Changing the Overdrive Shift Point
Thread Starter
Pro
Joined: Aug 2019
Posts: 596
Likes: 146
From: Minford, Ohio
Changing the Overdrive Shift Point
I have a 93 LT1 with auto trans. Is there any way to change the speed at which the transmission shifts from 3rd into overdrive? Mine shifts into overdrive at 45 MPH and I would like to change it to 55.
Thread Starter
Pro
Joined: Aug 2019
Posts: 596
Likes: 146
From: Minford, Ohio
All my shifts happen earlier than I like but the shift into overdrive has the biggest drop in RPS's. All the roads around me have a speed limit of 45 mph so its shifting in and out of overdrive a lot. GM just wants the best mpg it can get without regard to how it feels to the driver. I know I can always shift it into overdrive manually but if I have to do that I could just get a manual transmission. In my driving situation, it would just be better if it shifted at 55 rather than 45.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
More likely in and out of TCC. Transmission is cable shift. Playing with cable and/or governor would change shift timing. It would be more practical to drive in 3 unless you're on expressway. TCC is in ECM programming in PROM. You could get custom prom raising TCC to whatever speed you want. If you go that route, you could request tuner include minor tweaks to improve performance. PCM of NC is a popular tuner.
Advanced
Joined: Feb 2016
Posts: 68
Likes: 14
From: MotorCity
The shift points and torque converter lock up are controlled by the PCM you can check this out you'll get much better overall performance > www.lt1pcmtuning.com/service/
Advanced
Joined: Feb 2016
Posts: 68
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From: MotorCity
Yes, I had him do a different car quite a few years ago, an honest guy and has a good turn around time.
He only communicates by email.
The end result was proof that General Motors left a lot on the table with the factory tune and the transmission operated much better with different shift points and TCC lock up
He only communicates by email.
The end result was proof that General Motors left a lot on the table with the factory tune and the transmission operated much better with different shift points and TCC lock up
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
The shift points and torque converter lock up are controlled by the PCM you can check this out you'll get much better overall performance > www.lt1pcmtuning.com/service/
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Thread Starter
Pro
Joined: Aug 2019
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From: Minford, Ohio
Since it's controlled by aa governor does that mean the shift point can be changed? I know nothing about transmissions, either kind.
Race Director
Joined: Apr 2003
Posts: 17,700
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From: moraga ca
Yes, the weights and springs can be changed. The governor changes the shift points if all the gear shifts as well as part and full throttle shifts. You can’t just change the shift if 1 gear. They are all affected
Thread Starter
Pro
Joined: Aug 2019
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From: Minford, Ohio
Thanks for clearing that up! I really only want the 4th gear shift changed. I guess I'll just have to shift into overdrive.
Safety Car
Joined: Dec 2009
Posts: 4,363
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From: Birmingham Al
You can play with the TV cable adjustment a LITTLE . OK go to you tube TV cable adjustment and the guy will tell you to the cable adjustment is 71 In lbs for TV cable adjustment .now what I did was put some tape or just mark were the cable is right now before you release it ,them you can play with the cable adjustment a little .You don't have to go back to the org. adjustment you can change the cable I would say in 1/32 increments ( drive it ) if don't like it can slid it up or back a little .but make sure you make the cable to know were your at .. well if you don't get what you want got back to 71 in LBS . setting .. This will be all clear when you go to the U-tube video . The 1/32 adjustment up or back makes a BIG difference .. I went with the stock setting the 71 in LB setting very hard shift let off 1/32 was way better.This is easy way to make some small changes in the shift . I am sure this has its limits ..I played with it and I like what I cam up with .. Just saying what I did ..
Safety Car
Joined: Dec 2009
Posts: 4,363
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From: Birmingham Al
Changing the adjustment will Chang the shift points but it has its laments .Give it a try .. This thing runs off the TV cable not the and whats inside the trans so NO PC chip or anything will work ..Old school ..
Safety Car
Joined: Sep 2001
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From: Glenbeulah Wi
To all, There is only one correct location for the shift cable and that is fully extended at WOT, anything other then that can damage the transmission by not allowing correct line pressure at various driving conditions. The shift point is controlled by the governor in the transmision to raise the shift point you need to change the weight of weights or the springs in the governor. Less weight on the governor will have more impact on the 3 to 4 shift (raising it) and spring pressure will have more effect on the lower speed shifts. You could try grinding a little weight off the existing governor weights and see how it works. Go slowly, easy to take weight off not so easy to put it back on.
Last edited by bjankuski; Apr 24, 2020 at 12:34 PM.
Thread Starter
Pro
Joined: Aug 2019
Posts: 596
Likes: 146
From: Minford, Ohio
To all, There is only one correct location for the shift cable and that is fully extended at WOT, anything other then that can damage the transmission by not allowing correct line pressure at various driving conditions. The shift point is controlled by the governor in the transmision to raise the shift point you need to change the weight of weights or the springs in the governor. Less weight on the governor will have more impact on the 3 to 4 shift (raising it) and spring pressure will have more effect on the lower speed shifts. You could try grinding a little weight off the existing governor weights and see how it works. Go slowly, easy to take weight off not so easy to put it back on.
Safety Car
Joined: Dec 2009
Posts: 4,363
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From: Birmingham Al
True for sure but I have been driving the old 93 for 2 years with the cable changed a little 1/32 and no problem so far ,not saying it won't damage something just a little change makes a big difference ..
Advanced
Joined: Feb 2016
Posts: 68
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From: MotorCity
To all, There is only one correct location for the shift cable and that is fully extended at WOT, anything other then that can damage the transmission by not allowing correct line pressure at various driving conditions. The shift point is controlled by the governor in the transmision to raise the shift point you need to change the weight of weights or the springs in the governor. Less weight on the governor will have more impact on the 3 to 4 shift (raising it) and spring pressure will have more effect on the lower speed shifts. You could try grinding a little weight off the existing governor weights and see how it works. Go slowly, easy to take weight off not so easy to put it back on.
The governor is what controls shift points and if the TV cable if not adjusted correctly it will destroy your transmission. B&M sells a kit with weights and spring but I been told it may take more than a few attempts to get it dialed in.
There is a possibility the TV cable could be out of adjustment as mentioned small increments make a big difference.
Last edited by 1Sin; Apr 24, 2020 at 01:27 PM.