Diagnose failure, 4T45E

[AleroB888]

Tranny will be rebuilt soon, but I'd like to know which internal part failures are indicated:

1) With lever in "D", Trans can't auto shift into 2nd from 1st at WOT, hits rev limiter.

2) With lever in "2", trans shifts ok into 2nd at WOT, but not from "2" manually into 3rd at WOT.

3) Trans can auto shift into 3rd, but only at low RPM, and RPM must be kept lower than about 2K to accelerate at all in 3rd.
(but it's hard to tell if it's in 3rd or 4th at that point)

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[3400-95-Modified]

Sounds like a hydraulic issue, possibly valve body, but it's called "shift flare"

And you made me think of something quite interesting to try....

I've had these issues with my 4t60e, or at least a bad flare on the 1-2 shift due to the power I'm making, but I know when in L the hydraulic pressure is different and tends to shift a lot better, Maybe I'll try setting up L to shift at the right time and start in L the slap it up to D once it's in 2nd gear.

[1988GTU]

Clutches for 3rd probably are toast. I'd say abuse/power related.

[3400-95-Modified]

Everyone says the clutches would be bad but if it’s not even trying to shift then you can't point the finger at the clutch pack, the hydraulic system and shift mechanisms are what are failing. If it shifted and slipped then I would agree with that statement.

[unchained01]

i think its valve body contamination or valve body gasket failure and/or soleniond failure, to start And the 3rd /OD clutches are going , have you pulled the pan ? you might be suprised what you find.

[3400-95-Modified]

3) Trans can auto shift into 3rd, but only at low RPM, and RPM must be kept lower than about 2K to accelerate at all in 3rd.
(but it's hard to tell if it's in 3rd or 4th at that point)

I guess the question I have to verify clutch integrity is, what happens if you rev higher than 2k? does it slip and over rev or shift back down? Without stating that, thats why I'm not sure on those packs being cooked.

[1988GTU]

3) Trans can auto shift into 3rd, but only at low RPM, and RPM must be kept lower than about 2K to accelerate at all in 3rd.
(but it's hard to tell if it's in 3rd or 4th at that point)

That is what makes me point my finger at clutches. Which you pretty much just quoted... So I am with ya on that last post.

WE NEED MORE INFO!!!!!!!!

[AleroB888]

That is what makes me point my finger at clutches. Which you pretty much just quoted... So I am with ya on that last post.

WE NEED MORE INFO!!!!!!!!

I hate to admit it, but I let it get low on fluid level, very low. Then continued to run it hard during testing, and took it to the track, where it finally did the symtoms listed. Added fluid, but problems remain. I'm my own worst enemy.

Anyone got a pinout diagram for the '99 4T45E?
Thanks for all the replies!

[AleroB888]

Seems to be a little problem with 2nd gear

Are there any last minute suggestions for strengthening this tranny? I'm limited to what can be done for the 1999 year model and PCM, w/HP Tuners. The builder is experienced in performance GM trannies, but not as well with the 4T45E.

[1988GTU]

I was close. lol Best you can do is just source some blue clutches and I think there's a revised pump available still. Install a big cooler with a fan triggered to turn on when trans see 200*F.