Stock 4L60E shift points at 255MPH

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Sep 9, 2015 | 09:06 PM

double0me

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Stock 4L60E shift points at 255MPH

This is going to be one of those moments where I learn something. Here is a picture of my factory shift points. Now I know for my 99 TransAm to shift it needs to hit its MPH and its RPM to complete the shift. For the longest I had used the setting from the Excel that is floating around HP Tuners but had not done a solid WOT pull, well I finally started working on the WOT and 1-2 was strong, 2-3 was strong but 3-4 was banging off the REV limiter. I have a stock stall so no need to raise the REV as my power band is no higher than 5900. So just out of curiosity I pulled my stock tune and checked the settings for RPM and MPH, this is where my question lies. Why would the 3-4 shift MPH on a stock 4L60E be set to 255 MPH if I am supposed to achieve both tables for a shift.

Thanks for reading and any input you can offer.

Sep 9, 2015 | 09:35 PM

joecar

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From: So.Cal.

Yes, your WOT 3->4 Shift Speed set to 255 mph (i.e. some un-achievable speed) will inhibit this shift (obviously, as you have found out);

set the WOT 3->4 Shift Speed to about 6 mph above the WOT 4->3 Shift Speed...

but, take note that your WOT 4->3 Shift Speed set to 148 mph is too high...

change them as follows:
- WOT 3->4 Shift Speed to 126 mph,
- WOT 4->3 Shift Speed to 120 mph,

and do likewise on the part throttle tables.

Sep 9, 2015 | 10:23 PM

mrvedit

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From: Ann Arbor, MI

Why is the shift speed set to 255 in a stock tune?
I don't know for a fact, but have been told that the 4L60E is not designed to handle WOT in 4th gear. If you really are going 130+ mph on some race track, I would suggest at least a billet 4th gear servo piston and even both 2nd and 4th gear servo pistons. Sonnax makes excellent ones.

Sep 9, 2015 | 10:37 PM

double0me

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I have a built trans, just a stock stall. Those are closer to my actual shift MPH, but why would GM send out a stock tune with such a high 3-4 shift? I cant recall ever going WOT with the stock tune.

Sep 9, 2015 | 11:05 PM

LSX Power Tuning

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From: Brenham TX

They dont want you to go into 3rd-4th WOT, trying to help make the transmission live longer. Remember they had to warranty the car for 3/36k when it was new. Even with built 4l60e's I never have them shift into 4th WOT.