zf8 and 8hp70/8hp90 transmissions

Unless you have been living under a rock for the past 15 years you have probably heard about the latest ZF8 or 8hp90 transmissions. These transmissions are making waves throughout the racing scene due to a multitude of factors that i would like to point out on this page and potentially direct people with build ideas as to the correct transmission for the application they are looking to build.

First off the zf8 is a very prevalent transmission, used in a multitude of BMW, Audi and Dodge (cars and trucks), this makes them very cheap and easy to source parts for. For the most part the internal parts are almost all the same between the BMW and Dodge counterparts making the parts also extremely easy to come by. The BMW has a smaller bellhousing making it a hot swap item in the hot rod and drift community, while retaining all of the original strength of the transmission. The dodge (AKA 8hp70/8hp90) has the original dodge v8 bellhousing pattern and will bolt right up to your original 318/340 from the 1960's all the way to todays 2023 6.4 hemi.

The ZF8 is a very reliable, and tough transmission with a huge cult following, specifically in the drifting and road racing area. This is because it has the capability of a virtual clutch, basically a potentiometer attached to a fake clutch pedal that allows the driver to engage one clutch in the selected gear in order to "clutch kick" the transmission while at speed, basically a neutral drop or a clutch drop on a manual trans while remaining in the selected gear.

The good:
The ZF8 has a very high HP ceiling, and in stock form many people have pushed it past the 700-800whp mark for long periods of time and still lived to tell the tale. And unlike alot of other 4 speed transmissions such as the 4l80 and 4l60, the zf8 does not have the high rpm issues that plague the TH400/TH350 style transmissions with a factory rated RPM of 7000+ rpm.

Due to this transmissions prevalance it also has gained an "ls1" like following, shops are making adapter plates from the zf8, to all sorts of engines such as the k20 to zf8 adapters, 2jz to zf8, ls1 to zf8 and so on.

The bad: 

Depending on your build this may be considered a con, or it may not matter at all. Similar to the ford 10r80 the zf8 has a fixed output shaft requiring the driveshaft to be either fixed such as an independent rear suspension setup with a fixed rear differential. Or a slip yoke added to the driveshaft (high hp rating = $$$). While this is not the end of the world it is a consideration since the price of these slip yoke style driveshafts have gone up substantially in recent years.

The output flange of the zf8 (or dodge 8hp70) is different on each transmission, and each one has a different output flange and bolt style. The BMW has a 3 bolt "guibo" flex disc flange that domiworks has created a 3 bolt to 4 bolt adapter plate which you can then bolt a 1350 style 4 bolt flange to. For the dodge 8hp70 and 8hp90 applications it depends on if you have a car or truck 8hp70, the car transmission has a different yoke bolt pattern and it sits back about an additional 2 inches, where as the truck flange is a 4 bolt flange and is much shorter (see pictures for details). The transmission mounting points on the rear of the transmission are also different for some reason by about 6mm on the top bolts.

This transmission requries a sophisticated controller to properly control the valve body (aka "mechatronics unit") inside of the transmission oil pan. From the factory the zf8 has a similar internal transmission controller to the 6l80e which is self contained within the transmission valve body and communicates with the PCM over can bus. There are a couple of companies (specifically CanTCU) that are working on implementing strategies to control the original TCU over canbus by emulating the original system however it seems rather limited and not the best for racing applications. 

So whats the best option? rip out the original TCU, solder in a PCB board to bypass it and provide direct access to the solenoids to allow an external computer to directly actuate and control the valve body directly. This is the primary way that all true "racing" transmission controllers control this trans. Thankfully the 10l80 and 10r80 from ford and gm decided to do away with the internal TCU and mounted an external controller, but this is something to keep in mind and you can check out the conversion procedure on the HTG-tuning.com website.

There are four major companies currently that are controlling the zf8 transmission, CanTCU, HTG-tuning, TurboLamik and German Sound Automotive. Of those four, German sound and CanTCU are the most "plug and play" of them, while Turbo Lamik and HTG tuning are definitely more advanced.
 

Truck shown on top, Car shown on bottom Dodge 8hp70