Quickin

Here's another mystery in the life of me and my f#ckin car. I tried to find an old thread I might have made about this but couldn't find it.

I posted this here because I'm thinking its a PCM thing because the tranny is pretty much perfect otherwise.

The tranny is awesome.....BUT, if I cruise nicely on the highway at say 60-80mph, steady unaccelerated cruising, and I decide to gradually, normally accelerate to maybe go around someone. Nothing crazy, not racing, not letting the tranny downshift, but gradually pass someone....as I press the pedal down slowly the rpm's go shooting up EXACTLY as if I popped it into neutral. Zero acceleration, nothing, nada, ziltch. From that point on its as if its stuck in neutral. I can rev it to redline, or take my foot off and coast, than reapply pedal and it revs like its in neutral still. If I'm cruising and I stay at a given speed I can cruise forever like that.

This doesn't happen all the time either, just sometimes.

The only way to get it back hooked up in "D" is to manually put in "3" to let it downshift, than back to "D" and it'll be normal again. Or to let it slow way the hell down until it downshifts on its own.

Now, this never ever happens when I'm racing or just getting on the highway and I'm accelerating up to speed. It only happens AFTER I've been cruising steadily at one speed for awhile, than I try to accelerate a little from that speed.

Its not a huge big deal, but its friggin wierd.

Good luck to me and you for figuring this **** out.

horist

sounds like it's time for a new trans.... sounds like 4th gear may be gone

There are no PCM tables that could cause what you describe... it hast to be mechanical

0rion

iTrader: (1)

Sorry but that's funny right there.

Quickin

But....if I do a WOT blast from say 50mph to 160mph, it performs perfectly.

It only unhooks (if you will) after cruising for awhile. It never happens if I cruise for a short time or I beat the **** out of it. I would think if 4th gear were gone it would never work so perfectly.

BlackHawk T/A

iTrader: (3)

Sounds like TC...

If you tap the brake does it go back to normal?

foff667

iTrader: (2)

sounds like a TC issue to me as well.

Quickin

I'll try that next time it happens.

But..isn't a TC just non-moving fixed parts? I know the two opposing blade wheels are spinning. What could be wrong inside of the TC to cause this? Is there a moving clutch?

SSpdDmon

iTrader: (10)

Could be the torque converter clutch more specifically. I'd try it in 3rd and see if it does the same thing once the tcc locks up. I don't think you'd be able to move at all if it were the converter in general...

Quickin

Never ever does it in 3rd gear, I've tried that many times, its perfect.

joecar

2nd and 4th gears both use the 2-4 band, 2-4 servo, and 1-2 shift solenoid, so it can't be any of these;

3r and 4th gears both use the forward clutch, the 3-4 clutch and the 3-4 accumulator, so it can't be either of these.

4th uses a different hydraulic circuit, so it could be a checkball sticking...
Do you see sludge on the end of the dipstick...?
Did the trans. ever get overheated...?
When was the filter and fluid changed...?

Is the ATF the correct color and smell, and is the level correct...?

Edit:
It wouldn't be the TC or you would have loss of drive in all gears.
If the TCC was not locking, you would still have drive, so it's not the TCC.

Quickin

[QUOTE=joecar]

4th uses a different hydraulic circuit, so it could be a checkball sticking...
How does this get checked?
Do you see sludge on the end of the dipstick...? NONE
Did the trans. ever get overheated...? Never, just a street car with a 19,000 tranny cooler, I think its a 19,000
When was the filter and fluid changed...? 18,000 miles ago when the tranny was brand new, its clean as it can be and smells fine

Is the ATF the correct color and smell, and is the level correct...? Definitely

Can the PCM tuning be the problem? One other thing that happens that I didn't mention is: If I roll into the throttle to do a WOT run from a dig (can't floor it or I'll spin for a mile) each time the rpm's gets near redline where it should shift it hangs there for about 1/2 to a full second for 3rd and 4th ONLY, than shifts into the next gear. They don't really bang into the next gear at all. Second gear hits hard as hell every time. And again, this doesn't happen every time either..........sorry man, its wierd

.

joecar

valve body would have to come off to check this
(need a set of valve body and spacer gaskets to reinstall)
(this isn't hard to do, but you have to know what you're doing
and what the procedure is and not to lose any checkballs),
and could check pan for sludge and metal;
if you got no sludge, then it may not be this.

Use tune package to try WOT MPH and WOT RPM at lower values; if this doesn't help, problem may be mechanical.

May be a problem with 2-4 servo (on side of case), 1-2 accumulator (valve body), or checkball (valve body); use scan tool to see PCS pressure (or current) to see if high pressure is being commanded; if not, then problem is mechanical.

Yeah, it can get real weird sometimes...

Is trans. still under waranty...?

Just some thoughts.

Quickin

There are no good tranny shopsaround here, and the 1 year FLP warranty is up.

Thanks though, I'll have to find a shop somewhere do check these things.

horist

Didn't notice it was an FLP trans... in that case vacuum pressure is vacuum modulated... so the only things the PCM really controls are the mph/rpm to shift, and the delay between shifts... the PCM can no longer modify line pressure...

unlikely based on what you've described it's as simple as a PCM problem (especially if it just started doing this...)

Quickin

It didn't just start. It did it from day one for about 8 months, then it stopped for the past 5 months, now it did it again a couple times in the past 2 weeks. Its back.

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