60E No 1st 4th w/o Manually grounding pin, also no auto downshift in D
05-30-2017, 07:38 AM
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60E No 1st 4th w/o Manually grounding pin, also no auto downshift in D This is in a TBI truck application, but I know there are alot of very smart people here.
I have a 1995 4L60E that I had rebuilt as I thought it lost 3/4 pack, turned out to be a smoked converter clutch. Other than slipping with converter locked up, it had all gears. Had the trans rebuilt locally (bench rebuild, I did R&R). On start up after getting fluid all topped up I noticed some very odd behavior. Truck was up on a hoist for all of this testing.
Going from Park to Manual 1st I would get 1st gear, then I would shift to Manual Second, it would upshift, but will not manual down to 1st gear again or auto downshift after the initial upshift. If I continued and put it in 3rd, it would upshift into 3rd and I would have manual downshift to 2nd but will not auto downshift to 2nd or 1st even if I come to a complete stop. So aside from no 1st or 4th, even if I come to a complete stop the trans starts in the last gear it was running in.
I ohmed between the Trans Fuse and Shift solenoid A at the ECM and had 23 ohms. Solenoid B also ohmed 23 Ohms. Both were in check per the ATSG manual. Put the fuse back in, and had power at the ECM connector. Checked the pressure switch which checked good.
Started the truck back up, with the shifter in Manual 1st it was in 1st, upshifted to Manual 2nd and it shifted to 2nd, manually downshifted to first and trans stayed in 2nd. Put in OD, came to a stop, let go and it started in second. With the shift solenoid A pin backprobed, I can manually ground it, and it will downshift to 1st gear. I put in a spare ECM i had, thinking maybe the driver for the solenoid was flaky. Did EXACTLY the same thing.
Pulled the pan inspected the wire harness, found no issues, but still replaced wire harness, replaced shift solenoid A, EPC (Force motor), and pressure switch just trying to throw a dart and have it stick. Also tried another 95 ECM I had as a spare. Still have the same issues. Vehicle wire harness does not seem pinched anywhere.
I will admit, I never hooked a line gauge up, I can and will do that for all further diagnostics. Not sure what direction to go from here.
Thanks for the help.
Josh
I have a 1995 4L60E that I had rebuilt as I thought it lost 3/4 pack, turned out to be a smoked converter clutch. Other than slipping with converter locked up, it had all gears. Had the trans rebuilt locally (bench rebuild, I did R&R). On start up after getting fluid all topped up I noticed some very odd behavior. Truck was up on a hoist for all of this testing.
Going from Park to Manual 1st I would get 1st gear, then I would shift to Manual Second, it would upshift, but will not manual down to 1st gear again or auto downshift after the initial upshift. If I continued and put it in 3rd, it would upshift into 3rd and I would have manual downshift to 2nd but will not auto downshift to 2nd or 1st even if I come to a complete stop. So aside from no 1st or 4th, even if I come to a complete stop the trans starts in the last gear it was running in.
I ohmed between the Trans Fuse and Shift solenoid A at the ECM and had 23 ohms. Solenoid B also ohmed 23 Ohms. Both were in check per the ATSG manual. Put the fuse back in, and had power at the ECM connector. Checked the pressure switch which checked good.
Started the truck back up, with the shifter in Manual 1st it was in 1st, upshifted to Manual 2nd and it shifted to 2nd, manually downshifted to first and trans stayed in 2nd. Put in OD, came to a stop, let go and it started in second. With the shift solenoid A pin backprobed, I can manually ground it, and it will downshift to 1st gear. I put in a spare ECM i had, thinking maybe the driver for the solenoid was flaky. Did EXACTLY the same thing.
Pulled the pan inspected the wire harness, found no issues, but still replaced wire harness, replaced shift solenoid A, EPC (Force motor), and pressure switch just trying to throw a dart and have it stick. Also tried another 95 ECM I had as a spare. Still have the same issues. Vehicle wire harness does not seem pinched anywhere.
I will admit, I never hooked a line gauge up, I can and will do that for all further diagnostics. Not sure what direction to go from here.
Thanks for the help.
Josh
06-02-2017, 08:20 AM
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Just for reference in case someone has the same issue in the future it turned out to be a bad 3-2 downshift solenoid. Why that locked out 1st gear, I don't know but it did. Being OBD1 I never got a code for it, but that solved it.