Junkyarddog89

Ok so I got a problem. Almost stock '02 Camaro A4 with 40K. It wouldn't up shift at WOT, took it to the dealer, they put a new tranny in it (got a warrenty when I bought it for free)... I'm having the same problem still. It wont up shift into any gear weather I leave it in drive or over drive or shift manually it just bangs the rev limiter till I let off a little. I know I shoulda held out for a M6....... Any Ideas? Could this be fixed with an HP tune? Is it possible I got a bum tranny? also shifts funny into 3rd driving normally sometimes.

Junkyarddog89

Really? Nobody?

95_transam_lt1

iTrader: (6)

maybe a tps or vss issue? what you need to do is watch the computer command the shaft valves open and closed to see if it is physically trying to shift or something else is wrong where it wont allow it to shift.
to upshift governor pressure must overcome throttle pressure. in an electronic trans vss input must hit specific value to be higher than the tps.
are there any codes?

Junkyarddog89

No codes at all. When the dealer was checking the old tranny they said the computer was commanding the up shift. They test drove it with the new one and said the same thing. The tranny was replaced for excessive clutch wear wich I assume beacuse i bought it a year ago with 33K on it and drove it kinda hard but They found no computer issues with it. I'd look more into it myself but I don't even know ware to start. I'm still new to this computer stuff. It should trow a code if the TPS was acting up right?

01ssreda4

iTrader: (96)

Pretty sure the MAF has a lot to do with line pressures, and bad MAFs though they won't always throw codes can cause transmission to burn up prematurely. I would replace the MAF with a known good one or have somebody datalog and watch the MAF readings to see if they are normal.

95_transam_lt1

iTrader: (6)

^what he said. And also it could have a tps prob without a code.

Junkyarddog89

Thanks guys Ill start with the cheap stuff and work my way up, I had no idea it could be a MAF, I've heard the TPS before but I heard they will usually through a code. I do appreciate it.

performabuilt

iTrader: (25)

Yes MAFF,TPS,VSS also note that power adders may cause the time from comand to shift to need to be increased for instance at 300 hp you might comand the 2-3 at 6000 and it may happen at 6300 but 400 the same comand and it may not happen till 6500 or more hydraulics are not instantanious with a shift kit they can be faster but still this rule will hold true to varying degrees.

jimmyblue

iTrader: (11)

First you need to distinguish between "won't shift, ever"
and "won't shift before I get tired of hearing the rev limit
go pop-pop-pop-.....".

Another question is whether this is rev limit without slip,
or rev limit with slip (flare).

There are things that can be put wrong by careless tuning.
Who's stuck their pinkie up this bitch before you met her?

mrvedit

A quick test is to disconnect the MAF. It will throw a code, but the engine will then use only the MAP to determine load and generally will run just fine and almost perfectly.

It doesn't sound like you have tuned the car, but some tuning newbies miss that that the trans will not upshift at WOT until both the tuned WOT RPM -AND- WOT speed are reached. Assuming a stock tune, a defective speed sensor or a slipping torque converter could cause a lower speed value being sent to the computer and preventing it from upshifting at WOT. (This is my guess.)

bigken

iTrader: (8)

Not trying to hijack this thread but would the same apply for a car with over 400rwhp and a 3600 stall that since the stall the car will not **** under WOT?

mrvedit

I'm no expert on this matter, but since no one else has answered, it is my understanding that the answer is Yes. High stall converters often have a bit more slippage which means the RPMs are higher at a given speed than the stock converter. This is one reason it is recommended to get a tune after putting in a high stall converter. Generally the solution is to reduce the WOT shift speeds for each gear by 3 or 4 mph.

Junkyarddog89

The car is stock except for a cat-back and lid and it did it before I bolted those on.

It doesn't slip and only does it at WOT, it will shift if I let off about 1/8th throttle. I don't really know if it will eventually shift after hitting the limiter a few times I back off when I hear it hit. And from what I've seen nothing ECU wise or otherwise has been touched.

Car is not tuned as far as I know, it sure doesn't feel like it. So I disconnect the MAF and just see if a code pops up?

bigken

iTrader: (8)

JUNKYARDDOG89 I am in a similar situation only my car is highly modified and I have a 3600 stall converter. My tuner told me that it could be that the clutches could be worn down and under light loads there is enough material to engage the upshift but under wide open throttle there isnt enough material to shift. Mine does the same thing yoiu explained and shifts fine with no slipping until it is at WOT. I even had him try to command the upshifts at WOT at 4500RPM and it will still go to the rev limiter so I am just planning on rebuilding the tranny.

mrvedit

It will definitely pop up a code; ignore it. What I meant was to disconnect the MAF and then see if your trans still has the shifting problem at WOT.

However a CAUTION: I tune my car with and without MAF at WOT and have wideband O2 sensors with in-dash gauges. There might be a small chance that your engine would run too lean with the MAF disconnected and thereby damage itself at WOT. Hopefully someone more experienced can chime in here and say whether that is safe to try. (My experience is only with custom performance tunes; nothing "stock".)

Junkyarddog89

Thats what I was told as well, It turned out my clutches were worn and I had a pump going out. I have a brand new tranny in there now with less than 6K on it and I still got the same problem. If you figure anything out let me know.

Junkyarddog89

Oh ok I got ya now, sorry. Thanks for the tip.. Not sure if I'm brave enough to try that just yet haha

redbird555

iTrader: (14)

to the guy above who was asking about the stall... the reason a stall needs the shift points a little lower is that the higher stall allows the flash point to be much higher and it may actually "blow" right through the shift point by setting it earleir it gives the tranny more time to shift.

to the op you can unplug the maf on the stock tune and run it. it will force the car to run in open loop and it will just run off a predetermined computer tune if that helps the tranny out then i bet its the maf. my buddy actually had a problem with his tranny hitting the limiter going from 2-3 and it ended up being the ported maf he had on there was screwing up the reading, put the stocker back in and all is well again

mrvedit

As redbird555 agrees, in theory disconnecting the MAF should be fine even at WOT. This puts the PCM into "speed density mode" and the stock PCM uses the VE table (instead of the MAF table) to determine the load on the engine. It certainly is safe with a perfectly running car. However, in the extremely remote chance that e.g. your MAP (now the critical sensor) was flaky or your fuel pressure was low, it could result in a lean condition at WOT. You are probably 99% safe; I just don't want my novice advice to cause someone to blow their engine.

jimmyblue

iTrader: (11)

A scan would clear up a lot of questions, like whether this
is a matter of intention or action (Trans Current Gear is
the signal of intent - did it move on time,and the shift is
late or hung, or has it not decided to shift and you can
chase "why?"? Action would be seen in your input/output
shaft ratios, how quickly and abruptly they follow gear
select.