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Old 03-04-2014, 12:46 PM   #1
Join Date: Mar 2014
Posts: 6
231 transfer case

So I have a 1999 TJ with the 231 transfer case. Going to change out the
Fluid I know ATFIII Or ATFIIII should be used. But I read on a web page someone used 5-w30 synthetic oil! I live in Maryland is the 5-w30 sin. Ok to use???

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Old 03-04-2014, 12:56 PM   #2
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Location: Ridgway, Pa.
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Well, Fire Fighter, although you are in the YJ tech section instead of the TJ tech section, my answer would be NO. The reason is, a New Process 231J t-case has a pump and filter inside of it, and the heavier oil will cause problems with it. Just my 2 cents. I replaced my fluid with Royal Purple synthetic ATF 4.

5W30 syn. is thin, but the viscosity isn't the same as ATF. Some run regular oil in their t-case, but does it hurt? Couldn't answer that truthfully.

'87 YJ, 4.2L built and bored, 8.5" of lift, 8.8 rear, AX15/NP 231, Tom Woods drive shafts, Flat fenders, 12,000LB winch, Custom bumpers, Rattle can paint job. Never completed...
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Old 03-04-2014, 01:26 PM   #3
Join Date: Mar 2014
Posts: 6
Sorry about that thought I was in the TJ forum.
Thanks for the info, think I'll stick to the ATF and try Royal Purple!!
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