I have an '88 NA GXL automatic coupe. So far since i got it i've replaced the neutral safety switch, blown an upper radiator hose, blown a rotor housing, and wired a Fuel cut-off switch.
The rad hosed was replaced, the housings and rotors and gaskets were replaced, the spark plugs and wires were replaced, it's got a K&N intake and an after market cat-back exhaust.
Now, since a couple weeks ago, i've had some hesitation at about coasting speed. It only seems to happen wen it switches into Overdrive, its fine during acceleration and decleration, but when i try to keep it at an even 40 mph or even 60 mph the car bobs and i watch my rpm go up and down until i either give it gas and accelerate or let off the gas.
This happened before i put the exhaust on so i know it wasn't that, and i noticed the trans was overfull by a quart so i took it out so its now at an even level but its still doing it.
If anyone can help me out here i'd greatly appreciate it. I Love this car! but this ***** starting to get old...

 

How does it idle?

 

it's fine at idle, only when im trying to keep it at a certain speed

a friend told me it might be a vacuum leak?

 

im new at the rotary diag....so hopefully some of the experienced NA guys will jump in and help you out. good luck

 

just a guess but i think around 40 and 60 is where it might be shifting,so my guess would be that the clutches are going out

 

Automatics don't have a clutch. It's all hydraulically actiuated with the transmission fluid. There are complex fluid paths machined into the tranny to figure out when to shift. I don't think there's any computer. It sounds like it's shifting back and forth between gears. I dunno, maybe you have a bad front main seal and engine oil is getting into the tranny fluid and screwing up the shifting? I know a manual can get engine oil in the tranny oil like this. Does it happen on an automatic too?

 

i'm not sure its the trans fluid cause it only does it when im trying to keep a steady speed, it doesnt effect my acceleration at all. I'm changing all the fluid and filter out tomorrow though cause im not really sure the last time it was done

 

check your tps.

 

correction...anything with a transmission has a clutch these are just internal and are actuated by hydralics(tranny fluid)from inside...my point being..the clutches can still go out

 

is the transmission Shifting Operated from Vacuum?.I'm just Fishing here,as I am not into Automatics..also how did you Check the Transmission Fluid level.It can only be Checked When Warm,to give you an Accurate level.

 

yes i checked the fluid level warm, it was fine

 

azdk is right. With respect to street cars anyway. I think there are heavy machinery that use strictly hydraulic controls without clutches for their transmissions.

 

good news

i changed out all the fluid, replaced the trans filter, and replaced the transmission modulator which helps create VACUUM.

its runs much better now