Understanding the AW 55- 50 Neutral Control

Written by Jerry Huerter - Diagnostician at Overland Park, KS

We recently had a 2001 Volvo S60 come into or shop with a smoked AW 55-50 transmission that needed to be replaced.

The AW 55-50 transmission has a feature that Volvo calls “Neutral Control”. What it “Neutral Control” and what is its function? To tell you the truth, I wasn’t really sure, but below is what I was able to both find and figure out about it.

Sometimes Lucky is Better than Good

Written by Dana Deeke - Diagnostician at Lincoln NE

I had a mid-90’s Dodge Caravan come into the shop with the complaint of a rough noise/feel when driving above 45-50 miles per hour. The van had been into a couple of other local shops to try to find the noise with no success and the customer was getting frustrated.

As normal, I started with a road test to see if I could duplicate the Customer complaint. Sure enough, upon reaching 45 miles per hour the van started to make a low, growling sound and you could feel a little vibration thru the steering wheel. It was time to get the van inside and do a visual inspection.

Hot Off the Wire

Written by Dave Finley - Diagnostician at Bellevue NE

My first appointment of the day was a customer with a 2001 PT Cruiser.  Their complaint was, “It feels like all the gears are slipping, and a light is on in the gauge panel.”

I started my evaluation with a fluid check and pulled the codes.  The fluid level was normal, and the code I got back was a P0750 - solenoid error in the TCM.  There were no ECM codes.

After clearing the code I started my test drive. The transmission preformed well, but I did experience what felt like a slight engine stumble when going up hills. It was intermittent, but it did occur twice during the drive. The check engine light also came back on.

Simple Wire Problems

Written by Chris Foster - Topeka Store Manager

A few weeks back, we had a customer come to the shop and say “Hi! I was sent here by so-and-so, and he said you would be able to fix my car, because he does not have time to figure it out”. “Well I am always up for a challenge, what is going on with it?” We then got into a discussion of how long he has been working on the car, and how everything "works great”. She then explained to me that the dealer looked at it and said it was going to be $XXX to fix it, and she just didn’t think they were right because “everything works ok… It is just the ALL WHEEL DRIVE DISABLED light is on, and nobody can find out what is wrong with it”. “Sure” I said, “leave it with me and I’ll see what I can do.”

Chrysler Transmission Range Sensor

Written by Mike Steen - Technical Director

The Transmission Range Sensor (TRS) has 3 primary functions:

1. Provide a PARK/NEUTRAL start signal to the engine controller and the starter relay.

2. Turn the Back-up lamps on when the transmission is in REVERSE and the engine (ignition) is on.

3. Provide a transmission range signal to the instrument cluster.

This relatively simple sensor has caused us problems over the years.

Cooler By-Pass

Written by Mike Steen - Technical Director

External cooler by-pass valves are becoming more and more popular it seems. There are also many different variations of these by-pass valves. It’s important that you check the cooler lines and cooler closely to see if the vehicle your working on has one of these by-pass valves. In most cases they can be removed and cleaned.

Most all automatic transmissions incorporate some sort of by-pass in case the cooler becomes restricted, but they are typically found inside the unit.

Verify the Systems Before Condemning the Transmission

Written by Randy Peterson - Diagnostician

A few months ago a customer brought in a 2003 Dodge 1500 Pickup with a 5.7 Hemi and 545RFE transmission. The check Engine lamp was on and the truck would not accelerate from a stop unless you put the transmission in second gear. I started the preliminary check procedure by checking the fluid. It was full, not in great shape but no burnt odor. Next, I scanned for diagnostic trouble codes. The ECM stored a couple EVAP codes and the TCM had a P2706 – MS (multi-select) Solenoid Circuit. Oddly enough it did not have a P0700 (Trans Control System Malfunction) stored in the ECM. This vehicle utilizes an ECM and separate TCM. After a short road test the customer’s concerns were confirmed. I cleared the DTC and road tested it again to see if the code reset and it did. Further diagnostics were required. The vehicle owner authorized the diagnostics, and we began the process.

Solenoid Operating Pressures

Written by Jim Richardson - Technical Director

With the quantity and price of solenoids becoming a substantial additional investment in the price of a transmission reman, testing and reclaiming the solenoids has become mandatory.

Every once in a while you run across a scenario that has you scratching your head. This was one of those units.

Our warranty dept. received a call from one of our retail locations. They had a 2002 Volkswagen Jetta with the O9A transaxle. The unit had been out approximately 300 miles and came back because of a no reverse complaint. All the external checks that could potentially inhibit reverse were investigated, everything was working properly. It was determined the unit would have to come out for further evaluation.

Manual Transmission Fails due to Hydraulic Error

Written by Steve Logeman, Technical Director

Huh? NV4500 manual transmission fails in the field because of a hydraulic issue? You’re probably saying to yourself “This guys wacked or drinking his lunch if you know what I mean.” There’s nothing hydraulic about a NV4500 5spd manual transmission.

This all starts with a 2002 GMC 2500 with a complaint of sticks in fifth gear. Customer states that this has happened to him half a dozen times since the transmission was installed 2000 miles ago and to make matters worse the technician at our shop couldnot duplicate the complaint.

This struck me as very odd complaint for this type of transmission. Over the years there has been a lot issues with fifth gear and the nut that retains it on the shaft but I do not recall that it ever made the transmission stuck in fifth. No fifth, pops out fifth, hard to engage reverse; these are typical complaints of this unit.

Why Resistance Checks Don’t Always Work

Written by Chris Adams, Diagnostician

I think I can safely say that we have all been here before: “I ohm-checked the entire circuit and it checks OK.” This article started as a problem found on a particular vehicle, and then it morphed into an article on - in my opinion - a better, faster, more efficient way of checking electrical circuits on a vehicle. In this example I want to show how amperage-based testing on a live circuit can save you time and headaches versus traditional resistance testing on a dormant circuit.

AX4N (4F50N) Harsh 1-2 Shift

Written by Jody Carnahan

I received a call from one of our wholesale customers which is a shop that does general repair and transmission work on occasion. He called looking for help on a 2004 Ford Freestar that he could not get to leave his shop. In fact, the vehicle has been to several other shops in the past. He advised me that the transmission had been worked on recently by another shop and that it was now back in his shop. I asked him what the previous failure was and he indicated that it was a problem with a 2^nd gear slip. They had removed the transmission and found the intermediate clutch piston bonded seal was damaged and that was all that was done to repair the unit. Now that they have it all back together, the trans bangs hard on the 1-2 shift. It was not setting any codes and from what the shop could tell everything with the vehicle and load sensors were working properly. I decided to take on this challenge and advised him to drop the vehicle off at our shop.

4L60E EC Cubed TCC Control and Adapt

Written by Richard Middleton, Diagnostician

During the course of helping a co-worker repair a TCC slip, we analyzed some graphs and noticed some interesting info on how the PCM behaves and how it "sees" and adapts for a TCC slip.

All the following graphs were taken on one test drive of a 98 camaro with a 4L60E EC cubed.  The required fix was to overbore the TCC regulator valve and the AFL valve and replace them with oversize valves.  They both showed significant wear using a wet air test technique. No other repairs were made and the transmission was not removed from the car. The fix isn't the point of this article though, because I'm sure most people reading this article are probably aware of valve body wear issues that cause the TCC slip.   The point, is how advanced the computer strategy is, and its ability to "see" and adapt to TCC slip.