Over the summer I visited a friend about 20 miles away and took my bird on the highway, it has a VATS Bypass (this may be what is causing but Idk). I stayed for a few hours and then left to go home, I got about 100 feet down the block and my car would top out at 15 mph for a couple seconds and brake itself down to 0.

It stays running and will keep doing that, doesn't shift out of 1st and It wont shift into 2nd or 3rd if I set it in the respective gear (automatic trans.) Overdrive and produces same results as having it set into 1st gear, with winter here but no snow I want to get a better idea of whats going on come spring.


No lights come on. and by brake I mean the car lurches to a stop like the rear end locks up no brakes are applied it just the axle pops locks and drops it to 0. car remains running. any ideas?

 

pull the rear u-joint straps and rotate the pinion yoke with a mech. stethoscope to your ear.

Do the trans. fluid and filter and look for garbage / burnt fluid.

 

If it feels like the "rear end locks up" suddenly, it could be an issue with ttransmission attempting to shift into two gears at once. If a valve is stuck or if there is some sort of leak, it could cause: 1. a late shift (as if the tv is completely open or in the wot position) which is happening at 15 mph (should shift to second around 10 mph assuming you aren't heavy on the throttle) 2. two gears to engage at one time, which typically causes the engine to die. if one of the clutch packs has worn friction discs, or if your band is slipping, it could allow the input shaft to turn easy enough to keep the engine running, but it would have to be slipping pretty bad. Appearance and texture of the fluid will indicate worn clutches or band.

I am assuming it is a 700r4? and what year is it? there are several different models that use different amounts of electronics and have had several changes made throughout the years.

Let me know if any of this sounds inaccurate. I don't consider myself an expert by any means, but I have been working on my transmission a LOT lately. I have actually had some problems of my own.

 

Basically the fluid looks fresh It doesn't smell burnt and is pretty clear of any debris or dirt. I believe its the 700r4 1989 Firebird form with 305 tbi.