So my moms 99 bonneville SE wont go into 4th. My dad tells me that it was having troubles recently going from third to 4th/over drive and then it just stopped going into 4th. From what he tells me he says it sounds like the car wants to go into 4th but it cant. I'm sortof the family mechanic and am going to end up fixing this whether it be installing a new tranny or rebuilding the current one. I have read the trouble shoot guide and will be looking into those issues when i get the chance but i also read about some issue with the 4th gear output shaft there it wasnt hardened from the factory so they go out I guess. I guess I'm wandering two things: first, what tends to be the most common reason for this; second, are there any places out there where i can download a service manual or some good tranny rebuild info. I should also mention the fluid level is fine and the fluid has been flushed and filter changed within the last 40k and the vehicle has around 180k on it.

It does sound as if the 4th gear hub shaft has gone bad or a solenoid has failed.

I was under the impression that if the shaft failed you would need to hold it in manual 3 with the shifter to keep if from free reving.

If you can, try and have the codes read. There should be something stored that will give you more information or ideas about which way to go. As for rebuilders, where are you located?

I appologize for having to give second hand knowledge here but from what my dad say he can manually put the car into 3rd, and it works just fine. As far as scanning goes i forgot to ask my father if he had done that yet but thats a good point. We have two different scanners which i imagine the laptop based one that we have should be able to get us the code if there is one.

As for rebuilding, My dad was looking into getting a rebuilt one for the car since it will have a warrant and all but I am also thinking about rebuilding it myself. I think rebuilding a transmission is the only thing that i have never done before to a car so if i can find some good info on how to do it i think i may try.

My 1999 Bonneville is starting to have trouble shifting from 2nd to 3rd. Does anyone know why?