Truck falls on its face from a stop

D

Deputydog

Proud Fummins Owner
Joined
Jun 19, 2008
Messages
407
So I am trying to figure this out.. I went to the track last night. I can do a boosted launch at 15 or even 20 psi. Truck takes off hard (WOT), burning all 4 tires. As soon as it shifts, it falls on its face to where I lose boost and lose power. Its billowing out black smoke and I have to back off to get the turbo spooling again.

When I'm out on the street from a roll, I can get on it and it works perfectly.. It only seems to happen from a dead stop.

Am I drowning my turbo or some other issue I can check for?

Mods are in my sig.
 
What RPM is it shifting into second gear?

Does it lock up the converter as soon as it shifts to 2nd?

I assume you can custom tune the shift points and converter lock-up with the PCS controller for your 4R100 transmission. In my experience, short shifting is 100% responsible for snuffing out the charger on an upshift.
 
Big Blue24 said:
What RPM is it shifting into second gear?

Does it lock up the converter as soon as it shifts to 2nd?

I assume you can custom tune the shift points and converter lock-up with the PCS controller for your 4R100 transmission. In my experience, short shifting is 100% responsible for snuffing out the charger on an upshift.
Click to expand...

I have the converter set to lock at 20 mph @ WOT, and the truck shifts from 1st to 2nd at WOT at 31mph..

And you're right, I can control all that with the PCS controller.

Am I locking converter too early?

Now that I think about it, you're might be onto something.
 
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Deputydog said:
So I am trying to figure this out.. I went to the track last night. I can do a boosted launch at 15 or even 20 psi. Truck takes off hard (WOT), burning all 4 tires. As soon as it shifts, it falls on its face to where I lose boost and lose power. Its billowing out black smoke and I have to back off to get the turbo spooling again.

When I'm out on the street from a roll, I can get on it and it works perfectly.. It only seems to happen from a dead stop.

Am I drowning my turbo or some other issue I can check for?

Mods are in my sig.
Click to expand...
Sounds like even though you're trying to lock at 20mph your trans won't allow it in first gear then as soon as it shifts it's locking/ bogging.
 
little6cylinder said:
Sounds like even though you're trying to lock at 20mph your trans won't allow it in first gear then as soon as it shifts it's locking/ bogging.
Click to expand...

I'm messing with the PCS settings, its supposed to lock in 1st gear but you could be right, the trans won't allow it.. I changed the programming so the lowest gear to allow TC to lock is 2nd gear. I'll modify the speed to make sure its not shifting and locking at the same time.
 
If it doesn't allow the trans to lock in first make sure you raise the lock up speed high enough to be in the power band in second.
 
I messed with the PCS settings today. I have the TC locking at 35 vs 20 mph as well as not allowing it to lock in 1st gear and that cured it!

Did a few boosted launches on some back roads and no more falling on it face :clap:

So at WOT:

It shifts from 1st-2nd @ 30 mph, 2nd-3rd @ 55 mph, and 3rd-4th @ 74MPH

I hope to get out to test n' tune again next week at the track
 
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