Thought I was going crazy, but the last few weeks I've picked up a vibration in 3rd. It comes on after the 2/3 shift, or when coasting down at the 4/3 shift (35mph). Fairly high frequency, thinking it's RPM related. Anybody experienced anything similar?

 

I do...no explanation ive found. i figured it was my 35s...

 

heh...now that I've read a million "rough idle", "no power", "u joint", "E40D" threads, I had to go outside and make sure the truck hadn't self desctructed from any of a million calamities

 

Torque converter would be my guess....

 

I have the same issue on a 1999 GMC Sierra.

 

So a little O/T, but mine is more of a delayed shift from 2nd to 3rd.. and if im really hammering it...it delays MORE and then SLAMS into 3rd.
What would that be then?
My friends are saying that my 3rd gear must have a few missing teeth and finally when it catches thats the big slam, but why would it take so long for it to actually shift from second to third? Like you can feel it disengage at 25 or so and it hits at 30..or 35-40 if hammering it...
Yet it drives fine if im not hammering it.. so im babying it until I can afford to fix..or figure it out/replace.

 

Your transmission is working like it is supposed to. The torque converter normally doesn't lock in first and second gear. It normally locks right after shifting into third gear.

The reason it shifts hard when accelerating hard is that the torque converter is slipping more. If you accelerate lightly it might be slipping 100 RPM but it will slip 500 RPM or more when you're at full throttle.

That's a sign to never listen to your friends about anything technical. EVER.

First, "gears" don't slip when they are missing a tooth. They will bang and pound and fail REALLY fast.

Second, 3rd gear is direct. In this case there is no relative motion between any gear in the transmission.


If that's the only sign of trouble then stop worrying about your transmission.