FAO Autobox Gurus - Cleaning Governer valve on ZF 4HP22

[ChasR]

As above. How does one go about cleaning the governer valve in a ZF 4HP22 transmission? I understand that a number of people have cleaned these but little reference has been given to the procedure in addition to where the valve is located.

So, surely one of you techies must know .

[Llewelyn_]

I don't know but these links might help?

www.makcotransmissionparts.com/ZF4HP22.html

www.makcotransmissionparts.com/mm5/graphics/Catalog-pdf/ZF4HP22.pdf

[squonk]

It is generally thought that if the governor valve is sticking at least one of the clutches is breaking up. This will also contaminate the torque convertor so that will also have to be replaced. Hence its a bit pointless just trying to clean out the governor as the problem will still come back after a short while. I have had two of these fail on Range Rovers and had no success in trying to fix either. Incidentally, similar symptoms are also caused by the sprag clutch flipping so you may be chasing the wrong thing anyway.

From Ashcroft Transmissions web site:

A common problem with all ZF 4HP22/24 boxes is the failure of the one way "sprag" clutch. Once the cams in this one way sprag clutch "flip" the unit will slip both ways resulting in the vehicle only pulling off with the shifter in position "1" not "D" and driving OK when shifted up to position 2,3 and D until you stop then you need to pull it back to "1" to start off again. It is not feasible to change this unit in each rebuild as this one part is approx £400. By disassembling the "sealed unit" we were able to examine the profile of the cams and understand how they work, from here the challenge was to find another cam from another type of autobox that would fit and had the correct profile to make the unit stronger by not allowing the cams to flip. After quite a lot of searching we found one, "re-cammed" some of these clutches and thoroughly tested them, we have not had one fail since. This is an example of how we are able to use our engineering background to understand a problem and cost effectively make the unit stronger without having to raise our prices.

[ChasR]

The gearbox itself is rebuilt, but it was rebuilt a couple of years ago. I am hoping that it may be some stray dirt but I cannot say for sure.

The problem I am having is that the car will hold 1st gear until it warms up. Driving it first thing is an absolute pain with me having to pull over (unless I fancy a queue of traffic behind me LOL).