Making an A650 Transmission Survive on the Cheap – Part 3

Alright, so, we’ve talked about it and the theories behind how it works.  Now for some show and tell.


When you first remove the transmission pan, this is the first parts you see.  The grey thing in the middle is the screen.  Used to call it a filter, but it really doesn’t work that way anymore.  Circled in yellow is the pressure setting.  In this picture, it is turned up all the way.  It is normally in the middle setting.  To adjust, simply push in and turn.


Just a view without the filter or wiring in place.


This ball and the plastic piece / spring that comes with it is pretty important.  Make sure it goes back in.


Just a shot of the accumulators.



Here is a shot of all of the springs and accumulators and where they go.  Also pictured are my home made shims.

For the hard data, here is what you need to know.  I personally shimmed mine 12mm – yellow, 12mm – red, 15mm – green and 15mm – blue.  These shims were acceptable for daily driving with much firmer than stock shifts but not clunking in to gear.  Now that I’ve learned a lot more about these transmissions recently, I might have some ideas to make them more reliable still.  Also, it is very important to install the shims inside the aluminum pistons, not in the cylinder itself – doing this would block the fluid holes in the bottom.

Update: 5/12/2018, a couple local friends have documented this on video with some clarification as well:

RaceCar and Chill

IS300 Turbo Build

Update 6/2020:  A fellow IS300 owner started selling these shim kits – they aren’t the limiting rods that are bad, in fact these are a good replacement for your standard coins / washer tricks.

Here’s the link he provided:
disclaimer: I have not used them, but they appear to be the right thing!

16 thoughts on “Making an A650 Transmission Survive on the Cheap – Part 3”

  1. So basically, install coolers, turn the pressure control up, shim the springs, and do not replace the rods in the accumulators?

    By the way, I stumbled across your site somehow and I am very glad I did. You have amazing information, thank you for sharing.

  2. Great bunch on info here guys, well done! i am going to give this a try in a couple of weeks, looking forward to the results! 🙂

  3. Would you please post a picture from a side view of where to put the money/shims inside the aluminum pistons in accordance to the springs? Much appreciated

  4. I just did this on my is300, the shifts while cruiser are firmer but not to point where it’s uncomfortable you’ll barely feel it shift, but from what I saw is when shifting at full throttle it seems like it could use more shims to shift a bit quicker and the transmission over all just feels tighter. All in all for what it cost in change laying around it’s a great upgrade. One thing to note if your doing this in the car I would recommend having someone there to help put everything back in so one person can hold the accumulators in and the other to start a couple of the bolts to hold the valve body up . That’s for sharing, and I’m looking forward to know how to make this tranny even more reliable

  5. I can barely get the accumulators in,let alone hold them, in order to install the valve body,and I’ve turned up the transmission upside-down.
    Am I doing something wrong or is it just a bit harder to install accumulators because of spring pressure.

  6. None of your kits work because it’s the wrong kit. Sorry I am a tech and I have the right setup in and it work wonderfully. This design put pressure on the spring at all times as you see it pushing the shim way too far out, also putting too much pressure on the valve body itself. The correct kit are thin rods that go inside of the spring slightly shorter leaving no pressure on the spring or valve body at rest, but not allowing the spring to fully depress during shift.( i cherp 3rd on command)it’s hard to find somebody that can make these for you but they are very easy to make try SRT stage 1 VB upgrade rods. Best upgrade to a auto is300. DIY – Measure the spring per accumulator and cut a rod that fits inside the spring 2-3mm shorter. 2 for race 3 for street. Use stainless or hight grade aluminum, My first set was cheap aluminum and flattened after 2yr. They are under much pressure. Good luck gentlemen it’s worth it.

    1. You want to use steel because the aluminum rods got smashed? What do you think is going to happen to the aluminum case. Using those rods is like hitting the inside of your valve body with a hammer and chisel over and over again.

  7. Ps. Only do the 3 that are together. Idk what that yellow solo accumulator is. That solo one was not included in the kit or instructions. ??? Just saying mine works fine that way. You do you

    1. Those rods are the worst thing you can do to a transmission.

      The accumulator needs to be able to move more than a few mm – by keeping the spring in place and tightening it up, you still allow more movement (good) while making it react faster and harder.

      That slamming gears is what breaks these fragile transmissions.

      You being a tech means ZERO if you don’t understand how this stuff works.

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