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TCC Lock-up

I'm not sure on what scan tool the shop was using. I know he has a Snap On, but I'm really not sure if it is the newer Modis, or the older MT2500. Really not sure on that one. Could the temp sensor be bad and reading on the gauge. I recently replaced the temperature sensor on the side of the head that reads the temp on the dash. But my TC problem was long before the gauge stopped working. I really wish that the tranny shop didn't write this off and try to tell me that it's locking up when I know for a fact it is not. But apparently with no codes no shop around here can do anything for me other than throw parts at it, which I refuse to do. Can someone educate me on PWM? And how to check it and the valve bore wear? I will also check the temp sensor on the crossover anyways, won't hurt to look at it. Thank you everyone for your help so far. I have a feeling that you guys will either point me in the correct direction or come up with the solution to my problems long before any shop around here does.
 
Without a scan tool or scan software and a laptop it is pretty difficult to know whats happening. Maybe a member in your area with a scan tool or software can help out.
 
Warm idle is around 500 RPM's or so. The pulley is the correct pulley. I thought the alternator was changed, but come to find out its the original alternator. I'm located in Chelmsford Massachusetts. Anyone around me who wants to help? I'm obviously willing to travel. Coffee/lunch/dinner/cash offered. PM me if you'd like to help. Thank you everyone so far for your input.
 
By that do you mean it idles 5 ticks above the bottom? I think the tach starts at 500, so if its 500rpm over that then it would be 1000rpm. That is a cold idle value if its between 900 and 1000rpm.

How long is your glow cycle?

Maybe your Coolant Temp Sender on the t-stat x-over is bad.
 
PWM is pulse width modulation. It is like flicking a light switch really fast to dim a light bulb. In this case the TCC lockup signal is pulsed to allow the TCC clutch to slip and smooth out bumps and roughness from the engine or road. The valve body itself is generally repaired during a rebuild. Again these failures should set a slipping code. So I agree with the thoughts above that something is preventing TCC lockup from being commanded on.
 
And I guess the OBD2 guys also have a code for too low of engine temp, so that shouldnt be the issue either.

It may be difficult to feel TCC lock in a large vehicle like that. Its most notable to me when accelerating quickly but my little truck moves and feels a lot different.

The RPMs dont seem real off either for 5.13 gearing. I thought 4.56 gearing was low for the HDs.
 
The truck is about 9,000 lbs empty on the scales. So possibly I'm not feeling it lock up and everythings ok. Hopefully thats the case. The trannys never been rebuilt in this truck but I'm not sure about fluid changes. I may dump the fluid this weekend regardless....it needs to be done. I'll see if that clears anything up. On the highway at 65 the truck will be at 2500 RPM, get out of it and back into it and its still at 2500. The truck definitley moves pretty well for a large truck...you would think it would be a slug but the motors very healthy as well as the tranny(minus the lock up issue), and the gearing helps a lot. If someones in my area and wants to help just let me know...thanks again for the help so far!

As a side note....this truck has a twin. My truck was originally owned by the company my father works for they bought two of these trucks back in 1999...2000. My truck screwed up first long before I bought it and it wasn't addressed. The twin started doing the same thing around 25,000 miles or so. I think its wierd, considering these trucks have all lived very easy lives before I owned it and while I own them. Obviously they do the heavy pulling and hauling, but no abuse. They get worked like trucks but are very well taken care of. Both trucks are the same GVW, wieght, tire size, axle ratio, and motor.
 
I would try an ohm meter on the coolant sender in the cross over and verify the ohms with the chart AK provided before accepting anything.
 
Steve93mustanglx said:
Crap- I have the wrong pulley on my new(er) alt. In all my years I have never bought "just" a pulley for an alt- I wonder if Napa sells?
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That measurement is from the outer flanges, not the belt running surface. NAPA should have pulleys.
 
bmxdkj said:
The truck is about 9,000 lbs empty on the scales. So possibly I'm not feeling it lock up and everythings ok. Hopefully thats the case.
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See post #15 - you don't have to "feel" anything for that one. Keep your foot into the pedal, just goose it a little - don't get off it and then back into it.
 
My truck doesnt do the jump in RPMs thing. Tried it many times, but I can feel it lock. With his big truck and gears and weight his RPMs and speeds going into shifts will be totally different and lock may occur commonly right away or not at all in third. Depending on what speed you are going in third. Im sure 45mph in third is still makes the engine sound like it wants another shift but TCC lock isnt until 52mph at more than light throttle, and not at all unless over 46mph I think. Unless his program was actually tweaked to match his gears and truck type, if we can give GM that kind of credit.
 
buddy said:
TCC lock isnt until 52mph at more than light throttle, and not at all unless over 46mph I think.
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That sounds about right - I don't think I've ever been able to get to actually lock (extremely light throttle) until about 49/50 - but sometimes I've noticed it stays locked as I slow down (but still under slight throttle) to around 48 (could be 46).

I was wondering about the big gears, too - that maybe his would lock up well before the "general" lock-up point of 50mph? Either way, by the time he gets to at least 55mph, it should be easy enough to do the "goose" thing.

Just to make sure we're both on the same page (and not confusing things even more!!!) - the "jump in RPM's" I was referring to was... after the TC is locked, then you happen to put in enough throttle that the TC unlocks again. Until that point, there should be no increase in RPM that isn't directly related to speed increase.
 
Mine will not unlock unless it goes into downshift, and then when it upshifts to 3rd I get a distinctive lock like 2 seconds later, it will lug around all day locked up if I like. I tried holding the throttle but tapping the brakes, doesnt cause unlock, but I have had mysterious DTC42 in the past, so maybe part of my brake switch is iffy. I have monitored the scanner though and the PCM always picks up the brake flag when I tap it.
 
buddy said:
I tried holding the throttle but tapping the brakes, doesnt cause unlock, but I have had mysterious DTC42 in the past, so maybe part of my brake switch is iffy.
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I'll try that on the way home... but I thought the "tapping the brake pedal" thing only worked when you were off the throttle completely? Meaning when you let off the throttle, the RPM's go to about 1,000 - then tap the brake and they go to idle?

That's interesting that yours won't unlock before it downshifts. If I'm traveling, say 55mph, with the TC locked, and I give it just a bit too much throttle, the TC will unlock. If I give it a bit more throttle, then it will downshift.
 
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