I have a 6.0 truck engine with cam and a 4L60e trans, shift kit and 2800 stall in a Jeep TJ. The trans shifts fine in 2wd, but in 4LO the trans will sometimes not upshift 1-2 and will never shift 2-3 WOT. Have tried several adjustments and have been unsuccessful. The only thing I can assume is that the torque values are low enough in 4LO, it is throwing the shift pattern off. I assume I will have to install a "tow/haul" button for a performance setting so driveablility is not compromised. ANY help would be greatly appreciated. It looks like it is completing the 2-3 shift in the log, but it is not.
OK, tried the 4lo input, the speed sensor is located in the adapter between the t/case and transmission. The transmission shifted very quickly and was in 4th by 5 MPH. Tried hooking up a "tow/haul" button and modifying performance shift tables, still won't shift WOT. Only apply about 80 percent throttle and it shifts fine.
I removed the wire from red 16 for the 4lo input and added a wire to blue 71 and a momentary switch to activate performance shifting. Tried lowering shift points and speeds, still no success in 4lo. It does shift fine in high ranges.
you're best chance is to go back to the 4lo wire and relocate your speed sensor to the output of the transfer case. When you said it was shifting to 4th by 5mph, that would be correct since the output of your trans would be pretty fast compared to the output (actual vehicle speed) of the transfer case. Dakota Digital might have a pulse generator that would adapt to your Tcase.
If the 4lo input is only used to correct the shift points based on having the speed sensor after after the transfer case, then having the speed sensor before the transfer case should mean that no 4lo input would be required. Does the 4lo input change anything else, or does it just correct the speed sensor reading?
doesn't correct the speed sensor reading. Your Speed sensor will read correctly EVERY time if it is on the output of the transfer case. I don't have a 4Lo input in my truck, but my speed sensor is on the output and it shifts just fine in both 4lo and normal driving. I'd assume if i were to add the 4lo input it would scale my shifting towards just the RPM shift point rather than the RPM+MPH shift points.
You could use the performance shift option I think. You need to calculate how the 4lo effects your final drive, then use the final drive numbers to calculate shift points using something like blue cat software. Input those values into performance shift and have it activate when you go into 4 low. May have to disable a code for wrong gear ratio but I think it should work.
Figured it out, the problem is mechanical. The overrun clutches rob 3-4 apply oil, not letting the 3-4 clutches apply. When I shifted it manually, the trans shifted fine. Sonnax makes a heavy duty 2-3 shift valve to apply the overrun clutches in 1st, 2nd and 3rd when shifter is in drive.
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