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2001 GMC Sierra 4x4 5.3 4L60E shifting issue &P0757


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GNeric85
New User

Apr 9, 2022, 3:55 PM

Post #1 of 4 (848 views)
2001 GMC Sierra 4x4 5.3 4L60E shifting issue &P0757 Sign In

Hello, I am knew here but not new to the field. ASE Master Certified since 1990. Been building transmissions since 1988. Cut my teeth on the 700R4 and have probably built approximately 15k units. This is my first one to fight me so hard.
This truck was gone thru by another guy at least 5 times. I got it as a bench job and found all sorts of issues. 554 servo, 3rd accumulator capsule replaced with a cup plug, 10 vane pump, unknown solenoids and pressure manifold, reused clutches, sticking 2-3 shift valve, early 700 model low one-way. I cleaned and inspected everything, rebuilt the pump with the larger boost valve, hardened rings, new rotor and vanes and faced both halves to make sure 100% true surfaces. Proper clearance (.0015"). All new clutches, steels, sealing rings, bushings, thrust washers, steel pistons, new GM internal harness, solenoids and pressure manifold. Air test every component, proper end play, make sure gaskets are correct and both solenoid feed holes open. The R&R guy installs and test drives and it showed the same code P0757. Went to his shop and sure enough. Replaced both solenoids and filter. Another test drive and same thing. Replaced internal harness and solenoids again. Now we have a 1-2 with a neutral condition. Let off throttle and shifts into 2nd. Stays in second and shifts 2-3-2-3-4. Scan and still a P0757. Sticking 2-3 valve again and got a Reman valve body. No sticking valves but same P0757 and 1-2 with a neutral and one 2-3-2-3 shift when cold. He got another ecm and same problem. Pulled trans and went thru again and cannot find any reason for issues. Especially the code. Had converter cut open and inspected...perfect. Trans back in and a P0757 on Key-On, without starting. Just got done checking Neutral Swich, wiring, internal resistance values and everything where it should be. No cracks I could find with magnifying glass in case, internal components or valve body. Graphed solenoid On/Off operation and no capacitor bleed down. Instant On/Off. I am at my wit's end on this "piece of crap" truck. Help...
Eric
SR Performance

(This post was edited by GNeric85 on Apr 9, 2022, 11:45 PM)


gsferraro
Veteran

Apr 10, 2022, 9:53 AM

Post #2 of 4 (771 views)
Re: 2001 GMC Sierra 4x4 5.3 4L60E shifting issue &P0757 Sign In

Hello
Do you have any way you could bypass computer and shift transmission yourself like with a brakeout box to see if the problem is inside or outside the unit. Gary


GNeric85
New User

Apr 10, 2022, 10:04 AM

Post #3 of 4 (765 views)
Re: 2001 GMC Sierra 4x4 5.3 4L60E shifting issue &P0757 Sign In

Hi Gary, thank you for your reply. I was thinking about building one last night at dinner. I built one for a 4T65 I built that went into a V8 Fiero. I do have blueprints to make a manual valve body for the 4L60E from a contributor of Transmission Digest
Eric
SR Performance


GNeric85
New User

Apr 10, 2022, 10:28 AM

Post #4 of 4 (758 views)
Re: 2001 GMC Sierra 4x4 5.3 4L60E shifting issue &P0757 Sign In

Reading back thru this, I realized I didn't specify that this truck only acts up cold. Like, first start and immediately drive it. Slowly up my street to the stop sign is just about an 1/8 mile. Leave the stop sign and the shifting up thru 3rd is done acting up and it does fine by the time a little temp has built up.
Eric
SR Performance






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