4l80e no 4th unless commanded, no codes

[travmac79]

4l80e and 6.0 swap out of a 02 2500 silverado. Harness and trans from the same vehicle. I have replaced the internal harness(leaking from connector) filter, fluid, manifold pressure switch and vss/iss sensors. I have a solenoid kit but I can make all of the solenoids click through vcm scanner. I can also drive the truck in D, and command 4th through special functions and it works fine. Goes through all other gears fine and has no running issues. I have a solenoid kit I can replace all of mine with, but thought it may be a waste since I can hear them all working, as well as both the 1-2 and 2-3 working when I command 4th. The pcm knows what gear it's in and everything. Tps values look normal, and the engine and trans coolant Temps look normal to me. Anybody else got any ideas? I'll post a log file where I drove it and commanded 4th, later today when I get home. Thanks in advance for any help

[travmac79]

log file where i shifted into 4th with vcm scanner.

dt3.hpl

[RDF1]

What size tires and what gear ratios in this vehicle?

Only reason i ask is because last year i had 2 trucks back to back with 4L80 swaps and they had larger 37"ish tire and 4.88-5.13 gears. They data put in the tune and it wouldnt shift into 4th. I had to do some trickery to get it to work right.
I have 3 friends that tune and all of us come to the conclusion that the tire/gear combo threw something off in the tune and it didnt like it.
I fudged the numbers till it would shift into 4th.
So you have the Trans Rev/Mile and the VSS Pulses per mile. One is mainly used for shifting and TCC, the other is for SPeedo output to the cluster.
I found out in a vehicle swap one of them doesnt matter. THe other one is important to have right. But theres no way to make sure you have it correct.
What i did was setup the shifting at even numbers. 1-2 shift at 15mph from 0-100% TPS, 2-3 shift at 30mph from 0-100%tps, 3-4 at 50mph 0-100%tps
Make a drive and figure out how far off you are on the numbers and adjust till the Current Gear in the scanner matchs when the shift is commanded.

[travmac79]

Thanks for suggestion! Ive been wondering if that would cause no shift into 4th. I'm running 20s with 50 series tires that are about 29.5" tall. The rear gear is 3.42 but the ecm showed the vehicle it came out of had 27.3" tires and 4.10 gears. I may have been naive, but I did the tire/gear wizard thing and figured that may scale stuff to where it would at least work. the speedo works and is pretty much correct when I check against GPS speedo. I will definitely start playing with those numbers though. I feel like it may be difficult to find a tune for a 4l80e with 3.42 gears thats otherwise stock but I enjoy being proven wrong lol.

[RDF1]

Post your tune.
And your tire size.
245/50/20? Equals a 29.5" tall tire, is that what you have?

Ive got a bunch of tunes for a 3.42/4l80 trucks.

[travmac79]

I changed the shift points in normal shift mode to what you suggested and still no 4th. It did change the shift points but itsnot commanding 4th. 1-2 shift solenoid is never being told to activate.

[RDF1]

I found my tune when i had 29.9" tires on my turbo silverado with a 4L80.

[travmac79]

I will post tune when I get back to shop momentarily.Tires are 255 50 20. I just measured with a tape to get 29.5 but figured it was close enough

[RDF1]

Yea that will work.

[travmac79]

current tune

6.0 4l80 truck mod3.hpt

[RDF1]

current tune

6.0 4l80 truck mod3.hpt

Give this a try

[travmac79]

Tried your settings and it was the same. No 4th. I'm wondering about the pcm too at this point. Care wasn't taken with the harness/ecm, and most was covered in mud. Inside all the connectors looked fine though. I have the one off of the old 4.3 v6 which is physically the same. I may give that a shot as well.

[travmac79]

Changed ecm and same deal. No 4th unless commanded. Tcc locks and unlocks when commanded as well in 4th. I have the auxiliary air valve unhooked and plugged on the intake. That shouldn't effect shifting I wouldn't think but that's the only non stock thing about my setup

[travmac79]

Could a weak pressure control solenoid or its clogged little filter make all this happen without throwing codes? As in its still working but not allowing the correct fluid flow/signal pressure?

[RDF1]

NOt if you can make it shift with the scanner.
What is your shifter position showing? i cant rem the name of what HPT says. Its reading the manifold switch signal tho.

If your pressure manifold switch is bad and you have shifter in 4th but manifold switch is telling PCM that your in 3rd, it wont make the shift.

[travmac79]

I replaced the pressure manifold switch. No change. prndl status says d4 when in drive. The current gear field always shows the correct gear that im in while driving. Even when I command it with the scanner

[RDF1]

PRNDL gets its info from the park neutral safety switch on side of trans.
The PCM gets its gear indicator from the pressure manifold switch.

Ill have to find my HPT box and go connect to my truck to figure out what the PID name is. haha.
EFI has it labeled as Trans Gear Selector. It gives Manifold pressure switch data and PRNDL data. Ill have to dig and find it in HPT.

[edcmat-l1]

Does it command 4th gear and not shift or does it never command 4th gear?

[travmac79]

It doesn't seem to ever command 4th. "Trans current gear" never says 4 until I command it with scanner.

[edcmat-l1]

Shift tables were a little jacked up. Give this one a try.