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Discussion Starter · #1 ·
This started last weekend when I left for work (6 hour drive). I noticed there was no lockup with my trans at all. Shifting was great and no hesitation or slipping of the converter. Just no lockup. I changed the solenoid while out of town and had no change. No codes at all. Had a local guy put his Solus on it and the PCM is calling for lockup when it should. (2nd gear beyond 25mph when shifter is in 2nd, 3rd gear in tow/haul beyond 35mph and O/D beyond 45mph)

We assumed there was a plunger/valve stuck in the valvebody, so I removed the VB and inspected the 3/4 shift plunger along with the 2 that associate with the TCC. Everything looked well and clean. Reinstalled and it does the same thing.

So I installed a lockup switch with a 33 ohm 1/4 watt resistor and it shows me no difference whether on or off. Once again no codes.

I am lost. No fibers or debris in the pan, no chatter or slip from the converter, the PCM is telling it to lock, I am telling it to lock, no change in engine load at all.

I bought this trans used, it is a billet from Floor it, DTT super single, billet in, out and intermediate, DD pan. It had 45k on it when I bought it, I have put 4500 miles on it and it never missed a beat until now. Any ideas?
 

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I wanna go fast...
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Discussion Starter · #2 ·
Wow, nobody?
 

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Considering what you have tested and done, it sounds like the TC lockup apply piston\seal\clutch has failed.

The easiest thing may be swap in a new TC. There are other things in the VB and case that could case the lockup failure but it will take a tear down to find it.
 
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I wanna go fast...
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Discussion Starter · #4 ·
Would there be any fibers in the pan if the clutch itself has failed? I am not so sure that I looked at the VB just right, it was my first time into one. The two plungers that I was told to look at seemed like they were ok. Is there a fluid pressure test I can run in a certain port to see what it shows?

On a side note, every now and then (since I installed it) it would take its sweet time to lock up. Other times it would hit like it should. Just a guess of a leaking seal or the converter balloned a little and now it is just finished off? Thanks for the help.
 

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AFAIK, there is no external way to test lockup pressure.

If its a seal\piston failure there may be no evidence in the pan. Since its a DTT I would call them and describe the symptoms. They are pretty sharp on diagnosing what could fail and what you need to do.
 
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I wanna go fast...
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Discussion Starter · #6 ·
For future reference, the cooler pressure changes (doubles to a point) when OD is asked for and hydraulic pressure is delivered. Mine was showing 22-23psi while easy driving until it asked for lockup, then pressure changed to 70-75psi. This can be felt if the hoses are pinched by hand and the truck is on stands instead of hooking up a gauge. It was just real handy that I could hook up a gauge. Thanks to Dave Goerend for this info.
 

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I wanna go fast...
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Discussion Starter · #7 ·
Oh this means my converter is shot. Pressure delivered and no lockup. Dang it.
 

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Resurrecting this thread...

My converter stopped going into lockup just recently, no converter chatter/noise, nothing. I hooked the Solus tool to it and the PCM is calling for lockup at all the correct time and it just popped the P1740 code. I'm at school so access to gauges to manually check pressure would be hard to come by; but would I be correct in assuming that the lockup clutch is toast?
 

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That would be a good guess.
 

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Another update:

Replaced the converter with a DPC Super Single and everything seemed alright... until I made some hard pulls with the converter locked. It felt like the tires were trying to break loose at 65mph on dry pavement, which just didn't seem possible with less than 400hp to the rear tires. :confused:

Then I put my jeep (7500lb jeep/trailer combo) behind the truck and hit some hills on my "tow" tune. On a couple of the steeper hills the brand new converter started chattering hard; felt like a severe driveline vibration.

Wonderful.

I doubt it's the converter's fault, so where should I start in diagnosis so I can keep this one from eating itself?
 

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Start by doin gth epressure test and get a gauge on the apply pressures you are running when it chatters. Sounds like low pressures at certain points. If the pressures are good don't discount a bad TC.
 

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Well, you done spendt how much on convertertro no avail. And this is with a stock Valve body???? Duh!!!!
You could have a failed seal on input shaft or wear in that area.
The lockup solenoid could have debris in the ball shutoff, not allowing full lock up pressure. The spring retainer on lock up boost valve on top of VB could be damaged or valve hanging. The speed sensor on left rear of tranny could be bad although doubtful IMO.
What is voltage on ground circuit when in LU and not LU?? The lockup clutch in converter is the seal in converter. Debris show up when it fail and cooler gets plugged.
 

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Start by doin gth epressure test and get a gauge on the apply pressures you are running when it chatters. Sounds like low pressures at certain points. If the pressures are good don't discount a bad TC.
Thanks. I'll try that as soon as I can.

Well, you done spendt how much on convertertro no avail. And this is with a stock Valve body???? Duh!!!!
You could have a failed seal on input shaft or wear in that area.
The lockup solenoid could have debris in the ball shutoff, not allowing full lock up pressure. The spring retainer on lock up boost valve on top of VB could be damaged or valve hanging. The speed sensor on left rear of tranny could be bad although doubtful IMO.
What is voltage on ground circuit when in LU and not LU?? The lockup clutch in converter is the seal in converter. Debris show up when it fail and cooler gets plugged.
It's not a stock valve body.
 
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