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1999 Cadillac STS
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Discussion Starter #1
Hi all,

I just had front and rear oil seals and the oil pan gasket changed on my 1999 STS.

Everything is running fine, no codes, and the transmission fluid is at the right level.

It shifts fine and smoothly almost all the time, just like it used to. Goes into overdrive.

The problem is, when at WOT, it won't shift at the redline...it went past 6500 RPM into the red once and I noticed it at 7000 in the red and either backed off or it shifted, but I'm not 100% sure. I've since tried taking it up there a bunch of times (without letting it go into the red) but it will not shift. I drop off the gas and the RPMs drop back down and then I can feel it shift into 4th or whichever gear it should be shifting to. It ALWAYS shifts correctly all other times, this only happens when I put the pedal to the floor and keep it there. Again, no codes showing at all and no other symptoms.

I'm hoping this is an easy fix that has something to do with the trans/engine being out for the seals.

Before, it used to shift at 6500 at WOT, just before the red line, every time.

Any ideas?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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This just a guess, but there may be a harness connector loose or not making contact, or a line pressure sensor and/or input speed sensor has gone out.

You're correct: It should shift right at the indicated redline.

.....Did you check the fluid with the engine running, hot, in P - or off ??
 

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1999 Cadillac STS
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Discussion Starter #4
I'm hoping it's a loose wire or something like that. Checked the trans fluid with the engine running, hot, in Park.

Ranger: No codes. I'll check again but there were absolutely no codes coming up when I went through the procedure to check them.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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from the 2002 Seville FSM: pp 7-208 & 209.

Convertor ballooning: one or more shift valves stuck open - debris.
Extended or delayed upshifts caused by:
1. Calibration: Incorrect platform or program level
2. Pressure regulator boost valve stuck in bushing
3. Transmission fluid pressure manual valve position switch inoperative
(this valve receives an ignition voltage hi/lo signal)

"The transmission electrical connector is an important part of the transmission operating system.....dirt...moisture, bent pins......and a note:
Whenever the transmission external wiring is disconnected from the harness and the engine is running DTC's will set and must be cleared after reconnecting......."
 

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1999 Cadillac STS
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Discussion Starter #8
Thanks for that, submariner! I don't think #1 applies, but #2 or #3 might. Does it go into how to test for those? I still have absolutely no codes.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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You ain't gonna like this................In answer to your question about 2 and 3, it looks like the service manual follows the party line and says to utilize a Tech II and dealer diagnosis program.

Other than checking the main harness connector and pulling DTC's, (if any), that's the end of my line...............
 

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1999 Cadillac STS
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Discussion Starter #10
Ouch...that hurts...well, I'm going to do a drain and refill and see if that changes anything... doubt it will, but it can't hurt. Thanks for all the info. I'll update this thread with my end results.
 

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1999 Cadillac STS
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Discussion Starter #11
One more note on this...I found this old discussion thread:

http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/12475-specified-northstar-max-rpm-vs-actual.html

If I remember correctly, BBob isn't around anymore so he can't verify this....

I'm just a bit concerned that while trying to fix this, taking it up into the red constantly will damage the engine. From the thread above, it sounds like the rev limiter should prevent me from doing this? Could the tach be reading wrong and when it shows me at 7k, I'm really only at 6500?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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A late STS with a final drive of 3.71:1 will normally idle at 650 rpm in D, just about 2,050 in TCC, level road at 60, and, same conditions about 2,300 at 70.

If a member going on the road today with either a SLS (3.11:1) or STS would carefully list a set of level road non-forced part throttle shift point rpm's as well as rpm in OD at 40, 50, 60, 70, (80) then you would know where you stand. Easier with a passenger to do the notes.

Several such runs could be posted as a tech tip for future reference.

Understand that speed and rpm data are only good for a vehicle which runs the OEM tire/wheel combination. Any outer tire diameter other than stock and you have no idea where you are in the drivetrain management department.
 

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1999 Cadillac STS
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Discussion Starter #13
Thanks for your continued input on this thread, sub. I will double check my RPM at those speeds you gave above.

I have the stock wheels but I noticed the tires are 225 wide, not 235. But they always have been, and it used to shift right at the redline. I wonder if there is some sort of relearn procedure that needs to be done, all the mechanicals must be ok if I'm not getting any codes. Although I guess a shift linkage that is slightly out might not set a code? I also suspected the TPS and VSS but I'm sure those would be setting codes and causing problems all over the place...?

Does the below relearn procedure for an Aurora with the "baby Northstar" apply to our cars?

TPS reset-

1. Turn key to ON position. ( dont start motor) Then turn to off position. Wait 20 seconds.

2. Repeat step 1.

3. Repeat step 1. You're done.


Idle relearn-

1. Start car and bring to normal operating temp.

2. Let car run for 5 min at normal temp. ( 220*)

3. Bring up the RPM's to over 3500 and hold it there a few seconds. Let it drop back to normal.

3. Put car in D and hold it there for 2 minutes.

4. You're done.
 

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I know this won't apply to you directly, but I just went through the exact problem with my '95 sts after installing a fastchip. I believe they gave me the sls (3.11 or 3.21?) software where as I have 3.7x gears.

Tire size should not be an issue for you. I have a lot shorter tires than stock, and it didn't change the shifts points at all.
 

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1999 Cadillac STS
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Discussion Starter #15
Thanks darien. That would make sense too, but like you alluded to, doesn't apply for me..I know the computer stuff wasn't touched at all. Good to know about the tires.

I found a similar problem on the web with a solution, I know it's for a much lesser car :sneaky: , but does anyone think this could be the problem? I could see this getting misadjusted when the engine was put back into the car. Here's the link:

http://en.allexperts.com/q/Nissan-Repair-825/97-sentra-auto-trans.htm
 

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1999 Cadillac STS
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Discussion Starter #16
Well, I think I've KINDA figured this out. I don't think there's anything wrong, anymore...but I still can't explain the change.

I was looking at the tach today and realised it used to shift at 6250, actually, not 6500. I thought about what BBob said and decided not to worry about the red area on the tach and to just let the computer worry about protecting the engine. So I did a WOT and sure enough, at 6700/6800 or so it shifted without any drama. Did it again and same thing. So, I think it's actually shifting at around 6500 now but I'm just seeing the needle swing past like BBoz described. With no codes and a proper shift (no fuel cut out, so it can't be hitting the rev limiter at 6800), I think it's fine. The only thing I can think of is that the ECM was reset when the engine/trans was out and is now shifting how it should...maybe before someone really babied it and it lowered the shift point for WOT? Who knows.

97EldoCoupe (member on this board) did all the work (and did an excellent job, along with helping me track down this issue) suggested that maybe the over-torqued main bearing bolts restricted the engine before and now that he has retorqued them to the FSM specs, the engine is turning more freely. Hard to say.

But I think it's case closed on this issue, I'm not going to worry about it. If anyone needs Caddy work done, even if you are located a ways from Ontario, I'd recommend you talk to 97EldoCoupe (Jake)...he's honest and very reasonable and knows these cars.

Thanks everyone for your input on this, especially sub (appreciated your RPM numbers, mine match yours FYI).
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Jad2......Thanks for the comeback. Drive it like you stole it !!!


Darien......Outer tire diameter will not materially affect shift rpm points (except when torque sensing comes into play): what the rolling distance difference does is to throw the speedo and mileage calculations off by some + or -percentage, depending on whether the installed tire rolls further or less in one revolution than the oem calibration.

Think of tire differences this way: A John Deere tractor rear tire rolls one heck of a lot further in one revolution than a lawn mower tire does in one revolution. A bit extreme, but the analogy holds until all 4 tires match the design outer diameter.
 
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