What in the tranny changes locked/unlocked?
10-24-2009, 09:30 AM
#1
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What in the tranny changes locked/unlocked? 93 LT1
Forged 383, internally balanced.
Neutral flexplate
Stock 4L60 tranny with a Transgo II kit. (had it that way for 3 years)
Hard to say when it started.
It was sometime since the 383 went in ... but there was so much time between motor installs, removals, changes, tunes ....
where I couldn't drive it I couldn't say that I did or did not have this issue before we
sat it on the dyno and tuned it. (same thing with the broken 10bolt I didn't know I had
until after I put the 383 in and noticed a single tire burnout
)
When the TCC locks, I get a jerking every 2-3 seconds coming from the rear at cruising and highway speeds.
Goes away when you apply throttle or brake.
If I leave it unlocked (ECM tune or by lighting holding the brake) the issue goes away.
Then, when I dyno ... I find myself with 33% difference between locked and unlocked.
(300rwhp VS 460 @6000rpm)
- So I replaced the torque converter (Removed Yank SS4000 ... installed an ATI)
- Replaced the 10bolt with an S60 (did the driveshaft at the same time)
- Replaced the rear brakes with Strange race brakes
- Even balanced the wheels and tried two different sets.
- Swapped my balancer (Fluidampr for ATI)
Problem still exists ...
Runs and shifts fine otherwise (WOT or part)
So my question is ... what changes in the tranny when the TCC locks?
Could there be something worn/broken that needs to be repaired?
I was going to replace it with a built one this winter anyhow, but I'd really like to know if it's the problem.
I've tried running in open loop, does not resolve jerking the issue. (so no, it's not the tune)
Forged 383, internally balanced.
Neutral flexplate
Stock 4L60 tranny with a Transgo II kit. (had it that way for 3 years)
Hard to say when it started.
It was sometime since the 383 went in ... but there was so much time between motor installs, removals, changes, tunes ....
where I couldn't drive it I couldn't say that I did or did not have this issue before we
sat it on the dyno and tuned it. (same thing with the broken 10bolt I didn't know I had
until after I put the 383 in and noticed a single tire burnout
)When the TCC locks, I get a jerking every 2-3 seconds coming from the rear at cruising and highway speeds.
Goes away when you apply throttle or brake.
If I leave it unlocked (ECM tune or by lighting holding the brake) the issue goes away.
Then, when I dyno ... I find myself with 33% difference between locked and unlocked.
(300rwhp VS 460 @6000rpm)
- So I replaced the torque converter (Removed Yank SS4000 ... installed an ATI)
- Replaced the 10bolt with an S60 (did the driveshaft at the same time)
- Replaced the rear brakes with Strange race brakes
- Even balanced the wheels and tried two different sets.
- Swapped my balancer (Fluidampr for ATI)
Problem still exists ...
Runs and shifts fine otherwise (WOT or part)
So my question is ... what changes in the tranny when the TCC locks?
Could there be something worn/broken that needs to be repaired?
I was going to replace it with a built one this winter anyhow, but I'd really like to know if it's the problem.
I've tried running in open loop, does not resolve jerking the issue. (so no, it's not the tune)
Last edited by James Montigny; 10-24-2009 at 09:36 AM.
10-24-2009, 10:19 AM
#2
If you have a cam You may just be locking a to low and rpm and speed and feeling the cam surge would be my guess. Nothing else other than lockup is different from the transpoint of veiw on or off. But lockup makes for a direct coupling and you will feel everything the engine does including cam surge which can be a very anoying feeling.
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10-24-2009, 10:21 AM
#3
The issue might be as simple as your engine is not comfortable with the converter locked at those speeds. With a 4l60e this can be corrected by changing the lock up speeds. In your case it is a bit more difficult with the 700r4. A toggle switch might be something to consider so you can lock it up later then what the computer commands it at. Not sure if this can be edited in the computer but it is something to consider.
Take a look at the lockup solenoid and make sure that the snout is in good condition. In the old days the snout would develop a small crack where the check ball seats. This caused issues with the lock up. The other thing to look at is the oring on the solenoid itself and also the one on the input shaft. There is a valve directly above this solenoid in the pump that might be to blame here if the bore is worn. Sonnax sells a new valve with a Teflon seal to help correct this.
Take a look at the lockup solenoid and make sure that the snout is in good condition. In the old days the snout would develop a small crack where the check ball seats. This caused issues with the lock up. The other thing to look at is the oring on the solenoid itself and also the one on the input shaft. There is a valve directly above this solenoid in the pump that might be to blame here if the bore is worn. Sonnax sells a new valve with a Teflon seal to help correct this.
10-24-2009, 07:45 PM
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I've tried setting Part Throttle TCC lock at various speeds, it's up to 55mph (2000rpm) at this point.
Yes, it has a relatively large 23x/24x H/R cam with lots of overlap,
but I would think cam surge would go away as the behicle speed increased.
I assure you, it's still very much there at 90mph (3000rpm)
Thanks for the tips guys.
Any thoughts on the crazy HP loss locked VS unlocked?
10% I'd be cool with ... but 33? That seems a little odd.
Yes, it has a relatively large 23x/24x H/R cam with lots of overlap,
but I would think cam surge would go away as the behicle speed increased.
I assure you, it's still very much there at 90mph (3000rpm)
Thanks for the tips guys.
Any thoughts on the crazy HP loss locked VS unlocked?
10% I'd be cool with ... but 33? That seems a little odd.
