C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Missing 5 mph.... converter problem ?

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Old May 5, 2012 | 11:16 AM
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Default Missing 5 mph.... converter problem ?

Hit the 1/8th mile track the other night and my mph was between 96-98 mph all night, which is approximately 5 mph lower than what it has been. It should have been a little lower considering it was between 85-90 degrees and I was just running my stock front fatties on this night..... but not down by 5 mph.

I listened to the video, and it sounds like I might have a converter/transmission problem. I have never had a torque converter failure, does anybody know what it sounds like when it happens ? I feel like I was on the converter the whole trip, which is not normal.

Here is a video of it....

http://www.youtube.com/watch?v=4FydVQhaA5M

In contrast, here is a video of my old 383, in which there are no problems.

http://www.youtube.com/watch?v=4fzWpQe-ceM

Close your eyes and just listen and you can hear what I think is the converter loose all the way down the track. What happens when a converter balloons ? Or anything else ?

Thanks for any insight.
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Old May 5, 2012 | 12:18 PM
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Hi Todd. Good to hear your car is back on the road/strip. Did you check the rpms between the runs as you go through the lights. If your rpms are the same but you are going slower, obviously your converter/tranny is slipping. Do you record your runs? Can you lock up your converter after 3rd gear? I lock up after the 1-2 shift and it's good for a tenth and a half. Willie
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Old May 5, 2012 | 12:45 PM
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Hello Willie, No, I don't log, just listening by ear on this night. But, I just took it for a ride on the street and there is definitely something up with the transmission and/or the converter. It acts like it has a 5k rpm converter with a lot of slippage just driving it around the neighborhood. I assume that is what is eating my mph and et.

Oh well, such is life.... I'll pull it all out and figure out what and how to fix. Maybe go with a th350 and ATI converter instead..... haven't decided.

As a note, I tried locking up the converter with my old 383 and saw no improvement on the timeslip, but I didn't lock-up until 3rd gear. Maybe will try again in the future.
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Old May 5, 2012 | 06:20 PM
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Hey Todd, this is obvious, but check your tranny fluid. If mine is the least bit low, my tranny will slip.
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Old May 5, 2012 | 08:49 PM
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Great video Todd !
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Old May 6, 2012 | 12:13 AM
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Thanks for the reminder Willie, will give it a check tomorrow....but should be full. This is a new rebuilt HD transmission.... or at least in theory its HD.

Calderone, thanks and good to see you on here, haven't noticed you posting lately. Hope all is well.
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Old May 6, 2012 | 12:47 PM
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These trannies can fool you. I changed the fluid in my 4l40e last month. I put back in how much fluid I thought I took out and checked the level. On my first run, the motor was kissing the rev limiter on shifts which is set about 200 rpm above my shift points. A half quart later, everything was fine. I think after a tranny servicing, it takes a while for the air pockets to work themselves out of the hydraulic system and the fluid level drops from the inital check.
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Old May 7, 2012 | 08:49 AM
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Originally Posted by 383vett
These trannies can fool you. I changed the fluid in my 4l40e last month. I put back in how much fluid I thought I took out and checked the level. On my first run, the motor was kissing the rev limiter on shifts which is set about 200 rpm above my shift points. A half quart later, everything was fine. I think after a tranny servicing, it takes a while for the air pockets to work themselves out of the hydraulic system and the fluid level drops from the inital check.
Yeap, I have been fooled before.... I'll give it a thorough look through before I tear into it. Thanks.
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