Staying ahead of trouble

Jan. 1, 2020
Most of the problems we see with bad connections have to do with broken locking tabs, loose fitting connector pins, and hidden corrosion inside the connector or wiring.
Figure 1

There are times when the nuts and bolts of replacing an automatic transmission have little to do with the actual nuts and bolts.  Whether you’re a production rebuilder or a bench transmission rebuilder, selling carryout transmissions forces you to deal with the reality of the unknown.  Sure, we know the year make and model of the vehicle, but do we truly know what lies within?  In many cases you don’t really know what the customer’s original complaint was.  All you know is that the shop working on the vehicle called you requesting a reman or rebuilt transmission.

In my last article, we discussed problems that can occur when the wrong transmission is installed into an incorrect application.  In this article, I would like to discuss the problems that can (and will) occur during and after a transmission replacement.  I know that some of this information is kind of old news for most of you, but for some reason I continue to see these problems on a daily basis. 

Figure 2

Many of these problems can be self-induced, while others are caused by issues with the vehicle itself.  By far, the most common problems we see when replacing an electronic transmission is having a poor electrical connection somewhere on the vehicle.  In most cases, problems will not occur right away, and seem to happen shortly after you have released the vehicle back to the customer.  Most of the problems we see with bad connections have to do with broken locking tabs, loose fitting connector pins, and hidden corrosion inside the connector or wiring.

Another common problem you can have with electrical connectors is having parts of the connector stuck in the core transmission, and you will probably not notice them missing. This is a common problem on late model Chryslers with the RFE series and 62TE, and also with Ford E4OD and 4R100 transmissions.  On the 62TE and RFE series, the inner pin separator can come off of the vehicle harness connector and stick down in the case connector of core unit.  When this happens, it makes it almost impossible to get the harness reconnected to the new transmission, causing multiple electrical codes.  This also is a very common problem on the Ford E4OD/4R100 transmission.

Figure 3

You also will need to be careful when attaching the case connector on some late model Ford units.  These connectors are held in place by a bolt in the center of the connector, and care must be taken when tightening the connector bolt down. If the connector is over tightened, you can pull the inner nut out of the case connector causing a poor connection. The picture below happens to be on a Ford 5R110W transmission.

The case connectors on some of these late model transmissions are getting fairly sophisticated, especially in the locking mechanism that is used.  If any part of the locking mechanism is broken or not working properly, do not attempt to use it and just assume it will stay in and make a good connection.  Problems at the case connector result in 75 percent of transmission solenoid circuit trouble codes.  I cannot stress enough the importance of having a good, clean connection on these electronic units, so it is imperative to address any broken locking tabs, missing connector parts, corroded connectors and/or wiring during a transmission R&R.

Figure 4A

Installing the Proper Way
Now I would like to talk about some installation procedures that will cause an almost immediate failure of the transmission after install.  I’m going to pick on Toyota vehicles to make my point, as they seem to be the vehicles that will give you the most problems.

The issue here is with the torque converter to flexplate mounting bolts.  You need to pay close attention when you R&R a Toyota transmission, as some torque converter bolts will take a washer between the bolt and flexplate. 

Note: Not all applications use washers on the converter bolts.  If you have an application that uses a washer, and that washer is left out during assembly, there’s a good chance that the bolt will bottom out on the rear cover of the torque converter before its gets tight to the flexplate, and if the bolt is tightened down enough, it will dimple the rear cover of the converter.  This will cause immediate damage to the torque converter clutch lining and cause the transmission to fail.

Figure 4B

One other note regarding Toyota torque converter bolts. They are not all the same.  There is one bolt in the set that is different. It has a small shoulder that aligns the flywheel to the converter.  This bolt needs to be installed first so that all non-shoulder bolts will start without the chance of cross threading.  The shoulder bolt is usually a different color, so do not confuse it with a different bolt.

The torque converter mounting bolts always should be checked during every R&R job to ensure they are the correct length.  I have seen torque converter bolt threads stretch, which of course will make it longer in length.  Pay close attention to this small, but very costly, detail.

How to Sell Properly
Now I want to turn our focus to things a production remanufacturer and bench builder selling a carryout transmission needs to know when a shop wants to purchase one of their transmissions.  As a transmission rebuilder or remanufacturer, we are always faced with the dilemma of not knowing what the customer’s vehicle is used for.  For example, is this a vehicle that is primarily used for towing and hauling or does the vehicle have added accessories such as programmers, performance chips, aftermarket turbo chargers, exhaust?  It would be in the best mutual interest of the shop and vehicle owner to let the rebuilder know this information at the time of purchasing a remanufactured unit, or having your original transmission rebuilt.  These added accessories will drastically affect the way a transmission will work. 

Figure 5A

The reason I’m mentioning this is because the rebuilder probably will want to make changes in the way they remanufacture or rebuild the transmission, based on usage information provided by the customer.  Upgrades to internal parts such as clutches, bands, valve body modifications, a heavier-style torque converter are all valid considerations in order to match vehicle’s engine performance upgrades.  This also would be the case even if the vehicle had an OE stock engine, but is used primarily for towing or hauling loads that meet or exceed gross vehicle weight.

Performance chips and programmers are not new to our industry and are becoming more common in truck applications with diesel engines.  You need to be aware of these, because on top of providing engine power enhancements, some programmers change transmission pressure control and shift control strategy. 

Figure 5B

I’m bringing this to your attention because a stock OE reman unit and/or a stock rebuild is designed to handle a specific amount of torque, and when this torque is increased with the installation of a performance chip or tuner programmer, the stock OE transmission can no longer handle the increased power. 

Your next question might be, “How do I know if the vehicle has a programmer or a tuner, when nothing is present or visible on the vehicle?”  Obviously the vehicle owner probably will know this all-important information, but in some cases they will be reluctant to offer this information up front.  If you are unsure about the vehicle’s current calibration, and whether or not it may have an aftermarket calibration, you can easily check it by hooking up your scan tool and retrieving the calibration number.  If you are unfamiliar with how to check this, just hook up scan tool, go to your function test menu and select calibration part number (P/N). The next screen will show you the current calibration number.  You will then have to log onto the manufacturer OE web site to view what the vehicle’s current PCM or TCM calibration should be.

Figure 6A

Checking the vehicle for current calibrations should become part of your normal vehicle check-out procedure and diagnostic routine.  On top of being able to check and see if the vehicle has any aftermarket calibrations, it also will allow you to see if the PCM or TCM has any OEM software updates for any particular drivability concerns having to do with powertrain performance.

What Can Ruin Your Day
Last, but not least, we need to discuss a couple things that will ruin a perfectly good install on a rebuilt or remanufactured transmission.  This has to do with resetting shift adapts, resetting computer memory and performing a drive relearn.  Relearn and reset procedures are not new to most shops these days, and some shops already have equipment to perform reflash and reprogramming on most vehicles.  Unfortunately, however, performing relearn and resets on some Asian and European vehicles can be a challenge as most of these vehicles require a dedicated OE scan tool or software to perform the procedure.  Most of the vehicles we are working on in today’s world will require some type of relearn or reset procedure after the transmission has been repaired.

Figure 6B

Additionally, some vehicles will require PCM or TCM reprogramming before any relearn or resets can be performed.  This can be true even when doing a minor repair that does not involve removing the transmission from the vehicle, such as replacing a valve body or solenoid.  I’m going to pick on Toyota vehicles again, and specifically, vehicles that use the U140/ U150 and U240/U250 series transmissions. 

Here is an example of what I’m talking about. You have just performed a fresh install on a 2004 Toyota Camry with U151E transmission, and on the initial road test the transmission has what feels like a tie-up, bind-up, or even a spin-up/flare on the 2-3 shift.  After about two to three miles into the road test, you decide to return to the shop because the shifts are not getting any better.  Now you are probably saying to yourself, “What could the transmission rebuilder have done wrong to make the unit work like this?”  The answer is they did nothing wrong.  The problem is with the installer and not resetting memory or shift adapts prior to test-driving the vehicle. 

Figure 7A

And now for the bad news: Even though you have driven the vehicle only a few miles, that’s more then enough time to burn the direct clutch, and (you guessed it), time to pull the unit right back out of the vehicle.  This is the one that doesn’t make the rebuilder very happy. 

Needless to say, resetting shift adapts and tap cells is a very crucial part of the transmission R&R process, along with checking vehicle PCM or TCM calibration status.  I picked on the Toyota units specifically because of the damage that can be done in a very short order, but of course these are not the only transmissions that can be damaged on a road test by not resetting the computer.

Armed with this knowledge, installers will benefit from double-checking for the correct bolt usage, healthy and tight electrical connections, correct relearn/reset procedures followed, and unit built properly for the vehicle’s performance level and purpose.  Performing these checks every time will save you from a warranty call you don’t need and keep your customers happy.  

Figure 7B
Figure 7C

Subscribe to Motor Age and receive articles like this every month…absolutely free. Click here

Voice Your Opinion!

To join the conversation, and become an exclusive member of Vehicle Service Pros, create an account today!