trhardy

Can I replace the Boost Valve on a 4L60E transmission with Tag ID#7KLD172S
by just removing the Transmision Oil pan?

The reason I am asking is this has the Speed Sensor, and I read somewhere that the transmission needs to come because of it.

This is on a 2007 GMC Yukon XL

The reverse is slow to engage, (~10-15sec) but not all of the time. Sometimes it works just fine. Cold weather (0'F) seems to make if slow more often, but not always.

Other gears seems to shift fine, just the reverse is a little flaky.

I heard that changing out the boost valve might be the fix.

Thanks
Tony

trhardy

Also, I was getting an Oil Pressure gauge delivered, and was going to see what the Test port is telling me. I heard that the Reverse Pressure should be around 200psi and any thing under 130psi is bad...

mrvedit

You are correct that the pressure in Reverse should be close to 200, although I've seen reports of only about 170 psi. Still this is much higher than the typical 60-75 in Drive at idle.
I don't know if there is a trick to removing the boost valve on a trans with ISS (Input Speed Sensor). Hopefully one of the pros here knows.

Kawabuggy

iTrader: (1)

I don't think you will be able to do this. I have never tried it though as we usually have the transmission out on the bench for work. The ISS electrical connector is what will be in the way. It is only held in place with a metal clip. I'm not sure if there is enough space to push the connector out of the way as it will most likely be up against the case.

If it is an intermittent problem, you might want to just let it ride. If you attempt the pressure test, you will have to get lucky and have it delay while you have the gauge hooked up. Otherwise you probably won't see anything askew with the readings.

mrvedit

Darn, I was hoping one of the pros would have a trick to removing the boost valve from an ISS trans. When I first installed my 2010 4l60e (before rebuilding it with better internals), to get to the boost valve, I ripped out the ISS wiring because my 411 PCM doesn't support or need ISS.

While an intermittent problem is possible, the pressure gauge is always a very useful tool for checking that the Pressure Control Solenoid, boost valve and PCM/tune are all working correctly. And that that TPS and MAF are properly modulating the pressure.