Maintenance interval question

[fasteddie2015]

115K miles on my 15 LC. Today replaced diff oil, transfer case fluid, greased driveshafts. I've been told by a mechanic I trust to do diff and transfer case every 30K miles and grease drive shafts 30K or once a year. How often do you do those maintenance items? Since it will take me 2 years to go 30K miles, should diff oil and transfer case fluid be replaced at a time interval?

 

[tominboise]

30K is a fine interval for the diff fluid, depending on use. If you towed heavy a lot you may want to replace fluid in the diffs more frequently. If you run through some deep water, may want to do the same.

I grease the driveline at every oil change (about 8k miles).

I wouldn't change at a time interval.

 

[Sandroad]

I think every 15,000 miles would be a waste of money and oil, unless you have a very unusual type of use for for your vehicle. What does the owner's manual say for a '15 LC?

 

[CJ3Flyer]

My ‘13 LX maint schedule doesn’t really call out these items* for normal use yet for towing and off-road suggests as short as 15k for diff fluids, 30k for t-case and 5k for driveshaft grease. *It just calls for “inspect” and I assume replace if deemed necessary.

Similar but different: My 4Runner had a very similar schedule listed. I lubed the driveshaft every 10k, t-case and axles at 45k* and transmission at 60k with great success. I also add some moly to the gear lube (lower diff temps can be seen with IR). A final thing is every 10k or so I’d suck out the power steering fluid and refill the reservoir (cheap and why not?). For me that was a sweet spot between keeping it like new and not being wasteful. This is what I intend/have done with my LX.

*On the first change do it early especially the rear diff, it’ll probably be nasty. Next one will be better. There tends to be lots metal etc on that first change. Again, my 45k thing worked great with synthetic gear oil and moly. I don’t have any deep water exposure.

I do tow some (not as much as many with camp trailers). YMMV.

 

[KLF]

My standard oil change routine (5000 miles) is put the truck up on the QuickJack, pull the drain plug off the pan and filter, let it drain overnight. While it's draining, I rotate the tires (5 tire rotation), spray lube in all the door and other hinges, spray lube in the spare tire winch, then I get underneath with my headlight and inspect the healthy coating of Fluid FIlm, which gets touched up where necessary. Sometimes I'll crack open the KDSS bleeders to make sure they are still OK.

Driveshafts get greased every oil change. I actually keep the zerks out of the spline joints so the joints can move freely. I have a pneumatic grease gun with Amsoil grease, I put the zerks back into the spline joints, count about 20 "ka-pish" squirts from the gun, then pull the zerks back off and put them away in the rear drawers. Then I wipe off all the excess grease from everything so it doesn't splatter all over.

I've never heard of a U-joint failing due to too much grease.

Next morning I swap out the filter, plugs back in, dump in 8+ quarts of fresh Amsoil. Slap a reminder sticker on the windshield, log the change in the maintenance log.

 

[CJ3Flyer]

My standard oil change routine (5000 miles) is put the truck up on the QuickJack, pull the drain plug off the pan and filter, let it drain overnight. While it's draining, I rotate the tires (5 tire rotation), spray lube in all the door and other hinges, spray lube in the spare tire winch, then I get underneath with my headlight and inspect the healthy coating of Fluid FIlm, which gets touched up where necessary. Sometimes I'll crack open the KDSS bleeders to make sure they are still OK.

Driveshafts get greased every oil change. I actually keep the zerks out of the spline joints so the joints can move freely. I have a pneumatic grease gun with Amsoil grease, I put the zerks back into the spline joints, count about 20 "ka-pish" squirts from the gun, then pull the zerks back off and put them away in the rear drawers. Then I wipe off all the excess grease from everything so it doesn't splatter all over.

I've never heard of a U-joint failing due to too much grease.

Next morning I swap out the filter, plugs back in, dump in 8+ quarts of fresh Amsoil. Slap a reminder sticker on the windshield, log the change in the maintenance log.

Little plastic plugs or something in the Zerk holes?

 

[KLF]

Little plastic plugs or something in the Zerk holes?

Nope, I just leave them open. They are usually full of grease anyway.

 

[bloc]

As for diff fluid intervals.. I put OE toyota diff fluid in at 110k, and dumped it at 140k. It looked almost exactly like the fresh stuff I pumped in to replace it. Plus virtually no metal on the plug magnet. Only ~500 miles of towing 5k lbs, for the record. Obviously this isn’t as good as a proper UOA but the magnet is a good indicator.

Based on that I have no issues with 30k on the diff oil.


With no zerk I’d be very concerned about the rear driveline extending during a water crossing and pulling water in. Personally.

As far as I know as long as the splines aren’t over-greased there are no problems with free movement with the zerk installed. Air is plenty compressible.

 

[OregonLC]

I thought the shaft was designed so that the new grease purged the old down the splines and out past the seal? Without this purging wouldn't you be merely filling the void with grease that will then just come out the hole where the zerk was (assuming it was removed) when the suspension is compressed? Seems like you'd want to fill until you see the old stuff come out past the seal just like on a u-joint. And then leave the zerk in place keeping dirt/water out of the system. I think a lot of people don't get grease to come out the end because of a lack of maintenance. It turns hard and takes a lot of force to push the waxy grease down the length of the shaft and past the seal. But without doing this I don't see how all but the tip of the splines are getting lubricated.

The trouble is that it can harden, blocking the flow and turn the DS into a hydraulic cylinder putting pressure on the T-case and pinion bearings. I believe the correct solution is to remove the shaft, clean out the hardened gunk, and start afresh. Thoughts?

Here's a viddy of a guy with a 100 showing the grease coming out of the splines as it's filled.

 

[bloc]

They put the zerk at the end of the cavity specifically so the grease will walk out the root of the splines through centrifugal force. This will do a great job of pushing the old grease out.

As for filling it with grease to the point that old stuff is pushed out.. that’s a great way to make your driveshaft in effect non-compressible and put the mentioned crazy forces on your diff and transfer output bearings.

IIRC The official procedure for the 200 slip section is to pump in grease just until you see movement. Unsure whether compressing the air in there behind the seal is enough force to move things or if toyota plans for no dead space. I’ve always seen a comfortable amount of grease sling out between applications with ~12-15 pumps in there, and over many years of toyota 4x4s my shafts haven’t had any wear issues whatsoever. I’ll keep doing that.

Another random fact.. high-moly grease is better for slip joints than regular lithium stuff, but worse for the u-joints. So for best-practices two grease types are needed. Is it really necessary? Dunno.

 

[CJ3Flyer]

Another random fact.. high-moly grease is better for slip joints than regular lithium stuff, but worse for the u-joints. So for best-practices two grease types are needed. Is it really necessary? Dunno.

Due to boats, motorcycles and 4 wheel vehicles I maintain 3 labeled grease guns.

 

[KLF]

IMO it's a toss up. I just don't like the thought of having the splines hydraulically locked against the transfer case, so I pull the zerk so it can release pressure. I did this on my previous trucks, my last one had over 250K on the original shaft and U-joints, and that truck saw a lot more trail action.

I have pulled the rear shaft off the rear diff once, slid the joint apart to expose to expose the splines and put fresh grease in there. Not a fun process, but now that I have my QuickJack to get the truck up in the air easier, maybe I'll do that again next time at 70K.

 

[CJ3Flyer]

IMO it's a toss up. I just don't like the thought of having the splines hydraulically locked against the transfer case, so I pull the zerk so it can..

The Rear Driveshaft is the key. This is my concern too. I don’t give a thought to the u-joints or front driveshaft but worry over-servicing or under-servicing the rear spline-shaft. It’s a balance for sure...

 

[OregonLC]

They put the zerk at the end of the cavity specifically so the grease will walk out the root of the splines through centrifugal force. This will do a great job of pushing the old grease out.

As for filling it with grease to the point that old stuff is pushed out.. that’s a great way to make your driveshaft in effect non-compressible and put the mentioned crazy forces on your diff and transfer output bearings.

Not sure how centrifuged force extends grease longitudinally down the splines? If it’s not moving down there under the pressure of the gun then spinning it won’t get it there either.


I really think the issue is caked up grease and the solution is to remove the shaft, clean it up, and get grease to flow again. Pushing grease in and then relieving pressure is just lubricating the tip of the shaft and the cavity.

I agree that you don’t want to turn your shaft into a ram, though suspension compression will likely force the grease to flow toward the end before it causes any real damage.

As I understand it, spline wear (both on shaft and at hub flanges) is a contributor to vibration and clunks as the vehicle ages. Getting the splines fully lubed seems like a solid PM.

 

[bloc]

Not sure how centrifuged force extends grease longitudinally down the splines? If it’s not moving down there under the pressure of the gun then spinning it won’t get it there either.

I'll attempt to explain this without a diagram, but frankly I'm pretty dumb so this may not go well.

If the zerk is at the closed end of a cavity, and that is where grease is pumped in, even though it is non-newtonian it IS a fluid and with enough gravity it won't just pile up there on one side, it will get distributed relatively evenly as soon as the shaft starts spinning at any significant RPM. Now, as more time goes by with said RPMs, and as RPMs increase centrifugal force does too, the excess grease won't stay piled up there at the closed end of the cavity. The in-effect very high gravity environment (See note) will cause the technicaly-a-fluid grease to assume a "pool" shape, where the three sides of the container are the closed end of the cavity, the female splines on the outside, and the male end/splines/seal as the third side. The g-forces being so high will cause grease to migrate out between the male and female splines and past the seal.

Now for all of this to work there needs to be enough grease there. What is actually pushing grease to the relevant parts is more grease piled up behind it trying to get out of that high-gravity environment. If you only throw three pumps in that likely isn't enough to distribute around and actually coat everything.

Side note.. I got curious and did a little math. I'm not sure of the diameter of the splined section but guessed between 30 and 40mm. At 80mph vehicle speed (driveshaft 3437RPM on a 2008-15) it's between 198Gs (30mm) and 264Gs (40mm). Aka a lot of force to make grease flow.

Also interesting is how brilliant toyota's u-joint spider design is. For decades the US automakers put the grease zerk, if there was one, on one of the caps. When the cross is drilled, this allows you to pump grease into that cap and then get distributed around to the whole joint. But, it depends on the valve and tapered threads on that zerk maintaining integrity. If either fail, the high g-forces within that cap will let the grease drain out. The other three would be fine.. but that one not good.

For a long time toyota has put their zerk in the middle and cross-drilled the joint so that it can reach all four caps. But.. with all 4 caps being closed, they basically act like little bowls holding the grease inside, keeping the bowls full, no matter how fast you spin the shaft. The only way to get that grease out is to push it out from the zerk with another fluid.. generally new grease.

Anyway.. all of this grease distribution business makes sense in my head, but as mentioned I'm not the smartest by any stretch.

 

[OregonLC]

So then where does the bad/dirty grease go that we want purged out?

 

[bloc]

So then where does the bad/dirty grease go that we want purged out?

Once you reapply grease and you now have fresh stuff flowing out of the splines, it'll push the old stuff in that location out and replace it with the new stuff.

 

[OregonLC]

So you're saying you do get it to purge out the end of the splines rather than mixing with the new back in the cavity?

 

[fasteddie2015]

Hows this... grease is essentially a really thick liquid and cannot be compressed. That's how hydraulics work and why tsunamis are so destructive. I get that the Toyota engineers say that a gap is needed for expansion. But eventually, no matter if you pump in a little or a lot, over time, that gap gets filled. Or the action of the spline moving is closing that gap and pushing the grease somewhere.

Dirty grease has to have a corrosive property to it, like dirty oil. So where does the old, dirty grease go if you're not squeezing it out with new grease? Getting rid of the grit and metal particles in the old grease would seem to be a good thing.

 

[bloc]

So you're saying you do get it to purge out the end of the splines rather than mixing with the new back in the cavity?

I don’t repeatedly check the color of the grease coming out of the slip seal.

Any grease that hasn’t come out of the back of the cavity already is grease I’m not worried about mixing.. because it’s been sitting there this long with all those forces & suspension cycling. I care about what’s in the splines. Due to those forces and grease’s tendency to flow like a fluid that should be fresh grease.

Hows this... grease is essentially a really thick liquid and cannot be compressed. That's how hydraulics and tsunamis work. I get that the Toyota engineers say that a gap is needed for expansion. But eventually, no matter if you pump in a little or a lot, over time, that gap gets filled. Dirty grease has to have a corrosive property to it, like dirty oil. So where does the old, dirty grease go if you're not squeezing it out with new grease? Getting rid of the grit and metal particles in the old grease would seem to be a good thing.

It does come out. That’s the ring of grime under all our vehicles roughly lined up with the seal at the end of the slip section.

For u-joints you clearly see the old stuff get pushed out. The process of greasing is what displaces the old stuff. Which works fine because the volume of this system doesn’t change regularly during use.

The slip yoke however.. must be able to extend and retract, as you pointed out. Due to this there has to be an air space, and because of that critical air space we can’t just fill the whole thing with grease to push the old stuff out. Toyota designed it to use the forces inherent in this location (~200Gs) to distribute the grease to the places it is needed.