I've seen quite a few posts here about various failures of transmissions.
As a builder and watching posts here it seems the builder is usually the first one blamed no matter the cause.
I understand this from both perspectives. The automatic transmission industry has always seemed to have unscrupulous people. These guys usually get sorted out over time, and unfortunately they screw over enough people before they go that it leaves a bitter taste and mistrust of the whole industry for many.
The reason I learned to build my own transmissions and eventually got into the business if because of this.
Fortunately for most here, there are some very good vendors on this forum and within the performance industry as a whole. There are a few bad apples but most of well known vendors out there have built their business by taking care of the customer. RPM, FLT, myself, Ace Racing, Hughes Performance, BTE, ATI, TCI, Transmission Specialties, JW Racing, and dozens of others. Most of these companies were started because their founders had a love for cars and their use in competition.
None of these companies are perfect and none of them operate in a perfect world.
One of the biggest challenges to this industry is the fact that most of our transmissions are not installed in our shops. We don't get to see the job through to the end. Most of the builds go out to be installed by another shop or by the enthusiast. Our success as a builder and the customer's success relies just as much on the customer's ability to properly install the transmission as it does on us to properly build it. One important thing to remember is that neither the builder or the customer wants a failure. A builder wants to prevent failures because warranty repairs cost money and time, as well as customer frustration. A customer doesn't want it to fail because they have money invested as well, downtime, fluid, labor, and possibly other costs.

I've been working on a common causes of failures article. Any other builder who want to contribute I will give credit in the article. It will be going on my website when I have a chance to update it.
I will try to get some pictures to add to the article this week.

Transmission Failures

There are many reasons for automatic transmission failures. I’m going to discuss these to help enthusiasts understand them and hopefully prevent them.
Low Fluid Level:
As a builder we see evidence of this way more often than most would think. How do we know its low fluid level? Because the conditions inside the transmission will be the same as low pressure since low pressure is the result of low fluid level. One quick indicator is the condition of the forward driving clutch. In most transmissions this is a non shifting clutch and has plenty of capacity. If the forward clutch frictions are failed or showing signs of distress, and there isn’t a pump failure or anything damaged in the circuit (sealing rings, lip seals), it’s a good indicator that the fluid level may have been low. If the 2nd gear friction element also shows damage, but the rest are in good shape, it is further confirmation.
We’ve seen experienced shops damage transmissions because of low fluid level. I don’t believe this is done on purpose. I believe it to simply be a combination of poorly made parts (dipsticks), lack of knowledge of how to check the accuracy of the dipstick, and in some case being in a hurry or not fully completing a proper fill. A proper fill includes a short test drive with each gear change being made, and THEN final fluid level check.
However the fluid level check cannot be properly performed unless the dipstick measures correctly. Which needs to be done BEFORE the transmission is installed or by other methods that we’ll discuss.
1. Check the accuracy of the dipstick.
2. Add 4-6 qts of fluid before starting a new install.
3. Start engine and begin filling while checking the dipstick.
4. When the full level is reached, make a short low throttle test drive to go through each gear manually and automatically to ensure function.
5. Recheck the fluid level and add as necessary after test drive. Check for leaks.
Failure to complete any of the above steps may result in transmission failure. It is unreasonable to expect a hydraulically operated piece of equipment to have low fluid and live. Although it is a simple thing it is critically important.

Shifter adjustment:
Shifter adjustment is another often overlooked and important step to success when dealing with an automatic transmission. Some transmissions are more sensitive than others to the adjustment or lack of before it has any adverse effect.
Each range MUST line up between the shifter and the transmission detents. Some shifters don’t have detents and simply rely on the transmissions internal detents. However most racing type shifters must have detents to give the positive shifting and control to prevent unwanted shifts. It is most important that the range selected for most driving is PERFECTLY adjusted, but if the other ranges are not also perfectly adjusted, anytime you select them, you could be causing an internal pressure leak, which can cause failure. This is an installer’s responsibility, no matter how well built the transmission is, it cannot overcome faulty shifter cable adjustment.

Converter installation and spacing:
This is a very common cause of pump damage and ultimately transmission failure. It is also easy to detect on teardown. The pump gear or rotor has “ears”, “tangs”, or “flats” that mate with the converter drive hub. If the converter is roughly installed, or forced in while bolting the transmission to the engine, the pump gear or rotor will show damage, to the mating area and will often be cracked.
The converter drive hub will also usually have damage and can be cracked.
If the engine is started with an improperly installed converter the gear/rotor will grind into the rear cover.
Many times the transmission case will also suffer from a broken bolt hole area when this occurs depending on how evenly the bolts are tightened.

There is a common misconception that there needs to be a certain number of “clicks” when installing a converter. This is false. The converter must mate with the stator shaft, input shaft, and pump gear/rotor. The proper way to detect if the converter is completely installed is to measure it’s depth from the bellhousing mating flange. This requires a straight edge across the front of the bellhousing and measuring to the converter mounting area. On most GM rear wheel drive transmissions this will be between 1” and 1 1/8th “.
It is a good idea to check the converter fitment to the flexplate before installing the transmission. You want to check that the bolt holes line up, the converter pilot fits into the crankshaft or adapter, and the converter sits flush against the flexplate.
Once the transmission is in place but before completely tightening the bellhousing bolts, free rotation of the converter needs to be verified to ensure it didn’t move while jacking it into place. Tighten the bellhousing bolts and confirm again. If at any time the converter doesn’t spin, it needs to be removed, the transmission pump removed, disassembled, and inspected for damage.
Once bolted up, with the converter completely seated in the pump, it should have 1/8th” to 3/16” (.125 - .187”) of clearance between the mounting pads and flexplate. Many aftermarket flexplates may not be exactly the same as the OEM parts. There is also an allowance on the build height of the converter. If the clearance is too small, it will not allow expansion or movement of parts. If it is too great, you can use flat ground washers of equal thickness as spacers. Be sure that this doesn’t result in the converter pilot not being centered in the rear of the crankshaft or spacer.

Line Pressure Control and Rise Systems:
These systems include vacuum modulators, TV cables, and electronic pressure control solenoids (EPC or PCS).
A vacuum modulator is a simple system that defaults to max line pressure when unhooked. The max line pressure can cause problems if the transmission isn’t modified for it. However this is an almost foolproof system that many builders have adapted in electronic controlled systems to prevent tuning caused failures.
TV cable operated transmissions are another type of system that works fairly well when the installer FULLY understands the system, the geometry involved, and is willing to be sure it all works properly. A pressure gauge is a fundamental tool to check the function of this system and is helpful on all transmissions.
Electronically controlled pressure systems work well when properly tuned. The pressure control solenoids have proven very reliable and repeatable. Most issues with these system arise from a misunderstanding of the control system that tells the solenoid what to do. These systems are almost always defaulted to max pressure when voltage is not present, to prevent failure in the case that there is a loss of power to the transmission. GM units work off amperage. One full amp or 1.0 commanded amps equals minimal line pressure. Zero amps or a commanded 0.1 amp is maximum line pressure.
The actual pressure is determined by the pressure regulator system in the transmission and how the builder set it up.

 

The single most important thing that needs to happen on any transmission install is that a pressure gauge needs to be installed and pressures confirmed. The pressure gauge will confirm that the transmission is making proper pressure. Most reputable performance shops are using a transmission dyno to check for proper pressure after the build. It is a good idea for the installer/tuner to check for the desired pressures when dealing with a TV operated or EPC system.
We have seen failures from improper tuning and faulty controllers. These can be difficult for the builder to determine the actual cause because the transmission will pass dyno testing, come back failed, and show all the typical symptoms of low line pressure. After repair, it will pass dyno with good pressure again. If the cause isn’t found by the installer, it will fail again.
Some installers seem to think it is not their responsibility to check line pressure. A pressure gauge is a fundamental tool that should be installed on every new build and install to confirm proper function. It provides a huge amount of data. It will confirm proper build and pump pressure, it will confirm fluid level while accelerating, it will show issues with shifter adjustment, and it will show pressure rise related to the control system.
One of the first questions you will get from any knowledgeable builder will relate to pressure and for help diagnosing transmission issues from any builder, he/she will need data that will most likely involve pressure readings.
The diagnostic process for an automatic transmission goes in a logical order.
1. Check fluid level
2. Check shifter adjustment
3. Check modulator/TV system hookup and adjustment.
4. Check pressure.
We dyno test our transmissions for proper pressure, function in all gears with load, proper shifts (firmness), converter charge pressure and flow, any leaks from the front seal, and unusual noises. When we do this we have a good indicator that it will go in the customer’s car and function fine assuming it is properly installed. We do occasionally have failures that slip by the dyno, or are just an unusual “it happens” failure. However most of the failures we see are caused by improper installation and sometimes operation.

 

Thanks for this thread! this is a good checklist of things to do...

 

I've been meaning to do this for some time.
I answer dozens of phone calls a day, and literally 100-150 emails a day that MAYBE I can cut down on by writing this article.
I was having a conversation with Gilbert at Ace Racing last week and it spurred me to "get it done".
I try to be available to every customer and help each with real technical help, but most don't realize that I can only talk to so many people per day. I don't have a tech line of 10 "sales people" or techs to answer questions. I know Gilbert is similar since he's a one man show.

I often get phone calls asking "how much fluid does my trans hold?". The answer is, read the dipstick? There really is a more complete answer, and I could say 6-16 qts but it would irritate most if I told them that.
We see inaccurate dipsticks fairly often, so we can't blame low fluid level on the customer. We need to educate the customer to be thorough and know what they are looking for.

Part of the point is to make sure that the customer/enthusiast is aware of their responsibility when they install a transmission. (because I am writing this on behalf of the industry, hopefully it will help not just me and my customers, but everyone who reads it).

My company has a good reputation and it is hard earned, but occasionally we have customers who have issues. Sometimes this is due to our mistake, sometimes its the customer's mistake, sometimes it an associated part (bad converter, dipstick, controller, etc), and sometimes its just a weird quirk.

In the last month at my shop I have fixed one 4L80E that was definitely our error that made it past the dyno, I have fixed one unit that had a weird quirk with a pressure switch that had partial continuity to ground, I've repaired a couple of operator mistakes (rolled sprag in burnout on a TH400 on my unit and a killed OD sprag in a 4L80E from another vendor here, caused by launching in OD), and one with a damaged pump from installer error.
I have covered under warranty and out of warranty other's mistakes, as I'm sure almost every vendor here has.
Occasionally you get the guy who has no business being under a car and all of his frustrations are your fault.

 

Jake Thank You for sharing that info.

On the 4L80E what is the thread for the pressure fitting?
Is it NPT?


Mike

 

Awesome thread Jake! I can't wait for my stage 3 4l80e to arrive! After 3 4l70e failures in my TBSS, I'm hoping this is finally the answer!!!

Thanks for a great writeup here.

 

Very good info!

 

Also, typical customer tends to do the following:
- neglects to flush the cooler and lines before installing trans;
- fails to understand the external cooler and mis-installs it;
- neglects to replace worn trans/motor mounts, cooler hoses, shift linkage, u-joints;
- neglects to ensure engine is running without problems (misfire, DTC, overheating, tuning).

 

can you elaborate? Are you referring to orientation?

 

Examples: where there is lack of airflow, behind other core(s), in a manner that traps air (see B&M instructions for example), using unsuitable hose, letting hose rub on chassis, before the in-radiator cooler (if using it), other.

 

Sticky!!

 

very informative post

 

Hey Jake- can you discuss the correct way to verify that a transmission dipstick measures correctly?

 

It's in a lot of threads.
What I got was remove pan and verify hot fill line above pan rail by 1/8 to 1/4"
If it's below, mark dipstick with correct level and remove and scribe it.
Also, make sure car is level when you check level.
My Nova sits kinda stinkbug'ish and I pull my car up on the apron of my garage to level it out.

 

I've been in the transmission business for about 30+ yrs. About the fluid level and people "asking how much fluid does it take". It might be helpfull to write in the bellhousing...like 4L60 stock take 11.5-12.5 QTs,<--- depending on converter, With a aftermarket it might be less. Anyway you get the idea.If you provide the converter and unit together then you know how much it should hold,just write 10-12 qts or whatever on the tag/BH and that will add a little info to the buyer and maybe less-en the phone call you receive.
Just my2c

 

2 toe, I would caution against ever giving a customer a specific amount and ALWAYS have them double check the accuracy of the dipstick, and then the installer needs to check the level BEFORE the first road test (we over-fill at least 1/2 qt. over the full mark before the first road test), and then double check and top off AFTER the first road test.

When you give a customer a specific amount to put in-that amount may not account for the fact he has eliminated a factory cooler, or gone to a massively over-sized external cooler, or gone to an 8" converter when the factory required a 12"-and much more fluid. If you tell a customer a specific amount he may put just that amount in when his situation may require much more fluid, or even much less fluid, than you have instructed him to put in. If you give a customer a rope to hang you-the builder-with he most likely will do it every single time without fail.

I like the theme of Jake's post. He wanted it to be obvious that many times we the builders are responsible for internal transmission issues. However, when customers choose to do their own installs, or have their "brother", or "friend", or anyone else do the install for them, problems arise from mistakes that are made and customers are ALWAYS going to call and bitch the shop/builder out when it is NOT ALWAYS their fault.

When it comes to fluid level, only the installer at the time of trans install can be sure that it is properly filled. It is NEVER the builders fault when damage to the unit arises from improperly filled units-though the customers DO NOT EVER WANT TO HEAR THAT and they will always expect you to pay to fix their mistakes. How do shops account for this? They factor in a higher cost for the unit to cover these types of issues. So when people ask why automatic transmission work costs so much.. well, that's a part of it.

 

If the dipstick is known/assumed to be accurate, as a quick starting point, I recommend filling the trans WITH THE ENGINE OFF until the dipstick reads 1" above Full.
This is especially useful after a trans swap/rebuild or even after dropping the pan.
This will get you in the ball park, safe to start and probably only a quart or two low.
EDIT: Note Jake's comment below that the car should not be driven even one quart low and certainly not WOT until you are sure the level is correct.

Once the engine starts, the pump will fill the rest of the trans and converter and pull the level down.
The final level should be checked with the engine running and trans at operating temperature.

BTW - I plan to make this thread a sticky. Therefore while informational posts are welcome, please don't ask for help with specific problems as I will delete them.
Instead start a new thread which every member is welcome to do.

 

Someone who gets it...
If you tell a customer it takes 10-11 qts, half will dump the whole amount in, half will leak out the vent onto the ground.
Then they will call mad because their new trans leaks.
Some will never check it.

THERE IS A REASON THERE IS A DIPSTICK.

​​​​​​The dipstick MUST be checked for all performance installations. You are expecting the trans to work beyond normal limits, it requires beyond normal install procedures.

The advice above is obviously given by someone doing stock rebuilds. It DOESN'T apply.

And he other advice of driving before checking fill and it's OK to drive 1-2 qts low...Bad plan.
So what happens when you tell the customer to go down the road 1/4 mile and back EASY. Of course they will have it on blast, come back with already compromised clutch packs on a new build. Guess who's fault that is?
Theirs for not following simple instructions. I charge them full price to repair it.

It's not an engine, it will NOT tolerate low fluid level.

 

Thanks for updating your thread Jake.
I see my mistake of implying that it is OK to drive 2 quarts down, when obviously it is not.
I will change that to say it is safe to start the car and let it warm up so that the real level can be checked. Don't want to start the engine with a way low or way overflowed trans.
Correct me if this is wrong, but isn't a measurement of 1" over full with the engine off going to be very close to exactly right? Although it probably depends upon the size of the converter.

 

Also add: do not drive vehicle if trans is leaking fluid.