Select Trac NP242

[Ecomike]

I've read some choose to run gear oil in their np231's with no issues, maybe synthetic 75w90 gear oil might quiet down a noisy np242?

75W90 may be too thick for the NP pump and is likely to damage it. It needs to be very thin like ATF. Also being too thick may make it foam faster and help it maintain the foam due to higher viscosity. A thin fluid will defoam much faster.

 

[Ecomike]

Right now it's under warranty, so I wouldn't use anything other than factory recommended. I may just have to get used to the winter whine of FT 4WD. Seems to be a lot of variability in noise output in these things. Sometimes it's extremely quiet in FT but later gets whiny. Guess I'm getting whiny in my old age too.

When it gets whiny, I bet it is foamy and the pump in the TC is cavitating from the foam

Does it whine in cold weather when the fluid is thicker and more likely to foam?

 

[Ecomike]

Don't go heavy. Don't forget you have to operate in colder climates. I think 5W-30 conventional would be max. I say conventional simply because I don't know if the seals in the TC will tolerate syn oil.

If you do switch I recommend that you drain, fill with motor oil, operate for a short hop then drain and refill in an attempt to un-mix the fluids.

I wonder if syn oil is more aggressive on seals than Dex III tranmission fluid? I would have bet on Trans fluid being more aggressive, but I do not know for sure.

 

[Ecomike]

My 242 is slightly more noisy in Full Time. Probably attributable to the differential in the TC working.

I use B&M Trick Shift automatic transmission fluid. This stuff is supposed to have extreme pressure and foam inhibitors. It's expensive.

Foam inhibitor is needed in the 231/242 TC's because the gearing in the TC whips the ATF to a foam which leads to evaporation of the ATF through the vent system, thus a loss of ATF over time.

Some folks use 5W-30 conventional motor oil in their TC to get around the foaming/vaporizing issue.

I think ATF has more surfactants in it than oils and a lower surface tension making it easy to foam like detergent. Like I just posted, I would bet the foam makes the pump inside the TC cavitate and make noise.

 

[Ecomike]

Additives... There are power steering additives for noise but they are mostly anti-foaming agents that fight aeration which isn't the problem with these, might try some anyway.

While there may be other causes of whine, I think you just nailed it, read my last 3 posts here, as a defoaming agent, like a silicone defoamer would do the trick if I am right about foam making it cavitate in the pump in the TCs. I did not know there were power steering additives for noise, I need to check that out!!!! It would make perfect sense that the use defomers to stop pump caviation.

For anyone not familiar with cavitation it is a violent noisy colapse of gas bubbles under pressure like in a pump cavity where the pressures peak. Ultrasonic cleaners, the noise in them, is cavitation, the implosion of tiny gas bubbles produces huge sound shock waves. Oh, and cavitation in a pump can do serious damage.

 

[anderld47]

When it gets whiny, I bet it is foamy and the pump in the TC is cavitating from the foam

Does it whine in cold weather when the fluid is thicker and more likely to foam?

Nope, spent a week and a half off and on crawling in the desert end of March. Whined the whole time when I was in anything other than 2WD (as it has since I got the reman). Last Friday I picked up a load of shale in my trailer. I told the guy in the loader to put it over the trailer axil and got back in my truck. After he dumped it he honked and I drove off. After a few miles it started raining and when I started down a steep hill going into town the the trailer started whipping side to side. Tried giving it a little gas hoping it would straighten out but the back wheels just spun. Played turn into the skid until I was next to a pullout then cranked hard right. Trailer and I both did a 180 and I ended up in the pullout pointing uphill with the trailer behind me. After I cleaned my shorts I got out and saw the guy had dumped the load behind the axil and going downhill probably took most of the weight off the rear wheels. I shoveled everything forward, put it in FT and drove home and unhooked trailer. Later going into town noticed no noise. Took it in and out of 2WD to FT a dozen times. It was perfect. Then Monday tried it again and back to the whine. No rhyme or reason for this. That's when I started the thread.

 

[ehall]

Changed the fluids Friday and drove about 3 hours to WV, lots of whining at highway speeds, really picked up about 55. Wheeled it on Saturday low speed not much noise at all. Sunday drove home and it still whined at highway speed but much lower volume.

 

[anderld47]

If it was quieter on the return trip, maybe the Royal Purple MAX ATF is working. The whine in mine isn't as noticeable at lower RPMs.

 

[garr]

I know that ATF is recommended for use in the 231-242, but I do remember when I did the first drain/Fill years ago the stuff that came out of it was very dark & thick, recently my local JY had a wrecked low miles (70k) 2000 XJ come in & I grabbed the 242, the same dark/thick fluid came out of it, it did not look or have the thin viscosity of ATF to it.
Did the factory fill the TC with ATF or did they use some special type of fluid?

 

[anderld47]

The only thing Chrysler recommends (and ties to warranty) is their ATF. They do not recommend anything else. The fluid was probably dark because it was the original. Many folks don't do upkeep on anything other than antifreeze and engine oil and that often goes by the wayside. I can remember a neighbor telling me how great his vehicle was because he only had to add a quart of oil to it ever 9000 miles. I don't think he ever changed it.

 

[garr]

The only thing Chrysler recommends (and ties to warranty) is their ATF. They do not recommend anything else. The fluid was probably dark because it was the original. Many folks don't do upkeep on anything other than antifreeze and engine oil and that often goes by the wayside. I can remember a neighbor telling me how great his vehicle was because he only had to add a quart of oil to it ever 9000 miles. I don't think he ever changed it.

I generally agree with you, But My 2001 XJ's NP242 only had 30K miles on it when I first serviced it & the fluid was Dark (It looked Like new synthetic Motor oil) & Thicker than ATF.
Could Chrysler have Factory filled these Transfer cases with some special Transfer Case Fluid, Did Chrysler ever sell some special "Transfer Case Fluid"?

 

[anderld47]

I generally agree with you, But My 2001 XJ's NP242 only had 30K miles on it when I first serviced it & the fluid was Dark (It looked Like new synthetic Motor oil) & Thicker than ATF.
Could Chrysler have Factory filled these Transfer cases with some special Transfer Case Fluid, Did Chrysler ever sell some special "Transfer Case Fluid"?

My mechanic said Chrysler doesn't have a special TC fluid, but I guess they could. I've had 4 XJs all with 242s. None have been noisy in FT until the the 2 rebuilds and they were all changed many times with ATF. Even the one that Tera Flex made the 4:1 Tera-Low for in 2002/2003 was quiet in FT (whined like a banshee in 4 LO), but it went bad about 4 years ago.

But now that you mention it, I think Tera Flex told me to use Limited Slip Differential fluid in it. So maybe it was maintained with that. I think Ford used to have an additive for limited slip diffs. I'll dig through my poop and see if I can find the stuff from Tera Flex.

 

[ehall]

Chrysler does make a special transfer case fluid, but its for the units that have a clutch pack (245, 247, 249), and specifically says "not recommended" for use in other transfer cases. http://www.knowwhere2jeep.com/mopar-nv245-nv247-nv249-transfer-case-fluid-quart.html

And yes I tried running it, made no difference. Its running quieter with the Royal Purple MAX ATF