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The distance from the wheel mounting flange to the imaginary centerline of the wheel. Wheels with negative offset will protrude outwards more, while...
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Steve40th 1993 Transmission TCC issue?
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1109 Posts
Member since:
2005/12/20 0:00



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1993 Corvette, 396LT1 A4 2800 rpm converter Vigilante , 42# injectors, 3.75 gears, long tubes, heated O2 sensors. Runs great, with the exception of cruising at about 1800 rpm , plus or minus 200rpm, in OD.. It seems to buck a little, like a little surging, causing the driveline to slap, like hearing u joints are broke.
U Joints are new, driveline is solid with D44, Ikerds diff, and I cant move any of the half shafts or driveshaft by hand when in the air.
If I drop a gear, to 3rd it all goes away, even when I get in same rpm. Maybe not as pronounced due to speed, but I cant hear it
So, in tuning, what parameters can assist a barely above idle/throttle to keep car from bucking/surging a little.
TCC speeds for lock up and unlock. Right now its as follows.
TCC is lock 47mph low
42mph Unlock low gears
TCC lock high gears 56mph
TCC unlock high gears 42
TCC unlock prevention speed threshold is 64
Can I have a large spread on the lock vs unlock speeds, ie 60 lock and 40 unlock?
I am going to do some TTS Datamaster files to see if electronically the ecm is unlocking and locking today. If not, it must be surging from cam. Not small,
Gross Valve Lift: 510 I 520E 1.5RR
Installed at 108 Intake Centerline +4
Duration at .050 230 I 236 E
Lobe Lift .3400 I 3470E
Lobe Separation 112

Duration at .006 Tappet Lift 281 I 288 exh
I have 1.655 Roller Rockers too..
Comp Cams Part # 07-000-9 Engine :LT1/LT4
Posted on: 6/29 14:35
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Steve40th Re: 1993 Transmission TCC issue?
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Hey, I included a TTS datamaster run, if anyone is able to look at it. TCC is solid the whole time, not locking and unlocking.
So, I imagine, at very low throttle when locked, its surging.
Rpms are at about 1500 to 1800 rpms, 45 to 54 mph in run.
Very low TPS %. So, its an off idle issue. ]
Wonder if it is IAC. I change them often as they just suck..

Attach file:


uni 629run.uni Size: 462.50 KB; Hits: 5
bin Winter TCC lock up November PCMforLess 2015.bin Size: 32.00 KB; Hits: 5
Posted on: 6/29 23:57
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bogus Re: 1993 Transmission TCC issue?
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San Pedro, CA
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no clue... I am not knowledgeable enough about how torque converters work... the biggest void in my gearhead knowledge base, actually.

good luck?
Posted on: 7/2 18:46
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Steve40th Re: 1993 Transmission TCC issue?
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After looking at the run I just did, its not the torque converter.
I noticed the closed TPS spark advance is 4 to 6 degrees difference then when it barely opens. I am thinking that the timing is going back and forth causing it to surge/buck a little.
Converter was locked, at least according to the Data log..
Posted on: 7/2 18:53
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Matatk Re: 1993 Transmission TCC issue?
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I'm no expert with this stuff. When I had surging with my 383 and 700r4 2800 stall I put in a switch to unlock to the converter. I wouldn't lock the converter until about 50 mph. Might try a higher speed setting.
Posted on: 7/3 1:58
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Steve40th Re: 1993 Transmission TCC issue?
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I had changed the lock up to 55mph, made no difference.
I am hoping PCMforless address the timing issue. I could do it myself..Or wait for them to get back to me.
Today was tinker with 4runner day..
Posted on: 7/3 2:01
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bogus Re: 1993 Transmission TCC issue?
Grand Imperial Pooh-Bah
San Pedro, CA
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I like the timing issue... it fits and considering the changes made to the TC, continues.

if you wait, it might not be until Tuesday...
Posted on: 7/3 6:39
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Steve40th Re: 1993 Transmission TCC issue?
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I will research the timing. I think 34 is max for a LT1 at idle. So, I may have to bring the other timings down a few points and blend it..
Posted on: 7/3 12:27
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Steve40th Re: 1993 Transmission TCC issue?
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They got back to me and stated I have a code 15, low coolant temp sensor. Interesting, as I have no check engine light. I scanned the car with my OBD cable. Nothing, but Datamaster had it on there. They asked for me to address that, then relog data.
Hmm..
I imagine it is the one in the water pump.. Let me go find a good one...
Posted on: 7/5 20:45
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Steve40th Re: 1993 Transmission TCC issue?
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Changed CTS and checked for codes. Still there.
Going to disconnect battery and check later.
No Check Engine light in dash. Wierd.
5 volts at pins to it with key on.
Posted on: 7/6 18:24
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Steve40th Re: 1993 Transmission TCC issue?
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Back again. Old sensor was 2500 ohms at 75 degrees. According to this chart it was off. I am going to keep fiddling with it, check it in hot water, freezer etc..
Reconnected battery, all is well, as far as code being gone.
*F *C OHMS
210 100 185
160 70 450
100 38 1,800
70 20 3,400
40 4 7,500
20 -7 13,500
0 -18 25,000
-40 -40 100,700

Posted on: 7/6 18:58
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