Torque convertor lock-up?
Thread Starter
Burning Brakes
Joined: Dec 2003
Posts: 770
Likes: 0
From: Madison Mississippi
Torque convertor lock-up?
Took the Ruby out last night to test the new A/C and a strange thing happened when I nailed it around 3-4 up shift. I had it in overdrive but the tranny never upshifted into lock-up. It climbed to 6k so I let off the gas and it then decided to upshift. I backed off and tried it again manually shifting from drive to o/d, it then shifted into o/d lock-up like it normally does. Is my linkage or t/v cable out of adjustment? My question is how do I test the problem without breaking the sound barrier (if you know what I mean!) I only tried it twice for obvious reasons and would like to know. The lock-up is occurring normally at slower less throttle and it drove normal the rest of the way. Suggestions anybody? 
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
You don't give much back ground. What year? What trans? The 700R4/4L60 transmissions are shifted by the governor. The 4L60E trans is electronic. Has the trans ever been repaired or overhauled? Most 700R4s won't shift to OD at WOT. Corvettes, I believe will, but if it has ever been worked on, who knows what went back in. If it even HAS a TV cable, it has little influence on the shift points. It is possible to be the shift linkage, but not normally. Has something been done lately, that might have changed the shifter adjustment? Do you have a reason to suspect it? Also, it sounds like you are confusing two different functions, into one. Overdrive is the engagement of 4th gear. As stated, it is controlled by the governor (in a 700R4) and the valve body, inside the trans. Lock-up is the locking of the torque converter. THAT is controlled by the ECM. So far, I'm not convinced it is acting improperly.
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Thread Starter
Burning Brakes
Joined: Dec 2003
Posts: 770
Likes: 0
From: Madison Mississippi
It is a 1993, 700R4 original condition 103,000 miles. I re-chipped the engine and the transmission shifts very nice and firm at 5,800 Rpm @ W.O.T. For some reason it did not up shift into o/d lock-up last night; it kept pulling into the 6k plus RPM range. On my car, top gear and lock-up are the same (i think). At 100+mph it would normally lock-up, dropping rpm's providing it is in O/D. If I manually hold it in D it will wrap-up to 6k, THEN I shift into O/D and the convertor would lock-up and RPM's would subsequently drop and no more shifts, up to top speed. The only thing I have done lately is change my A/C compressor out. Last night, I had the a/c off when I nailed it. last time I ran it hard with the A/C on, it blew the compressor clutch around 6,000 RPM..... lesson learned! If you have any ideas on what to check, let me know. Could my fluid level cause this? 
Thread Starter
Burning Brakes
Joined: Dec 2003
Posts: 770
Likes: 0
From: Madison Mississippi
Ok, so it must be shifting into 4th gear @ 100 mph and the convertor is already locked. So, When does the convertor lock-up? I am getting confused. I thought that holding it in drive meant going through the gears except overdrive (mistaken for convertor lock-up). I know very little about the transmission set-up hence, the reason I am posting now. Can you clear me up a bit regarding the lock-up? It doesn't drop RPM when it locks and I am already locked-up at 100plus. So, my situation must be the delay of the 3-4 upshift verses lock-up. Right?
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Probably. Overdrive is 4th gear. It has a gear ratio of .70:1. That means at 6000 rpms in third, the engine will drop back to 4200 rpms when it shifts to fourth (OD) gear. "Lock-up" is merely the locking of the TCC (Torque Converter Clutch). When the TCC engages, it locks the crankshaft of the engine to the input shaft of the trans, like the clutch in a stick shift car, eliminating all the slippage inherent in a normal torque converter. With this info, you can determine if you are experiencing the 3 to 4 shift or the converter lock up. Different years have their shift quadrants marked differently. When you say you are shifting from drive at 100 mph, are you shifting from the 3rd position up from the bottom to the 4th (last) position? That SHOULD be the 3rd (direct drive) to overdrive shift. You would have to consult your owners manual or Helms to determine when the TCC should lock. Some won't lock at WOT. I hope this helps.
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Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Also, most 700R4s won't shift into Over-Drive at WOT. Those in 'F' bodies are a good example. If you go to the ThirdGen.Org forum you'll find posts from 'F' body guys trying to get the Vette tranny parts to allow them to run WOT in OD.
Not being a tranny guy, I'm not familiar with the specific part they change out, but whatever it is, it allows Vette trannys to shift into OD at WOT while 700R4s in other cars won't.
Typically, when the converter locks-up, rpms drop about 200. I don't believe the converter will lock at WOT, but I may be wrong.
Like I said, I'm not a tranny guy and I try really hard to stay under 100 MPH so I can't speak from much experience. I did hit 130 on a recent trip, but I was too busy running away from a modded Mustang to pay much attention to what the converter was doing.
Jake
Not being a tranny guy, I'm not familiar with the specific part they change out, but whatever it is, it allows Vette trannys to shift into OD at WOT while 700R4s in other cars won't.
Typically, when the converter locks-up, rpms drop about 200. I don't believe the converter will lock at WOT, but I may be wrong.
Like I said, I'm not a tranny guy and I try really hard to stay under 100 MPH so I can't speak from much experience. I did hit 130 on a recent trip, but I was too busy running away from a modded Mustang to pay much attention to what the converter was doing.
Jake
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