This is the first time I have driven a stalled vehicle. I recently put a Stage 2 Performabuilt trans along with a Circle D 278 converter, with a 3,000-3,200 stall range. It runs well, noticeably better in first and second under moderate throttle. It's a heavy truck with big off road tires, but it will now break them loose a bit from a dead stop, where as before it was difficult to even power brake the thing.

Anyway, I just got back from a long trip and it's first highway excursion. I did a 150 mile and then back trip with a normal cruising speed of 75mph, which along with my 4.88's and 35's puts me right around 2,500 rpm. Well I got on the highway on the way there and the truck did not want to lock the converter. I played around with throttle, the tow/haul button and it did not want to lock for the first five minutes. Then out of nowhere it did and behaved pretty well the rest of the way, meaning it stayed locked when it should for the most part. On the return trip however it hardly EVER locked. And even when it would it wouldn't stay locked for more than 3 or so minutes at a time. I was in upstate NY and the weather is cool thank G. I stopped at a rest stop and shot the trans pan with a temp gun and it was around 180 degrees. On the intake side of the trans cooler I was seeing 160, around 100 on the output. So no heat issues, but if it was the middle of summer I think it would have gotten really hot.

So what am I supposed to do about this? Is it normal? Is there something that can be tuned so it locks in OD after reaching a certain MPH and under a percentage of throttle load? I just got my computer back from my tuner as I had him set the line pressure back to stock, I never asked about the effects of the converter. Thi struck sees a lot of highway time, and the thing is flashing to 3,300 rpm easily when going uphill at 75. That's not good. Any help or insight would be appreciated. Thanks. Sorry for the bible BTW, and hope this is in the right section.

It's got a decent sized trans cooler, it was what came with the new trans. If I have to live with this I could probably get one double the size, or an additional one depending on room. Dunno if that's the right answer though.

 

For the converter to lock you need to meet a few requirements, speed vs load/throttle position, minimum engine temp, and no misfires. So a variety of things can prevent lockup, id start by examining if lockup is being commanded.

 

Misfires is interesting. I did have a check engine light on most of the way back home. Seemed to run fine mostly. This thing is old, 310K miles. It's had a check engine light on for one reason or another 50% of the time for the past several years. Usually stupid EVAP ****, etc. But as I pulled out of the last toll booth last night I got on it and when it shifted to second it bogged for a second then picked right back up. Has never done that before. I can't really see if lockup is being commanded. Best I have at my disposal is an OBD bluetooth transmitter, and then I can down load torque on my phone again. The ligh was not on today, but should still be in the memory. Any other way to tell?

Engine temp was spot on according to the gauge. 75mph is certainly enough speed wise, and I tried all types of throttle positions from heavy to none.

 

Anyone else have any input? Kind of a noob when it comes to auto and aftermarket converters.

 

you need a tune after swapping the converter...higher stalls make the pcm freak out thinking the trans is slipping more which it is. You have to turn off a few codes in the PCM... P0741 & 748 codes to No Error Report and the misfire detection codes 1380 &1381 No MIL light.

 

Thats correct.....during shifts. But shouldnt effect lockup.

 

FWIW i have a 2000 camaro nearly full weight with a Performabuilt lvl 2 and 4k stall. When just 2 people are in the car it locks into overdrive each time. But I've driven it to the dragstrip with 3 people, tools, chairs, etc and it would unlock itself when i went up hills with this extra weight, so what these guys are telling you makes sense to me.

 

IS this just so I don't throw codes or does it affect operation of the trans? The trans seems to shift OK.

 

Well that sounds like what I would like, problem is that it wasn't locking even going down hill.

If this is a tuning issue I'm gonna be fairly pissed. The tuner knew I was putting an aftermarket performance trans in, a converter would be a logical thing to inquire about. I suppose I should have been smart enough to mention it as well, but still.

 

Moved over here. This is obviously an automatic transmission issue, not an external engine consideration.

 

FWIW, I've never had to address these codes on the '98-'00 cars with ~3500 stall speeds or less; their PCMs seem to be less sensitive to the change. '01+ cars tend to have greater concerns in this area with stall speeds of this range and higher.

On my 2000 car, for example, when it had stock internals the only stall related tuning it needed was a slight bump in idle speed (to prevent minor surge in gear) and some WOT shift point changes. After the cam went in, misfire counts needed adjustment to allow proper lock-up, but that wouldn't be an issue with a stock engine (unless there is an issue causing misfires.)

However, I have no idea how all of this would translate to the truck PCMs.

 

The 278mm is a pretty mild converter and sometimes does not require a re-tune. That said I agree with the above posters on the misfires/knock sensors possibly causing your issues. Work on the tune some and see what happens.

-Brian

 

Just pointing what I had to do to keep the trans from unlocking randomly and going into limp mode. It's common practice at least on 01-02 cars, not talked about because most just have somebody tune their ride. I try to do all my own tuning, except when I went SD then I had a tuner step in and assist.

Google will provide all the information about tuning after installing a Stall converter. That is how I figured mine out. Been shifting solid for 5yrs and the stock trans is still holding up great with a shift kit and cooler to 500hp and 7k rpm shifts.

 

Did you have your speedo recalibrated for the tires/gearing?

 

Yes, I had the speedo recalibrated when I had the truck tuned initially a few years ago.

Brian, thanks for chiming in. I'll contact my tuner and see what he has to say. Bummed though because it's all through the mail and I got a retune in order to not blow the trans up right before the install. Just wish I thought to ask more questions.

I don't know what the difference between truck and f-body computers are either, but the truck weighs 5,500lbs and is spinning 80lb tires, so I could see there being a lot different behaviour even if everything else was identical.

 

Various engine codes will affect the operation of the trans; and not all codes enable the MIL light. Therefore you need to good scan tool to check for all codes.
As mentioned, misfire codes will prevent converter lockup.

 

A bad brake pedal switch will cause no lock up.
There are separate contacts for the brake lights and tcc lock up. So just because your brake lights work doesn't mean the switch is working properly.

 

I would contact your tuner first and see if he made adjustments based on the new stall

 

Thanks. ^^^^It's on my list. Often hard to get a hold of him.

I have noticed that cruising around on back roads it locks up frequently by say 45mph-ish in third. And sometimes at slower highway speeds. Sound odd?

 

Throttle position sensor ? Just had a nightmare with my lockup being intermittent, locking up at odd speeds and loads and not locking at all when it should. My throttle position sensor was at fault.