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Greetings all,
I finished rebuilding the 4T60E mentioned in an earlier post. Many thanks to those that replied to that thread. Now I have a different problem with this thing. After the rebuild, it slips in low and reverse, unless I disconnect the vacuum modulator line. (valve is not sticking/modulator is new). Up and downshifts are fine, TCC lockup is fine, and it's not making any noises. There is no slip or shudder in 2nd, 3rd, or 4th and no trouble codes are set (not even an 1870, which is odd).
I was extremely cautious during reassembly, and am positive that I don't have any cut lip seals, damaged clutch pistons, excessive clearances, etc. All seals, sealing rings, clutch pistons, steels & frictions were replaced, as were the vanes in the pump (which was fine, by the way). Everything is torqued, and I air-tested everything during re-assembly and all clutch-packs and servos applied and released properly. Also replaced the TC (and pre-filled it before reinstallation) and flushed the cooler.
As a sanity-check, I took hundreds of 'before-and-after" photos to be able to refer to, just in case something like this happenned. I went though all of them to ensure that I didn't miss something or install something improperly. Everything looks as it should. The correct valve body, spacer plate, and channel-plate gaskets are there, all check-balls are present and accounted for in the proper locations. Made sure I didn't mix early and late parts, etc.
I also completely disassembled, cleaned and lubed the valve body and ensured that all valves moved freely when I finished. Also tested all the solenoids. About 20K miles earlier, I had the valve-body out to replace the 1-2 & 3-4 shift valves, and to install a TCC regulator & isolator kit, TCC clutch-apply kit & modulated line boost valve kit. I never had any valve-body problems after that, but I disassembled everything again because this trans had just ground up a lot of hard parts and I didn't want to chance having any stray metal fragments causing sticky valves.
I'm trying to find somewhere local to purchase a 400psi guage so I can take some readings and not guess at what might be causing this, but in the mean time, I'm trying to gather some information and would appreciate anyone's feedback that may have had similar problems with a 4T60E, or at least just know a lot more about them than I do. I'm trying to understand what's in common between low and reverse in this particular transaxle, and at the moment, the only thing I can think of is the reverse boost valve. As I understand it, the reverse-boost valve is responsible for boosting line pressure when in low or reverse. It seems possible to me, that if it sticks, it could be causing slipping in low & reverse. I'm guessing that when I pull the vacuum hose off of the modulator, line pressure increases, and that's why the slipping stops. Almost like simulating the effect of the reverse-boost valve.
What do you folks think? I know it's hard to tell without knowing what the actual line pressure is, and that's why I'm hunting for a guage. But until I find one, I'd really appreciate your feedback as respect your expertise. I'd much rather pull the valve-body than the whole tranny again to fix it. Thanks in advance!
--mike
I finished rebuilding the 4T60E mentioned in an earlier post. Many thanks to those that replied to that thread. Now I have a different problem with this thing. After the rebuild, it slips in low and reverse, unless I disconnect the vacuum modulator line. (valve is not sticking/modulator is new). Up and downshifts are fine, TCC lockup is fine, and it's not making any noises. There is no slip or shudder in 2nd, 3rd, or 4th and no trouble codes are set (not even an 1870, which is odd).
I was extremely cautious during reassembly, and am positive that I don't have any cut lip seals, damaged clutch pistons, excessive clearances, etc. All seals, sealing rings, clutch pistons, steels & frictions were replaced, as were the vanes in the pump (which was fine, by the way). Everything is torqued, and I air-tested everything during re-assembly and all clutch-packs and servos applied and released properly. Also replaced the TC (and pre-filled it before reinstallation) and flushed the cooler.
As a sanity-check, I took hundreds of 'before-and-after" photos to be able to refer to, just in case something like this happenned. I went though all of them to ensure that I didn't miss something or install something improperly. Everything looks as it should. The correct valve body, spacer plate, and channel-plate gaskets are there, all check-balls are present and accounted for in the proper locations. Made sure I didn't mix early and late parts, etc.
I also completely disassembled, cleaned and lubed the valve body and ensured that all valves moved freely when I finished. Also tested all the solenoids. About 20K miles earlier, I had the valve-body out to replace the 1-2 & 3-4 shift valves, and to install a TCC regulator & isolator kit, TCC clutch-apply kit & modulated line boost valve kit. I never had any valve-body problems after that, but I disassembled everything again because this trans had just ground up a lot of hard parts and I didn't want to chance having any stray metal fragments causing sticky valves.
I'm trying to find somewhere local to purchase a 400psi guage so I can take some readings and not guess at what might be causing this, but in the mean time, I'm trying to gather some information and would appreciate anyone's feedback that may have had similar problems with a 4T60E, or at least just know a lot more about them than I do. I'm trying to understand what's in common between low and reverse in this particular transaxle, and at the moment, the only thing I can think of is the reverse boost valve. As I understand it, the reverse-boost valve is responsible for boosting line pressure when in low or reverse. It seems possible to me, that if it sticks, it could be causing slipping in low & reverse. I'm guessing that when I pull the vacuum hose off of the modulator, line pressure increases, and that's why the slipping stops. Almost like simulating the effect of the reverse-boost valve.
What do you folks think? I know it's hard to tell without knowing what the actual line pressure is, and that's why I'm hunting for a guage. But until I find one, I'd really appreciate your feedback as respect your expertise. I'd much rather pull the valve-body than the whole tranny again to fix it. Thanks in advance!
--mike
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