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Unread 03-11-2011, 07:38 AM   #1
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1994 YJ Wrangler 
Join Date: Jul 2009
Location: Illinois
Posts: 62
trans and fuel economy

Alright. heres a good one. to start off my jeep is equipped as follows. 4.5 inches of lift, 33 in DC mud countrys, dana 30, chrys. 8.25 w/ 3.55 gears, aw4, 231j, factory speed sensor. Now for the fun stuff.
Last summer, on average driving (no wheeling, no hauling) i would average about 190-210 of my incorrect trip odometers miles per tank and thats running down till the light comes on and then some. Recently i have been averaging about 150 and less miles per tank. i know my odometer is off so just bare with me and dont tell me im averaging less than 7 miles per gallon!
I have no engine light on (bulb is good), fuel pressure was within spec but low. I appear to have no injector leakdown. she idles smooth and still sounds good. Last night on my way into work, i noticed that either overdrive or t.c.c. was slipping. i have been having difficulty maintaining highway speeds on level roads(no grade).
now this morning coming home from work i could not get it to drop down into passing gear and when it would engage overdrive if i would back off the throttle just a touch it would shift out of OD and rev up to 3000. a quick jab of the loud pedal and it would upshift.
So, is there some sort of trans controller other than the main pcm or has my tranny had it? if i do replace the trans do i have to stick to pre-95 aw4's or can i use 96-up ones? any other stuff i should consider or test before i condem my trans for my fuel economy?

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Unread 03-11-2011, 02:27 PM   #2
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2000 XJ Cherokee 
Join Date: Apr 2002
Location: out in the garage - Minneapolis, Minnesota
Posts: 21,608
Can we assume that all your tune-up parts are fresh and all your routine preventative maintenance items have been taken care of ? When was the last time your replaced the transmission fluid ?

Test the Throttle Position Sensor, test the O2 sensors, clean the NSS.

Test before you start randomly replacing parts in the hopes that you accidentally fix what is the actual source of the problem.

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Unread 03-11-2011, 07:10 PM   #3
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1994 YJ Wrangler 
Join Date: Jul 2009
Location: Illinois
Posts: 62
the pan was dropped a year and some ago (late summer 09) and with that i replaced the filter and filled it back up with the correct fluid. never had a problem until just recently. as far as engine, o2 sensor got put back into service june 2010. soon after was plugs n wires, cap n rotor, just changed the oil and filter during christmas. IAC valve was replaced at the beginning of 2010. The engine does not missfire or run poorly. exhaust doesnt smell rich. i run premium in her every since that motor went in. Motor is a fresh rebuild with some head work done. motor itself is now 4 yrs old. i put that in at 189,000 miles and the clock now sits at 243,853. it is the original trans and t-case. Today i pulled the trans dipstick out and wiped it on a napkin. its brown. i mean its very brown and theres quite a bit of metal in it too. i grabbed my magnet wand and i was able to lift the napkin up by the fluid stain. so im really leaning towards a trans.
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94 xj , aw4 , fuel economy , trans
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