Rear Diff Servicing

[glend]

I usually change the rear diff fluid every two years, which is pretty simple with my RuffStuff diff cover, which has a drain plug and high filler port. This time I had to remove the diff cover because the RTV seal was leaking at the bottom, something I attribute to the sheer mass of the Ruff Stuff plate steel cover, being held vertically in place against that silicon bead, the cover moves against the silicon (probably on corrugations), breaking the seal over time.

It is a messy job, not as bad as a transmission service but still not pleasant. I use the optional heavier diff fluid because I tow my camper trailer a fair bit, so that means 80W140 Syn Penrite. Photo attached. Some may notice that this is the open diff version, as is normal on the later model (2007) traction control equipped KJs. Cleaning off that old RTV and degreasing the mating surfaces is a pain, but necessary before installing it again.

PS: Note that little rock stuck in the fuel tank bash plate drain hole, I have been carrying that thing around since my Simpson Desert trip in 2010, and short of dropping the bash plate it is probably there forever. Keen observers will note the still white factory notation inside the diff, the Polyair bag inside the rear spring, and up forward the Magnaflow muffler which replaced the stock one back in about 2008. And Cmohr might recognise his rock rails.

[rockski]

noting some 10 fastening bolts, must have been some serious corrugations to 'break' the RTV sealant (even taking into account the weightier Cover plate)

Have just done mine (std backplate) using slurp-out/pump-in approach : used Penrite 80W140 "full syn for Diffs including limited slip".
Have some Mopar Friction Modifier additive on standby should the LSD in our 2005 start to get narky

[cmohr]

Interesting Glen, I'm thinking with ESP vehicles, does that mean all would have the open diff in the rear??? I was about to organise some fitting kits the new KJ to put my DTT's in I wonder what effect this would have with ESP activating?? Or, would I need to turn ESP off all the time????

Those rockrails are certainly awesome things, So So solid.

[glend]

Chris, I am not sure about any KJs other than mine, but believe all the 2007s and 2006s with TCS, will have an open diff. Looking at the manual (page 52-53) it discusses the operating modes of ESP. In high range, 2WD, 4wd part-time and 4wd full-time, ESP is normally on. You can turn it "Partially Off" by momentarily pressing the button, and when in this mode the TCS part of the program is turned off, except the limited slip feature. If your in low range it is turned off, but again limited slip remains on. Once you go over 48kmph it turns ESP back on full mode. If you drop below that speed it turns it partial off again assuming your still in low range. So in general you cannot turn limited slip off in these vehicles.
I used it partially off in high range part-time, on the Old Telegraph Track on the Cape, and also in low range through some of the slow crawl sections, and certainly had limited slip locking up now and then.
I am not sure what this means if combined with DTTs. In my eleven years with my KJ I have never missed having a locker, and have driven right through plenty of stuff that had other vehicles reaching for their lockers.

Now concerning lockers in the front, I seem to recall that the aluminium front diff housing is prone to case cracking when lockers are used but DTTs might be different. Who was it that broke their front diff out at Landcruiser Park? But pretty sure that was not a TCS equipped model.

[dhula]

To add further info to Glend's post above, I have a 2006 and it has a open rear diff so suspect open diffs are the go for all KJ's with electronic traction control

[glend]

Dhula, thanks.

Just abit on how 'limited slip' works on ESP/TCS equipped KJs:

What is suppose to happen is that the ESP detects a wheel spinning via the ABS inputs, and then it applies the brake to that wheel, effectively stopping it, and directing the torque to the wheel on the same axle with drive.
This was very evident in a video I saw of my KJ at the Jeep Jamboree in 2010 down in Victoria. The video was shot by a Sydney Jeep Club guy ( I think he called it Lizards Lair), of my KJ climbing out of a steep rutted wet creek bed, in low range (so ESP partially off, except Limited Slip), and you could clearly see my left front wheel in the air during the climb with the wheel braked. You get a bit of pulsing as the ABS system checks the wheel to see if it has traction again, but it will stay locked until it touches down again and gets grip as detected by the system.
I will see if I can track down that video.

[cmohr]

Originally Posted by glend

Chris, I am not sure about any KJs other than mine, but believe all the 2007s and 2006s with TCS, will have an open diff. Looking at the manual (page 52-53) it discusses the operating modes of ESP. In high range, 2WD, 4wd part-time and 4wd full-time, ESP is normally on. You can turn it "Partially Off" by momentarily pressing the button, and when in this mode the TCS part of the program is turned off, except the limited slip feature. If your in low range it is turned off, but again limited slip remains on. Once you go over 48kmph it turns ESP back on full mode. If you drop below that speed it turns it partial off again assuming your still in low range. So in general you cannot turn limited slip off in these vehicles.
I used it partially off in high range part-time, on the Old Telegraph Track on the Cape, and also in low range through some of the slow crawl sections, and certainly had limited slip locking up now and then.
I am not sure what this means if combined with DTTs. In my eleven years with my KJ I have never missed having a locker, and have driven right through plenty of stuff that had other vehicles reaching for their lockers.

Now concerning lockers in the front, I seem to recall that the aluminium front diff housing is prone to case cracking when lockers are used but DTTs might be different. Who was it that broke their front diff out at Landcruiser Park? But pretty sure that was not a TCS equipped model.

Yes, That was Greg in his 2002 V6, we all suspected bad casting in the housing itself, but, that could never be proven.

I have been running the DTT's in my 2004 V6 and moved that front diff to my 2003 CRD always excellent, and I really want them in the new 2006. It's not so much about hill climbing or anything, It's more about beach and dirt driving , for me I can really notice the difference on the beach, none of that pulling to the left then right in soft stuff, just drives straight and true.

I think the DTT's should actually work with the system, if the diff itself is stopping slipage to the wheel, the ABS sensor will not be activating the ESP as there is nothing to act on. Well, that's my theory and I'm sticking to it (will chat to the guys at Driveline services, I'm sure they have had experience with diffs and traction control systems)

Originally Posted by dhula

To add further info to Glend's post above, I have a 2006 and it has a open rear diff so suspect open diffs are the go for all KJ's with electronic traction control

Thanks, Yes, I'm thinking that mine does have the Open diff in there, will check the sticker on the rear axle to confirm.