What you are supposed to know about your ZF6HP26, 6HP19, 6HP28 and similar ford Transmissions.

It applies to all BMW, Jaguar, Bentley, Rolls Royce, Maserati, Audi and others with ZF 6HP26, 6HP19, 6HP28

In this post i will be explaining why you have transmission issues like:

-harsh shift 2-1

-not able to shift into park when hot

-weak torque feeling

-gear speed ratio faults

-other faults

All highlighted problems you can experience even on low miles cars less than 70-80k, it depends on at what speeds your car mostly runs. On the highway this tranny will easily last 200-300kmls. AND EVERYTHING IS RELATED TO VALVE BODY PRESSURE LOSS DUE TO SOLENOIDS OR ACTUAL VALVE BODY SEALING GASKETS LEAKING INSIDE, BUT BETTER DO BOTH. DRIVING WITH LEAKING VALVE BODY WILL EVENTUALLY WEAR OUT ACTUAL TRANSMISSION HARDWARE.
 BEST ADVICE FOR YOU: SINCE 99% issues with this trannies are related to valve body fluid pressure loss, I strongly recommend new (re manufactured) valve body from ZF (expensive 1600$), (you can find some companies offer this rebuild, but they charge almost new VB price, or rebuild it yourself with NEW SOLENOIDS PACK (300-400$) and  SONNAX zip kit (150$). If after you rebuilt or replaced valve body and RESET ADAPTATIONS USING BMW SOFTWARE INPA OR ISTA IS A MUST, OR YOU WON’T SEE ANY DIFFERENCE AFTER REBUILT, BECAUSE TCM KNOWS VALVE BODY PRESSURE VALUES AND THEY MUST BE RESET. IF AFTER REBUILT, it’s not shifting well, it means YOU WAITED TOO LONG WITH VALVE BODY REBUILT AND DESTROYED transmission hardware (bushings or actual clutches failed) and you need to rebuild it, but like i said main problem STARTS at valve body and then if not fixed in time you get worn out transmission. All those jolts, bumps or harsh shifts cause premature wear and tear on your tranny. Rule of the thumb is not to drive it if it jerks,or shifts wrong.

replacing just solenoids without rebuilding valve body, where accumulators/pistons always go bad after 60-70k, will not get you perfect results, but might improve shifting quality. Remember-cheap people usually pay twice (no offense).

So you hate the way tranny shifts and dealer and other shops didn’t find any faults and told youit is what it is and this is how it is intended to work! Well it is total lie they are trying to get rid of you with.

In fact ZF 6HP26 6hp19, 6hp28 is a very good transmission, powerful, bullet proof pretty much if serviced in time and proper fluid pressure maintained! This tranny is still considered one of the best and has carbon clutches vs cheap paper ones you can find on Japanese cars. But this tranny has very serious and very

important weak spots you have to take care of:

-First thing first check tranny temperatures. If it is higher than 95C, then most likely you have a problem with tranny cooling system or your engine cooling has some leaks causing running it very hot.

Usually high temps indicate following:

1) engine cooling system problem- air bauble or airlock

2) if everything is good with cooling system, check your tranny oil cooler- it gets clogged up pretty often and also indicates that some clutches or TC clutch is worn out and that debris clogged oil cooler.

3) worn out TC clutch slipping overheating transmission fluid.

Your good engine temps are 103-105C and if it climbs to 107-110C in traffic, it means you’ve got a leak :

-lower radiator hose sensor leaking (usually shows a white residue around the sensor)

-valley pan under intake

-rear cover plate between tranny and engine. Very common after 100k or 8-10yrs.

-coolant tank cracked

-radiator cap leaking pressure

-coolant pipe seal leaking

-other cooling issues

It is very important to keep temps in specs not only because of few degrees, but because with leaking

cooling system you lose coolant pressure introducing air in the system, causing uneven cooling and overheating both engine and tranny. Good OEM specs are 103-105 cycle when idling and lower hose should be hot around 60-80C. When you drive it tstat is controlled by ECU therefore it keeps it cool on the freeway.

Easy way to test your cooling system

1) Disconnect aux pump connector assuming aux pump is working (they fail often)

2) Drive your car to warm engine well

1. 1. 3. Turn on heater on hot but low speed
      4. check if you get hot air from vents for 10 minutes.
      5. If after a minute you noticed your heater is not hot anymore, it means you’ve got a leak!
      6. This Engine has self bleeding cooling system, which means you cannot get air pocket if system is well sealed.

So if engine temps are good and tranny still runs hot 100-110, it means heat exchanger is clogged with tranny clutches, TC wear and tear dirt. Replace it and check if it got better. This tranny will die quick if temps are not good.

–MECHATRONIC ADAPTER SEAL.

This adapter (number 2) usually lasts only 60-70kmls (BMW lifetime). Replace it every 60kmls even if tranny shifts well. It is very important because it keeps your mechatronic valve body under specified pressure therefore it controls how clutches are pressed! Which means if your gasket is weak your tranny clutches are not pressing well on each other causing premature wear and tear, also tranny pump and TC clutch will be affected. This square seal also can CRACK, in this case you will get tranny fail safe errors and even clutches slipping ERRORS, causing very quick TRANNY DEATH. DON’T DRIVE YOUR CAR IF YOU’RE GETTING ANY TRANNY FAULTS, EVEN AFTER RESTART TRANNY ERRORS GO AWAY FOR A WHILE, IT IS NOT A TRANNY COMPUTER GLITCH!!!

http://www.thectsc.com/products/mechatronic-seal-adapter-6hp26-6hp28-6hp32-42-52.html

YES THIS SMALL, CHEAP GASKET CAN DAMAGE YOUR TRANSMISSION PRETTY BAD.

-OTHER 4 RUBBER PIPE SEALS.

They 5,6,7 also control clutch pressure, but even if they are flattened pretty bad transmission won’t give you any errors. Its always good idea to replace it- you’ll notice a difference how your tranny shifts. Online retailers has these seals under transmission parts section.

–SOLENOID KITS. 2 TYPES

-MOST COMMON E65, YOU DON’T NEED PARKING SOLENOIDS SINCE THEY DON’T GO BAD OFTEN, SO YOU CAN USE M-SHIFT SOLENOIDS, BUT YOU CAN GET E-SHIFT PACK AS WELL, WHICH IS 200$ MORE.

http://www.thectsc.com/products/solenoid-kit-6hp19/26/32-m-shift-36-45.html

Yes they go bad and are not simple solenoids you used to know from old school trannies. Now these are pressure regulators and they do not only work open\close operation, they control pressure and after so me time they get clogged, overheat, etc. So if your tranny temps are good and your tranny shifts hard, it could be your solenoids. Its good idea to replace them every 100k, because they control everything in the tranny. You will be surprised how tranny shifts with new solenoids. And you don’t need 2 parking  solenoids, so you can use 200$ cheaper kit, which fits 5,6 series without E-SHIFT. Also dont be scared if you open your transmision and find out that color is not the same- relax it changed color because of temps and age.  There are two types of kitsAll the parts at very good prices can be found here:

http://www.thectsc.com/catalog/mechatronic-parts-52.html

-GUIBO FLEX DISC. They usually go bad after BMW lifetime period 60-70k.

Common Symptoms:

a) hard 2-1 sift

b) at stop you can hear clunking when shifting from P-R-D

c)overall tranny shifting quality

-Tranny fluid level.

Yes due to leaking oil pan gasket you might loose some fluid. Always check tranny oil pan for leaks and tranny fluid level (use BMW sealed tranny fluid level check procedure). It is always better to install metal oil pan- it never leaks and cheaper to maintain!

You can add BMW OEM PENTOSIN brand fluid or you can use MOBIL1 or CASTROL synthetic ATF fluid (10$/qt) import multi vehicle formula, believe it or not it has same specs if not better than BMW fluid and works great. Tested for 160kmls. BMW will only recommend OEM FLUID of course, but its up to you, so please do not comment here that different than OEM fluid will kill the tranny. But always make sure it has the same specs of course. Mostly Dextron 6 fluid applies  as well for this trannies.

UPDATE: TRANSMISSION RUNS MUCH BETTER WITH OEM ZF FLUID OR SHELL M1375.4 FLUIDS, SO BETTER SPEND FEW MORE BUCKS FOR CORRECT FLUID. FEBI OR ZF WILL WORK GREAT. SOME USE FORD FLUID, SINCE ITS THE SAME TRANSMISSION BUT FLUID IS MUCH CHEAPER.

-Torque converter clutch.

Yes it can go bad just like any clutch, because this tranny engages this clutch very early causing premature wear and tear. In sport mode it can engage clutch as early as at first gear!! That’s why we get decent mpg from this tranny. In other words it is more like a manual tranny with torque converter working only at very low speeds and low rpm. So I would not recommend driving it very aggressively in the city, unless you enjoy paying 4-5k for a new tranny. Don’t forget this tranny handles 300-400hp and some impressive torque. Driving in normal mode, TC can last up to 300kmls!!

most common symptoms of bad clutch:

-sometimes when clutch is very bad it will throw 1721 error clucth slip

-bad MPG. Without TC clutch your car is still driveable, but you can feel its very weak even though engine feels strong

-after 4th gear tachometer arrow is not steady

-weak pickups, downshifting when driving uphill

-bad slipping  clutch will overheat tranny pump and finally will kill internal tranny parts (clucths, valve body, seals, etc)

good news you can have your TC rebuilt for around 300$ and from personal experience i must say its not as perfect as new, but decent still.

IMPORTANT NOTE: DON’T FORGET TO RESET TRANSMISSION  ADAPTATIONS  AFTER ANY REPAIR DONE ON THE TRANSMISSION!!! IF YOU DON’T RESET IT, TRANNY WON’T SHIFT ANY BETTER BECAUSE IT REMEMBERS BAD VALUES. SOME PPL THINK PRESSING GAS PEDAL AND SAYING SOME MAGIC WORDS RESETS TRANSMISSIONS EGS ADAPTATIONS IS A TOTAL MADE UP JOKE. YOU CAN ONLY RESET IT WITH BMW SOFTWARE INPA, ISTA, AND SOME OTHER SOFTWARE SNAP ON ETC.

I know its a long list of issues, but if you take care of your tranny every 80-100kmls it pays for itself pretty good. Most important thing for this tranny is correct fluid pressure and temps, other parts like clutches are very durable and made with highest quality standard. Don’t forget the same tranny they still install on newest Bentley, Rolls Royce, Audi, Maserati and other luxury brands. This tranny is way more reliable than Mercedes one or Lexus trannies with same specs. All transmission parts you can find here  http://www.thectsc.com/catalog/6-speed-parts-113.html