Do fluids in AW4 and NP231 have to be Exactly the same?

I should have just enough Redline C+ ATF for the AW4 but that leaves me short for servicing my NP 231. I've read many threads where they say you must use the same fluid between the transmission and transfer case. Is this actually true? I ask because I'm having a difficult time tracking down Redline C+ ATF, but there is plenty of availability of the Redline D4 ATF. Apparently they have pretty similar properties, do you think that this would be a safe substitution? Is there any communication of fluids between trans and transfer case? Thanks for your time!

I guess there could be an issue if you had a seal failure and the fluid between the two mixed.

devildog0 said:

I guess there could be an issue if you had a seal failure and the fluid between the two mixed.

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If you did have a seal failure between the two, you'd be dribbling fluid.

You'll be fine running D4 in the t-case. If the seal in trans goes you will overfill the t-case. They don't share fluid.

Redline D4 is the correct ATF for both the transmission and transfer case. I don't suppose it would hurt to use the C+ in the transfer case, but I would get D4 for the transmission. The AW4 and NP231 use GM/Dexron spec ATF. They do NOT use Chrysler spec ATF.

For many years on this forum, it has been recommended to never to use synthetic ATF in the AW4, instead staying with the recommended Dextron III.

Redline C+ ATF is a fluid made for various Chrysler transmissions, the AW4 is a Toyota transmission.
https://www.redlineoil.com/c-atf
Redline's own literature doesn't show compatibility of C+ with Dextron III.
Redline has no recommended fluid for the AW4.

Don't know about you, but I'm sticking with Dextron III, one of my AW4s has over 200,000 miles on it and still going strong on the fluid Toyota specified.
It's also a lot cheaper than the synthetics.

I've been running synthetic since mile "Zero", 18yrs later....... when I put the Trans-go shift kit in, the pan was totally clean showing zero wear!

RCP Phx said:

I've been running synthetic since mile "Zero", 18yrs later....... when I put the Trans-go shift kit in, the pan was totally clean showing zero wear!

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Same as when I pull the pan on my high milage AW4, that has used Dextron III since new. Changing the fluid every 30,000 miles, it has never looked dirty or smell the least bit burned.
When changing fluid, it normally gets a full flush, including the torque converter.
I wouldn't mind trying a synthetic ATF but the cost of totally flushing the trans, which take about 18-qts, would be over $200. That's hard on the budget.
With so many AW4s lasting 200,000 mile+, running Dextron III, the cost/benefit isn't readily apparent.

Redline's vehicle specific vehicle finder, shows its D4 ATF to be the right fluid for the AW4.
The transfercase, not having clutches and bands to worry about, isn't all that picky about what is run in it. It just needs an adequate lubricant for the bearings, chain and planetaries.
I have seen transfercases, filled with 5-20-wt motor oil and well as various other ATF fluids, that have run fine for many years..
I run Mobil 1 synthetic AFT in my XJ's XCs.

I always have to stop and read with a touch of humor the things others say and do when it come to choosing the correct lubrication for their XJ.

I personally have taken a more radical approach to every thing XJ than most others on this forum. For oil, I run Amsoil in everything except the Ected in the D44 and have done so for more than 200,000 miles. Oil leaks from the both the engine and transmission are non existent. The transfer case developed a leak at the output seal of the SYE eliminator. About 3 ounces of motor oil fixed that. My oil change intervals are 3 time the OEM recommended for the 4.0L and 4 times or more for the AW4 and transfer case.

Talk about a radical approach, in 2004 when everyone was saying electric cooling fans would cause the 4.0L to spontaneously combust into a pile of ashes I removed the mechanical fan and installed dual electric fans.
https://www.naxja.org/forum/showthread.php?t=25336&highlight=oem+electric+fans

I would not go out and do something stupid to my beloved XJ but, I enjoy taking a path less travelled,...but ain't that the reason most of us have and love our XJ?

Back to the original subject, some motor oils and ATF's among other things I would not want to use in my XJ. If a person have to ask if oils and coolant is OK for the XJ, do not use it/them.