High RPM, doesn't shift into next gear

[slick]

So... all electrical problems fixed, and most of my gas mileage problems fixed, my car is running really good. But.... only one big thing wrong I am noticing right now. At higher RPM's (above 6000 RPM), it doesn't want to shift into the next gear. I actually have to let off of the accelerator and let the RPM's drop before it will shift.

 

I have a few things in mind what could be wrong, but I'd just like some of your guy's opinion's.

 

Thanks.

[z34_nut]

:shock: ...lets just say thats EXACTLY what my tranny started to do before it took a shit....um...fluid change?

 

Also, check your vaccum lines, just to be sure, and do a pressure check if you can find the tools. This could also be electrical, but more then likely its not.

[Regal_GS_1989]

I've had my old 88 regal hit the Redline a few times before it would shift into the next gear :shock:

 

I''ve never had to read a tranny data stream off an OBD1, nor do i know if its possible, but if you can get a scanner to read the tranny data stream, drive the car and see what happens when it doesnt shift. If a shift has not been commanded, than there is an electrical issue. If a shift is commanded, but it doesnt shift until you back off, than there is a fluid/mechanical issue.

[slick]

Well... I know I am due for a fluid and filter change, so I will go ahead and do that. And, I know of a few connections that I need to check up on, so I could do that as well.

 

Could anyone provide me with a tranny vac. diagram?

[GOT2B GM]

How's your fluid look? Is it foamy? Underfilled? Overfilled? Pan drop and filter change would be a good start.

 

I'm having issues in my auto Z right now too. No 3rd gear, on a tranny that's only 40,000 kms old, thinking it's electrical related.

[z284pwr]

My trans is doing the same thing, shortly before it started doing it in every gear, I heard a pop while trying to manually shift it into 3rd at high rpms. This is with brand new filter and fluid as well. I don't think it likes running 6500+ RPMs when it used to be 5700 or so?

[patgizz]

vacuum diagram:

 

1 line from vacuum modulator up to engine vacuum

 

no more vacuum lines.

[Canada]

Low fluid can do this.

 

I'm sure you know this....BUT...check with the engine and trans hot, in park, and at idle.

 

Just changed fluid in my friend's 2000 GTP with 80k on it....fluid looks brand new.

[slick]

Thanks Pat and Chris.

 

Yeah, so I'm figuring it's probably the overdue needed filter and fluid change (about 30,000 on the rebuilt tranny), so she's about due for another change.

 

I'll check the vacuum tomorrow between classes.

[mihela816]

Another thing that can cause this is a misadjusted or broken throttle valve cable. It's the cable that loops from the throttle body, behind the plenum and attaches right by the tranny vent on top. It basically tells the transmission what throttle position is to control shift points.

[Canada]

I don't think that car has a TV cable.

 

The vacuum line would just would only effect shift firmness....as its only controling transmission pressure.

[94CutlassXtreme]

When you say the car won't shift at high RPMs, do you mean it won't go into forth during crusing. If so, is your service engine light on? I had a similar problem, and it turned out to be the neutral safety/MLPS (manual lever position sensor) switch. Once I replaced it, the car shifted fine.

[patgizz]

Another thing that can cause this is a misadjusted or broken throttle valve cable. It's the cable that loops from the throttle body, behind the plenum and attaches right by the tranny vent on top. It basically tells the transmission what throttle position is to control shift points.

 

there is no TV cable on any 3.4 equipped car or any of the electronic trannies.

[z284pwr]

Doesn't the TV cable just control the down shift points, doesn't the vac. modulator control line pressures and shift points on the Non "E" trans?

[Guest Anonymous]

Try the fluids. Mine was having a problem shifting (very similar to yours) and it turned out my fluid was very low.

[slick]

Well, as a few of you said, and I suspected, tranny fluid was a bit dirty. Picked up a new filter and tranny fluid today, so I'll probably get that done Saturday afternoon, as long as the weather holds up atleast.

[slick]

My transmission fluid was much dirtier than I had originally thought. And this transmission only has about 30,000 miles on it, so I'm really suprised. But, I am to assume this is due to the high revs, and more power than stock flowing through it.

 

The tranny pan was also pretty scratched up, none piercing through, but definately some scratches that dented the pan that were visible.

 

No update if this is helped or not yet, but I should have an answer within the next few days. I kinda want to get a few miles on it before I get on it.

[slick]

Wow, totally forgot to update this.

 

Changed the fluid and filter. Fluid was much dirtier than I had originally thought. No significant flakes or anything, so that was good. New fluid and filter helped the shift a little.

 

But no fix.

 

Bought a new adjustable vac. modulator, and it came with the small amount of soft vac. line as well. When I pulled mine off, my vac. line was completely cracked through. Put the new one on along with the line, and went for a drive. The shift was improved.

 

But no fix for the high rev shift.

 

Next plan of action is to get the fluid flushed. There may be something clogging up the valvebody preventing it to shift properly when it is flowing that much fluid.

[slick]

Another update for anyone that cares:

 

Adjusted the vac. modulator with no luck. It did firm up the shifts a bit more, so I am happy about that, but thats about it.

 

Guess I will take it to a trans shop for a free estimate.

[Brian P]

mine would do that on occasion with the 1-2 shift at WOT. It wasn't electrical, and never got around to diagnosing it further. I think it was a pressure-related problem since the failure of the transmission was a gradual loss of pressure, and I found the pump shaft damaged at the bearing (common thing to happen) any other problems besides that?

[slick]

Nope, not really. Normal driving is fine.

 

Heres a good break down of the symptoms:

 

Around 6000 rpm, the trans will slip or fall out of gear. It engine will continue to rev to the limiter, but will just bouce off of it. Once I let off of the gas and it falls to a lower rpm, it will fall or go back into gear.

 

Normal shifting is fine, no slipping, no other problems.

 

Along with your thoughts on a pump, i've also thought of one of the balls in the valve body getting stuck, or else something blocking a passage in the transmission itself.

[Crazy K]

Can someone elaborate on weaken tranny pump details? it may be a problem one of my cars has. my 91 vert... it won;'t go unless pushed in gear of lifted, operated in gear while in the air, and then dropped... It can even be off when dropped, it's just the very first time you try to move the car cold.

[94CutlassXtreme]

Around 6000 rpm, the trans will slip or fall out of gear. It engine will continue to rev to the limiter, but will just bouce off of it. Once I let off of the gas and it falls to a lower rpm, it will fall or go back into gear

It is the MLPS..Manual Lever Position Sensor, which also acts as the neutral safety switch. It would throw a code when it goes, which would read "Park Range Switch Error" or something. Those same symptoms happened to me and that's what it was.

[slick]

Around 6000 rpm, the trans will slip or fall out of gear. It engine will continue to rev to the limiter, but will just bouce off of it. Once I let off of the gas and it falls to a lower rpm, it will fall or go back into gear

It is the MLPS..Manual Lever Position Sensor, which also acts as the neutral safety switch. It would throw a code when it goes, which would read "Park Range Switch Error" or something. Those same symptoms happened to me and that's what it was.

 

I guess I could scan my codes, but there is no SES light flashing, so I am assuming it is fine.

[slick]

Another question thats making me think my trans is going. When you first pull into my driveway, the first part in front of the house is about at a 30* angle going uphill. Now, there are times that I am forced to park on this hill due to my driveway being full of vehicles. Now my question is, when I am able to pull forward into my driveway, I move my gear selector from park to drive, shouldn't the transmission being in drive prevent the vehicle from rolling backwards? This is just at idle, not talking about anything over 900 rpm here.