I have a 2002 silverado 4.8 new 4l60 and sometimes it wont shift from 1st to second until way past the WOT shift setting and the WOT RPM setting. Ive logged it hitting 6700 and 61 mph in 1st when its set at 55 and 6200 max. Brand new performace trans. Cammed 4.8 can use that rpm but im having to run on 87 for a while since im broke. I believe i adjusted everything down. What else could be making it not shift?
Lower your mph and shift times
I have been dealing with this as well. After numerous changes and many many track passes I have come to the conclusion its a mechanical issue. For your situation consider lowering just the MPH at WOT to say 5mph 1-2 and 2-3 9mph. That has seemed to help others.
'05 GTO E40
'01 TA
you can also adjust the trans line pressure alittle I think max is set to 96psi. Try setting it to 96 and see if she shifts then. You can always go back and play with it but it could be your trans pcs (pressure control solenoid is crap) seen it before in new tranys worth a try you can always set it back. But id try a mix of lower mph shift times, and higher line pressure. 1-2 shift was always sloppy on the 4l60e I have a vette servo in mine to mechanically increase line pressure for 1 to 2 shifts
i have done that and it yields the same result. With my original trans i was hitting 100+ in 2nd gear. Maybe thats because it was so worn? Im not sure but this new one seems to be stronger but more sluggish.Originally Posted by Rigo_eff1fitty
yeah i will do that for the mean time, but when i get back to using it for real pulls, i am losing almost 13 mph at the top of 2nd gear. It kills my top end because im not back into the powerband goin into 3rd and it take ages to even reach 110. Im going from 3.42s to 4.10s but thar in the future.
Make sure you don’t have a wonky tps. Also don’t forget you can lower lower the shift rpm also. If the mph and rpm are close enough it will hang sometimes. Had the same problem. Pay attention to your logs and what your actual shift rpm and mph are. Get them close to each other.
I had a similar problem in the past. I found out that my tire size/ring gear ratio-and trans & VSS pulses were off in HP Tuners. Go to HP Tuners>Speedo>Calibration> and make 1000% certain that your VSS pulses per mile are correct, trans revolutions/mile are correct, final drive ratio is correct.. My speedometer would register correctly, but my shift points WOULD NOT follow the inputs in the shift table. Once I fixed all of the data, the trans began following the exact programmed shift points.
Also, you are trying to run a 4L60E in a performance environment, in a heavy truck.. If you have not made significant internal upgrades (read-replaced all the factory junk) then you can expect the flimsy factory band to slip and not be able to stop the reverse input drum on a high-rpm 1-2 shift. A slipping band will cause the shift MPH, and RPM, to happen much later than programmed. Don't worry though... After several high-rpm 1-2 shift attempts, the problem will fix itself when the band smokes and you no longer have 2nd, or 4th gear AT ALL. You say it's a "new" trans, or new build. Did you advise the builder that you were tuning the shift programming AND have him build the unit to MUCH BETTER specs than factory? I hope that you were honest with him about how you intended to use the truck.
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