AW4 Problem

Jeep: 1996 4.0L 2WD, stock everything (expect for the parts that have fallen off).

Problem: This has been a long term problem, about 6 months if not a year. My Jeep seems to have trouble shifting gears, usually from 1st to 2nd. My transmission is leaking fluid (not sure on the exact amount but I'm putting in about a quart a month).

Typical experience: Jeep starts fine, has hard time shifting from 1st to 2nd, have to rev up the RPMs, slight jolt into 2nd, car shifts fine up through 4th.

Now 2 things can happen:

1. If I am able to drive about 5 minutes in 4th, then the rest of my drive is fine, no problems shifting between any gears.

2. If I get caught at a light soon after I start driving, then more problems arise. Sitting at a light causes "stall-like" symptoms. My Jeep will not actually stall but RPMs drop and rise like it wants to stall. Once light turns green, I have similar problem listed above with Jeep not wanting to shift from 1st to 2nd. Then repeat cycle.

*** Additional problems, when sitting still with foot on brake, Jeep has a jolting/lundging feeling between Park/Neutral/Reverse/OD.

Alright, I think that is everything, any ideas out there? Any advice or similar experience is appreciated.

The stalling issue may, or may not be related. Interesting problem combo. You might try disconnecting the TCU computer, and shift manually to see if the problem goes away. If the problem stays, then it does not involve the TCU and it's electrical areas. If the problem goes away, you need to look at the TCU, Tranny solenoids, TPS, VSS, etc.

Hi all,

I just got my oil changed and as usual had low tranny fluid when I went into the shop (they always freak out about this). They tried to talk me into a tranny flush and i'm like, "I'm pretty sure my leak is flushing the system enough. No fluid lasts longer that 3 months in the tranny anyway before it leaks out."

Anyway, I was talking to the shop manager and he was saying that the idle problem is most likely not related to the tranny problem. He said I should probably replace the Idle Air Control value and see if that fixes the problem. Any thoughts?

Also, on the tranny leakage, he recommended some I get some of this Lucas Auto Transmission Slip stuff, http://lucasoil.hodgsoncorp.com/slipping_transmission.htm Anyone ever tried it or have any opinion on it?

Thanks.

idle problem could be your IAC, could also be vacuum leaks, or your throttle body could be very dirty, or you could have an exhaust leak upstream of the first O2 sensor making the ECU feed the engine more fuel than it should to counteract the false lean reading. Cheapest/easiest stuff first, so try using throttle body cleaner, if that doesn't fix it, check for exhaust leaks (you'll hear em), then check for vacuum leaks, if that doesn't fix it look into the IAC valve maybe.

Tranny leakage... where's the leak coming from? Front of transmission? Rear of transmission? Cooler lines? The fluid won't just disappear so you will be able to see it somewhere.

What fluid, brand and spec are (have) you been using?

Have you tired any of my earlier suggestions?

First, let me say, that the tranny problem seems revolve around the amount of fluid in the system. When I have the tranny fluid completely filled, the problem pretty much disappears. The more that leaks out, the rougher it gets.

Hey Ecomike,

My lack of knowledge is really preventing me from trying your steps.

TCU - (Transmission Control Unit?) I am not sure how to unplug this.
Shifting manually - You mean drive the car while shifting through the gears once the TCU is unplugged?
If the problem goes away, you need to look at the TCU, Tranny solenoids, TPS, VSS, etc. - I really don't know what any of this means.

Yep, that'll happen... when it's low, you are burning up your clutches and they aren't grabbing properly, and possibly hurting your torque converter too. Sounds like fixing the leak may be your first priority.

The TCU on yours is on the back side of the passenger lower dashboard. There is a connector you can unplug that will put the transmission into "manual automatic" mode. You won't have access to 2nd gear, it'll go right from 1st to 3rd, but it will tell you if your issue is hydraulic/mechanical (problem continues, my bet) or electrical (problem goes away.)

tranny solenoids = the solenoids inside the transmission controlled by the TCU. They allow fluid to the shifter pistons and clutches to be controlled electronically while the lever is in D.
TPS = throttle position sensor. Tells the TCU electronically how fast you are trying to go.
VSS = vehicle speed sensor. Tells the dashboard, ECU, and TCU how fast you are actually going.

kastein,

Thanks for the definitions, this will be helpful.

Also, I am not quite sure where the leak is coming from. When the lube shop was under my car doing the oil change, they said the tranny fluid was coming out from the pan. I am not sure if they meant that the pan itself had a leak or if it was just dripping from their but actually leaking out from a different point. (not sure if this helps)

If the problem ends up being a hydraulic/mechanical issue and not an electrical issue, do you think the Lucas Transmission Fix would be a good product to limit the leak? or should I really take this to a Transmission shop? however, spending really any money on transmission work doesn't seem worth it to me, this thing isn't even 4WD

It might fix it. I run high-mileage "snake oil salesman" oil and transmission fluid in all my Jeeps because I figure that while it may not do anything, it might help, and with the mileage mine have (nearly 140k, 208k on the other) I feel it's worth the small price increase.

As for fixing it... don't pay someone to do it if you have another vehicle to use in the meantime, pick up a used transmission in good shape for a few hundred and learn to install it yourself. You could easily save over a thousand dollars.

With the TCU unplugged (or its fuse removed--inline fuse, yellow wire running into the TCU) you will have 1st when in 1-2, 3rd when in 3, and 4th when in D, reverse, park, and neutral. As stated above, if you unplug the TCU the transmission is strictly hydraulic/mechanical, so if the problems do not exist with the TCU out of play, then the problem is electrical in nature. If the problem remains, then the transmission needs rebuilt or replaced.

Are you using Dex III transmission fluid? If you are having a shop put fluid in it, odds are they are using ATF+4, and that could be aggravating your problems.

Either fix the leak or top up the fluid daily. Check the fluid level when hot, after 20 minutes of operation.

Your throttle body pressure cable could need adjusting so go ahead and do it. Search and there are plenty of threads on how it is done, and it is dirt simple to do.

Also, if your TPS--throttle position sensor--is out of specs then that will screw with your transmission AND your idle.

adjust the TV cable....its free and wasy.

Since your problem seems to be fluid level related and you have a leak, clean up, wipe off all the leaked fluid, dry it up, drive it and then get under it and look for the leak source, or source of the leak. It might be an easy fix. Have you checked to see if the pan bolts are loose?

joe_peters said:

With the TCU unplugged (or its fuse removed--inline fuse, yellow wire running into the TCU) you will have 1st when in 1-2, 3rd when in 3, and 4th when in D, reverse, park, and neutral. As stated above, if you unplug the TCU the transmission is strictly hydraulic/mechanical, so if the problems do not exist with the TCU out of play, then the problem is electrical in nature. If the problem remains, then the transmission needs rebuilt or replaced.

Are you using Dex III transmission fluid? If you are having a shop put fluid in it, odds are they are using ATF+4, and that could be aggravating your problems.

Either fix the leak or top up the fluid daily. Check the fluid level when hot, after 20 minutes of operation.

Your throttle body pressure cable could need adjusting so go ahead and do it. Search and there are plenty of threads on how it is done, and it is dirt simple to do.

Also, if your TPS--throttle position sensor--is out of specs then that will screw with your transmission AND your idle.

Click to expand...

That pretty much covers it......:thumbup: Follow Joe's advice here....