1976Mustang

I've decided to compile a small list of general tuneup and maintenance tips, to help people learn what these Jeeps like best. First off, remember our engines are not high-tech engineering marvels (although they are said to be unkillable), so don't go super expensive with stuff.

- Oil Filters: FRAM oil filters are junk, if you have one get rid of it immediately.
FRAM filters have a high failure rate and cause dry starts (Meaning the engine is running without oil for a few seconds), not to mention their insides are mostly paper. The most preferred brands of filters are Wix, Napa, and Mopar. All three of those are easy to find and are well built. Also, K&N Oil filters are also not worth their cost. Napa filters essentially Wix re-branded and using different part numbers. Note for the Napa filters: If you change your oil every 3,000 miles, use a Napa Silver filter. Every 7,000 miles, use a Napa Gold filter. Extended intervals using synthetic, use the Napa Platinum.

-Oil: Don't go super fancy expensive. A good name I keep hearing is Shell Rotella, since it has a Zinc additive which our 4.0 engines need. "Exotic" European oils are not worth the extra cost since our engines are tractor motors, not high performance racing engines. If you're trying to stop the notorious lifter tick or other noises experiment with different oils to see that your engine likes best.

-Spark Plugs: Don't get the fancy 4-pronged plugs from hell, they're not worth the money on our engines (not to mention the simple physics behind multi-pronged spark plugs is all nonsense, doesn't matter how many prongs you have, the spark will only go to one of them. Simple physics.). NGK brand plugs are OEM spec on later Chrysler models and are cheap at $4 each.

-Cleaning additives: Two popular names are Marvel Mystery Oil(MMO) and Sea Foam. Both are obtainable at your local auto parts store, just follow the instructions on the can/bottle. But be careful if adding to your oil for the first time, as you can knock sludge loose. It's best to run a chemical flush first (The kind you do in the garage just before an oil change), then run the additives (Seafoam for a max of 150 miles, then change the oil. MMO just follow the instructions). If using the vacuum line method for Seafoam, add it using the line off the brake booster on the 4.0 engine.

-Air filters: Oiled filters (I.E. K&N) are nice, but if neglected they allow dirt into the engine. Just spend the $12 on a cheap paper filter and always make sure to check it often. Also if you run a turbo charged engine (Either an aftermarket Turbo or a Diesel engine), oiled filters are extremely dangerous for the engine due to the shear volume of air the engine sucks in.

-Cooling system: Use a 50/50 coolant mix, no need to add water. For those with closed cooling systems get the Volvo coolant cap(P/N 703-1396). Those with open cooling systems should get a 16psi radiator cap. And flush the system regularly, filing it with new coolant. Old coolants allow corrosion to build up since the additives wear out. Open cooling systems on the 4.0 engine hold 12 quarts total of coolant.

-O2(Oxygen) sensors: OBD-II model XJs use upstream AND downstream in their fuel trim calculations. NTK is the OEM supplier for the Chrysler years(91-01), Bosch for Renix(84-90). Lifetime is approx 80k miles.

-Differential fluid: API GL-5 75w90 for normal use, 75w140 synth if you really beat on them (towing, offroad). Many fluids today include the LSD friction modifier.

-Transfer case fluid: Multi-Vehicle ATF, ATF+4, Dexron-II/III, Mercon

-Automatic Transmission fluid: The AW4 transmission calls for Dex3 fluid. Nowadays that is harder to find so a Dex3/4 fluid will work. Do not use Dex5. Check fluid level when at normal operating temperature, on flat ground, and transmission in neutral.

-Manual transmission fluid: Avoid modern gear oil as it will destroy the brass synchros. Pennzoil Synchromesh, Redline MT-90, Royal Purple Synchromax, or any 75w90 that does not use sulphur EP additives.


Got anything to add or corrections? Go for it!

rmoore1031

Cooling system advice: Always use a 50/50 coolant mix, no needed to add water. For those with closed cooling systems get the Volvo coolant cap. Those with open cooling systems should get a 16psi radiator cap.

Transmission advice: The AW4 transmission (automatic) calls for Dex3 fluid. Nowadays that is harder to find so a Dex3/4 fluid will work. Do not use Dex5. Check fluid level when at normal operating temperature, on flat ground, and transmission in neutral.

Please add or edit anything I said if wrong.

xjsnake

For 99-01 Cherokee's use NGK spark plugs instead of the copper. NGK was OEM for the coil style ignition.

salad

Actually, on XJs Champions were the factory spec. Chrysler replaced them with NGK within a few years due to premature wear from the reverse/waste spark.

salad

O2 sensors: OBD-II model XJs use upstream AND downstream in their fuel trim calculations. NTK is the OEM supplier for the Chrysler years, Bosch for Renix. Lifetime approx 80k miles

Differentials: API GL-5 75w90 for normal use, 75w140 synth if you really beat on them (towing, offroad). Many today include the LSD friction modifier.

Transfer case: Multi-Vehicle ATF, ATF+4, Dexron-II/III, Mercon, or 5w30.

Manual transmission: Avoid modern gear oil as it will destroy synchros. Pennzoil Synchromesh, Redline MT-90, Royal Purple Synchromax, or any 75w90 that does not use sulphur EP additives.

1976Mustang

Added to the main post, thanks for contributing guys!

cruiser54

Good stuff. NGK all the way!!!!!

XJriot

Good source of info all in one spot.

84zmyfavorite

salad has Alot of incorrect info. Champion plugs have Always been OEM for Four Point Ohz. That dosent mean you have to use Champions. I have had Alot of good luck with AutoLite 985 Copper Core in all year 4.0s, 87 thru 06. European Oils are not Needed, but Fun to use.

CCKen

84zmyfavorite playing with his AutoLite 985 Copper Core's and his European Oils.

salad

Oh really? Such as?

cruiser54

I couldn't find anything....LOL.

salad

Might be upset because I misunderstood transmission compatibility on 90s and prior XJs

PNWjeeper

I'm surprised you didn't mention the Volvo pressure cap PN. Which is 703-1396.

cruiser54

You're catching on , sonny!!