94 camaro z28 - lt1 - 4l60e

decided to take my car for a late highspeed cruise down the interstate.. i turned onto the interstate, and put it in overdrive and started to accelerate and about 90 mph it was hitting the rev limiter and not shifting.. so i pulled over to think about why it could be doing that.. and i thought maybe it was over-drive blocking that gear.. so i tried it again in drive, and once again it doesn't shift into 4th gear..

Can anyone point, or know why it may be doing this?

The tranny has app. 84,xxx miles on it, and i just put Royal purple auto trans fluid in the transmission.

 

Was it shifting fine before the fluid change???

 

Time for a rebuilt!

 

yes, it was. For a week or so after that it shifted fine as well.. just started happening.. I took it into town tonight and noticed a..wierd / harsh sound towards higher rpm range..only hear it about 2.7-3.4k rpms.. any higher than that the engine is to load, and any lower it wont do it.

 

My T56 service manual says:

Condition: Hard shift or control
lever will not move into
gear

Possible Cause:
Clutch not releasing
Improper or low transmission lubricant
Shifter rail binding
Binding of sliding synchronizers or gears
If reverse only, seized backup switch
Worn or damaged flywheel pilot bushing
Bell housing misaligned
Skip shift solenoid activated (plunger
extended)

Remedy:
Adjust or replace clutch
Add or drain and replace with proper lubricant
(refer to paragraph 1-1-3)
Remove extension or adapter and case cover.
Check for damaged parts. Replace damaged
parts
Remove extension and case to check that
synchronizers and gears slide freely on shafts.
Remove and replace damaged parts
Remove and check backup switch. Replace if
seized
Replace pilot bushing
Align bell housing to within 0.010 inch TIR on
face and in bore
Check solenoid function-replace

 

I think she's got an a4 car, I think that because of the statement about trying it in drive, maybe I misread, but if so, u must have 3:42 gears because I can go well over 100 before I get close to my limiter. When my tranny puked it lost first and over drive, went into limp home mode and had no tcc. Idk why u would lose overdrive and nothing else other than a solenoid, or a valve in the tranny. Check ur fluid, see what it smells like, feels like. The car is a 94 so I don't think there are any vacuum lines to worry about, possibly a fuse? Check the wiring going to the tranny, I've heard of fraying causing a similar problem, and headers burning through wires doing it too. Oh wait I don't see headers on ur sig. I'm lost, but if u wind up going for a new tranny depending on what u get for quotes u should send me a pm and let me know, I can give u the number to call where I got my tranny, right now it's the one constant in my car unfortunately.