Transmission "hunting" at low speed/low throttle

[skneeland]

cruising around at low speed (30kph to 60kph) under light throttle the transmission is shifting back and forth between gears quite badly. It goes away when i put it in tow/haul mode (or hard throttle/high speed)

I had been messing around with the throttle span to try to help my towing shift pattern, but i have since returned it basically to stock & still have this condition.

any thoughts?

edit* when i bought the transmission from DTT they made sure i wasnt having this condition from the get go. apparently its something that can affect random trucks after the install. Mine worked fine, so i wasnt required to purchase their "shift enhancer" to fix the problem....just hoping i can tune it back out now & its not just some coincidental transmission problem....

[icemanjc1]

Thank god I'm not the only one having this problem...

[Ira]

If I was guessing and it would be a wild guess at best, I'd suggest you've moved the operating parameters of the engine that the transmission uses to decide when to shift into an area that's confusing the transmission. I'd try logging the parameters that effect shifting with both the tune that didn't show the problem and this one and see if you can see what is different.

Ira

[DoghouseDiesel]

Okay, the only thing you can change in EFILive that will effect the transmission shift schedule is the throttle postioning, or more specifically the pedal position to fuel desired.

This trans uses 3 things to determine the shift schedule; engine load, speed and the throttle position. The throttle position is what screws with shift quality.

There are 3 things that you can do with this condition; the easiest is adjusting it out with the tables.

If that doesn't work or you like the throttle response but not the shifting, you need to drop the pan and adjust the throttle valve stop. It's on the driver side of the trans on the valve body. It's a socket head bolt with a wide shoulder for the TVA arm to catch.

The factory setting is .903" from the shoulder to the VB. If it's hunting, it's usually because you're asking for more throttle than it's calibrated for and you need to bring it out a bit. You only want to bring it in or out .020" at a time. Tightening it up will apply more throttle and will raise the shift point. Loosening it will lower shift points and usually cures the shuttle shift associated with tunes.

Now, if that doesn't work, more than likely you need a new governor solenoid, but you need to test the pressure and the governor pressure test port on the passenger side of the trans for this. Not hard to do, you just need a 100 psi gauge, 2 x 1/4 npt to 1/4" barb fitting and about 10 feet of 1/4" hose so you can see the gauge in the cab.

[Motorzane]

We have had this issue also but around 30 mph. Trying to hold at 30 mph it will shift between 3rd to 2nd to 3rd to 2nd and so on. Even with a DDT shift enhancer. By putting it into tow/haul mode it engages the converter clutch once it shifts to 3rd and the computer won't shift back to 2nd. We lowered the pressure a little through the shift enhancer and seems to fix the problem.

[icemanjc1]

Finally get to expand on this (my) problem a little. I've tried everything Rich has posted here. Changed the TPS map back and forth with no real difference in 2nd-3rd shift quality. I've adjusted the TTVA stop tighter, then even more tighter with only a change in 1st to 2nd and 3rd to 4th with a constant CEL because of it (soft code). Changed the PATC gov solenoid conversion kit I was running back to my oem base plate with a new BW governor solenoid. Still not much change. Sorry for this, just venting a little....

[TexasCummins]

If you are still under the 5yr/100,000mi engine warranty then take the truck to the dealer for an upgraded operating system and calibration. Was having 1-2 and 2-3 shuttling and this fixed my problem.

[icemanjc1]

Warranty, lol! I don't think my poor truck ever had a warranty. The other thing, I'm running a Garmon towing valvebody, and I've ran two different 06 OS and now an 07 OS with no change. Oh yeah, something else funky. "Occasionally" my truck will lock up in 4th w/ little throttle input @ like 41 mph for a fraction of a second, then unlock. Weirdness.

[comnrailpwr]

Finally get to expand on this (my) problem a little. I've tried everything Rich has posted here. Changed the TPS map back and forth with no real difference in 2nd-3rd shift quality. I've adjusted the TTVA stop tighter, then even more tighter with only a change in 1st to 2nd and 3rd to 4th with a constant CEL because of it (soft code). Changed the PATC gov solenoid conversion kit I was running back to my oem base plate with a new BW governor solenoid. Still not much change. Sorry for this, just venting a little....

DogHouseDiesel stated that the ttva stop should be backed out, not tightened.

Jake

[DoghouseDiesel]

Adjusting the TV minimum is to adjust where the trans will shift under part throttle. It really doesn't effect the hunting issue.

If your trans is shifting at too high of an RPM under part throttle, you back the TV minimum out. If it's too low, you tighten the bolt. It won't effect WOT shifts.

Now, what I find is the issue with the shuttle shifting (i.e. 1-2,1-2,1-2 or 2-3, 2-3) or delayed shifts and slamming into the next gear is the governor solenoid and pressure sensor.

The OEM solenoid is garbage. The BorgWarner unit is much nicer and holds up to modified VB's a lot better.

This is the piece I'm talking about right here. 99% of the time, if you are having the shuttle shifting, this is your demon....

The small one is the OEM one, the larger one is the BW unit. It's a direct replacement.