Peculiar AW4 Behavior

[F1Addict]

A couple months ago my AW4 began to slip badly. I managed to limp home (about 2 miles) and started investigating. This is my first automatic so I'm pretty clueless when it comes to diagnosing problems. The first thing I did was check the fluid which seemed fine but I discovered I was reading the dipstick wrong. I guess the little windows are supposed to have an oil film in them and neither one did so the dipstick was just being splashed by oil. I pulled the pan and while the oil was a clear pink, it did have a little burnt aroma to it. I replaced the filter and checked the solenoids (all were at 14-15 ohms).

I replaced the gasket and refilled with Dexron III. It's now been two months and I've had no problems with slipping but I have had an odd issue. The transmission shifts normally in all gears but going from 4th to overdrive it revs if I'm not gentle. For example, if I'm accelerating to get on the freeway the transmission shifts crisply from 1st to 2nd, 2nd to 3rd, and 3rd to 4th but when it shifts into overdrive (usually around 45 mph at around 2500 RPM) it will quickly rev to 3250 RPM before engaging overdrive and just as quickly drop 1500 RPM down to 2000. As I said, it never slips, it's just this weird rev when engaging overdrive. After it's engaged there are no problems. The problem has remained consistent since I changed the transmission fluid, it's not gotten any worse or better. Any ideas?

[XJ Wheeler]

In AW4s, the 4th gear is overdrive. So i wonder if you're having a problem with the torque converter locking up. Although i don't have much knowledge on the subject, so i'll relay to someone with it.

[Cheromaniac]

if I'm accelerating to get on the freeway the transmission shifts crisply from 1st to 2nd, 2nd to 3rd, and 3rd to 4th but when it shifts into overdrive (usually around 45 mph at around 2500 RPM) it will quickly rev to 3250 RPM before engaging overdrive and just as quickly drop 1500 RPM down to 2000. As I said, it never slips, it's just this weird rev when engaging overdrive. After it's engaged there are no problems.

The AW4 is a 4-speed transmission (including overdrive 4th). Your sensation of the tranny upshifting to a "5th gear" is actually the torque converter locking up, whereupon the engine rpm drops abruptly.
It sounds like what you're getting is transmission "flare" where the tranny momentary stays in neutral before it engages the next gear. Does this happen all the time regardless of throttle position (light throttle or WOT)? Is it worse after a spell of stop-start driving in heavy traffic? If it's the latter, an auxiliary transmission cooler may help.

[F1Addict]

The AW4 is a 4-speed transmission (including overdrive 4th). Your sensation of the tranny upshifting to a "5th gear" is actually the torque converter locking up, whereupon the engine rpm drops abruptly.
It sounds like what you're getting is transmission "flare" where the tranny momentary stays in neutral before it engages the next gear. Does this happen all the time regardless of throttle position (light throttle or WOT)? Is it worse after a spell of stop-start driving in heavy traffic? If it's the latter, an auxiliary transmission cooler may help.

It does happen all the time but only when, based on what you've written, the torque converter locks up. Here is a graphical representation of the transmission behavior. Note that all shifts occur normally except for that last one that has the strange spike. Is this the torque converter having issues with lockup?

http://i140.photobucket.com/albums/r34/F1Addict/Jeep/ShiftGraph_zpsa3803ddc.jpg

If I accelerate gingerly it does not do this, it's only when I'm accelerating more aggressively that it happens. That isn't to say I'm being aggressive with the accelerator, just more aggressive than a grandma might be. When I filled the transmission I first poured 3 quarts (through the tranny dipstick) and then drove until at operating temperature, there was some initial slippage but that went away. I then, while stationary, shifted through all gears, checked the level, and added about another quart (for a total of 4 quarts (~8 pints)) with the engine running and the transmission in "P" until both circular windows in the dipstick had a film of transmission fluid. IMO, that fill procedure is stupid. Even for someone with reasonable mechanical skills, it seems like there's a lot of room for accidental over-filling. I checked the fluid level again this morning and, according to the dipstick, it appears to be at the correct level.