Author Topic: Auto trans shift RPM (Read 14730 times)

TC-GXP · « **on:** December 03, 2011, 10:59:28 AM »

Twice now my transmission has held the 1st to 2nd gear full throttle shift to 7000 RPM or thereabouts till I let off the throttle. It first happened a few weeks ago and then happened again yesterday. I rarely beat the car so it spends very little time at full throttle but yesterday I felt like getting on it.
I was getting on the highway when it happened both times and the engine had been running quite a while so it was fully warmed up. I had floored it from a dead stop when it happened both times. So after it happened yesterday I went down the road a bit, pulled over and tried it again. This time it shifted at 6500 which I thought was still a little high so down the road a but more I did it again and this time it shifted at 6000 RPM. As a side note I see it shifts 1-2 at 60 and 2-3 at 80 which is pretty cool.

I thought these electronic transmissions had no governor so the shifting is controlled solely by the transmission computer? Computer's don't "stick" like an old school governor could (though I know they are far from perfect) so what's making the shift point on the 1-2 vary? I believe I read there's a limiter for the ECM to keep the engine RPM to a max of around 6250 (I have the GMPP turbo upgrade kit/reflash) so is it possible it really hit 7000 RPM or was my tach giving me bogus numbers?
I don't want to blow this thing up so I wanted to ask you guys if this is a known issue with the 5L40-E before I call the dealer to take look at it. If I know there's a common problem I could fill them in on it rather than have them blasting up and down the highway with my car at full throttle trying to duplicate a problem they may or may not find. I have no check engine lights on that I see either.

Arabas · « **Reply #1 on:** December 03, 2011, 11:44:04 AM »

did u buy the car brand new or used?
if the second, maybe the prvious owner had done some computer tranny tuning that he didn't tell you?
you could work with DDM, Westers, Trifecta or another tuner of your choice, log and see if there is a tune on your auto tranny or not. they could probably have a look at this "problem" too..

TC-GXP · « **Reply #2 on:** December 03, 2011, 11:58:44 AM »

I bought it used and the previous owner was an older guy who wanted a little red sports car. He added the GMPP exh, CAI and Turbo upgrade because he wanted to "make it unique. Like no one else had"

I guess he never went online and saw that a lot of people added the same stuff.

He never said he did anything to the transmission but I never actually asked him about it. He works at the dealership I bought the car from and the service department knew about the parts he added because they did the work for him so they all filled me in about the history. I'll have to inquire if they did any transmission work to it.

Has anyone else had similar problems like this?

BSRL · « **Reply #3 on:** December 03, 2011, 12:50:19 PM »

Sounds like the best thing to do is go back to the dealer and talk to them about it. They will probably want to do diagnostics on it and of course this will cost you unless it is still under warranty. I doubt he had an aftermarket tune on it so I seriously don't think that is the issue.

miller11386 · « **Reply #4 on:** December 03, 2011, 01:22:00 PM »

Under warranty = go to dealer

Not under warranty = go to DDM or westers and get a trans tune

TC-GXP · « **Reply #5 on:** December 03, 2011, 02:29:12 PM »

OK I'll give the dealer a call. Thanks! What is a normal full throttle shift RPM for these things in stock configuration?

Gentleman Jack · « **Reply #6 on:** December 04, 2011, 11:56:05 AM »

MARVIC 1 · « **Reply #7 on:** December 04, 2011, 02:00:58 PM »

Quote from: TC-GXP on December 03, 2011, 11:58:44 AM

I bought it used and the previous owner was an older guy who wanted a little red sports car. He added the GMPP exh, CAI and Turbo upgrade because he wanted to "make it unique. Like no one else had" I guess he never went online and saw that a lot of people added the same stuff.

He never said he did anything to the transmission but I never actually asked him about it. He works at the dealership I bought the car from and the service department knew about the parts he added because they did the work for him so they all filled me in about the history. I'll have to inquire if they did any transmission work to it.

Has anyone else had similar problems like this?

Sure the "Old Guy" wanted to be different

, He floored it brother with his GMPP Upgrades....

Uranium-238 · « **Reply #8 on:** December 04, 2011, 05:07:12 PM »

Turbo upgrade? As in the GMPP engine tune? Doesn't that tune up the redline to 7k?

TC-GXP · « **Reply #9 on:** December 04, 2011, 09:03:43 PM »

Yup the GMPP turbo upgrade/flash kit, whatever you want to call it. I thought I read it increased the engine RPM cut off from 6000 to 6250 so I wouldn't think GM would want the transmission to shift higher than that. AFAIK the GMPP reflash is just for the engine and doesn't have anything to do with the transmission computer so unless someone went in there and changed something I'd imagine it's set up as GM intended it.

kennysabarese · « **Reply #10 on:** December 09, 2011, 12:20:57 PM »

Quote from: Uranium-238 on December 04, 2011, 05:07:12 PM

Turbo upgrade? As in the GMPP engine tune? Doesn't that tune up the redline to 7k?

GMPP raises it, but not all the way to 7k

tazz · « **Reply #11 on:** December 09, 2011, 04:27:44 PM »

only to 6500.

kennysabarese · « **Reply #12 on:** December 12, 2011, 09:17:00 AM »

I just drove a Wester's tuned automatic trans, and well, it was not like anything I'd experienced before in an auto. Awesome for smashing it. But not for cruising. Good thing is you can just turn it on and off by moving the lever to L

ChopTop · « **Reply #13 on:** December 13, 2011, 11:15:39 AM »

So this doesn't have anything to do with the computer constantly telling the transmission to adapt to your driving style? Meaning the more you mash the auto pedal on a consistent basis the higher or quicker the computer will learn you have a dead or lead foot?

SKY888 · « **Reply #14 on:** December 13, 2011, 12:27:49 PM »

TC-GXP.....how far are you from Bellingham/Hopedale, MA?

kennysabarese · « **Reply #15 on:** December 13, 2011, 12:32:49 PM »

Quote from: ChopTop on December 13, 2011, 11:15:39 AM

So this doesn't have anything to do with the computer constantly telling the transmission to adapt to your driving style? Meaning the more you mash the auto pedal on a consistent basis the higher or quicker the computer will learn you have a dead or lead foot?

No learning is done by the TCM afaik

SKY888 · « **Reply #16 on:** December 13, 2011, 12:35:23 PM »

has Wester able to control/tune when automatics shift?

I mean.....for example...instead of shifting at 4000...he can now make it shift at 4300rpm?

my friend worked with Lyndon this summer, and Wester wasn't able to make it shift at a higher rpm on his solstice.....

kennysabarese · « **Reply #17 on:** December 13, 2011, 12:37:47 PM »

Spiky's car has the TCM tune as does DickW's and a few others. I drove Spiky's car and I was hitting the rev limiter. So yeah. He changed the shift points. He is not able to do it remotely, they had to mail the TCM to him. I think DickW actually drove up there.

SKY888 · « **Reply #18 on:** December 13, 2011, 12:45:13 PM »

hmmmmm...interesting.

Project scarab did the same thing...and had Wester do his.

both SMG and Project Scarab can prove that the shift points were not changed

kennysabarese · « **Reply #19 on:** December 13, 2011, 01:04:32 PM »

I can't comment any more than I have. I don't know the details. I wonder if the year of the car has anything to do with it.... Spiky is 07. *shrug*

SKY888 · « **Reply #20 on:** December 13, 2011, 01:07:02 PM »

trying to txt josh, and get more info from him as well.

we're txting right now.

he told me he sent his TCM to wester.....but nothing.

that's why they scrapped that idea........

howcome two other cars are getting higher shift points though....hmmmmmm...

kennysabarese · « **Reply #21 on:** December 13, 2011, 01:10:55 PM »

I have no clue. Other's can chime in who know more.

tazz · « **Reply #22 on:** December 13, 2011, 01:23:10 PM »

Max RPM in a gear at least in a auto can actually be controlled somewhat with HPT. I know that there is a table that has cut off rpm vs gear and you can raise that table and effectively raise your Max RPM shift point through the gears.
With that said the TCM probably can do this as well but in more detail as well as changes the way the auto engages the shift at lower RPM's and load to give you more of a hard hitting/quick shift at varring RPM's and Loads.
I don't know if the TCM's are different from year to year but I do know that the 07 GXP TCM can be changed but I opted not to do so at the time but I would think the TCM's are the same but who know's?

SKY888 · « **Reply #23 on:** December 13, 2011, 01:25:48 PM »

Max RPM in a gear at least in a auto can actually be controlled somewhat with HPT.

you mean manual???

tazz · « **Reply #24 on:** December 13, 2011, 01:30:13 PM »

No
I have an auto and I can raise or lower my MAX RPM's in any gear with just HPT but if I want to change the way the tranny actually shifts at lesser loads then I need to send Lyndon my TCM.

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Author Topic: Auto trans shift RPM (Read 14730 times)