Auto transmission question
Thread Starter
8th Gear
Joined: Oct 2002
Posts: 8
Likes: 0
From: Pittsburgh PA
Auto transmission question
I just purchased my first Corvette (1996 bone stock auto coupe with the LT1 engine) about a month ago and love it but have one small complaint. On a relatively flat road if I floor the accelerator at less than 40 miles an hour it downshifts into second but if I'm even a little above 40 miles an hour it only downshifts to third (unless I'm on a steep grade then it will downshift to second). I've tried doing this both in Drive and Overdrive with the same results. Will a shift kit correct this or do I need to mess with the computer? Also, how does a better torque converter factor into this if I were to purchase one of those along with a shift kit? I am not interested in drag racing per se, I just want better performance on the street. Thanks. :conehead
Team Owner
Joined: Sep 2001
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From: Athens AL
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Re: Auto transmission question (Psychlone)
you have the 4L60E transmission, which is computer controlled
but what you describe sounds normal
but what you describe sounds normal
Thread Starter
8th Gear
Joined: Oct 2002
Posts: 8
Likes: 0
From: Pittsburgh PA
Re: Auto transmission question (Psychlone)
Vader,
I'm glad to hear this is normal. Would a shift kit help overcome this because I much prefer the downshift to second then third when I'm cruising between 45-55 mph. Thanks. :cheers:
I'm glad to hear this is normal. Would a shift kit help overcome this because I much prefer the downshift to second then third when I'm cruising between 45-55 mph. Thanks. :cheers:
Drifting
Joined: Mar 1999
Posts: 1,931
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From: Norcross GA
Re: Auto transmission question (Psychlone)
There are many shift points that the VCM controls for that trans. (Throttle, gear selector, rpm,...) These can all be programmed, if you have the tools.
I don't believe there is a govoner that can be reworked in that trans. i.e.No shift kit. Least nothing like a TH350 or TH400 kit. (I'm not 100% on this.) The VCM contols the clutch pack pressure.
There are electrical add-on gadgets that will alter this clutch pressure.
I don't believe there is a govoner that can be reworked in that trans. i.e.No shift kit. Least nothing like a TH350 or TH400 kit. (I'm not 100% on this.) The VCM contols the clutch pack pressure.
There are electrical add-on gadgets that will alter this clutch pressure.
Drifting
Joined: Jun 2001
Posts: 1,997
Likes: 1
From: Lake Ozark MO
Re: Auto transmission question (Psychlone)
My '96 will downshift to second at WOT at anything under 96 mph.
When I get home to check my LT1 Edit files I'll post the exact Up/Down shift points the computer commands.
[Modified by Dan Parker '96, 10:22 PM 11/13/2002]
When I get home to check my LT1 Edit files I'll post the exact Up/Down shift points the computer commands.
[Modified by Dan Parker '96, 10:22 PM 11/13/2002]
Drifting
Joined: Jun 2001
Posts: 1,997
Likes: 1
From: Lake Ozark MO
Re: Auto transmission question (Dan Parker '96)
Okay.. Here's my LT1 Edit results.
WOT upshift points (2.59's):
1-2: 50mph
2-3: 98mph
3-4: 255mph (i.e. no 3-4 upshift)
WOT downshift points:
2-1: 40mph
3-2: 90mph
4-3: 254mph
Note that these are minimum speeds required for the program to shift. It makes it kind of funky to figure. You have to use both the up and downshift tables to calculate a range for each gear that the tranny will downshift to at WOT.
But it's easy to see how it works from a dead stop run. Just use the WOT upshift points.
WOT upshift points (2.59's):
1-2: 50mph
2-3: 98mph
3-4: 255mph (i.e. no 3-4 upshift)
WOT downshift points:
2-1: 40mph
3-2: 90mph
4-3: 254mph
Note that these are minimum speeds required for the program to shift. It makes it kind of funky to figure. You have to use both the up and downshift tables to calculate a range for each gear that the tranny will downshift to at WOT.
But it's easy to see how it works from a dead stop run. Just use the WOT upshift points.
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: Auto transmission question (Psychlone)
Just pull the lever back to 2nd from 3rd manually. Lot cheaper than opening up the transmission. Rev limiter should protect you in such a manual downshift situation, stock rev limiter is set at 5800rpm. Absolute mechanical rev tolerance on stock LT1 is I think 6400rpm but for all intents and purposes I think 6200rpm is the most a stock LT1 will endure before something bad may happen inside the motor. The stock programming by the PCM for shift firmness is a little on the soft side. Hypertech Power Programmer Plus has an "increase shift firmness" option that can be programmed which causes the PCM to bump up the line pressure in the transmission to firm up the shifts.
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Joined: Dec 2000
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From: Jacksonville Fl
Re: Auto transmission question (Lone Ranger)
Even with the manual lever control, I don't think it will downshift at too high a speed because of ecm limits ( the trans gears are all controlled by the ECM ).
BTW: On ANY car, the built in rev limiter will not protect a forced over-rev by forcing the trans to downshift at too high of an RPM. Just think of putting a manual trans car in first gear at 120 MPH...you will destroy the motor, well, if the trans doesn't explode just getting forced in the low gear at all.
BTW: On ANY car, the built in rev limiter will not protect a forced over-rev by forcing the trans to downshift at too high of an RPM. Just think of putting a manual trans car in first gear at 120 MPH...you will destroy the motor, well, if the trans doesn't explode just getting forced in the low gear at all.
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: Auto transmission question (BBA)
BTW: On ANY car, the built in rev limiter will not protect a forced over-rev by forcing the trans to downshift at too high of an RPM. Just think of putting a manual trans car in first gear at 120 MPH...you will destroy the motor, well, if the trans doesn't explode just getting forced in the low gear at all.
Also, I was assuming common sense would be in play, in that he would not do a 3rd to 2nd drop at 90mph, but rather, at the 40mph or so he was talking about... :p: Obviously you have to have your brain in gear too and not do a manual downshift at too high of a speed for the lower gear. :yesnod:
[Modified by Lone Ranger, 8:52 PM 11/14/2002]
