Hello everyone, long time reader first time poster here!
The problem: my truck started pouring fluid out of the transmission bell housing, it left a trail of atf from the time I turned onto my street all the way to my driveway, kinda embarrassing lol. Anyways, I had the truck towed to a local transmission shop that has a good reputation, they told me the pump seal was leaking but we decided to have the trans rebuild because it had 325,000 miles on it with no prior rebuilds.
well, after the rebuild when I got the truck back I noticed it was shifting funny, when the torque converter locks up in 4th gear the rpm’s jump up 200-500 rpm just before lock up, regardless of how hard I’m accelerating. I took the truck back to the shop and they told me it was a “timing” issue with my tune. What’s confusing me is the transmission was stock before the rebuild, it shifted perfectly no problems other than the fluid leak. They said it was rebuild to factory specs so why would there be any difference in the shift?

Truck info:
2003 f-250 7.3 4x4
swamps 175cc single shot injectors
ts 6 position tuner, pcm programmed by swamps for the single shot injectors
regulated fuel return
volant air intake
Kc turbos s300 kit with wicked wheel2
Oil crossover kit
there may be more I’m forgetting, I’ve had the truck along time but that’s the majority of it.

 

I can see why you'd be confused. It the trans was OEM and you got a purely OEM rebuild I'd expect it to behave the same. Nothing else changed right? Speedometer normal?

Any chance you could get a video so we can hear and see the tach flare before it locks up?

 

Welcome to the posting side of the forum.

TC locking up cannot cause a rise in rpm. It’s either slipping as a fluid coupling (not in lockup) or 1:1 (in lockup).
[note: not discussing PWM partial lockup]

So maybe it’s flaring while going into 4th?
Or unlocking after the shift for a second?

Either way it does seem odd that it didn’t happen with the completely stock transmission. I’m surprised they aren’t willing to help figure this out.

Unfortunately you can’t just “remove the chip” to try it since it’s flashed on the PCM.

Edit: speaking of PWM… I’m not familiar with how it may act in our trucks. My understanding is it’s an early (old) version of slip control engagement of the LU clutch.
Did they change the TC? Did they use the correct version TC?

 

as far as I can tell nothing else is different, the speedometer is working fine. The truck is still at the shop now, and I’m in Texas for the week doing some training for Cummins. I spoke with the manager at the transmission shop this afternoon and he said they are going to firm up 4th gear and if it doesn’t change anything they will be looking at the torque converter.

 

A new torque converter was part of the rebuild, the manager told me they used a precision billet converter. The truck is still with them, and what they told me this afternoon on the phone is completely different from what they originally said so I hope they’re onto something, I should know more by the end of the week.

 

Update: picked my truck up from the shop and unfortunately, after everything they did, the truck still has a flare on the 3-4 shift. They said they exchanged the torque converter with precision, rebuilt the valve body again, they replaced the accumulator again and they replaced the solenoid pack. The shop claims it’s something to do with my tunes and there is nothing else they can do. I’m just not convinced it’s my tunes, the truck has the shift flare on all 6 tunes. I would hate to pay to have my ts-6 re-flashed with new tunes only to still have the same problem. What do you guys think? Should I just go with what they are telling me and get new tunes? They also mentioned the problem they seen with the tune is that the torque converter is already locked up while it’s making the 3-4 shift, but isn’t that what should be happening? I’m just not really sure how to move forward with this.

 

Have u tried manually shifting gears and comparing the results?

 

Are you able to run Forscan on your phone? The TCC parameter will show you what's being commanded. Logging it, RPM, and TC slip may help you figure out what's going on.

I assume the OD light is not flashing, correct? Have you tried to read the codes?

Mark

 

yes, if I turn OD off and press the button allowing it to 3-4 shift, the flare still happens.

 

I do have forscan and I can look into that. The OD light is not flashing.

 

There was a local guy having same issue and had the transmission rebuilt...long story short, it was the bypass valve that needed a rebuild...

 

How about sharing a video of the condition?

 

I attached a video, it would only let me upload the last 10 seconds though.

 

Is that part of the valve body?

 

No it's not.