Ok the car is an 89 Formula automatic 350 T-tops, all original and stock. Only thing that is different on the car is a muffler from a 4th gen TA.... Everything else, original. Oil changed about 1k ago back in September. New tires in October. Daily driver. Driven about 30 - 40 miles a day. Tune up about 3 years back. New Fuel pump and injectors. New starter, Radiator, alternator, water pump within past couple of years. So hopefully that helps when trying to help me determine what is going on.

Lately, well the past month or so.... The car has been driving rough...
In late September/early October (Can't remeber when exactly) I changed the Tranny mount. Regular OEM replacement. Not the Polyurathane (Correct Spelling?) one...

After I changed it, the normal shifting thud dissapeared.
Not too long after though I started getting another issue. Not sure if its tranny related, but just incase I tried to give you back story....

Now when acclerating smoothly and the car reaches just above the 2k RPM mark normally before she wants to shift, I get a very bad stuttering/shaking/vibrating. I feel it through the pedal and its so bad that the entire dashboard shakes..... If I let go slightly or accelerate hard it goes away..... but when I do it if I stay at whatever speed Im at and not slow down or accelerate harder it will just stay doing that. Any ideas of what this could be? Also my thud when shifting has returned... so I think I need a new mount again already....WTF?! Its very subtle though the thud when shifting and only in the lower gear (1st- 2nd and maybe 2nd - 3rd cant remember).

Now would this be the tranny?

I also have an exhaust leak in one of my cats that I have to attend to that gives me a power loss spuddery feeling every now and then through the pedal, but not like what I described above....

I dont know what it could be. Im gonna change the mount again this weekend and try to get the poly one...Supposedly its better? The one I got was some cheap jap **** that was like idk 5$ or something cheap like that.

I dont know whats causing this. Its mainly during highway driving. Not around town at lower speeds... usually in the 50-70ish mark...

Maybe engine mounts?
Bad rear end?


Any ideas? Thanks in advance.

 

Just a shot in the dark here, but something very easy to test while you are driving...

Maybe your TCC is acting up. A real simple way to test the TCC operation is while driving at cruising speed, with your right foot holding the accelerator pedal at a constant rpm, touch the brake pedal with your left foot (just enough to make the brake lights come on but not enough to actually start braking) while watching the rpm's. The rpm's should flare up a couple of hundred rpm's when the TCC disengages.

The TCC solenoid is wired through the brake switch, so that anytime the brakes are applied the lock up dis-engages. This is why you should see the rpm's flare. If the solenoid is sticking (electrically or mechanically) then you will not see any rpm change.

You can try this when it starts shuddering again, just as something quick to try to help rule out the TCC operation ...

Edit... you need to do this at a cruising speed above 45 mph or so, 50-60 is better, based on what rpm the computer is programmed to lock up the converter.

 

I wouldnt say Im the most knowledgeable car person. Never even heard of the TCC .....lol I'll try this...

Oh,. dont think I mentioned this. the whole thing isnt random either happens every day when Im gradually accelerating between 50 and 70 on the highway... Like I said, if I floor it or let go of the pedal it stops...

 

TCC is the Torque Converter Clutch. What this does is while at cruising speeds the torque converter "locks up", so that there is no slipping, and it is basically as if the crankshaft was directly linked to the input shaft on the transmission.

This is done for better gas mileage... especially on the highway. I doubt this is your problem though, because usually when the TCC won't dis-engage the shuddering will occur when you are decelerating from cruising speeds, but I figured it would throw it out there anyways.

 

tuenport350... think maybe he has a drive shaft issue ? like out of balance?

 

Yeah I dont know. I have been reading some threads by others all over this forum that have similar issues and it seems like it can be a wide array of things... I dont recall it happening before I got the new tires put on. Actually I believe it happend right after I got them put on....now that I think about it...Maybe they were balanced incorrectly? Would that cause them to vibrate only under those conditions? Maybe it being just above 2k rpm is just coincidental. Would an in-proper tire balance cause the car to vibrate when accellerating gradually (Normal, not spirited driving) between 50ish to 75ish?

 

Just did some google searches of bad tire balancing...
Most of what I read symptoms wise, seems to fit the problem perfectly.
Im hoping that this is it.

When I get paid tommorow I will take it to get balanced. If anyone has any other suggestions on what I can look for if it turns out to be that the tires are fine I would greatly appreciate it.

 

Yes.

I also had a tire with a broken steel belt that caused bad vibrations on the highway.

 

Could be, I think at this point Robb needs to nail down whether it is a Drivetrain (RPM related) or Suspension/Steering (MPH related) issue before he/we can help figure this out... though the recent tire information seems shed a little more light on the possible problem.

 

yes it does tuneport350 ... rob i would take it back where you had the tire service done and they will prolly make it right ... or they should depending on how long youve had the tires on and if you purchased any kind of warranty with the tires

 

Hey i am having a similar problem as Rob. Except mine kinda goes away at cruising spped and during "spirited" driving. Would a MAP sensor, catalytic?, or is it even motor related. My car sounds like a dog acclerating (like the creepy dudes van down the street except mine doesnt smoke the neighborhood. I have lost much power it sounds awful, shakes back and forth at slower sppeds and just before actually stoping. then it will do it again taking off then smooth out until after a shift (so with lower RPMs i have this problem). Help?