lewingjr

I have a 2006 Silverado 1500 that the 3-4 clutch went bad. I rebuilt the transmission with new seals, clutches, pistons valve body, 3-4 accumulator, valve plate and torque converter.

The transmission seems to shift ok under normal driving but when I get on the throttle (1/2 or above) it seems to slip/slide into 2nd and 3rd gear. It is solid in gear and does not slip if I punch the throttle while in that gear.

I followed a video series on You tube to do the rebuild that seems pretty thorough.

I checked pressures and they are
65 PSI in Park
65 PSI in Drive
95 PSI in Reverse

When I tested the pressure while driving it was over 150 PSI when it slip/shifted.

Any thoughts?

mrvedit

The Reverse pressure is very low.
The Reverse feed line moves the boost valve and should give you more pressure than that.
Since you should drop the pan and check the boost valve, you might as well install a biggr one. The Sonnax 4L60E-LB2 (not the LB1 for your year!) would be a good choice.

Actually my choice of the -LB2 assumes your 2006 has the later-style pump. Look at the Sonnax instructions to be sure:
http://www.sonnax.com/parts/2169#tabs1-instructions

severancej

The boost valve is in the pump and is a commonly worn item correct?

I am using that same transmission bench video series on YouTube. It does seem thorough.

mrvedit

I don't have the experience to answer that, but the Sonnax boost valve has 2 o-rings to ensure good sealing even if the bore is worn. Transgo also makes a .500 boost valve but it does not have the o-rings, hence I think the Sonnax is better especially in a trans with many miles.

Thinking about my previous comment about the -LB1 versus -LB2 boost valve, if you put the -LB2 into an older trans, you would have very low boost pressure. '06 is also a confusing year as it seems some vehicles still have the older style non-ISS pump while many vehicles have the newer ISS (Input Speed Sensor) pump which takes the shorter -LB2 boost valve. I also suspect that some 4L60E were made with the new-style pump but with the ISS left out.

In any case it is critical to know whether you have the old-style pump or the new style. The old style pump is round in the area of the boost valve; the new style pump has a square cutout in the area of the boost valve.
Use the longer boost valve (e.g. 4L60E-LB1) for the older style pump and the shorter boost valve (e.g. 4L60E-LB2) for the new style pump.

Also, if you use the Transgo Boost valve, e.g the one in the HD2 kit, notice that the instructions show to install the supplied thick washer on the boost valve. Only do that with the older style pump; with the new style pump leave the washer off or the pressure will be sky high. (Officially the HD2 kit says it is only compatible up to '05; this is one reason.)

lewingjr

Thanks for the reply. I did buy a Sonnax boost valve but it was the wrong one. Mine is the shorter one so I have the new one on order. What should the pressure be in reverse at idle? I did it at 1500 RPM and it went up to 120 PSI+.

I used the Transmission Bench videos and they seemed pretty good.

lewingjr

Will either pump work? I think mine is the earlier cover looking at the Sonnax diagrams. but I measured the sleeve and mine was definitely the shorter one.
I think this transmission has been apart before since it had an aftermarket valve body separator plate.

mrvedit

With the (correct) Sonnax boost valve, the Reverse pressure will be in the 175psi range. When you blip the throttle you should see 200+.

Sound like you have the earlier pump and installed the shorter -LB2 boost valve. That absolutely explains your low pressure.

Not sure why you ask "Will either pump work"? I would not recommend swapping to a different type pump as the pump has to be compatible with the input shaft. (ISS and non-ISS input shafts are NOT interchangeable - they have different spacing on the teflon rings.)

lewingjr

I asked since this is what was in the transmission when I bought truck. It had a bad motor so I swapped motors and drove 1000 miles then the transmission failed. There is no input speed sensor on my pump and I do not see any associated wiring that may have been disconnected.

mrvedit

That explains why the trans failed - the line pressure was too low due to the wrong boost valve. In the first part of my first post I thought you had the new style pump because that is what most, but not all, 4L60E have.

lewingjr

The Sonnax sheets say that some old style pumps have the new style valves so I will have to measure the inside of pump to be sure, but since I will have both valves I will install the correct one. I also found some information on drilling the orifice feed holes in the valve plate to (4) .078 (3) .093 (2) .093 to change the shifting. Since I installed a new plate that I believe is an OEM version is this something I should think about?

mrvedit

Those are good drilling numbers that will tighten up the shifts.

lewingjr

Not having much luck with this transmission issue. I have the valve installed and seems some better but still not what I feel is should be like. If I am over 2500 rpms when it shifts it feel like it slips then locks in. I have a 2004 2500HD that shifts way better than this. I did just figure out that when in tow haul mode it shifts like I feel it should even though it is at 3500+ rpms.

mrvedit

What is your new line pressure in park, reverse and when you blip the throttle.

lewingjr

Park is 70 PSI
Reverse is 90 PSI
If I blip it in park it jumps as high as 220 PSI

lewingjr

I took it for a drive and it would go to 120 PSI at 1-2 and 2-3 shift. In tow haul mode it jumped to 180 PSI going into 3rd. Of course it was at about 4000 RPM.