Is royal purple high performance manual transmission fluid good to use for replacing my transfer case fluid? I have a 1998 tj 5 speed manual, and a 231 transfer Case.
Is Royal Purple a good transmission fluid choice for my TJ?
- Thread starter Lane miller
- Start date
OP
But that makes no sense. I already read that and that’s why I’m going with the synchro max royal purple for my transfer case. If you think it’s not going to work tell me why because nothing I’ve read says otherwise.
I used the Royal Purple Synchro Max for my Manual Transmission. I had Redline MTL before. Royal Purple is significantly smoother than Redline.
EDIT: for the TCase, use ATF!
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OP
No, your chain-based 231 transfer case is supposed to run on ATF not gear lube. Only gear-based transfer cases use gear lubes. Any type of good quality ATF is fine, it is not fussy about the particular type of ATF it gets.
Not to mention I'm no fan of RP's overpriced/overhyped products that are only purple because of the purple dye that is added solely for marketing purposes.
For your transmission, which is very fussy about the type of gear lube it will run properly on, I'd go for Redline MT-90 which is a widely recommended GL-4 75W-90 gear lube as your AX-15 (and AX-5) transmission is spec'd for.
OP
I certainly see a lot of people don’t like royal purple. I guess I just see the results differently. I’m going to have to talk to a guy I know who built Jeep’s and see what he has to say about me using royal purple synchromax on my transfer case. Thanks for the help tho!
You're a stubborn guy so just one last attempt at this recommendation... your chain based transfer case is spec'd to run on ATF. Not gear lube.
OP
OP
I’m on my phone and didn’t see this whole paragraph. It only showed the royal purple part but I scrolled down and saw your recommendation. I understand I need the redline MT-90 because of the chain and the weight is 75w-90. Thank you and sorry for coming across as rude.
06TJ35's
TJ Addict
I’d listen to Jerry. I also use redline.
Edit: You listened. Good job.
Also your title says RP for your trans and not your t-case.
Edit: You listened. Good job.
Also your title says RP for your trans and not your t-case.
I have no dog in the fight as far as what brand you want to use in your vehicle. Use whatever you're happy with.
However as @Jerry Bransford has indicated, the oil for your manual transmission is different from whats specified for your transfer case. Jeep recommends an automatic transmission type fluid for your transfer case and a heavier fluid for the manual transmission.
If you want to use a 80-90 weight oil in your transfer case, let us know how it works out for you.
You can run motor oil in the transfer case, it isn't picky. Please don't take my word for it, Novak Conversions deals with these cases all the time and that's where I got the idea. I've run 5w40 synthetic for tens of thousands of miles and it makes a big difference in noise from my case.
Again, ATF (any type of ATF) is the factory specified lube for your 231 transfer case... because of its chain drive.
Redline MT-90 gear lube is recommended for your transmission since it is gear based.
Couldn't agree more about the Redline and you can't argue that the factory didn't know what was good for the transfer case, that's a fact.
Sorry for my confusion, thought transmission fluid was being asked about. Yes, follow the recommendations above for the TCase. 
You still have it wrong, Redline MT-90 in the tranny and ATF in the gear box, Download the service manual and do some reading. And a word of advise, don't fuck with the TJ Guru;s on this site, it won't take you long to figure out who they are, some are nice about it, some not so much! Welcome and have fun wit you new Jeep!
OK I had to LOOK for a few minute but I did find that on their web site. I'm not sure if I'd want to try it or not.
https://www.novak-adapt.com/knowledge/transfer-cases/np231/
It's at the bottom of the features section on the 231 page.
It helps with the noise, that's one of the only reasons I run It. Also allot cheaper than ATF+4 and I'm as cheap as they come. I'm pretty sure it's not "better" for the case. Thanks for posting all the details.