Prepare The 5H24 Transmission In Your 840i BMW For Racing

Posted by on Wednesday, January 22nd, 2014

The 5HP24 is a five-speed automatic transmission made by the ZF Corporation. It is very similar in design to the 5HP24A. The 5HP24 was first used in 1996 and remains in production today. It was used in many popular makes and models, including the BMW 540i, the Jaguar Vanden Plas, the Ranger Rover, the Audi A8 and the Volkswagen Phaeton. It was also used in the very popular 840i.

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BMW 8-Series image from

The 840i is a very cool car. When it first came out it looked way ahead of its time. It even looked a little exotic. They were fast – very fast.  As the cars aged, they became more affordable to enthusiasts, especially those looking for an affordable car to go racing with. The 840i fit that bill perfectly.

Many BMW Clubs hold racing events around the country. Cars can reach speeds over 150 mph. Racing can be very hard on a car and all its systems, especially the automatic transmission. Let’s take a look at a couple of things you can do to protect the 5HP24 transmission in your BMW 840i.

The biggest issue you are going to have to deal with is excessive transmission temperatures. The 5HP24 is designed to operate at a maximum temperature of around 200 degrees. For every 20 degrees you go above that limit, you greatly risk cutting the life expectancy by a factor of two. You need to do everything you can to prevent exposing your transmission to overheating conditions.


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The best way to rid your 5HP24 transmission of excessive heat is to install a performance aftermarket transmission cooler. Most transmission coolers are made to be a universal fit. They come in many different shapes and sizes. There are literally 100’s of different options available to you.

Ideally you want to choose the largest transmission cooler that will fit your 840i.  Be sure to mount it in a location that will see maximum airflow when the vehicle is in motion. For the maximum cooling benefit, mount cooler in cooler line exiting the factory cooler.

Another recommendation is to swap out your organic oil based transmission fluid for a synthetic fluid. Organic fluid will start to break down and turn to varnish at temperatures as low as 240 degrees. Synthetic fluid will not. Likewise, in extreme cold conditions, organic fluid will start to thicken up like honey. That is not the case for synthetic fluids.

Eventually, due to high mileage or abuse, you will be faced with a decision to replace the 5HP24 transmission in your BMW 840i. I highly recommend going with a re-manufactured transmission over one that was simply rebuilt. A re-manufactured transmission comes with a much better warranty; three years compared to an average 90 days for a rebuilt transmission. In the rare event that you need to contact the company that re-manufactures transmissions, they are just a quick phone call or email away!

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