Sonnax VB boost valve kits for 5R55E

[Wrench]

I see that there are two versions of the VB boost valve - OEM and an increased ratio. When the description for the boost v/v says that it improves line pressure rise, what exactly is happening. Why would you use the increased ratio version?
Also I notice that an o-ring end plug kit is offered for certain VB ports. I was wondering if you put the sealed end plugs in you might be cutting off the flushing effect that minor leakage might create, cause the port to become contaminated prematurely and destroy the bore/spool. When would you use this kit?

 

[BrooklynBay]

The increased ratio boost valve is for a few extra PSI of pressure. The 3.0L uses the OEM version, and the 4.0L uses the one with the extra boost. You could use the extra boost on the 3.0L too, but the shifts are a little firmer with the added pressure. The OEM version doesn't have O rings. The other version has O rings. It is supposed to make a tighter fit to avoid excessive leakage. I once called Sonnax for this information. The O ring end plug kit is for decreasing leakage on the bores. This should improve the shift times to make them more responsive.

 

[pj8847]

The OEM version is supposed to correct soft shifts and low pressure in reverse. Basically it fixes a worn out stock part.

The increased ratio version does exactly that, increases the line pressure, which can eliminate delayed engagement and/or allow for more positive shifts.

The end plug kit is great, as it stops leakage past the plug, which is not supposed to happen, as that can cause all kinds of problems with pressure loss, shift problems and slipping, etc... You can use this kit if you find that the bore plugs are loose/worn in the VB, or just as a preventative step so that problems such as those don't occur.

 

[Glacier991]

BB is correct. As a VB ages, there is increasing pressure loss through blow-by.. in many areas. Aftermarket kits are designed usually to reduce or address problems in known high wear blow-by areas, and in the case of the High Ratio boost valve, increase pressure to compensate more generally.

 

[Wrench]

Thanks for the replies. Any idea what the cracking pressure for the EPC blow-off valve kit is set at?

 

[Glacier991]

Don't take this as gospel, but I think it is around 135 PSI.