the drivetrain, for example when "hopping" offroad, can cause the sleeve to crush further, thereby pushing the pinion further into ring == major problems. This, or when pressure is released which would allow the pinion gear to back out or deflect, causes irregular wear, chipped teeth, or general destruction.

 

[tlin]

@little_joe - excellent description, thank you!

 

[Jstawgn]

I tried to replace the crush sleeve with solid spacer just by measuring the old crush sleeve when I rebuilt my elocker. It does not work. End up having to add a bit more shim. This is prove that the crush sleeve does crush a bit more after hard use or high miles.

 

[runningdrew]

I'm assuming this covers the preload R&R you're referring to, correct?

+ @runningdrew since it sounds like he's also interested in better understanding this...

Yep, I have 170k miles and plan in doing light off reading, I'm guessing this is a thing I need to plan now. Can it be done while on the vehicle?

 

[fastlane1000]

Yep, I have 170k miles and plan in doing light off reading, I'm guessing this is a thing I need to plan now. Can it be done while on the vehicle?

You have to slide the rear axles out and then unbolt the drive shaft and remove the third member from the housing.

 

[GXO]

It's easy to get out. Just pull the brake lines and 4 bolts for the bearing/axle mount and they will slide right out. No need to mess with the brakes.