solidaxel

When shifting from 4th to 3rd it feels OK but the shift from 3rd to 2nd there is a surge and from 2nd to first a surge, LM4 & 4L60E stock tune and engine

solidaxel

This happens with normal driving when slowing down and coming to a stop

mrvedit

Sorry no one has responded.
When you say "surge", do you mean a harsh downshift? How are your upshifts?
Or do you mean the engine revs?
Have you scanned for codes? Various engine codes can cause the trans to shift differently (usually more harshly).

solidaxel

Norman upshifts, but the second and first (gear) down shift the engine sounds like it is reving a bit, wanting to override the brake a bit.
The only codes that have been seen are lean bank 1&2
Thanks for the reply

mrvedit

I don't have any experience with your problem and don't recall any similar threads.
There is a 3-2 downshift solenoid whose purpose is to prevent a flare during the 3-2 downshift, but I don't think it has any effect on the 2-1 downshift.

Hopefully one of the pro builders/mechanics will have more info and some suggestions for you.

solidaxel

Update, still having the same downshift surge, "flair"

I did take the truck to the transmission shop and asked him to check thing out, the solenoids, he put his stand alone "box" on the trans and said there was nothing wrong with the transmission!

Said it up shifts and down shifts just fine and goes into and out of lock up so he said the problem was with the wiring

I pinned the wires with the help of Clienbargers info and there is continuity end to end thru the connectors and the colors matched the schematics

Would a bad VSS have any cause for this problem?

mrvedit

It might take a full scanner like HP Tuners and experience with it to figure this out. Is the surge coming from the engine or the trans? I would log things like MAF and PCS current to determine if the PCM is causing the surge (e.g. due to sensor problems) or the issue is internal to the trans.
Sorry you wasted time checking the wiring - if the trans is basically working it would never be a wiring problem.

How many miles are on the trans?
Has the fluid ever been changed?
Is this a drive-by-wire or drive-by-cable vehicle?

You could try replacing the 3-2 downshift solenoid which is trivial after dropping the pan.
Maybe a 25% chance of fixing your problem.

solidaxel

Thanks, at least I know it is not the wiring to the ECM

The fluid and filter were changed and we have put 2100 miles on the "good used" trans
The 2003 Tahoe engine is a DBW from the same vehicle

I did swap out the VSS with another 2003 4L60E that I have, and first of all it was a different "color" brass looking , and the trans acted very strange, it did not like that one!!
I replaced the old one and things started working again like before

I then changed the ECU with another one that I have had in my other truck and the problem still exists!

I do like your odds of 25% so I may change the solenoid, is this a plug and play or do I need the whole harness?

mrvedit

The solenoid is just that - a $20 part that is trivial to replace; it has a connector to which the harness snaps.