diff oil questions - lsd w/ towing pkg? - additives required?

[brucecooner]

Buckle up!  Another oil thread, but this time for axles.

 

I noticed the other day that my rear differential MAY have a decent seep going. 

The truck appears to have been well maintained, so I doubt it has been run a long time without a change.

But I figure I should probably change the oil in all the gear-containing things so I have a solid timeframe for the next change.

So I started looking into what's involved.

 

I don't know much about diffs to begin with so I pointed my camera phone at them and started comparing to pictures on the internet.

 

The front one looks like the standard Dana 30.

 

 

...which may have a decent seep going, but the prevalence of moist fluid indicates it could be something above.

 

In the back I was surprised to find what looks like a Dana 44, wearing an LSD tag.

 

My understanding is that these were only added with the towing package.

The Jeep has a receiver in the back, which would indicate it very well could have tugged some weight in its past.

But I checked my VIN thread, and it does mention limited slip but does not mention the two package.

 

I guess this could have been an aftermarket addition, but everything is long since too dusty and crusty to see any signs of a swapped axle.

Practically everything else on the truck appears stock, whoever got this did not appear to be into making mods.

 

At any rate, I'm not as worried about how it got there as I am about its proper care and feeding.

 

I actually have the laminated card with fluid specs on it that came with the Jeep.

For the Comanche front/rear axles, it lists API GL5 75W-90

 

BUT, there are subscripted notes below the fluid specs.

 

These notes indicate the Cherokee with tow package should get Synthetic 75W-140, but with Trac-Lok and no tow package, you should add "one bottle" (no volume given) of P/N 8983 100 003.

 

HOWEVER, a separate note says for the Comanche with towing package, use 80W-140 (does not say synthetic).

It does not say anything about Trac-Lok for the Comanche.

 

There are lots of variables at play here.

 

I could see towing a small travel trailer with it, but I'm not sure the tired old BA10/5 would be too happy with that, especially if it thinks it's towing days are over.

 

If I am (or aren't) towing, should I select a different oil weight?

 

At over thirty years of age, the clutch packs have probably gripped their last time long ago, but do I still need to take the LSD into consideration and get an additive?  Or do I just ignore them with a heavier duty oil?

 

Or is there a modern, do-it-all synthetic that can handle both light and heavy duty work?

 

And can I just fill both front and rear with the same, or does the front get lighter oil regardless?

 

So many questions...

 

I'm wanting to go with gaskets to seal them back up, they seem to have a good reputation.

 

And at the end of the day, my seep theory may not even be correct.

I took a picture of the rear pumpkin from a different angle and the widespread and vertical nature of the moist area says this might be something else I'm looking at, which would probably be brake fluid.

 

 

 

 

 

 

 

 

 

 

And "make the brakes work better" is already on my todo list.

 

But still, I feel I should re-oil the diffs and transfer case anyway.

Any info/pointers is appreciated.

 

[gogmorgo]

The heavy axle was available as an option both with the offroad pack and just on its own, doesn't specifically come with a towing package. In terms of what oil to use, either weight would be fine for regular use, although if you're planning on stressing the axle with regular towing the heavier weight is a better choice for the higher heat, but it comes at a slight mpg penalty. It's not going to hurt anything to have friction modifier in the oil even if you didn't need it for the diff. Some specialized gear oils intended for differentials come with it already added. There isn't a ton of benefit to running 85W140 in the front diff unless you're really planning on loading it up or you get a heck of a deal on bulk oil that makes up for very slight mpg penalties, but it's not going to hurt it either. Doesn't look like you'd be seeing -40 weather with it either so having diffs full of glue at those temperatures isn't going to be a problem for you.

 

Agreed, if you don't know how old the fluids are it's probably better to change them. The transfer case usually calls for ATF not gear oil, just FYI.

 

My guess on the location of that leak, all over the axle tube, is it's coming from the diff breather line. Possibly the diff was overfilled, possibly the breather hose is cracked. There is a brake line going to the same point, but brake fluid tends to get rinsed off with water so it doesn't leave huge seepage stains like that.

In regards to making brakes more gooder, it's a safe guess they're not adjusted correctly and could probably use a good bleed. You've still got the load sensing valve in the system, so there's a bypass line for it that also needs bled. Crack a front bleeder to simulate a front failure while bleeding the rears, then close the front bleeder and bleed the rears again, then the fronts.

[brucecooner]

11 hours ago, gogmorgo said:

The heavy axle was available as an option both with the offroad pack and just on its own, doesn't specifically come with a towing package.

 

True, someone could have just checked the box for a different axle.

 

11 hours ago, gogmorgo said:

 

In terms of what oil to use, either weight would be fine for regular use, although if you're planning on stressing the axle with regular towing the heavier weight is a better choice for the higher heat, but it comes at a slight mpg penalty. It's not going to hurt anything to have friction modifier in the oil even if you didn't need it for the diff. Some specialized gear oils intended for differentials come with it already added.

I assume friction modifier is for the lsd, I'm going to have to study that.

 

 

11 hours ago, gogmorgo said:

 

There isn't a ton of benefit to running 85W140 in the front diff unless you're really planning on loading it up or you get a heck of a deal on bulk oil that makes up for very slight mpg penalties, but it's not going to hurt it either. Doesn't look like you'd be seeing -40 weather with it either so having diffs full of glue at those temperatures isn't going to be a problem for you.

We definitely won't see -40, rarely would see +40. 

But even without towing this thing will be running in high heat during Phoenix summers, sitting right over pavement that can get to the upper 100's,

so maybe a heavier oil's not a bad idea regardless.

I put maybe 4K on a vehicle in a year so mpg's aren't as big a concern for me.

If the front one don't care, I would probably just buy enough of the heavy fluid to fill both axles.

 

11 hours ago, gogmorgo said:

Agreed, if you don't know how old the fluids are it's probably better to change them. The transfer case usually calls for ATF not gear oil, just FYI.

I wanna say the transfer case was originally Dexron II, which was discontinued, but Dexron III is backward compatible.

 

11 hours ago, gogmorgo said:

My guess on the location of that leak, all over the axle tube, is it's coming from the diff breather line. Possibly the diff was overfilled, possibly the breather hose is cracked. There is a brake line going to the same point, but brake fluid tends to get rinsed off with water so it doesn't leave huge seepage stains like that.

In regards to making brakes more gooder, it's a safe guess they're not adjusted correctly and could probably use a good bleed. You've still got the load sensing valve in the system, so there's a bypass line for it that also needs bled. Crack a front bleeder to simulate a front failure while bleeding the rears, then close the front bleeder and bleed the rears again, then the fronts.

Ah, so I should check the breather line.

 

And I was not aware the load sensing valve requires a special bleed procedure, good to know.

The brakes aren't spongy, they just don't stop the vehicle that quickly.

It doesn't pull to either side under braking, which I've always thought indicated proper adjustment, but I could be wrong on that.

The brake fluid reservoir is full but the fluid is  dark and ready for a change.

I'm already on the hunt for a booster replacement (current one is hissing when I press the brake, and the engine will race when pressed past a point), but I'm thinking a new master cylinder is a good idea too.  I'm wondering if the old one is just not putting up sufficient pressure, boosted or not.

 

 

Thanks for the pointers!

 

[Pete M]

yup, MJs require a different braking procedure than most anything else because they don't have a front prop valve, but rather a rear height sensing prop valve.  directions should be in the link in my signature.   also in there are a couple writeups for the dual booster from a later model Jeep. 

 

 

[gogmorgo]

You won’t get brake pull to either side if both sides are equally out of adjustment. Even self adjusting brakes get out of adjustment pretty easily. You need a reasonably firm stop in reverse to adjust them, and most people don’t drive fast enough or stop quick enough in reverse to make it happen. 
 

Yes, the friction modifier is for the LSD. Because the ring and pinion have to slide past each other under extreme pressure, gear oil has to be really slippery. But if it’s too slippery, the clutches won’t grab properly. The friction modifier makes the oil grippier under lower pressure, or something like that. 

[Eagle]

It's easy to check if your limited slip differential i still limiting. Block the front wheels. Jack up ONE real wheel off the ground. Vehicle in neutral, parking brake off. Try to rotate the tire by hand. If it turns easily, the LSD isn't working.

 

[brucecooner]

On 11/4/2022 at 10:47 AM, gogmorgo said:

You won’t get brake pull to either side if both sides are equally out of adjustment. Even self adjusting brakes get out of adjustment pretty easily. You need a reasonably firm stop in reverse to adjust them, and most people don’t drive fast enough or stop quick enough in reverse to make it happen. 
 

Ah.  If I remember, I'll get some juice in reverse and hit the brakes next time I'm out.

 

 

On 11/4/2022 at 10:47 AM, gogmorgo said:

Yes, the friction modifier is for the LSD. Because the ring and pinion have to slide past each other under extreme pressure, gear oil has to be really slippery. But if it’s too slippery, the clutches won’t grab properly. The friction modifier makes the oil grippier under lower pressure, or something like that. 

Okay,

 

On 11/5/2022 at 9:57 PM, Eagle said:

It's easy to check if your limited slip differential i still limiting. Block the front wheels. Jack up ONE real wheel off the ground. Vehicle in neutral, parking brake off. Try to rotate the tire by hand. If it turns easily, the LSD isn't working.

 

Okay, I think what I need to do is use Eagle's test and see if the LSD still works. 

If they do, I'll worry about some friction modifier.

If they don't, I'll skip the modifier and worry about fixing things up there later. 

I don't plan on doing any extreme offroading, yet.

With the heavy axle I'm a little more likely to though.

 

I've already got the gaskets for both diffs, just got to start buying oil.

I've heard good things about Red Line, thinking of looking into some.