Black98T/A

iTrader: (5)

Ok so I have a 98 WS6 automatic with a newly rebuilt 4l60e with a Transgo HD2 shift kit which I had installed three years before the rebuild and a brand new 2600 torque convereter. Before the rebuild last May I noticed the trans did not shift out of gear at WOT on the highway one day passing someone, then the trans started to slip right after, the car has been sitting since May and I just had the rebuild done 2 weeks ago.
I sent my PCM for reprogramming for headers and the convereter and the WOT problem and that didn't fix the problem. I took the car back to the transmission shop today went for a test drive with a scanner and my mechanic said the PCM isn't commanding the transmission to upshift at WOT and it's a computer problem. TPS voltage is correct, I had the PCM reprogrammed over two years ago when I had an LS6 installed and it shifted perfect up until that day I noticed it would not upshift. My tuner said it's not a programming problem but the PCM itself is faulty.
Before I shell out a few hundred bucks on a used PCM does anyone have some suggestions?

Black98T/A

iTrader: (5)

If it is the whole PCM..am I better off buying and converting to a 99+PCM?

mrvedit

If you decide to switch to a '99 PCM:
The '99 PCM has a completely different wiring pinout, even though the connectors are the same. The best way is to buy new connectors ($50?) and move all the wires one by one from the old connectors to the new ones. There are several guides posted on the Net for doing this.
Personally I would switch to the '02 PCM which some say is the latest-and-greatest for that generation engine. However you should definitely get other opinions on that.

Black98T/A

iTrader: (5)

I can get a 98 PCM retuned for $250. If that solves my problem I can live with that, I just want to make sure that's the problem first.

Black98T/A

iTrader: (5)

Still not sure if this is a computer or trans problem?

Black98T/A

iTrader: (5)

anyone anyone... Bueller?

mrvedit

If you trust the mechanic who said your PCM wasn't commanding the shift (and it seems reasonable to assume your new trans is OK), then it sounds like a PCM problem.
I assume the mechanic has some type of scanner on board; it's not hard to check this with a good scanner; this should rule out the transmission. It could still be a sensor problem (TPS or VSS), but again a good scanner should indicate whether these are working.

Black98T/A

iTrader: (5)

I went for the drive with him with the scanner hooked up...aside from not wanting to do free warranty work, I don't know why he'd tell me it's a computer problem and not the transmission.

Snap-On

iTrader: (2)

Start with the basics first. check the fluid. Is it low? Is it burned?

Vince B

iTrader: (1)

Bottom line is if the transmission does not see the command from the computer it is not going to shift. I'm with your trans guy on this one and the issue is not in the trans.

Black98T/A

iTrader: (5)

Looks full and smells fine and it should it's only 2 weeks old.



Yup, I'm leaning toward something inside the PCM itself...it did it before the trans rebuild..started doing it a year and a half after the first tune and still does it after the retune...I'm going to take it to another trans shop by my house just to get a 2nd opinion before I buy another PCM.

Black98T/A

iTrader: (5)

3/4 throttle the trans downshifts a gear and upshifts like it's supposed to. WOT it downshifts but does not shift out of gear and just goes up to redline. Basically the trans shifts perfect in every way, nice firm 1-2, lockup etc except any WOT shifting.

lt1pwr1

iTrader: (1)

Hmmm, that is interesting. I don't see why the PCM would command shifts everytime except during WOT...that would indicate that the PCM is indeed ok in my opinion. I would think more sensor related at this point. Do you have a spare MAF you can swap in? I wonder if when going WOT your MAF is screwing with the PCM and affecting the shifts (or lack thereof).

Black98T/A

iTrader: (5)

I do have a spare maf I'll try it

Black98T/A

iTrader: (5)

Ok tried a different MAF...no luck. I also took the car to a different trans shop..the mechanic said he's had that happen before and it was a seperator plate in the valve body hole being too big. He said the guy who drilled the holes(which is the same guy who rebuilt the trans and is tellin me it's a computer problem) could have drilled the holes too big and they've gotten bigger over time and could be causing it to not shift at WOT. All I know is I just spent $1500 on a new trans and I can't use my car the way it's supposed to be used.

mrvedit

That is not consistent if you are sure that the trans is not getting the upshift command. If there is no upshift command it doesn't matter how the separator plate is drilled. Usually an excessively drilled separator plate will give you a harsh shift, a flare problem, etc., but not a no-shift condition. When the solenoids say shift, it will shift.

I agree with lt1pwr1 that your PCM is probably fine if it shifts at all but WOT.
Either a sensor is off, the tune is wrong, or some combination of the two.

Its been a year since I last played with forced shifting in the HP Tuners scanner, but a trans shop should have such a tool. If a scanner can force shifts into each gear, then generally your trans and pcm are working fine.

It seems we had a very similar thread here in the past few months.

Black98T/A

iTrader: (5)

I'm not sure the trans is not getting the upshift command...the builder is telling me that. I'm going in circles here...builder is telling me computer problem, tuner is telling me not the tune but pcm itself and another trans shop is telling me it's the trans.

I have to agree with the tuner not being the tune...it shifted fine with the retune for a year and a half then all of a sudden it wouldnt shift at WOT.

sabersaw30

iTrader: (10)

I know this sounds crazy but I had to drill out my throttle position sensor holes to get a voltage where the trans would shift.i had to get like .72 at idle I know that is high but mine would not shift no lower.Dont ask me why because I have no clue why.http://www.golenengineservice.com/do.../Adj%20TPS.pdf

mrvedit

Your frustration in understandable. I'm certainly no trans expert, but am confident I could figure this out in 10 minutes with my HP Tuner scanner. I really don't think its your trans. Unfortunately your two trans mechanics may have a "hidden bias".

Lets assume it is not the trans...
In WOT mode the PCM needs two (tuned) parameters to make a shift - speed and RPM. If either is not above the tuned value, it will not shift, no matter how high the other value is. On the other hand, when you are not at WOT, then only speed is needed to make the shift. The tune also determines what throttle percentage is considered "WOT". I don't see how the PCM could get the wrong RPM and still run the engine. I don't know how/if a flakey VSS could send the wrong signal to the PCM and still have the speedometer correct??? Somehow it still seems related to the TPS and VSS sensors and sabersaw30 claims a TPS change fixed his problem. Again a good scanner and moderately experienced user should be able to troubleshoot this quickly.
Also, in another recent thread the author is now pretty sure that his tune did change (drastically) when his battery went dead; he also could not shift at WOT.

Perhaps a trans expert here will have the magic solution.

Black98T/A

iTrader: (5)

mrvedit..thanks for the response and yes it is very frustrating I have 3 different people telling me it's 3 different things. My speedometer at the moment is not correct..its off 15mph at 80 from this last tune 2weeks ago. I put on my order sheet I have 18 inch tires in the rear. It still didn't shift at WOT when the speedo was correct but could this be related?