4th Gear / OD on highway. rpm's jump up.

[Q-Ball]

Well, when i'm in 4th/OD on the highway and doing about 60mph. My rpm's are at about 2000. About a minute will pass and all of a sudden my car jumps to almost 3000 rpms to stay at the same speed. Any idea why this is happening?

[PCGUY112887]

Sounds like the torque converter is falling out of lockup.

 

Maybe a TCC solenoid?

 

It doesn't sound/feel like it's shifting down into third does it?

[Crazy K]

pull back on the brake pedl with your foot and see if the rpms drop, it may mean a misadjusted brake switch.

[geenick]

MY 94 Cutlass 3.4L did that 2 different times last summer. Only when it was REAL hot (90+), and I had been driving for a long time. After the car cooled down, it would shift just fine.

 

 

[Q-Ball]

I do know I have a vacuum leak for my cruise control. Would that cause it?

 

Sounds like the torque converter is falling out of lockup.

 

Maybe a TCC solenoid?

 

It doesn't sound/feel like it's shifting down into third does it?

 

Honestly, thats what I thought it was doing. Going back into 3rd. I'll have to test it again when I get my car back today from the shop.

 

pull back on the brake pedl with your foot and see if the rpms drop, it may mean a misadjusted brake switch.

 

Getting my brakes fix right now, maybe thats the problem. Cause when my brakes first started to fail I just began to have this problem, so maybe they are connected?

MY 94 Cutlass 3.4L did that 2 different times last summer. Only when it was REAL hot (90+), and I had been driving for a long time. After the car cooled down, it would shift just fine.

 

Well, the weather hasnt been hot here at all. Just feels like spring weather now.

[1990lumina]

Sounds like the torque converter is falling out of lockup.

 

Maybe a TCC solenoid?

 

It doesn't sound/feel like it's shifting down into third does it?

 

To simulate this, go down the hwy @ 60mph and drop the shifter into "D" and see if it's the same type of thing.

[Q-Ball]

Sounds like the torque converter is falling out of lockup.

 

Maybe a TCC solenoid?

 

It doesn't sound/feel like it's shifting down into third does it?

 

To simulate this, go down the hwy @ 60mph and drop the shifter into "D" and see if it's the same type of thing.

 

 

ooooo good idea. and if it falls out that means my torque converter is bad?

[Crazy K]

Sounds like the torque converter is falling out of lockup.

 

Maybe a TCC solenoid?

 

It doesn't sound/feel like it's shifting down into third does it?

 

To simulate this, go down the hwy @ 60mph and drop the shifter into "D" and see if it's the same type of thing.

 

 

ooooo good idea. and if it falls out that means my torque converter is bad?

no I don't think so. It means your tranny is operating in third gear for other inexplicable reasons... like overheating tranny, or an out of adjustment downshift cable.

 

to stimulate torque coverter clutch release as well, lightly apply the brakes, just enough to activate the brake lights biut not actually apply the brakes. you would normally see the RPMs jump up from 2000 by maybe 300-500 rpm with light brake application. try this next time it is goofing up to see if the tcc is applied or not as well as manually downshifting (as well as pulling up on the brake pedal)

 

[Q-Ball]

Ok, I had the car in 3rd doing about 65 mph. Dropped in into OD and it shifted and rpm's went down. I guess everythings working well again. So I shouldnt trust the rpm's on my gauge? I have a 88 GP's in there. Maybe I should go back to my stock one?...

[1990lumina]

When this was happening, could you tell the engine speed had increased (audibly/felt)?? If you did then I doubt it's just the cluster

[Q-Ball]

Yeah, I feel the car shift and it has a lower grumble when driving. Instead of the high whine in 3rd.

[RobertISaar]

pull back on the brake pedl with your foot and see if the rpms drop, it may mean a misadjusted brake switch.

ive had this problem for a while and fixed it with a couple layers of duct tape(i'm a redneck) on the section of the pedal where the brake switch make contact, what is the real method of fixing it?(95 monte)

sorry about hijacking the thread...

[dsgrntld187]

I had this problem when the air deflector on my 94 SL broke off, causing the engine and transmission to run a lot hotter. Its like the car didn't have over drive, but at higher speeds 4th gear still worked.

[JakeMetz63]

I have the same problem, it used to just be when it was really hot out (90*) but now its every time I am in OD and going up a hill at 60+MPH. It sucks because I rev at like 4k and burn through gas.

 

I can actually feel the transmission slip out when it happens and the car down shift and the RPMS jump from 2.5 to 4k, I will try switching to fully synthetic tranny fluid and change the filter, hopefully this will cause it not to over heat. Maybe add an external transmission cooler.

 

If this doesnt solve it is it likely the torque converter?

[Q-Ball]

Well I took the car for a drive today, out of town now and i notice my rpms jump from 2500 rpm to 3000 rpm. Doing about 75 MPH. I think its pretty normal now. I just wished there was a way to find out if im burning more gas now since my cruise control isnt working with a vacuum leak.

 

And for you Jake, if your tranny is slipping check to see the fluid. And a tranny cooler would just help. When my tranny was acting up I immediatly checked it and dropped the pan and filter. She is good to go now.

[JakeMetz63]

Fluid is at a good level and was changed ~30k miles ago, I guess its time to drop the pan again.

[Addicted To Boost]

Fluid is at a good level and was changed ~30k miles ago, I guess its time to drop the pan again.

Trans. fluid should be changed AT LEAST every 30K.