I apologize if this seems a little long, but I am both asking for advice, and documenting a procedure I have not seen mentioned before. I have a 1998 XJ 4x4 4.0L AW4 Automatic with about 60000 miles. Early this summer, I dropped the pan on the tranny, changed the filter, and changed the fluid (With Dexron III/Mercron, of course). Everything seemed fine.
Now the transmission is acting very strangely, and slipping. When I step on the gas from a stop, more often than not the engine will rev, almost like it's in neutral. The Jeep will creep forward slowly, and then BANG, something engages, the jeep lurches, and I start moving. However, even at that point, the motor revs higher than normal, and it feels like the transmission is slipping. If I let off the gas just before it engages I can avoid the BANG, and drive it almost normally, but it still slips, especially starting on a hill. When I step on the gas on the highway, it feels like it's slipping, too.
It happened very suddenly. Two days ago, I drive to work in the morning, everything's fine. Drive home at night, big problems. This would seem to indicate it isn't a progressive problem related to, for example, the wrong ATF.
I stopped by the dealership, and ended up talking with a technician there (who reinforced the generally held view that AW4's are bulletproof.) He said many times the problem is related to the Throttle Pressure Sensor (?). What he was
talking about is described by AllData as a Throttle Valve. This has nothing to do with the TPS on the engine. The second cable coming off the throttle is a "Transmission Throttle Valve Cable." It goes down to the valve, located on the left hand side of the tranny, just forward and above the gear selector linkage.
I've never seen the throttle valve mentioned in previous posts about tranny problems. Paraphrasing the manual: The tranny throttle valve controls shift speed, quality, and part-throttle downshift sensitivity. If cable is too slack, it will shift early, and slip between shifts. If it's too tight, shifting will be delayed ( Revving the engine!? ), and downshifts will be overly sensitive.
Anyway, I followed the procedure to adjust the throttle cable: Make sure both the throttle and valve are in the fully closed (idle) position. Slide the cable clip off the throttle linkage. The manual said to use a small screwdriver to remove the retaining clip on the cable's bracket. Then you can adjust the position of the cable to make sure the end of the cable is centered over the
attachment stud on the throttle. Put the retaining clip back on to lock the cable (sleeve) in position, and reattach the end of the cable to the throttle. The tolerance is 1mm! The throttle valve has to be synchronized with the throttle, or else the transmission gets confused. My cable was too tight by
almost 1/4".
Manuals lie. The one I was following did not mention that on my '98, there is no longer a "valve lever" outside the transmission. It's internal. The cable just disappears into the tranny. It also did not mention that they made the adjustment even easier. All you do is disconnect the end of the cable from the throttle linkage, and PUSH DOWN ON THE METAL BUTTON ON TOP OF THE RETAINING CLIP. Then you can slide it to any position you need, and let go, and it's locked. I almost broke the connector with a screwdriver trying to remove it.
So, I take the XJ out for a test drive, and it seems about a 70% improvement. There's still slipping, but the problem with the engagement from a stop is almost gone - even uphill! I get the impression that the "throttle valve" is supposed to let fluid bypass the torque converter if you take your foot off the gas, and the moment you step on it, it sends fluid to the right places to make the Jeep go. This would make stopping easier, because there'd be less force coming from the tranny, and would prevent creeping when stopped. I have not confirmed this, though. And it doesn't explain the slipping.
Now the frustrating thing. I drove the Jeep to work this morning, and when it was cold, it seemed okay - still slipped a little, but didn't lurch when starting out. By the time I had been on the road for about 15 minutes it was as bad as before.
I'm at a loss! What now?? TPS? New Fluid? Throttle valve problems? I've seen mention of fuses, but the '98 owner's manual doesn't show a specific tranny fuse, and none under the hood were blown.
I've got MOPAR ATF on order ( The dealer didn't have any Dexron III, because "they always use ATF+3, and never had a problem." )
Now the transmission is acting very strangely, and slipping. When I step on the gas from a stop, more often than not the engine will rev, almost like it's in neutral. The Jeep will creep forward slowly, and then BANG, something engages, the jeep lurches, and I start moving. However, even at that point, the motor revs higher than normal, and it feels like the transmission is slipping. If I let off the gas just before it engages I can avoid the BANG, and drive it almost normally, but it still slips, especially starting on a hill. When I step on the gas on the highway, it feels like it's slipping, too.
It happened very suddenly. Two days ago, I drive to work in the morning, everything's fine. Drive home at night, big problems. This would seem to indicate it isn't a progressive problem related to, for example, the wrong ATF.
I stopped by the dealership, and ended up talking with a technician there (who reinforced the generally held view that AW4's are bulletproof.) He said many times the problem is related to the Throttle Pressure Sensor (?). What he was
talking about is described by AllData as a Throttle Valve. This has nothing to do with the TPS on the engine. The second cable coming off the throttle is a "Transmission Throttle Valve Cable." It goes down to the valve, located on the left hand side of the tranny, just forward and above the gear selector linkage.
I've never seen the throttle valve mentioned in previous posts about tranny problems. Paraphrasing the manual: The tranny throttle valve controls shift speed, quality, and part-throttle downshift sensitivity. If cable is too slack, it will shift early, and slip between shifts. If it's too tight, shifting will be delayed ( Revving the engine!? ), and downshifts will be overly sensitive.
Anyway, I followed the procedure to adjust the throttle cable: Make sure both the throttle and valve are in the fully closed (idle) position. Slide the cable clip off the throttle linkage. The manual said to use a small screwdriver to remove the retaining clip on the cable's bracket. Then you can adjust the position of the cable to make sure the end of the cable is centered over the
attachment stud on the throttle. Put the retaining clip back on to lock the cable (sleeve) in position, and reattach the end of the cable to the throttle. The tolerance is 1mm! The throttle valve has to be synchronized with the throttle, or else the transmission gets confused. My cable was too tight by
almost 1/4".
Manuals lie. The one I was following did not mention that on my '98, there is no longer a "valve lever" outside the transmission. It's internal. The cable just disappears into the tranny. It also did not mention that they made the adjustment even easier. All you do is disconnect the end of the cable from the throttle linkage, and PUSH DOWN ON THE METAL BUTTON ON TOP OF THE RETAINING CLIP. Then you can slide it to any position you need, and let go, and it's locked. I almost broke the connector with a screwdriver trying to remove it.
So, I take the XJ out for a test drive, and it seems about a 70% improvement. There's still slipping, but the problem with the engagement from a stop is almost gone - even uphill! I get the impression that the "throttle valve" is supposed to let fluid bypass the torque converter if you take your foot off the gas, and the moment you step on it, it sends fluid to the right places to make the Jeep go. This would make stopping easier, because there'd be less force coming from the tranny, and would prevent creeping when stopped. I have not confirmed this, though. And it doesn't explain the slipping.
Now the frustrating thing. I drove the Jeep to work this morning, and when it was cold, it seemed okay - still slipped a little, but didn't lurch when starting out. By the time I had been on the road for about 15 minutes it was as bad as before.
I'm at a loss! What now?? TPS? New Fluid? Throttle valve problems? I've seen mention of fuses, but the '98 owner's manual doesn't show a specific tranny fuse, and none under the hood were blown.
I've got MOPAR ATF on order ( The dealer didn't have any Dexron III, because "they always use ATF+3, and never had a problem." )