Sluggish shifting?

[ryan.hess]

4t60e... shift from 1-2 seems "slow" and can sometimes be harsh. The 4t60e has a vacuum pressure modulator right?

What sensors would cause a slow or late shift? TPS? VSS? I guess first I better check fluid level though, heh...

[sharkey]

the 4t60e is an electronic and vacume operated transmission. the shifts are myde by solonoids, comanded from the computer. the computer moniters tps, map and vss for shifting, and the line pressure is controlled by the vacume modulator.

id start with checking the fluid level, and have a look for vacume leaks, especialy on the line going to the modulator. when you remove vacume you will get hard shifts. if its having sluggish shifts at full throttle, id be thinking its more of an internal issue (hard seals, burnt clutches, ect)

[gpse3400]

If your vacuum modulator had a ruptured diaphraghm it would Be shifting biased hard. Another indication would trans fluid in the vacuum line, also trans fluid leaking out of the vacuum port of the modualtor.There is also the possiblitty of wear on the 2nd clutch, in this case an adjustable vacuum modualtor from your parts store would be what you need. There is a best way I've found to fine tuning it. Most come preset to factory specs if not enabling ma little more system pressure. Finally if this doesn't solve it, I'd pull the lower pan and remove the accumulator houseing, dissasseble and inspect the accumulators. Severely scratched bore or shaft, broken, shaft. spring, piston and/or seal are unacceptable. Parts are readily available and inexpensive at the dealer. Not a hard task to perform.

[IsaacHayes]

Hard seals likely. Mine always was slow and drawn out. Then I put in the $6 GM seal conditioner to fix a different issue, and low and behold now it shifts so fast, and always smooth. Amazingly fast 1-2 shifts that isn't hard but is good enough to make the tires break free and the front slide sideways on the on ramp with worn 205 tires. (hard rubber 80,000 mile rated tires).

When mine shifts to 1-2, it sounds so perfect. Like you can't hear it almost go between the gears. Before the engine would sing all different notes as it was shifting. Now its the same note pretty much WOT 1-2 shift. Nice!!

[ryan.hess]

What I'll probably end up doing is changing the fluid, maybe add that seal conditioner and see what happens. Of course, I have yet to check the fluid level......

[sharkey]

seal coditioner is over rated. what i usualy find with transmissions that have had that added to it, is they work alright to start with then down the road a few months is starts causing other problems. what this stuff does is make the seal soft again, but what happens is the rubber also swells up and over time becomes too soft.

basicly the stuff is a band-aid. id use it to get through another week, but not as a permenant fix.

[IsaacHayes]

I went for the GM stuff. I got the idea from someone else who was having the same cold weather problems, it would slip and not engage until warmed up. He told me to try it, and that he did it 3 years ago or so and it's been working fine since. Mine is going on over 2 years since I did it, and I give my trans lots of abuse and its still working great so far.

[zhd1000]

my trans is doing the same thing.. would there be differences between the 4t60e and the 4t45e regarding a sluggish 1-2 shift? or could there be something completely different causing the problem?

[sharkey]

well, the 4t45e is a completly different design and dont share anything in common. about all they share is the fact that they are both 4 speed fwd automatics.

[zhd1000]

well that's exactly why i was asking.. i don't know what the differences are and i have a sluggish 1-2 shift under moderate accelleration.. is there anything that i can do to help fix my problem?

[gectek]

alot of it could be a dirty MAF, or the appropriate sol isnt engergizing fully, possibly a bad solenoid or bad wiring. the shift time is the amount of time it takes for the shift sol to energize fully and appy all the pressure to the appropriate channel in front/behind it/ whether it is exhausting or pressurizing. i would have to look at the sol usage compared to shift, i dont really remember on the 60. but the 45 is first 1-2 on 2-3 off, second both off, third 1-2 off 2-3 on, fourth both on

[sharkey]

shift solonoids are either on or off, no inbetween. some transmissions use pulse width modulated solonoids for downshift feel (4l60e uses a pwm 3-2 kickdown solonoid), however thats not used in a 4t40/45e. if you can issues with a solonoid, you will get a short/open code or performance code for that solonoid.

i would get a scanner on it and have a look at the shift adapts. shift adapts are how long it takes to make a shift. it is measured from the when the pcm commands the shift to when it detecs the shift is completed (through looking at speed sensors).

[gectek]

well yes, on/off, but sometimes the windings get resist, and they dont energize like they are supposed to. and they dont have to be pwm to have that happen to them. they(on the 4t45) fully engergize when voltage reaches above 7.5 volts and retract when voltage falls below 1 volt, so if there is only partial voltage and not 7.5, then they will partially energize, but i dont have the info for a 60,65

[ryan.hess]

Well.... finally got around to changing the transmission fluid. Removed the old fluid, and flushed 2 gallons through it.

Drove it around for a bit and didn't think it improved much if at all. So picked up some GM seal conditioner (for free!) and poured it in. Says to drive it for 1000 miles, so we'll see what happens. (crosses fingers)

[ryan.hess]

Put maybe 300 miles on it.... One weekend i didn't drive it at all, and the following monday it was perfect - fast upshifts and all. Now it's back to it's usual self. I don't think it's any better, but we'll see after another 700.