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Topic: Think my torque converter has a problem? Stalled too high perhaps? (Read 2816 times) previous topic - next topic

Think my torque converter has a problem? Stalled too high perhaps?

So I am finally getting good pulls in my car. I have a PI Stallion 9.5" 3000-stall converter in my 4r70w. When I floor the pedal from a 10mph roll, the converter appears to flash to 4500-5k and hang out there for awhile as the speed increases. I know some of the initial issue is traction, but I don't think I'm loose on traction all the way up to my 5k shift point, which is around 45mph. I can't hear any tire noise when I know I'm spinning, so it is difficult to tell.

Who has experience with looser converters, and rated versus observed flash speed behind different torque amounts? Maybe I need to have my converter re-stalled to something lower? 2400rpm is the lowest I can go with this converter. I'd be tempted to go multi-disc lockup on any re-stall work.

For more information, I can take off from stoplights at a sane level of acceleration (with traffic) while keeping the motor around 2k rpms. 2.5k it starts to pull harder/jackrabbit. I don't think my converter is stalled incorrectly from its rating, but I can't easily test. Even locked into second gear from a roll, mashing the pedal breaks traction.
1988 Thunderbird Sport

Think my torque converter has a problem? Stalled too high perhaps?

Reply #1
Find a safe place and come to a complete stop.  Bring the RPM's up to about 1200 or so while still stopped.  NAIL IT and let go of the brake.  Where's the RPM's shoot up to?
-- 05 Mustang GT-Whipplecharged !!
--87 5.0 Trick Flow Heads & Intake - Custom Cam - Many other goodies...3100Lbs...Low12's!

Think my torque converter has a problem? Stalled too high perhaps?

Reply #2
Call the manufacturer.  Buddy of mine had a custom converter for his C4 behind a 408W and when he nailed it from a stop is just blew through the converter and went up on the chip.  Called the manufacturer and found out that when they freshened up the motor and it gained some compression and the heads had been ported so the converter was no longer what he needed.  Sent it back to get reworked, needless to say it was like night and day.  That 86 GT felt like it was just about to break the front seats when it left of the slicks after that.

Darren

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

Think my torque converter has a problem? Stalled too high perhaps?

Reply #3
I have observed with mine that if I go wot and it starts to spin the engine stays around 4500-5000rpm. Seems spinning doesn't put much of a load on the trans so it doesn't shift till it gets traction. Fwiw I have spun all the way to the 1-2 shift point and the engine just kinda hung around 4500-5000rpm till the shift. This is why I do not go wot from a stop on the street. If you've been having temps below 60* I would imagine you would be having traction issues going wot from a 10mph roll.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Think my torque converter has a problem? Stalled too high perhaps?

Reply #4
Yeah drive around a bit, get things warmed up, make a lot of turns (it will warm the tires some even on a cold day) get up to 3rd gear...slow down enough that it'll downshift, and firewall it.

My red cougar only has realistically 270-280 crank horsepower. It's one of the heaviest of these cars. 3.73s, 3000 rpm converter. To any random idiot watching me go WOT from a dead stop, they'd think it was a big-block 500-horse muscle car because it just spins wildly, upshifting through it all until 30-40 mph--ish.
Nothing like unleashing your peak torque in the blink of an eye....
1987 20th Anniversary Cougar, 302 "5.0" GT-40 heads (F3ZE '93 Cobra) and TMoss Ported H.O. intake, H.O. camshaft
2.5" Duals, no cats, Flowmaster 40s, Richmond 3.73s w/ Trac-Lok, maxed out Baumann shift kit, 3000 RPM Dirty Dog non-lock TC
Aside from the Mustang crinkle headers, still looks like it's only 150 HP...
1988 Black XR7 Trick Flow top end, Tremec 3550
1988 Black XR7 Procharger P600B intercooled, Edelbrock Performer non-RPM heads, GT40 intake AOD, 13 PSI @5000 RPM. 93 octane

Think my torque converter has a problem? Stalled too high perhaps?

Reply #5
Yeah, I can't tell what is going on. I went through 1 gallon of gas tonight trying to fix my tune after putting in default datasheet specs for my MAF and injectors. Also didn't have my old transmission tune on hand, so I took a default 5500rpm shift point tune and wrote it.

You can also see my wideband going weird when the engine is first started. I know it is out of range at 5.2V when the engine if off. I haven't probed it manually with a cold start.

https://www.youtube.com/watch?v=UuYKFJqiFyk&feature=youtu.be
1988 Thunderbird Sport

Think my torque converter has a problem? Stalled too high perhaps?

Reply #6
Tomorrow I will look at what the transmission is doing. I think it is starting to command a shift, before it should due to traction. I'm at 5800rpms, and datalogs show 5900+ rpms reached before the shift completes. Also got the tune improved a bit for driveability, but power is still down a bit over yesterday. Injector duty cycle is barely hitting 80 today, but that may be because I've changed the slopes and breakpoint to get the fueling under control. I got them adjusted with adaptive learning disabled, and not touching the MAF curve. MAF was later tweaked for small corrections. More than that, I need to look into whatever is causing some rubbing sound when I turn left - not even sharp.

Tomorrow I will be changing the WOT lambda to 0.85. The stock tune is shooting for 0.80 due to the wot rpm multiplier function.
1988 Thunderbird Sport

Think my torque converter has a problem? Stalled too high perhaps?

Reply #7
Now I'm thinking I may simply have a line pressure issue in the transmission. I think I'm getting a little more slippage than I should at WOT, and my ancient problem of torque converter lockup issues at closed throttle with a stock tune is there. I have to boost the closed-throttle pressure a little to get rid of this issue (did this initially when the car was my daily driver years ago). I'm guessing I've been running lower on pressure to the torque converters for years. The pressure boost was a bandaid.

I wonder if I have a boost valve issue, but I can't find any information out about how to properly test for a bad EPC solenoid of boost valve. I'll have to get a gauge on the line pressures at WOT to see what's going on, but idle pressures were good. The pressure to the converter may be lower than it should be, at all times. I also can't find what pressure port to test for converter pressure...

Maybe just a new TCC solenoid is needed? That'd be a real easy swap - no valve body removal needed.
1988 Thunderbird Sport

Think my torque converter has a problem? Stalled too high perhaps?

Reply #8
Very old thread, but I replaced the entire transmission 2 years ago. Same torque converter. New trans works great.
1988 Thunderbird Sport

Think my torque converter has a problem? Stalled too high perhaps?

Reply #9
Might have had a failing pump, or internal leakage...VB or piston seals, hard to say. Unfortunately there *are* quite a few things that can go wrong when they do and you'll definitely piss yourself off chasing them if you don't have all of the tools and knowledge (I know, sounds like a been there done that story doesn't it? LOL)

I have a '97 F250 7.3 that I have a switch hooked up to momentarily disable EPC. I basically need this for the 1-2 shift, everything else is GREAT. Truck has 330,000 miles on it. A moderate annoyance but again literally everything else works EXCELLENT. With full pressure it holds under the 40 and 60 hp tunes, without, it flares. Intermediate piston seal must be leaking, I've had the VB down like 6 times did all of the Sonnax fixes and a TransGo kit.

The truck towed a lot prior to me, no aftermarket cooler. I bet heat did it in. But it sucks that all of the friction elements are probably OK but a simple seal failure way inside, is forcing me into a remove and rebuild at some point. And yaaaaa MIGHT as well do everything, while you're in there....
1987 20th Anniversary Cougar, 302 "5.0" GT-40 heads (F3ZE '93 Cobra) and TMoss Ported H.O. intake, H.O. camshaft
2.5" Duals, no cats, Flowmaster 40s, Richmond 3.73s w/ Trac-Lok, maxed out Baumann shift kit, 3000 RPM Dirty Dog non-lock TC
Aside from the Mustang crinkle headers, still looks like it's only 150 HP...
1988 Black XR7 Trick Flow top end, Tremec 3550
1988 Black XR7 Procharger P600B intercooled, Edelbrock Performer non-RPM heads, GT40 intake AOD, 13 PSI @5000 RPM. 93 octane

Think my torque converter has a problem? Stalled too high perhaps?

Reply #10
Quote from: Seek;463802
Very old thread, but I replaced the entire transmission 2 years ago. Same torque converter. New trans works great.

Did you figure out what failed in the valve body?
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.