Aisin Warner AW55-50SN and AW55-51SN Transmissions

Aisin Warner / Graziano A/T

Japanese Aisin Seiki – American Borg–Warner

The Aisin Warner AW55-50SN and AW55-51SN automatic gearboxes are used in a wide array of motor vehicles on the roads today and gauging by the amount of complaints they should never have been manufactured or at least they should have been replaced by a better gearbox. That’s how the story goes in any event. Truth of the matter is that these gearboxes are plentiful and because of their popularity they would reflect as having a high failure rate but the true test is how many have been manufactured versus failure rate.


Aisin Warner / Graziano A/T
Graziano Transmission – ZF 6 gear automatic gearbox 6HP-28A with integrated, electronic all wheel allocator for cars.
By Stratos L –, CC BY-SA 1.0

General motors have also used the Aisin Warner AW55 series under their naming code AF33 which is identical, also a trans axle designed to drive the front wheels. Whatever naming convention is used,  AF23/33-5, FA57, SU1 or RE5F22A the reliability of these gearboxes has been more often than not taken a beating from car owners because of solenoid failure and usually expensive repair. Many auto technicians do not like computerised gearboxes and will refer the owner to a specialised repair center. Although the internet is full of DIYers completing successful repairs on the valve body it is ill advised to dive into the electronics or mechanical aspects of these gearboxes unless one has a full understanding of their inner workings and has the specialised tools.  It is generally accepted that certain malfunctions can leave one stranded but the more cautious of us will be aware that a faulty gearbox can be dangerous.

I came across this little nugget during the course of the week whilst looking for common problems with these gearboxes which just makes one think how many other gems we miss by not doing a proper search: The AF33 Is A Common Transmission That All Shop Owners Should Learn About. GM technical training on the AF33-5 is listed on the site.

Tech Files:  AW55-50SN

AW55-50SN/AW55-51SN  (from our friends in Russia, the ATSG service manual)

Do you have a personal favourite company specialising in gearboxes, engines, suspension, clutches and brakes? Please use Business Entry to add the company.  You will do all of us a favour. You will need to be registered or logged in.

Please add your experiences with the Aisin Warner gearboxes under comments.

Oh yes, why are Volvo resale prices so cheap?  Is your Volvo hard-shifting?





Racing engines – gas to electric


Noisy engines versus silence in a Formula E

A question recently posed by a colleague in our electronics prevalent industry was in which direction motor racing was going with the current V6 technology in formula one as opposed to the formula-E which many technologists believe is the future. From a personal belief I would rather never want to see internal combustion engines disappear off the race track which I see as akin to the disappearance of two stroke racers. Sure they may not have been green but wonders just how much of a pickle we would be sitting in if there was proper population control.

Electric engines - the Tesla S Tesla Model S – hugely popular in the USA.

By free photos & art –

Electric versus ICE

Well as luck would have it Le Mans is going to see some exciting stuff from Nissan this year, a car with a 1.5L 400HP engine known as the DIG-TR delivering 380Nm of torque.  What is more spectacular is that it delivers this power with only three cylinders and weighs in at less than 100 pounds. The car, known as the ZEOD RC will do one lap on only electrical power and thereafter powered by the DIG-TR. Some awesome pictures here at Asphalt and Rubber.

Electric motors have been around for longer than any internal combustion engine and the inner workings have remained almost the same. Their main advantage over any ICE is the mere fact that they deliver huge amounts of torque from start which makes a gearbox really not necessary. Formula E cars do have a two speed gearbox where drivers usually do a shift at over 100km/Hr.  Tesla’s motor vehicles bear testament to the torque range of these motors, spinning wheels at intersections at the push of the throttle, doing doughnuts with ease and easily attaining the magic 100 mph in a few seconds. They have a drawback however. They don’t run on petrol (gas).  They are powered usually through a multitude of Lithium Ion cells delivering a few hundred Volts at many Amperes.  Their capacity is measured in kW/Hours which sadly, although sounding immense does not equate to many hours on the race track but more in the range of a few minutes at full engine power.

Limitations of the Electric Propulsion Induction/Brushless Engine

Petrol (gas) engines run for as long as the fuel supply is present, they are quick to refuel and still carry man to the ton in a few seconds. Formula E racers have two drivers and two cars per driver per team.  Even with two cars the teams are at the mercy of the battery bank. The electronics we believe is stable and reliable. Likewise the engines. The excitement will possibly be likened to that of owning your first Scalectrix set with the same sounds and smells. Possibly not in the rubber burning department.  The upside of this is that electronics engineers will have a lot more to do on their week-ends redesigning, cooling and doing extreme tests on brushless motors and inverter packs.

The downside to any motor sport will always be the cost. Although high speed electric motors have their place on the DIYer workbench this is not sadly the case for the fuel supply. Battery banks are horrendously expensive and the unknowns of the effects of a rapidly discharging Lithium Ion battery far outweigh that of a petrol (gas) engine making high energy battery supplies possibly more dangerous than that of a flammable fuel type.

Home tinkerers – DIY Engines and Batteries

There is a place for the home tinkerer however and that would be in the utilisation of 72V battery power through lead acid accumulators, the control circuits and brushless motors. Industry types could lay out a framework which would include chassis weight, gearboxes, differentials or multi-motor and a solid safety mechanism to prevent injury.  This may be a cue for the budding scientist to design a lightweight solution to our current affordability problem as well as pave the way to better engineering practices. Of course Tesla springs to mind – how could they leverage off this? And all the other electric vehicle manufacturers.

Looking at Nissan’s DIG-T R and Volvo’s 450HP 2L engine it is hard to believe that these internal combustion units are slowly creeping up to the power-to-weight ratio of their electric competition but there is one thing we need to bear in mind. Just how many mechanical parts are required to get this power and what is the lifespan?  That we don’t know right now but what we do know is that the simple brushless cooling fan used at home runs for years without a problem. Adding heat into the mix may cause premature breakdown but with electric motors running with ease at over 100 degrees Celsius we doubt that this will ever be a problem.

Taking the battery supply out of the equation for a few minutes one need no longer deliberate, electric powered vehicles are the way of the future and the sooner we get there the better.  My money is on the Asians, most probably the South Koreans in getting us there.



Who makes that Auto Part?

Why are my auto parts not made by Mercedes?

Damn, this is getting silly!  Almost every motorcycle or car website has a forum which complains about one specific model car (or motorcycle) which was a lemon. Either the engine or transmission is a dud. Then we have the electronics. That model “xxxx” is a piece of crap because of the high ECU failure or model “yyyy” has a known problem with solenoid B in the valve body.  Well here’s the gen:  Most car manufacturers do NOT make their own transmission, engine, electronics and even seats.  Yes, this is correct. From brake pedal rubber to lightbulbs, these can be obtained by the Original Equipment Manufacturer or OEM at a better price than at your dealer. Ever priced a headlight bulb at the dealer?  Be cautious, look at what you drive and then discover the truth about auto parts. A complaint often heard is that because you purchased a pirate part the bottom is going to fall out of your world. Well, here’s the thing – maybe, just maybe your car has always used that so called “generic” or “pirate” part.

Auto Parts - the worlds biggest supplier: Bosch
The Bosch R&D center in Abstatt, Germany, which is a major site for the development of automotive components. Work by Timo Engelmann – Wiki Commons

ZF Friedrichshafen – high end gearboxes for BMW, Land Rover and Jaguar

Years back I had a Kawasaki 750 twin which unfortunately through stupidity on my part ended up with a damaged voltage regulator. I ended up purchasing through Toyota a Volvo ( yep! ) regulator which worked just fine.  This regulator cost me at the time about 6 US dollars.  (in the 1980s)!  The same Kawasaki part was offered to me at 150 dollars.  Interestingly enough this was not even a Kawasaki part and I really don’t recall the manufacturer except this was a blatant rip-off.  Then we move on to Lucas, the Prince of Darkness and the butt of many other jokes e.g. “get home before it’s dark” and inventor of the intermittent wiper. Lucas was in fact a very proud and able manufacturer and the many experienced technical resources complain more about lack of maintenance causing issues than anything else. Having owned a Morris Minor 1000cc as a kid I do recall the pathetic cotton insulation covering wires and harness (and the positive earth). But yet all electronics had cotton insulation for everything, just look at the old valve/tube radios.  An article I recently read covered the imbecilic generator which used commutator brushes which wore out. I wonder whether the author is aware of slip-rings in alternators and that they also wear out.

Can modern cars handle a reverse polarisation (battery in the wrong way) as wonderfully as the older vehicles. Definitely not! If there was damage it could be quickly and cheaply put on the road again. Modern vehicles use semiconductors and if there is no way to shunt the reverse polarised battery to ground through protection circuits and blow a multitude of fuses you are in for a very, very costly wake up call. So Morris Minors may have had a bad rap but first look at the power distribution system maintenance before pissing all over your Lucas.

In THE dreaded situation of having the gearbox fail on you don’t be quick to blame your auto manufacturer, have a look at the maintenance on the vehicle. Some cars look really neat on the outside but positively suck once you get to the suspension, engine or gearbox. Some DIYer types just bypass the radiator / cooler for transmission with an external cooler. They have proven NOT to be reliable and cost some to replace, costing even more once there is water ingress into the transmission.  Here we can quite easily blame the manufacturer.  There is plenty of BS floating about pointing fingers to lack of maintenance but truth be told we also know of just too many car owners that did go through the full maintenance and warranty process only to find themselves out of pocket when things went belly up.  The shame here is that the manufacturer did decide to go with the combi radiator/transmission cooler. The negative side here is that to date we still continue with this process. Older sedans never had this problem. So Aisin Warner, GM and many others should not always be blamed for a shoddy product but rather chastised for keeping quiet. Oh yes, just read about CVT transmissions now, transmissions fast on to the market with possibly too little research into durability.

Will an automatic transmission last if left in the sun or your dog pisses on it?

In a recent article the technical writer come author talks of traffic congestion being the biggest cause of premature transmission failure through overheating. Some gurus will tell you to put the car into park whilst idling in heavy traffic. But we read about lack of lubrication whilst in Park. We also read about putting the transmission in Neutral because of the extra wear on brakes etc whilst in Drive. And finally we settle on keeping the car in Drive with parking brake up. What does the manufacturer state?  I have looked high and low and there seems to be a lot of misguided information out there. What I can say is that if in Park and a car rear ends your vehicle you will have a serious problem with the gearbox afterwards – parking pawl breaking etc. In Neutral which is where you would be in a manual shift there will be no damage to the gear train. In Drive, your car is always edging forward so the result may be even more devastating. All logic tells me that the vehicle should be in Neutral. Yet drivers through the ages will recommend to always leave in Drive, it causes less wear and tear. Hoo Boy! So back to square one, what does the manufacturer recommend and not the vehicle manufacturer?

Next comes your fluid changes. ATF should be changed every 15 000 miles, some say 30 000 miles and the car manufacturer recommends that the fluid should never be flushed or changed – it is sealed for life. What does the manufacturer state? Not the car manufacturer.

Car engines nowadays are remarkably resilient. I have heard that the older Opel Astra models have a problem with the oil filter – now this is an interesting one. A mechanic told me they just drop off and the engine seizes. What the…..  I have never read about this idiosyncrasy. Surely there is a Haynes manual for these vehicles?  There is of course a bigger problem – hearsay.  I know two mechanics, one is a Ford lover and the other, VW. Do you too? Listen to why the one hates the other. Like politics and religion there is just no stopping mechanics when they get together unless they both work for the same company. But not always. Personally I find both VW and Ford both very good companies with great cars. Just sometimes they bring out something which makes us wonder what the design team were smoking. And at what price to you.

Why expensive cars die but never roll over (or stay on the highway for long)

Problem after problem after problem. Nobody likes the unnecessary stress of being caught in traffic with a dead car. Yet we have all seen it countless times. In my experience these are almost always Audio, Mercedes and BMWs, all cars I’d love to own. And they all look new. (don’t forget the Volvo). So where to from here? – these cars cost a lot and they are expensive to repair. Road side assist for expensive cars but never entry level. I have never seen a Polo on the side of the road.

Blogging on auto parts

As this is purely a blog and most probably a highly opinionated one at that I do feel that manufacturers and car owners should take a strong stand about where their priorities lie. I’d rather have a cheap reliable car than one which boasts all the bells and whistles which falls over at the drop of a hat. Sure, fuel economy is important but not more important than losing 5 000 dollars through some shoddy design work on a car which impresses the neighbours. When one starts paying upwards of $50 000 for a trophy on wheels we expect it to do 350 000 miles with regular maintenance. This is not happening. When we do buy a 4 wheeler, especially, we do need to know where the engine and transmission is manufactured and their specifications given to us, not the manufacturer of the car. We need to have access to these parts and spares. We need to know what they expect from us. As a driver and owner of a car I expect manufacturers of both the OEM parts and vehicle to be in touch with us via email and not only through the dealership when there is a recall. There’s just too many cover-ups taking place leaving owners out of pocket.

Just as  motherboard manufacturer will not build their own capacitors the same is true of your vehicle. The ECU was not made by Volkswagen. The heater fan motor was not built nor designed by Mercedes. The brake rotors and pads do not come from Volvo or Ford. There needs to much more transparency. BS to the person that says makings too much transparency is leading to confusion and misguiding the public. Tom’s Hardware makes users more informed and critical of what they buy. Our goal is to do the same.

For many, auto part resellers are just another cog in the trasnmission. They aren’t – getting the right part every time and knowing where else these are used will go a long way to see just how much we are being ripped off.


Breaking the bank for an Automatic Gearbox

Automatic Transmision 8 Speed

Automatic Gearboxes – are they really all that unreliable?

There has been a lot of controversy surrounding the reliability of automatic transmissions over the last five years, not least the semi or manual automatic. In a survey done of the numerous forums covering the steady migration of drivers over to automatically assisted drive trains in all make of vehicles one thing becomes abundantly clear:  Are manufacturers really doing us all a favour by computerising their transmissions?


Automatic Transmission 8 Speed gearbox
By Ritchyblack – Stefan Krause – Own work, CC BY 3.0,

Most drivers in Europe, Australia and Africa have one thing in common and that is their preference for manuals or stick shift. Whilst drivers in the USA have never felt the need to have stick shift thrown at them a lot must also be said for their vast open spaces – akin to Australia roads perhaps? Lazy driving doesn’t always point to roads with less sharp corners and cheaper gas. Modern manufacture has veered in the direction of computerisation, better shifting, lower emissions, faster acceleration and a smaller gas bill.  But at what cost to the owner?

Manual shift has long been the favourite of racing drivers and those wanting to have control over their vehicle. Manual shifts are also cheaper and gauging by the user forums, a lot more reliable. And here is the topic of the conversation – almost every forum is going to have someone whom will never buy a specific vehicle again because of the automatic transmission. Always at a ridiculous cost! Now this is interesting because there aren’t that many manufacturers designing and building their own trannies. Aisin Warner is one of the most commonly used transmissions on the market but it gets a bad rap. GM likewise. Yet some forums claim them to be the best. VW the worst? Some claim the VW direct shift to be the best. Honda is bad, Honda is good! We can rattle on and on but here we need to come into this with an open mind.

Gearbox Abuse

The best transmission is the one that will handle abuse over as many years as you like and not fail. Manual transmissions can do this. I’ll stick my head out here and say straight off that an automatic gearbox is not a dandelion. It can handle plenty of hard riding and will not fall over but NEVER load it beyond manufacturer spec. Likewise manual transmissions. Three out of three people I know having damaged their transmission which was caused by doing stupid things – driving over sand dunes, pulling a tree out of the yard and driving through the sea. But there is another gremlin at work – the cooler.

The Grim Reaper:  Water/ATF combination

The radiator and transmission cooler often sit in the same frame and corrosion through the separator causes the higher pressure water to flow and mix with the ATF in the cooler. If caught in time your transmission can be rescued but sadly this seldom happens. It is the death knell of the transmission – the small ingress of water is sufficient to damage the friction material used in the bands and clutches, moreover dissolving the adhesives used in the bonding process of clutches and brake bands. The higher running temperatures cause the water to boil off causing damage to bearings and seals as well. Although there have been cases where the auto technician has managed to salvage the gearbox through a total flush manufacturers will tell you the bad news, that the transmision is going to break down possibly even a few months from the flush. And this will be a costly repair. Is this fair to the owner of the vehicle?

To answer the above question one needs to see what the average Joe DIYer does to prevent this problem again, indeed often doing this as soon as the vehicle is out of warranty. He will put an aftermarket cooling system which is completely isolated. One would think this is common sense. I know of Volvo and BMW owners that sat with $3 000.00 repair bills. This DIY remedy cost 200 dollars. The forums are full of drivers or vehicle owners which succumbed to the dreaded water/ATF mix, 99% of them had to redo their transmissions.

Older kit

In the early 80s I purchased a Rover SD 2600 (1977 vintage I think).  The car cost me about 350  dollars and did about 150 000 miles with only the engine being serviced. I forgot completely about the gearbox except to top the fluid up on occasion. The gist of this story is what many forum users are complaining about – modern automatics aren’t as reliable as their older sibs. With modern technology one would think this would be the other way round. Gearboxes are just not making the same age as the engine.

Maybe it’s time to go back to the drawing board?

Some Do’s

Always inspect and change fluid every 30 000 miles. (minimum)

Manufacturer claims to have a sealed for life gearbox is for warranty purposes only. It also prevents you from putting the incorrect fluid into the box.

Burnt fluid does not mean a damaged transmission – but do replace it immediately.

Fluid or ATF as it is more commonly known is not always a pink colour. Read up on the fluid type.

Always use the right fluid – given by the manufacturer and/or hopefully owner’s manual.

Always get a second opinion – the web is full of stories which will put you off auto trans “experts” for life.

And the eye opener of the year – read up about why auto technicians sometimes shouldn’t even work on a wheelbarrow – the 2002 Volvo XC70 which shot it’s bolt……
Some interesting videos

Understanding the basics of automatic transmissions, solenoid hydraulic fluid control, drive train and how your gearbox interacts with the engine and driver. Links to top websites or videos are below.

Planetary Gear Set Operation – Automatic Transmission

This planetary gear set operation video edited by John D. Kelly at Weber State University is a true classic. Much of what is seen on You Tube with regard to auto transmissions is either covered by a person that is also clueless or the video footage is weak. Here we have both a strong classroom lecture as well as exceptional footage. Thank you!

Automatic Transmission – Basic hydraulic flow (Weber State University)

Torque Converter Operation and Components – (Weber State University) – tutorials and section quiz