First a little history,
I done several mods power wise as well as a blower just a few months back, and lost the stock transmission (2nd gear) pretty quick with the new found power.
I had a upgraded trans built to hold the new power level, and well as a small stall converter. NOW here is the problem.
When the car reaches 5500 rpm in second gear, it just lets go and shoots straight to (6500) the rev limiter. I am not sure if it would do this in first gear as that gear is use less with the power the car is making on a set of Nittos. The Tuner with (HPTuners) has been back and forth going over the tune, and yet has found what may cause this. I have a call in to the trans builder, but have not gotten a hold of him to get his thoughts. I did talk to Doug at ECS, and he told me to just pull the Computer and send it to him so he could look over the tune, but before I do that, I would like to put it out here in case someone may know what would cause this.
Thoughts and opinions are appreciated.

 

Man that sure sounds like 2nd is slipping. Hard to imagine it right after a rebuild though. My A4 does that in 1st gear at the top of the rpm range. My A4 recently started slipping after my mods last summer. Mind you, the A4 had 120K on it and my mods were putting out 430rwhp. Poor ol' A4 just needs a bit more to handle that for the long term. I'm having mine rebuilt to handle 750hp so hope that will end this worry spot. Throwing in some 3.42 gears while I'm at it with an ECS differential that will handle 1000hp (just in case of future mods )

 

1st what do you mean by "small stall converter "? small in stall or small in diameter ?
Please tell us exactly which converter you bought
2nd---IF the problem is NOT mechanical and in the tune--sounds like the ECM is skipping over the shift point RPM and hitting the safety rev limiter
What makes it do that usually is rather complicated to explain---The answer lies in both the WOT upshift MPF and downshift MPH-----They are both too HIGH--
In order to command a shift at WOT the ECM must hit 2 parameters--1st the "shift at WOT speed---- and second the shift at WOT RPM
Say you have 70 MPH for the 2-3 shift---and the RPM's at 6000 at WOT
Look at what RPM's the tune says you have at 70 --the difference between these 2 numbers is called the "split" The more modded the eng is the larger the split has to be---A stock split is around 700 RPM --In your case with boost your's may have to be more like 1500 RPM's
EFILIVE automatically shows you the Split on both the upshift/downshift tables so I'm sure HP does too----
My guess is that it's a mech issue--sorry !!!--as the problem seems new---and my guess the TQ converter----

 

All the stuff that you replaced/upgraded, Its MANDATORY to have the PCM tuned with the correct shift points and all the other transmission parameters the need to be changed to support the modifications.

Without the proper tune transmission parameters, its going to be tough to really figure out what is wrong and yoiur transmission shop is going to blame it on the tune.

MY 2 cents

PS

tblu92 Knows WAY WAY WAY more about PCM tuning and trans programming that I EVER thought about trying to learn.

 

The stall converter is a 2600, and that is what I meant when saying small.
tbl92, thanks for your input, we will take a better look and see if we are missing something, and follow up on the points you mentioned. I think maybe the rev limiter is 800 rpm higher than the shift. I do think the shift is set at 6000 and it actually revs up around 5400-5500 rpm.
we will give it a look over again.
1 more thing, since the trans was built, the car is shifting into 2nd at light throttle very hard,, could the trans be in limp mode for some reason, I have not got a code?

Bill, i always welcome your input, you actually helped me a great deal with your input on my SWPS issue..........All fixed now, thanks.

 

OK, I am back in civilization with internet access. I have been working with Mark on tuning his supercharged '01 convertible. Yesterday I posted on HP Tuners asking for opinions HP Thread Here. Looks like we have a little better support from Bill and Tblu over here though.

So here is what I wrote in the other thread:
Here is a screen capture of the scan where we tried a 2-3 shift at WOT. Notice in the circled area where the RPM rate of increase (angle) turns up immediately after the shift was initiated by the ECM.



For reference from the existing tune:
2-3 shift Performance 70 mph
3-2 downshift Performance 66 mph
2-3 shift Performance WOT 5,800 RPM
Rev limit set @ 6,400 RPM (all gears)

From the scan you can see at 74 MPH it's at 5,400 RPM. The 2-3 shift numbers that shown above were actually 200 RPM and 3-4 MPH higher at the beginning but I lowered them to those values in an effort to get it to shift.

Going forward I was planning to drop the Force Motor Current in 84 - 100 columns and bump the Max Pressure and shift pressure to 96 psi. The other night I told Mark I just wanted to bounce the idea off some more seasoned transmission guys before I increased the line pressures.

Thanks for any and all help. We really need to get this hot rod to the point where he can enjoy it.

 

Hey Clyde,

I looked at the tune and the log.
You are commanding the shift at 70mph in the tune. The log shows the shift commanded at 74-75 mph.
Are you shifting this manually? PRNDL status would indicate that. It seems that the lever was moved at 70mph? I've never logged that status as I leave mine in OD when racing.

These transmissions act weird when shifting manually, you need to move the lever to 3 way before the mph in the tune, otherwise the trans gets confused, it will not see the tune mph in time and it will refuse to shift. Mine made an idiot out of me at the drags until I understood how to drive it manually. As soon as you put it in D3, all the auto features take over.

Probably too powerful of a car to just leave it in drive and stand on it.

A couple of points.
The part throttle shift table, last 2 columns should match the WOT shift points. Even though they are part throttle tables, note that they contain 100% TPS data.

The trans needs time to shift. And it looks for mph first, then does it's thing and will shift at the or close to the desired rpm. As tblu92 alluded, there needs to be a split. With more power like this, it needs to be widened.
I set my shift times to 0, just let the mech time rule.

I don't think I'd mess with the force table.

What do you know about the trans rebuild? Was a shift kit installed?

Lastly, does it shift after you lift off the throttle?

Ron

Ron

 

Ron,
Clyde can answer the technical questions better than I can, but here are the simple answers.
I have to shift manually just to get the car under power in second before shifting it into 3. Reason is simply because the car will rip the tires at will in 2nd gear at speeds around 55 and below. So on these tune pulls, I lay into it slowly to get the car moving. I did the same thing while tuning it with a stock transmission, and the car shifted fine. I am not sure about a shift kit, I do know stronger springs was mention to assist the shifts.
To me, it does not feel like it slips at the 2nd - 3rd shift, it seems to just rev and slip around 5400 straight to the limiter, BEFORE the shift. And again, this is from a drivers opinion, the laptop may show the gear change and slip at the same time, this is a Clyde question.
Mark

 

I suspected as much. It's possible the converter slippage confuses the shift points because the rpm no longer matches the mph.
It's not clear to me that the 2-3 shift happens in that log.

But, I see that the lever was moved in time in the next part of the log, which rules out my prev theory.......so Clyde, have a look at the engine rpm vs trans input rpm. It quits tracking right where the rpm takes off.
I'm thinking converter issue.
What kind of converter?

Let's see what Clyde thinks.

 

tblu92 sent me a lot of info that I have forwarded to Clyde, and for that, I really do appreciate it.
As for the converter, it is a 10" PTC 2600 stall

 

Before messing with the force solenoid current or shift pressure tables you should get a line pressure gauge on it so you know what the line pressure is.

 

You are in good hands

 

Just a question here, but if I were to take the car through 2nd gear manually to redline, and it goes past the 5300- 5400 rpm rev up., would that not eliminate the torque converter?

 

Good idea. Keep the shift out of the equation.
Log it too

 

Great to get all the input from my online friends Ron and Tblu92. It's cool how familiar I've become with Ron even though we've never met. We both have modified C5s and turbo LSx powered Gen3 Novas so it was just natural to become online friends.
I just got back from a work trip to New Orleans last night. Ate some oysters, crawfish, shrimp po-boy, and gumbo. So now I can get back with Mark and experiment with adjusting the shift mph/rpm spread to see if we can't get past this issue. We will be sure to report back on the progress.

 

Just took the car out for a test drive.
The car WILL PULL TO RED LINE when you shift manually. So maybe this will eliminate some of the theory's.

Mark

 

I wanted to look at your graph, couldn't at work and it's not showing at home either. Can you post the screen capture again and the log here?

If the shift actually was commanded right when the rpm jumped then that would point to it being a transmission flaring problem where 1st has released but 2nd isn't grabbing.

 

So any progress on this?
Hey Clyde.....I'm street tuning the nova now. Feels pretty damn good at only 5 psi.....

 

Ron,
A quick update. Clyde and I talked after all the input we got, and we both kinda felt this was going to be either in the Trans, or the converter instead of the tune. So I pulled the trans out, sent it back to the builder to open it up for a recheck. I also am having the TC looked at again to cover all bases. I have a set of 315/35/18 Drag Radials being shipped in and should have them this Thursday. If all goes as I have planned, I will have the car back together by Friday so Clyde can work with the tune from all the input we have got from everyone here.
If all goes well, I plan to put this car on a mid 6 sec pass with a big mph this Saturday.
A big goal for a car that is in pieces right now just for days away....lol.
Mark

 

Man, that's a bunch of work on a C5!
I look forward to hearing the results!
Say hello to Clyde for me. I know he is a busy guy.
Ron