No 4th Gear!!!
No 4th Gear!!! Hey guys need some help/ideas. I pulled the tranny out 2 weeks ago, and replaced the 3-4 clutch pack with the Raybestos Z-Pak clutches, pump spring, rev-kit, and the "Beast" sun shell. If I remember right, when it was all done, everything was fine, but now....I went to a town about 50 miles from here this weekend and I never did get 4th to engage. It seems like the converter is locking up in 3rd but it runs about 2800-3100 running 70 down the highway. I hooked up a Tech2 to it and it IS commanding 4th gear and the TCC is commanded on but it's not shifting. Every once in a while it will shift into 4th at VERY light throttle but it will slowly shift back down into 3rd, almost like the band applies then slowly bleeds off pressure and shifts back down into 3rd. Could the inner seal on the 2-4 servo cause this?!?! Everything else with the tranny is fine, it shifts snappy into all the gears and I don't have any external leaks. The fluid on the dipstick isn't foamy, the level looks to be a tad high, but it still isn't filling up the holes, the fluid is all the way across though when you check it. Like I said any ideas or suggestions would be greatly appreciated!!!! Thanks again guys!!!!
It has a Sonnax 2-4 Servo on it now...do you think you can get another 4th piston or do you have to buy the whole 4th servo? I've heard that the seal on the 4th piston is like a neoprene or something like that, basically not an O-Ring, so if it is cut my only choice is to replace the piston at least. Is this true?!?! I'm just wondering what I'm gonna need because the car is my daily driver and I don't think that I can get that servo out with the tranny in the car so if I have to pull the tranny I want to be able to fix whatever I need to while I'm there, that way I will have as little down time as possible. By the way, thanks for the response.
There is a seal kit for the forth sonnax servo. The seals or d-rings are made of viton rubber. It would be pretty hard to cut one of those rings in the 4th servo due to the fact that it goes together as one piece. Did you install the washer on th the servo pin and then the 4th servo? Are you running the sonnax 2nd servo as well? I do believe that it can be removed in the car. When you had the trans out last did you put an overhaul kit in it? I'm also wondering if you possibly cut or left off the 3-4 accumulator seal. I've seen wierd things when this happens. Did you put a shift kit in? Are you sure it's 4th and not lockup that your losing? Well just a little more info. Good luck!
The first post lists everything that I did while I was in the trans. I used all GM special tools and took my time with it. When I pulled the 2-4 servo out, it came out rather tough and when it finally broke loose and slid out, a couple of pistons slid on the pin but I don't think it came all the way apart, and yes I have the Sonnax 2nd servo. No shift kit in there yet. I'm positive that it is 4th. Like I said, every once in a while, especially if the trans is cold, it will shift into 4th but not very long and will slowly pick rpm's back up until it is back into 3rd. While it is in 3rd you can keep your foot on the gas and tap the brake and the convertor will unlock and pick up about 200-300 rpms.
Be sure that this is not just misfires unlocking the TCC,
and the resulting slip -looking- like 3rd. Log TCC_Slip
RPM as well as TCC PWM duty, commanded gear and
TCC_Mode. Log the input/output shaft ratio and see
whether this dead-matches 3 (1.0) or 4 (0.7) or maybe
neither (friction slip). All slip should be in the TCC and
no slip/error in the shaft ratio.
and the resulting slip -looking- like 3rd. Log TCC_Slip
RPM as well as TCC PWM duty, commanded gear and
TCC_Mode. Log the input/output shaft ratio and see
whether this dead-matches 3 (1.0) or 4 (0.7) or maybe
neither (friction slip). All slip should be in the TCC and
no slip/error in the shaft ratio.
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jimmyblue: I will do some logging tonight after I get off of work and there is a tech2 available. If this helps any, it did have a p1870 code set for trans compnent slipping. But this could also be set if the 4th servo piston is losing pressure and allowing the band to slip on the drum right? And all other gears work perfectly and shift like they should/did.
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