Hey everyone, I had installed a built 4L60E, rated at 700 rwhp, in my 2005 GTO a couple years ago. At the time of the install I had a Magnachager, blower cam, headers, catback, Vigilante 3200 stall converter, and a high quality transmission cooler. The car made 508 rwhp on the dyno and the transmission worked great at the track and on the street… didn’t have any problems with the new transmission whatsoever.

After putting around 1k miles on the transmission I decided to take off the supercharger and have a twin turbo setup fabricated. Once the turbo kit was installed the car made 639 rwhp on the same dyno, however, now the transmission would not upshift at full throttle all of the sudden. Nothing was touched with the transmission, transmission settings, etc during the transition from supercharger to turbos, and again, there was only around 1k miles on the same new transmission that was previously working great.

Now at full throttle when it came time for the upshift it would seem like the engine would just hit the rev limiter due to the shift not taking place. I brought the car back to the tuner and we then tried making a bigger gap between the upshift RPM and the rev limit. For example, we may have set the upshift RPM at 6000 and the rev limit at 6600, where it was previously working fine with upshift at 6400 and rev limit at 6600. I noticed that with the charge pipe off (building no boost at all) the transmission would shift fine at full throttle, but as soon as I connected the charge pipe back up it went back to not shifting at full throttle. The car shifts fine at anything under probably 80% throttle with boost, but when you really plant the throttle at least the 1-2 shift, and the 2-3 shift won’t happen. Not sure about the 3-4 shift as I haven’t had an area to test that kind of speed safely.

Someone suggested to me that since my torque converter was spec’d for my original Maggie setup that it was very likely that I was “blowing through” the converter, and needed to send it back to have it spec’d for the turbo setup. I sent the converter back and was told that a different stator was installed that is used in turbo setups typically, and they raised the stall from 3200 to 3400 RPM. I re-installed the converter once I got it back and was hoping that was going to fix the issue, but still no luck with the car shifting at full throttle.

So now I’m trying to determine if the amount of horsepower or torque is too much for the transmission, or if there is still something electronically preventing this thing from shifting. Is there any scenario where over-powering the transmission would allow it to not upshift at full throttle when it is a freshly-built transmission that never slipped and worked fine when making less power??????? Thanks a bunch for any advice that you all can provide!

EDIT: I should also clarify that when the upshift doesn't take place at full throttle the transmission WILL upshift once I back off the throttle a bit. But if I keep my foot planted the transmission just allows the engine to keep revving.

We have also tried lower the shift speed to a speed below the RPM shift point but the issue persists.

 

Its really tough to nail down shiftpoints with a stall even when the car is n/a. Since you changed the combo I would up the limiter to 6700 and do some runs when the car is hot. I think the reason is the car is reving faster than before. Make sure your tire height in the tune is right on as well.

Have your tuner put the car on a dyno and play with the shift points/rev limiter. Sounds like a tune problem-no biggy. I would not do WOT runs on the 3-4 shift.

 

There is no mechanical issue that would cause that however it can be as mentioned very hard to nail down shift timing. Trouble is when you increase power you increase the rate the RPM rises and that get you to the rev limiter much quicker yet the actual time from comand to shift on the trans is unchanged, It can be tricky to get this worked out and with your power, stall and gears 600 rpm is really nothing its a blink really . I would lower the shift MPH and RPM down to whatever it takes to shift then work on refining from there. But it will likley indeed have to be done live on a dyno or the track anything else would just be random guesses

 

as stated before is the tire and gear ration correct in the tune? Sounds stupid but is always a possibility but I am going to assume they are good since it worked fine before. Its kind of common since it would shift WOT with no boost cause its not making any power. I have dealt with every kind of shift issue you can think of, it has to meet the MPH first then it looks for the commanded shift rpm. It doesnt matter how fast it gets there thats the 2 parameters its looking for speed then mph. If you have tried lowering the WOT shift mph to something like 5mph and 6000rpm from 1-2 and it still doesnt shift then plain and simple its not going to hold the power your now making.Ive been there and done that and tried and tried to make it work but it simply wasnt holding the power. I see whos trans it is in your sig and the response they gave. Just food for thought.

 

Thanks a bunch for the input guys, that was all very helpful. I am pretty sure that the tire height was calculated, at least according to the tuner I believe he said it was when I may have asked him almost 2 years ago when the car was last tuned and last running but I can't say for absolute sure-- so that's certainly something to go back and check on. Mike and Frank, I'll definitely make an even larger gap between the rev limit and the shift point. You're right.... I have a better shot at starting with a low shift point and working my way up, so I'm going to go that direction. Thanks fellas! And Frank, just wanted to make sure this sounded more electronic than mechanical so I knew that I wasn't wasting time paying the tuner to attempt to adjust something that can't be fixed. Good to hear that it doesn't sound to be mechanical.

Brian-- very good piece of info on having to meet the MPH before the RPM. I hadn't known that and hadn't read about that before.... so I'm sure that's quite possibly a problem right now. As soon as I can get someone with HP Tuners or EFI Live to look at it I will let you guys know of the outcome. Thanks again!!

 

and also make sure the misfire thresholds are turned off, if I wasnt in Afghanistan right now I could tell you exactly which parameters to mess with but trust me I have seen and tried everything to get a fried trans to shift but just couldnt do it.

 

Mph will hold back no matter what your RPMs are ask how I know I started low then slowly went up with them to get my shift points example start with 35 mph 1-2 and you may end up with 37 when you are done! Make sure that in you wot mph table matches your 100% tps column in your normal part throttle shift table!!

 

Thanks for the additional suggestions! I'll have to have someone check that TPS table comparison for me to make sure things are right-- that's something I'm totally unfamiliar with.

What exactly are misfire thresholds?? The off thing is that like I mentioned in my original post-- everything worked just fine at WOT before I took the Maggie off and went to turbos. The only thing that changed is that I'm now making more horsepower, and making that power differently. The tune that was done for the turbos didn't touch upon the transmission settings since everything was already working great in that department at the time.

I remember we even loaded up someone's stock 4L65E tune off another '05 GTO, and then tried making a bigger gap between the upshift RPM and the rev limit after finding out that the stock trans tune didn't work either. Blah.

 

then im willing to bet your trans is just not holding the new power, think about it, you said your making 130 more rwhp, thats roughly 200 more at the motor, which is a lot more power than before. Hate to say it but gotta pull it and get it built right. Just sayin

 

Pull the pan, take a look at the fluid condition and what's in the pan... a pic or two would be useful.

 

Hey Brian... yeah I was originally kinda worried that I was making too much power for this transmission, and I do realize that I'm making around 200 more crank hp than previously, but this dyno usually reads a little high. But even that said, I was making 640 rwhp on this dyno @ 8 PSI. I'm now running 7 PSI and swapped my 243 heads for 317 heads (less compression, less power) and still have the same problem. I'm probably down to somewhere around 600 rwhp right now if I had to guess, and the transmission again is rated at 700 rwhp. I would imagine that it can realistically support more than 700, as it's probably under-rated, but that's only my theory which I understand could be wrong.

I currently have 7 psi springs in the wastegates and I still have 2.9 or 4.3 PSI springs laying around somewhere so maybe I'll pop those in place for kicks, start at the lowest PSI, see if the trans shifts, then work my way up in boost with the boost controller and see when it stops shifting. I might be able to do this on a Dynojet and actually know what kind of rwhp I'm making when it stops shifting.

 

I do think I drained a little fluid when this first started happening and found no discoloration nor metallic flake in it. Maybe now that the car is running again and the issue has continued would be a good time for me to at least drain more fluid and inspect it.

Just to possibly save myself the cost of a bit of fluid to pull the pan (have a deep pan and external cooler, and it's filled with Royal Purple-- a good few $$ just to pull the pan).... what would there be to look at besides the fluid by pulling the pan? Thanks!!!



Also.... would it be strongly considered to drain the synthetic fluid and refill it with non-synthetic? Maybe the synthetic is too slick????????????

 

Yes, get that synthetic **** outta there go to Walmart and get you a good DEX III and refill. I believe mine is the Castrol Dex III IIRC, been runnin it with no problems, and as my builder can attest to, still looked mighty pretty when my unit was refreshed roughly a year ago.

 

+2 Do you have a vacuum modulator on your trans? Sounds like the clutches are not holding the power.

 

Personally I would first make a real time determination of when the shift is being commanded The trans if commanded has two options shift or slip it has no mind of its own its cant randomly decide what it wants to do. I had a guy about a year ago complainig of the same issue and this is what I had him do if you would like to do the same it may give you some insight I am posting this below. With this tool he determined that in fact even though he was setting the tuning to make the comand at a given RPM and MPH it was infact not making the command at that time. We have several Level 2 and 3 units running in the 9s one of which is a GTO with a level 2. Fact is if it was slipping rather than making the shift you would only be able to do it a few times particularly on the 2-3 before you would have no 3rd gear at all at any speed as the 3-4 clutch would be toast after only a few times slipping. Another indicator is if the shift will happen just off WOT this also tells the story. Anyway below is a diagnostic tool if you choose to make it that will prove very helpful in your case I am sure. In his case though I do not remember the details he found that there is indeed more to getting a shift to happen at a given point than simply MPH and RPM If remember correctly his issue ended up being related to MAF verse TPS in his case.
Frank

Parts- all from radio shack cheap
1-Three 12v LEDs They can be different colors(NO LIGHT BULBS WILL NOT WORK)
2-Some sort of bevel to mount them in Or you can mount them in a panel in your car permanent.
3-Three lengths of wire. Perferably different colors to avoid confusion.
4-Blue side wire splicers the type you use pliers to push down the tab to make a splice.

Ok you want to hook the three wires to the following in the harness either at the trans or find them at the PCM
A-Light green wire. This is the 1-2 shift solenoid.
B-Yellow with black stripe. This is the 2-3 shift solenoid
C-Tan wire with black stripe. This is the lockup (TCC)
solenoid.

Do not cut the wires use the slicers and connect your wires one to each and then run them into the car.
Inside the car take each wire and hook up to the negative side of the LEDs choose which ones you want to represent each solenoid.
Tie the POSITIVE side of all the LEDs together and run a wire to a 12v switched source(radio fuse)

Ok now its simple

(1-2)on and (2-3) on is 1st gear
(1-2)off and (2-3) on is second gear
(both off ) is 3rd gear
(1-2)on and (2-3) off is 4th gear
TCC on means your converter should be locked.

 

Don't know if this will help. I just had a problem where mine would not shift into 3ed @ WOT. I drove around watching the vehicle speed input on my diablo and the input was jummpin around above 60 and when i went WOT it would start dropping into the 40 mph range, so the pcm was not getting the signal to shift. The connection to the speed sensor was good so i swapped sensors and all is well.

 

So I just tried replacing the speed sensor in the transmission last week using a new GM sensor, but after taking it out for a ride I still have the problem. I'm still arranging to get the trans tune looked at again and modified, so if I continue to not be able to get things to work after that I will try what you said, Frank. Just too darn hot outside lately to crawl under the car and find/splice into those wires lol. I'll keep you all updated though.

 

This post is money. As power increases, the converter will flare more causing reduced mph per rpm. Meaning at 6k in first you may be going 35mph, now add 200hp to that trans/converter setup and now the converter slips more and at 6k you are only going 31mph. So at WOT you must hit mph frst THEN rpm. So if originally you commanded a shift at 35mph AND 6100rpm, it would meet the two requirements in the correct order. Once the new power is applied, you hit 6100 first then at around 6300 or whatever you hit the required 35mph and the computer freezes up and the shift does not take place. The requirements must be made in order or shifts don't happen as expected. As an example, I had to lower my shift mph by about 5 mph when going from a 3200 converter to a 4k simply because the bigger converter slipped more at high rpm meaning I was not hitting the required mph first like I was before. You simply need to log rpm and mph, then use that real time info to set your WOT shift MPH. Every converter/engine combo will be different, there is no perfect preset figures, it must be calculated real-time.

 

I had the same problem till we went with a vacuum modulator. Rossler recommends them on his builds. I also replaced the connector on the wiring harness going to the VSS. All has been well since.

If the tranny is built correct it should handle the power, on spray we are making 700 plus hp.

 

Beleave me I understand the heat problem outside it sucks.