I noticed someone else in another thread has this problem. I have it on my '87, so rather than hijack, I figured I'd post a new thread.
When I put my '87 in overdrive and drive around town, it shudders. It's almost how a car feels when it's missing. If I drop it down to drive, no problem at all.
Anyone know what this is, and what it would cost to fix it?

 

Normally, the clutch lining on the lock up plate is shot. This requires replacement of the torque converter if my guess is correct.

 

Is there any damage to running it this way? Works fine in drive.
This is probably beyond my mechanical ability, is it an expensive repair?

 

It will cause problems over time. A quality converter is approx $300. You can spend less. The trans must be removed to change the converter. 4 hr job for a pro shop.

 

Use the regular D around town and for speeds ofer 45 or 50 shift to overdrive. I think all auto trans will do that at lower speed in overdrive.
my 87 and 88 did that. The 93 with the LT1 is not quite as touchie

 

I do that now. How long did you run it that way?

 

Both the 87 and 88 had less that 60K miles. I always drove in regular D under 45 or so. Never had the problem using it that way.

 

I sometimes run my '88 down to 40mph in OD with the TCC locked up at 1,000rpm with no lugging nor shudder.

I can tell thee is not much torque down there but accel is still smooth.

 

If its a fast hard shudder that really vibrates the car it could be the 3-4 clutch packs. This happened to my 1990 Suburban with 700R4. It started out of nowhere, never did it before, then it just started one day. It would shudder in 4th and when pulled down into 3rd it would stop,then eventually 3rd did the same thing since I think they share the clutches for 3rd & 4th. Had to get the clutches replaced by trans shop. If it is the clutches and not the converter locking & unlocking it will only get worse with more driving.

 

Not a fast hard shudder. More like a miss, or kind of a bogging down. When I put it in drive, not a problem. Good response, smooth shifts.

 

3-4 pack would involve a complete overhaul.

 

IF I were to have this serviced, a new torque converter, or whatever... I'm saying IF... would it be worth it to have a shift kit put in? Are shift kits any good?

 

Some are good, some are bad. The company of choice seems to be transgo. B&M simply lock the accumulators to make the tires bark.
B&M has a bad reputation, but I have not seen any failures that could be directly blamed on their kit. I have had one in my trans for 15 or 16 years.

Fairbanks has a kit also. I have never used it, but would like to try it.
Most that have installed the Transgo kit have praised it.
When rebuilding Daves trans(93 blackrose),
I did notice that the band was a wee bit burnt. Not sure if the transgo kit contributed to it or not.

 

Most of us use a bad torque converter as a good reason to upgrade it. This usually involes stalling it higher. For this reason, a shift kit is nice.
A looser converter tends to soften shifts as stall speeds get higher. A shift kit is a nice way to restore the shift quality.

 

The automatic transmission is a complete black box to me. I freely admit to being clueless.
Higher stall speed converter would mean shifts at higher RPMs? Rougher shifts as well? Would getting a higher stall torque converter and a shift kit be redundant?

 

The torque converter is a torque multiplier. The higher stall allows for the rpm's to flash up a bit higher(especially under load). The shift points on a non electronc trans(pre94) is controlled by the governor. Therefore shift points remain the same.
Looser(higher stall) converters tend to soften the shifts.
When I mentioned that alot of people raise the stall as an upgrade, they typically make a small jump. For example 1600 could jump up to 2000-2200 with little drivability issues.
It is especially satisfying to replace a defective converter with an improved converter. Alot of us change out a perfectly good converter to satisfy our greed for power

 

Sounds like good bang for medium bucks?
I'll be right over.

 

Torque converters are tough to understand. They are so simple (almost no moving parts) but are tough to grasp. They are even harder to describe without a visual aid. I am going to have a stock converter cut open so I can use it as a tool to describe how it works. If I ever learn to post pics, I may do a write up on it.

 

You do the write up, I'll proof it and I'll post the pics. Heck, you do the write up, and I'll burn it onto a cd for you. Just send me the write up and where you want the pics in the write up.

 

My '91 had the shudder you describe.

I felt it MOST when I was cruising along with the TC locked and I'd press the accelerator enough to make it come out of lock.
At that point I'd feel a vibration that felt sort of like missing but it wasn't missing.
It seemd to be more apparent, on mine, in the higher gears , 3rd and 4th.

I never felt anything unusual when it would lock up. Just felt it when it un-locked. I guess lock-up happens so fast there's not a lot of revolutions when the clutch disc inside the converter is slipping.
Guess it must un-lock slower and those few revolutions with the clutch disc not totally disengaged would cause the shudder.

Once the TCC is locked or unlocked completely there will be no shudder.
I've never cut one open but 'my' theory is the clutch friction disc is warped ot else the part it interfaces to is warped.

It really feels a LOT like a stick shift car with a warped pressure plate or flywheel. It's 'close kin' to that same type vibration you can feel just as the clutch starts to engage on a stick shift car with that type defect.

Drove it that way for over a year before I got a 'round-tuit'.
Never seemed to hurt anything but it was one of those 'nagging' things that makes yo feel uneasy.

Since I had to pull the transmission I went ahead and got a 2800 RPM stall converter.
Replaced the transmission just 'because' with one of those prehistoric animal ones. A Dinosaur or Raptor. Something like that.
I really can't tell much difference at all in this converter and the stock one.

You'll never know you have it unless you really bury the throttle on take off. Then the engine will rev up a few hundred more RPM than stock which get's it farther up on the 'torque curve'.
THAT feels a LOT better than stock, LOL.

In normal driving, you'll never know it's not a stock converter and I like that.