vblakev

My 1989 Jeep with 198K Miles Had the transmission slip for the very first time. And very few are surprised I am sure.

Here's the equipment:
Pretty healthy old cherokee, 4.0, automatic.

Last tranny flush in late '09 when I bought it with around 115K Miles, no new filter- guy didnt offer and I assumed it came with it. I did this as used car preventative maintenance.

No known transmission fluid leaks. fluid levels always check out every oil change.

No previous transmission problems.

Here's what happened:
I was late for work, reversed out of the driveway calmly, Gassed to end of street, rode the main residential street around 45mph about 1 minute after start. Lots of slowing down and gunning it at lights and around slower objects.
A mile from work- vrummmmmmmmm says the Magnaflow- and I start slowing down. I knew the tranny slipped. My ridiculously busy week with school starting has just turned into a nightmare. I cant cancel school or work or any other business.
This morning was the hardest I've rode my jeep in a long time and she just couldn't take it.

Here's what it's doing now:
Park- fine. 100%.
Reverse- Right as rain. 100%
Neutral- As neutral as it gets with a dirty NSS. 100%

Drive, 3, 1-2 -The issue. forward gears past first gear. First gear works like a dream. Try to go faster than 15 mph and its a joke. first shift around 2500 then free rev and slow down until you hit 2800 rpm then around 3400 itll shift again but then slip more until 3k+ rpm.
I may have rode my jeep hard this morning but I dont beat on my cars like that.
From a stop I usually breeze through the first couple gears at less than 2000 rpm.

I panicked and added a bottle of lucas conditioner and trans X stop leak and slip today so its probably about 2 quarts over filled currently.

I've been reading the AW4 Manual.PDF and it directs me to Electronic Control Problem, Solenoid Faulty and Valve Body Faulty for Delayed Shifts.
Slipping Up shifts and shuddery take offs also share these same possible causes with shift linkage, lp cable and transmission faulty added in.
Manual is from Automatic Transmission Service Group.

Some reading online leads me to believe the Vehicle Speed sensor located near the driver side rear of the transmission affects shifting and cleaning it may help the problem. I plan on trimming my shift linkage mount to pull the sensor and seeing what I can see. From what I understand the VSS has a mechanical gear rotating when vehicle is in motion which an electronic signal reads 1 click per rotation of the gear. If the mechanicals jam then the electronics send no signal and the TCU doesnt activate the proper channels of forward gearing.

Checking the Throttle Position Sensor may also be wise I read.

Rather than ohm testing my harness like a goon, I will soon coast to a transmission shop so they can hook up a snap on machine and tell me possible causes.

My Plan, before resorting to a shop repair, is to test/clean/replace anything I can do in my garage. On the schedule as of now: Speed sensor and the other doo-dad next to it. exterior solenoid? external valve bodies? Im learning still. Many people are intimidated by transmissions- I am not, its just a balance of time and money for me to get this worked out. Maybe the Neutral Safety Switch will be serviced when I start to really get desperately bored.

I will be freezing on my motorcycle until this gets cleared up. I know better than to ride an injured jeep.

Transmissions aren't my specialty but that doesn't mean I cant learn the easy stuff right? Thanks for any help. Wish me luck for my first day of the semester tomorrow and the worst week in a long time

tjwalker

This is BAD news. Overfilling a transmission can create a "frothing" condition internally which can lead to incomplete lubrication. Also can be tough on seals.
This is one of those situations where more is definitely "not" better!

1. Job #1 is to get the fluid level back in the SAFE zone on the dipstick.

2. Test your throttle position sensor. If you have true slippage, it may be something else, but the TPS is definitely involved with the shifting characteristics of the AW4 and it needs to be ruled in or out early in the process. More on that below.

Start with the above two things, then if not resolved..... follow the flow chart provided in the AW4 Factory Service Manual for further testing.
------------------------------------
RENIX TPS ADJUSTMENT

Before attempting to adjust your TPS be sure the throttle body has been recently cleaned.
It's especially important that the edges of the throttle butterfly are free of any carbon build-up.

IMPORTANT NOTE: Using one lead of your ohmmeter, probe the B terminal of the flat 3 wire connector
of the TPS . The letters are embossed on the connector itself.
Touch the other lead of your meter to the negative battery post.
If you see more than 1 ohm of resistance some modifications to the sensor ground harness will be
necessary. The harness repair must be performed before proceeding.
I can provide an instruction sheet for that if needed.

MANUAL TRANSMISSION:

RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body.
This manual transmission vehicle TPS provides data input to the ECU. The manual transmission
TPS has three wires in the connector and they're clearly embossed with the letters A,B, and C.

Wire "A" is positive.
Wire "B" is ground.

Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors..
Note the voltage reading--this is your REFERENCE voltage.

Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your
OUTPUT voltage.
Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For
example: 4.82 volts X .17=.82 volts. Adjust the TPS until you have achieved this percentage. If
you can't achieve the correct output voltage replace the TPS and start over.

AUTOMATIC TRANSMISSION:

RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a three-
wire connector, same as the manual transmission vehicles have, and it is tested the same as the
manual transmission equipped vehicles--FOR ENGINE MANAGEMENT RELATED ISSUES.

However, the automatic TPS also has a four-wire connector clearly embossed with the letters
A,B,C, and D.. For the automatic transmission equipped vehicles the four-wire connector
provides data to the TCU.

Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your
REFERENCE voltage.

Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT
voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage.
For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage.
If you can't, replace the TPS and start over.

So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and
the other side feeds the TCU. If you have TRANSMISSION issues check the four-wire
connector side of the TPS. If you have ENGINE issues check the three-wire connector side of
the TPS.

For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is
stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.

xjbeadlocks

AW4 are all over the place with low miles for under $100. buy one and have some buddies come over and replace. shouldn't take more then 4 hours. AW4 are simple trans to remove and replace