P0742/ Converter dragging when cold...

[chevyburnout1]

I'm having an issue with my converter dragging only when the trans is cold. First thing in the morning or with real cold temperatures I go to take off and the converter is locking up instantly. Doesn't appear/feel to drag in first or reverse, only once in second or higher. Watching on the Tech II slip drops to 0 on the second gear shift. However if I lightly-moderatly accelerate it will push through the converter and get about 300-400rpm slip. Just lightly let off and drops straight to zero. After driving for about 3 minutes the problem goes away but still sets the P0742/Range Shift Inhibited.

The trans is a Suncoast stg 4 kit with a 1056 that I built with some help from Mike about three years ago. Did a trans service about 10k ago which included both filter changes and flushing out the cooler lines. The problem was still there before the service.

Talking with the tranny guy I work with here at the dealership and he is suggesting to pull out the converter solenoid and throw it in the freezer for a bit, then put it in his solenoid air checker manifold and see if its leaking. However he is not familiar with what entails with Allison trans upgrades. So I figured I'd ask here and see if there are some common issues. Any help would be great as its getting cold here and I don't wanna trash the converter.

 

[Mike L.]

I would change the F trim solenoid first even though I don't suspect that it's bad. It is easy with just a pan drop.
What I realy think is wrong is the retricter fell out of the Transgo converter flow valve. That will require pulling the staor support out of the pump and checking the valve. Call me.

 

[chevyburnout1]

Thanks for the quick reply Mike. You've helped me out a lot back when I was installing it (machined my valve body for free). I'll call you once work dies down a bit.

 

[chevyburnout1]

K Mike figured I'd update on this real quick. Threw in a new F solenoid and a spin on and its still doing the same thing. I watched the Tech II to see if the TCM was actually commanding it on and it was showing 0% engage the whole time. I have yet to swap with another TCM as you had mentioned. I've been waiting for a used truck to come through my work to swap with.

When I swapped out the F solenoid there was an aluminum cap right behind it with a hole in the middle. It sat in between the solenoid and the actual valve assembly. The sides of it seemed pretty boogered up but I didn't think it moved. Plus it slid perfectly when installed. Dunno if that's something of concern. The actual valve and bores looked great.

But I have noticed another characteristic about it. So like I said, when cold it instantly locks up when it hits second gear accelerating, and when I let off and start coasting down it will stay locked up as well, however once the engine hits about 1100rpms it feels like the converter instantly unlocks. RPM's drop to idle and it doesn't feel like its dragging. Scanner still shows it to be in 2nd gear. I've verified it does this in the rest of the gears besides first. Basically it feels like a very aggressive Tow/Haul mode except it will unlock the converter around 1100 instead of about 1500 like usual. If I touch the throttle it'll instantly lock back up around 1200 again.

Since I have yet to have another TCM to swap with I was thinking of pulling out the terminal #32 in the TCM connector for the voltage supply to the TCC solenoid. Possibly eliminate the TCM from the equation. However would that make the truck undrivable seeing that circuit open?

Again like I said after about 5 minutes of driving the transmission works just fine. Usually has to be parked overnight in our 20° weather before it acts up again.

 

[duratothemax]

K Mike figured I'd update on this real quick. Threw in a new F solenoid and a spin on and its still doing the same thing. I watched the Tech II to see if the TCM was actually commanding it on and it was showing 0% engage the whole time. I have yet to swap with another TCM as you had mentioned. I've been waiting for a used truck to come through my work to swap with.

When I swapped out the F solenoid there was an aluminum cap right behind it with a hole in the middle. It sat in between the solenoid and the actual valve assembly. The sides of it seemed pretty boogered up but I didn't think it moved. Plus it slid perfectly when installed. Dunno if that's something of concern. The actual valve and bores looked great.

But I have noticed another characteristic about it. So like I said, when cold it instantly locks up when it hits second gear accelerating, and when I let off and start coasting down it will stay locked up as well, however once the engine hits about 1100rpms it feels like the converter instantly unlocks. RPM's drop to idle and it doesn't feel like its dragging. Scanner still shows it to be in 2nd gear. I've verified it does this in the rest of the gears besides first. Basically it feels like a very aggressive Tow/Haul mode except it will unlock the converter around 1100 instead of about 1500 like usual. If I touch the throttle it'll instantly lock back up around 1200 again.

Since I have yet to have another TCM to swap with I was thinking of pulling out the terminal #32 in the TCM connector for the voltage supply to the TCC solenoid. Possibly eliminate the TCM from the equation. However would that make the truck undrivable seeing that circuit open?

Again like I said after about 5 minutes of driving the transmission works just fine. Usually has to be parked overnight in our 20° weather before it acts up again.

You will lose reverse and obviously have no converter lockup.

Otherwise it will drive normally...just make sure you dont drive into any place where you'll need to back out.

 

[chevyburnout1]

It happens every morning I drive the truck to work so I'm used to not having reverse lol. If that's the case then I will pull the terminal out real quick and see what she does tomorrow morning. Thanks for the input Ben.

 

[Dirtymaxx03]

my converter does something wierd when its cold too. i'll pull out of my driveway and shift into second going down the road then need to stop for a stop sign, start slowing down and it feel like my truck downshifts into 1st way too soon and throws me into the steering wheel.....is that the converter?

 

[chevyburnout1]

my converter does something wierd when its cold too. i'll pull out of my driveway and shift into second going down the road then need to stop for a stop sign, start slowing down and it feel like my truck downshifts into 1st way too soon and throws me into the steering wheel.....is that the converter?

I've felt a few stock trucks do that in real cold weather (0°F). May be normal but I'm no expert haha.

So the truck sat all day today in about 25-35° weather. Hasn't ran since 7:30 this morning. A lot of times it will act up leaving work as well if it sits all day, so I pulled the terminal out just now and went out for a quick drive. Seems like its its doing just fine, TechII shows some slippage. So we'll see what tomorrow morning brings.

 

[chevyburnout1]

So this morning brought no good luck. Converter still locking up and hard shifting in/out of 2nd and 3rd.

 

[rgullett83]

Well that sucks, but I think Mike is right. I would pull the trans, and inspect the tcc bore in the stator, and the transgo valve. I have seen a few high mileage trucks with scored bores, causing the valve to hang up.

 

[chevyburnout1]

The trans has lived a hard life so it may be time for a refresher anyhow. But one last thing that just arose yesterday. Did a decent amount of Christmas shopping and driving in slow traffic. Look down at the trans temp gauge and its almost touching 300° So I got it out on the interstate and drove it about 30 miles home and the temps didn't really drop at all. Would this contribute to the converter issue or just a coincidental problem.

 

[Mike L.]

The converter is probably going out.

 

[chevyburnout1]

Bummer... Thanks for all the help guys.

 

[chevyburnout1]

So just to update this thread for anybody the converter finally failed. Went through two spin on filters in a month and now finally the converter clutch isn't holding. Pulling the trans out this weekend and gonna get Er rebuilt

 

[GeneralTJI]

Bummer.... hope the rebuild goes smooth and your up and running soon

 

[chevyburnout1]

Thanks! I'm hoping the transmission is still in good shape but I'm going to tear it apart as well since I'll already be there.

 

[GeneralTJI]

Yea, if you can get away basically just a converter that would be a plus! hopefully that's all you need. Have you taken it down the strip, just curious what it runs?

 

[chevyburnout1]

Hoping so! I haven't had a single issue with the trans in the four years since I built it. Besides a harsh 3-4 shift, but I got that fixed with tuning.

I see your from Colorado. I ran it at Truck Fest last year and it ran a 12.96@103. That was in 100° weather with some tuning I wasn't happy with. I've tweaked the tune a bit and raised the shift points since then so I can't wait to get her back to the track :thumb:

 

[GeneralTJI]

Right on... I went to Truck Fest in 2010... would like to get back up there this year.

 

[chevyburnout1]

I should be there once again. Placed 2nd last year as a bone stock powerstroke beat me out by like .005 seconds lol. I'm out for revenge now!