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About 5000 miles ago, I did some routine maint. on my 2000 Jeep Cherokee. This included a flush/fill of the transmission (AW4 automatic), drain/fill of the transfer case (NP231), replace the spark plugs and replaced the serpentine belt. Both the AW4 and NP231 require the use of Dexron III fluid and since I know that the AW4 does not react well to synthetic fluid, I chose Valvoline Dex/Merc fluid.
I immediately noticed an approx. 3 mpg drop in my overall mileage after performing the above maintenance. Out of the four things that changed, I am most suspect of the trans fluid as I have never had any trouble with NGK plugs and a belt is a belt.
So, I did some addl. research and found a TSB that states only Dexron III with a certification number (GM certification number I assume) should be used. So, I looked on the Valvoline bottles and could find no reference to a certification number...which based on what I read should begin with a "D". I also found reference to where others have experienced the same drop in mileage and draining and refilling with a certified fluid brought back the lost mpgs.
I have been searching the local parts stores for a Dexron III fluid with the certification number but have yet to find anything. With that in mind, I was hoping some of your trans fluid experts could shed some light on this for me and let me know what fluids currently hold that certification?
__________________ F350 4x4/ Dodge 2500HD 5.9L Cummins
Leaving the Picture of the Ford cuz I miss it
Pacific 2325 cc
Honda bf225
aluminumalloyboats.com
It seems to run a little better now, so I dont' think it's a plug or coil issue (no plug wires as there is a single coil pack that spans all 6 cylinders).
Haven't tried the dealer for fluid yet. Most of what I've read states dealers are pushing ATF+4 since it's a Chrysler vehicle. But it's not a Chrysler trans...
I believe the significant difference in tranny fluids are the "friction modifiers". Some tranny shops dump Dexron in just about everything. I wouldn't think the fluid would affect mileage.
If you disconnected the battery, it could be the engine management system has started back at zero, and forgot all the long term memory it learned.
Are the NGK's platinum or copper...because I can tell you that Jeep 4.0s do not do well with plat plugs...they do just fine with the OE Champion copper plugs...just have to change every 30K miles....plat plugs in some of the old school ChryCo engines (V-8 Magnums as well as the 4.0 six) can cause poor running...
__________________ 1988 Four Winns 200 Horizon
4.3 OMC Cobra
1998 Jeep Grand Cherokee
4.0/NV 242 Selectrac
2007 Jeep Grand Cherokee Limited
5.7 HEMI/Quadradrive II
when gm went to dex6 they discontinued licensing for dex3 fluid. so you wont be able to find approval # for dex 3 anymore on new fluid only old stock. with that kind of mileage drop the tranny may not be going into lockup [ engaging the convertor clutch] or since it runs better you have your foot into it more. all trany fluids are basically 10w fluid with different additive packages to give the shift feel the carmaker wants. and interact with the type linings on clutches properly.
if the spark plugs were platnum type that might cause the loss of fuel economy as many of the chrysler vehicles use resistor plugs and they get replaced every 30K. The fluid is just standard dexron/mercon fluid. I would drive the vehicle at 55 mph and hold steady speed then with left foot tap the brake pedal and watch the tach and see if it goes up 200 RPM's the the tach should drop 200 RPM's as the converter goes back into lock up. . This will check to make sure the TCC is working and the converter is in lock up.
when gm went to dex6 they discontinued licensing for dex3 fluid. so you wont be able to find approval # for dex 3 anymore on new fluid only old stock. with that kind of mileage drop the tranny may not be going into lockup [ engaging the convertor clutch] or since it runs better you have your foot into it more. all trany fluids are basically 10w fluid with different additive packages to give the shift feel the carmaker wants. and interact with the type linings on clutches properly.
Plugs are standard NGK, but I was probably going to try another set of NGK or Champions as those are easier to change the tranny fluid.
The TC appears to be locking up just fine. I can watch the tach/listen to the engine and tell exactly when the shifts and lockup occur.
I don't believe I disconnected the battery when I did the maintenance, but even if I did the ECU should have relearned my driving style w/in 5000 miles.
I have a bottle of the old Castrol stuff left over from when i did a trans flush/fill on my old 2000 Cherokee (same exact drivetrain), but can't read the numbers on it anymore. I don't remember noticing any drop in mileage after using that fluid, so if the new Multi-Vehicle ATF is the same stuff, I'm hoping it will solve my problem. I put a rubber gasket on the trans pan so at least I won't have to deal with cured RTV if I drop the pan again...
Are the NGK's platinum or copper...because I can tell you that Jeep 4.0s do not do well with plat plugs...they do just fine with the OE Champion copper plugs...just have to change every 30K miles....plat plugs in some of the old school ChryCo engines (V-8 Magnums as well as the 4.0 six) can cause poor running...
Had a 94 XJ for years. Go back to the Champion plugs before you do anything else. I bet it will fix the problem. For some reason, 4.0L only likes the regular old copper Champions.
Had a 94 XJ for years. Go back to the Champion plugs before you do anything else. I bet it will fix the problem. For some reason, 4.0L only likes the regular old copper Champions.
I had NGKs in it before though...and have run NGK is 3 or 4 previous XJs with no problems. Never hurts to try a $12 something new though...
headhunt gms type 6 retros for type 3 so they are not licensing it anymore period when a manufacturers license ends they cant sell it
I have read that as well. But Dexron 6 is a semi-synthetic fluid and there are many documented instanced of the Cherokee AW4 not performing properly with semi-synthetic or full synthetic fluids.
Going to stick in a new set of Champions and see if that does anything (I don't expect it to, but it's worth a try). If not, I'll be putting the Castrol Dex/Merc Domestic Multivehicle stuff in...
Thanks again guys. I'll keep you posted. Averaging 17.8 mpg now...
used and tired aw4s may show prefrence to fluid type but not a fresh rebuild. rebuilt my neighbors cherokee that is a mudder and used mobil 1 synthetic. on worn tired some type f helps for a while.. 95% of aw4 problems are tied to tps / corroded or poor electrical connections causing voltage problems and the hidden fuse . fluid type has never been an issue after rebuild
Everything I have read states that the AW4 will usually have driveability issues when you have electrical gremlins. Mine is perfect. Other than this mileage thing, it runs great. Up shifts are nice and firm, TC is locking up properly and it down shifts with a little tap on the gas pedal.
Is there any way to check the TPS or other electronics?
I put a code reader on it yesterday in hopes that the ecu would tell me it had a bad 02 sensor or something, but not dice.
Any Dexron III trans fluid experts out there? 
