Synthetic or Non-syn for Trans & Transfer-box

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RhinoRange02

Well-known member
Feb 18, 2005
231
0
44
Nashville,TN
I'd like to get some opinions on oils for the:
1.) Transmission fluid
2.) Transfer box fluid

I have an '02 P38 4.6, and I'm about to perform a fluid maintanence on Front/Rear Diffs, Transmission drain/fill and filter replacement, and also Transfer box fluid.

I'm going to order Amsoil 75w90R oil for the diffs, and I'd like to go ahead and also run fully synthetic Amsoil in the Transmission and Transfer box.
But, I've been told it's a no no in the Transmission but "o.k." in the Transfer box. :confused:
I just wanted some opinons on this. And they do carry an ATF Dexron III called for specifically per the manual.
Some say, it's a matter of opinion on the quality of oil to use, in reguards to conventional or synthetic oils. They just suggest to keep frequent cycles on changing the fluids.

I agree with this aspect, but also would like the best for my truck.
For engine oil that I change every 3000-3500 miles I'll stick to non-synthetic oils due strictly to price. I change my oil regularly so coventional shouldn't be a problem.
But for the Transmission that only gets service every 30K miles, and Diffs at whatever interval, I'd like to go ahead, spend a little more $$ and be assured my parts are happily bathing in premium oils.... My Rangie likes it, it told me so... :D
 
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geoff

Well-known member
Apr 23, 2004
164
1
Austin, TX
I used Mobil1 syn ATF in my '93 RRC with no problems- essentially same xfer case. I have also used it in our Isuzu Trooper which has a chain driven BW as well. I used Mobil1ATF in the transmission in the RRC. Similar ZF as yours without the electronic governor. It meets Dexron III specs, so don't know why it would harm yours either.

Dealer uses some synthetic 75w-90 in the diffs of my '04 Disco (which uses same as P38). The change interval was at 7500 mi - check your manual.
 
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agro1

Guest
Mobil 1 Syn for all my fluids - no probs as of yet. Except for brake lines, I run ATE Superblue.
 
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RhinoRange02

Well-known member
Feb 18, 2005
231
0
44
Nashville,TN
Argo, did you do your "Gearbox Fluid" also, or just your Transfer box fluid?
The gearbox is like 10.5 qts isn't it?
And so you're running synthetic in both the Transfer box, and the gearbox?
I'm just waiting for a final say so on fluids before I order Amsoil ATF for both applications.
 
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agro1

Guest
Yeah - both. Transfer case Mobil 1 Synthetic 75-90
Automatic Transmission fluid Mobil 1 ATF

It's expensive, but worth it IMO. Last time I changed the ATF, it came out looking brand new.

I'm sure Amsoil is good stuff. But, I can't say if it worth the extra $$$. The way I look at it; if Mobil 1 is good enough for my Porsche, it's plenty good for my Rangie.
My 993 operates at MUCH higher tolerences than that POS Buick motor in my Rangie. ;)
 
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agro1

Guest
Hmmm - maybe so...can't remember. Need to look at my spreadsheet with all my maintenance. Either way, I use Mobil 1 syn, ATF or gear oil.
 
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