Hello, this is my first post here. My dad owns an 85, stock, Corvette, and has a few questions with it.

The car shakes at light throttle over 40 mph. It goes away if floored. I think its the torque converter, but a local shop says I need a full rebuild (a reputable shop supposedly). Has anyone else had this problem? Will just a torque converter change fix it? If not, what will?

Thanks for any help you can provide

Ben

 

While it probably IS only the torque converter that's causing the shudder, if the car has high miles it would probably be worthwhile to go ahead and do a full rebuild on the tranny. You'll basically have to pull it to change the converter anyway, so labor-wise it wouldn't be much more. Usually by the time the converter clutch gives out, the other clutch packs in the transmission are on their last legs. That's my non-professional opinion.

Jason

 

Welcome to the forum :)

 

good to be here =), and thanks

 

I had an Oldsmobile that developed some shuddering under light throttle cruise on the highway. I was concerned it was the tranny, but it was bad wires and coils. The miss under light throttle high load condition of over drive was enough to confuse the tranny and cause some light to moderate bucking. I replaced the coils and it worked great for a few months and started to do it again, so then I changed the wires and it went away for good. Make sure your ignition is up to snuff. Good Luck

Bob

 

It sounds as if he has the basic, common C4-auto lockup shudder. If you look at the posts in this section, someone asks about this problem every two months or so.

Condition: Accelerate to 42 mph where the stock torque converter lock engages. Continue down the road. Then try to perform very light, part-throttle acceleration that does not cause a downshift. The transmission will shudder and hum because the lockup is trying to disengage but can't quite get the job done. It also happens under part throttle when you need more power to climb gentle grades.

There are, unfortunately, several conditions that lead to this. Fortunately, all of them are accessed by dropping the transmission for the same basic maintenance, except for the TC lockup solenoid.

First thing to do would be to lift the car and disconnect the wiring harness from the TC lockup solenoid, or go behind the brake pedal and foul up the calibration on the brake pedal TC lock disengage sensor by pushing it in a bit - the wiring harness for this switch is wired with purple sheathed wire.

Test the car with the solenoid disengaged/ disabled to see if the problem goes away when the TC will no longer lock up. Do not leave the trans in this state for longer than you have to, because lack of lockup causes overheating problems in the trans.

If the problem goes away, then the problem is in the solenoid (weak), lockup clutch (worn out, loosened up), or converter (blown, ballooned, etc.)...

If the problem doesn't go away, you may have a harmonic vibe from where either: 1) the TC bolts are loose; 2) the flexplate bolts are loose; or 3) the flexplate is cracked.

After this, you'll have to look elsewhere.

Consider this an opportunity to save up for a high-potential converter and trans rebuild. Perhaps a shift kit as well. All problems are opportunities if the cash is available.

For what it may be worth.

Paladin


[Modified by The Paladin, 7:55 PM 10/12/2002]