94 GT Shifting Issues (weird vibs)...

[Alpine]

Hello,

My fiance has the above-mentioned Mustang GT. For awhile now, we've had some annoying problems with the automatic transmission. At highway speeds, the transmission will intermittently downshift, upshift, downshift, upshift. Some days it will behave just fine, and some days it's a pain in the rear end to drive.

At city-driving speeds (around 40 MPH), it will intermittently feel like it's "stuck" between gears. It will vibrate like it's trying to shift, but doesn't. If I'm not-so-gentle on the gas, it won't misbehave. If I drive it like a grandma (how my fiance drives it), it acts up.

I've already changed the transmission fluid and filter, with little effect. The fluid that came out didn't smell burnt and it wasn't excessively brown or anything. There weren't an excessive amount of shavings on the magnet in the bottom of the pan either.

I'm fairly mechanically inclined, but unfortunately Mustangs are fairly alien to me.. so be gentle.

Any ideas?

TIA

 

[Chythar]

It sounds like your tranny is dropping out of overdrive. To see if this is the case, hit the "O/D" button on the shifter. This will, in addition to turning overdrive off, also light up a green light in the instrument console. If your tranny now stays in the lower gear, you're slipping out of overdrive.

I believe the tranny will slip into overdrive around 40mph if you're just maintaining that speed. That happened to me as well.

Sadly, if this is the case you're looking at a tranny rebuild. Slipping out of overdrive is the first sign something's going bad. In my case, my tranny eventually started slipping out of other gears until it was basically undrivable. I haven't heard of any other solution to the issue, other than a rebuild.

 

[Alpine]

Ahh... bummer. Well, until the day I get it rebuilt (I'm not tackling that myself), what do you think of a Lucas tranny fluid additive? Do you think it would cause more damage than what was already taking place?

 

[Chythar]

Never tried it myself, so I can't say if the additive will help. Perhaps someone else in the forum could answer the question...?

 

[mo_dingo]

Ahh... bummer. Well, until the day I get it rebuilt (I'm not tackling that myself), what do you think of a Lucas tranny fluid additive? Do you think it would cause more damage than what was already taking place?

IMO, the absolutely worst thing you could do for the transmission is continue to drive it in this condition. Procrastinating will only add to the amount of parts that need to be replaced.

The type of fluid you are using is a DISTANT second.

Save yourself the money and get it rebuilt now. Maybe they can do the "basic rebuild" and just replace what is bad. You will save a lot, IMO.
Scott

 

[DaveL]

New fluid won't help any. You can try to replace the neutral safety switch to see if that helps. But speaking from experience you need a rebuild. I had the same problems as you and it didn't take long till the car was undriveable.

 

[Alpine]

I see what all of you are saying now. As with anything, there's no good way to put a band-aid on a bullet wound.

Thanks all.. you've clarified quite a bit for me.

 

[Alpine]

Ok, I've been looking over some different options. I've been trying to compare replacement vs. a rebuild.

What do you guys think about junk yard tranmissions? What years of donor vehicles would have a bolt-in replacement (electronics, etc match right up)?

Thanks in advance.