Getting ready to change all of the fluids(differentials, transfer case np231, transmission, coolant, brake, etc.) in a 93' YJ Sahara 4.0 5 speed and need some recommendations from the experts. Would like to stay away from the synthetics, but if that seems to be the overall favorite, I will abide. Rarely take it offroad, and getting ready for the cooler weather in the NE. Currently don't have an owners manual, or wouldn't be posting. Thanks for any responces!
These are just my recommendations, I'm sure others have their own opinions.
Oil depends upon your climate and usage. The manual basically recommends a good 10w-30, with a dip to 5w-30 in extreme cold.
Coolant is fairly simple, use Prestone or any green-colored standard product. You don't need the orange stuff, which is for aluminum engines. When you change it be sure to pull the plugs on the side of the block. It's a major PITA to get them out sometimes, but it holds nearly two qts in there that can't be removed any other way. BTW, if it's never been done this may be a good time to change the hoses. Expensive but worth the money if you plan to keep the rig. Change the serpentine belt as well.
In the AX15 gearbox I use Redline MTL oil. It eliminates cold running gear clash in second & third. I just dumped some that had been in my '94 YJs AX15 for 30k miles and there wasn't a trace of metal on the magnet. Great stuff, get it at a local speed shop. FWIW, the factory recommends a 75w-90 GL5 gear oil that can cause havoc with the synchros unless you add a recommended additive available at the dealer. Not sure what it is since I've had such good luck with Redline.
Transfer case uses Dexron III automatic trans fluid. The factory recommends a Chrysler derivative but it's really not necessary to be that specific.
Recommended fluid for the axles is 75w-90 GL5 synthetic. Only other requirement is that with Trac-Loc limited slips, where the factory recommends adding a tube of Limited Slip friction modifier. (Need to check to see if you have a Trac-Loc diff.) Get it at the dealer, parts house, etc. Even though the gear oil will say it's compatible with the Trac-Loc, the modifier needs to be added to prevent clutch pack chatter.
Lat thing I'd recommend is that you flush the brake fluid completely using a high quality non-synthetic product. Rather than pump the fluid through the system, which just stirs up all the muck & possible rust, either have the system pressure bled, or vacuum bleed it yourself. You should also flush the clutch system as well. Don;t be surprised at all the black crud that comes out of the system!
use GL-5 or 80W-90 in your transfer case, front diff and rear diff. dexron III in the automatic transmission, unless you have a manual, GL-5. no additives necessary as far as i know with stock dana 30 and 35 diffs. dot 3 in the brake system, standard green coolant in the radiator
Watch out for the tranny fluid. GL5 is a no no in some like my T-5. It messes up the synchromesh parts big time. Been there, done that with a 'GL4/GL5' compatible oil.
Didn't work for shit, started crunching going into gear when shifting. Drained it and put GL4 in and it shifts sweet again.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
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