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4L60E manual TCC lock

This is a discussion on 4L60E manual TCC lock within the Technical / Maintenance forums, part of the General Discussion category; I have built a manual TCC (torque converter clutch) lock up system for my 97 Chevy pickup with a 4L60E. ...

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    4L60E manual TCC lock


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    I have built a manual TCC (torque converter clutch) lock up system for my 97 Chevy pickup with a 4L60E. The system operates from a switch on the panel which trips a relay which simultaneously grounds the TCC wire from the transmission, and connects the wire from the computer to a dummy load. The computer otherwise is connected to the trans normally. The dummy load is actually an old TCC solenoid connected to a hot wire on one side and the computer on the other side. The wire that connects the switch to the relay passes through two parallel normally closed relays, each of which has it's field connected to 12V+ on one side, the other being connected to the circuit that operates the 1-2 and the 2-3 shift servos. The result of this is that when both 1-2 and 2-3 are engaged the circuit is broken that the TCC is released. This would be the case ONLY in low gear. The works is mounted in a box under the hood, and wired into the transmission harness using a breakout harness built from male and female plugs and a short connecting harness (salvage stuff)...... so that I didn't have to cut into the vehicle harness at all.

    HERE'S THE PROBLEM: This is a GM rebuilt tranny, and the PWM (pulse width modulation) valve which modulates the pressure to the TCC (torque converter clutch) servo is operational, leaving me with conditions where I still have some slippage in the converter. My purpose here is to be able to lock up the clutch when pulling a trailer occasionally, and I want NO slippage at all.

    I know that I can pull the valve body and install a special over stiff spring which will effectively disable the PWM.....this is common practice in rebuild shops. I have no particular desire to pull the pan and do this, and as the system is electrically actuated I should be able to give the computer a dummy load, and simply clip the PWM wire or short it as the case may be. There is absolutely NO purpose in having the PWM functional under ANY circumstances.

    Can anybody tell me weather this PWM system goes to full pressure or zero pressure when de-energized. I suspect open circuit goes to full pressure but don't know. Also it would be useful to know the resistance needed so I can spoof the computer with an ordinary resistor......I may simply end up using a PWM solenoid coil as I did for the TCC as inductive loads behave differently than fixed resistances.

    The system works exactly as I intended other than the PWM interfering with it's operation...... I can flip the switch and run through the gears without the torque converter ever slipping....... of course the shift points are way out of whack without the converter providing intermediate ratios, but my intent is to shift down manually and lock up the TCC when pulling trailer rather than using the converter and making heat. For example third lock is a far more useful gear for pulling than 4th free, likewise 2nd lock as compared to 3rd free. It makes a big difference as I found out quite a few years ago with an A4Ld (Ford). I also achieve a slight improvement in mileage under some circumstances......not all, and achieve some engine hold back on hills which is otherwise not the case for automatics. It is a simple and cheap conversion thus far.

    I have schematics, diagrams, and photos posted on a Yahoo group if anybody is interested in duplicating this experiment.

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    Re: 4L60E manual TCC lock

    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


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    Re: 4L60E manual TCC lock

    Thanks...... I've got a lot of stuff on the systems, but not that particular item. It had been my belief that snipping the PWM feed would put the system to max pressure........ The diagram suggests that the opposite is true. This explains why people disable the PWM by replacing the standard spring with a stiff spring rather than simply disabling it electrically. I am not particularly enthusiastic about dropping the pan and pulling the valve body down to do this as it is unfamiliar territory for me. My feeling is that unmodulated pressures are a better option for my type of use than modulated pressures. These transmissions are designed to be soft and nice "car" transmissions rather than being suited for a pickup application.

    Howard owly@ttc-cmc.net

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    Re: 4L60E manual TCC lock

    you ever thought about getting into tuning your pcm? ie shift points, adjusting line pressure and tcc lock up as well as performance for the engine?
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


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    follow up: 4L60E manual TCC lock

    Just a followup on my previous posts (5 years ago). I have been using my manual TCC lockup for several years now very successfully. I disabled the PWM valve with a very stiff spring and things work very well. I pull trailer frequently with my '97 two wheel drive extended cab C1500 with a 4.3 V6 and 3.07 gears, and not light trailers either. My current trailer is an 18' flatbed with a single 18000 lb rear axle with 19.5 duals and electro hydraulic disk brakes (a truck axle by Eaton with the gears removed). Driving in Montana, which is NOT flat, I have pulled a payload as much as 10,000 lbs. The 4.3 is not a "powerhouse" by any means, but does just fine as I don't like to pull a trailer at 70 mph like so many idiots out there. Pulling, I simply flip the lockup switch and shift manually to keep the RPM high enough to enable me to negotiate whatever hill I am on, build up speed approaching a grade and shift just like I would with a manual. The objective is always to keep OUT of first gear where the torque converter does not lock up, and that may mean shifting early enough to keep the RPM between 3500 and 4000 on a steep grade. First and overdrive are both weak gears, and I try not to use either when putting serious horsepower to the ground. The 4.3 Vortec is rated at 210, but I cannot normally achieve more than about 160 on my scan gauge. If I could reprogram my shift points it would be great.... I would simply leave the lockup on all the time. The manual shifts are not hard, but I don't do them under full throttle as I would like to be easy on the transmission.
    People think I'm a bit nuts pulling a trailer with this little engine, and with 3.07 gears, but the pickup makes 22 on the highway cruising with an eye toward economy, 18 if I just stick my foot in it like my fellow idiots on the highway, and pulling a loaded trailer I typically make about 12mpg, but I typically don't like to pull a load on a bumper pull trailer faster than about 60. The key is thinking ahead..... strategy, and not being in a hurry. This transmission now has about 90,000 miles on it. If and when I have to replace it, and there is no sign of problems so far, I will be putting a high stall converter in it to allow me to reach higher RPM at low speeds. I've very nearly powered out with a trailer on behind on steep dirt roads in low gear because of the need to run at not much above walking speed, and not having low enough gearing. I've never been abusive to my vehicles....... In 40 years of driving pickups and trucks, I have yet to take out a clutch tear out gears or spiders, or blow an engine (except for an Autocar semi tractor with an 855 Cummins that someone had worked on and not put in new rod bolts..... That left a BIG puddle of oil when the rod came out the side).

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    Re: follow up: 4L60E manual TCC lock

    Quote Originally Posted by Owly View Post
    Just a followup on my previous posts (5 years ago). I have been using my manual TCC lockup for several years now very successfully. I disabled the PWM valve with a very stiff spring and things work very well. I pull trailer frequently with my '97 two wheel drive extended cab C1500 with a 4.3 V6 and 3.07 gears, and not light trailers either. My current trailer is an 18' flatbed with a single 18000 lb rear axle with 19.5 duals and electro hydraulic disk brakes (a truck axle by Eaton with the gears removed). Driving in Montana, which is NOT flat, I have pulled a payload as much as 10,000 lbs. The 4.3 is not a "powerhouse" by any means, but does just fine as I don't like to pull a trailer at 70 mph like so many idiots out there. Pulling, I simply flip the lockup switch and shift manually to keep the RPM high enough to enable me to negotiate whatever hill I am on, build up speed approaching a grade and shift just like I would with a manual. The objective is always to keep OUT of first gear where the torque converter does not lock up, and that may mean shifting early enough to keep the RPM between 3500 and 4000 on a steep grade. First and overdrive are both weak gears, and I try not to use either when putting serious horsepower to the ground. The 4.3 Vortec is rated at 210, but I cannot normally achieve more than about 160 on my scan gauge. If I could reprogram my shift points it would be great.... I would simply leave the lockup on all the time. The manual shifts are not hard, but I don't do them under full throttle as I would like to be easy on the transmission.
    People think I'm a bit nuts pulling a trailer with this little engine, and with 3.07 gears, but the pickup makes 22 on the highway cruising with an eye toward economy, 18 if I just stick my foot in it like my fellow idiots on the highway, and pulling a loaded trailer I typically make about 12mpg, but I typically don't like to pull a load on a bumper pull trailer faster than about 60. The key is thinking ahead..... strategy, and not being in a hurry. This transmission now has about 90,000 miles on it. If and when I have to replace it, and there is no sign of problems so far, I will be putting a high stall converter in it to allow me to reach higher RPM at low speeds. I've very nearly powered out with a trailer on behind on steep dirt roads in low gear because of the need to run at not much above walking speed, and not having low enough gearing. I've never been abusive to my vehicles....... In 40 years of driving pickups and trucks, I have yet to take out a clutch tear out gears or spiders, or blow an engine (except for an Autocar semi tractor with an 855 Cummins that someone had worked on and not put in new rod bolts..... That left a BIG puddle of oil when the rod came out the side).
    wow this is exactly what im looking to do on my 94 1500 with a 305. Found this thread on a google search and was to replicate it 100%.

    edit: but i THINK my 1994 does not have the PWM feature...
    Last edited by jmcfee; 03-04-2013 at 02:35 PM.

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    Re: 4L60E manual TCC lock

    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


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    Re: 4L60E manual TCC lock

    CSFI Vortec 4.3 L35's in the FSC trucks were rated at 200hp@4600rpm and 260 lb/ft@2800rpm.

    In this case I might look at changing gearing instead of a higher stall speed TC. My reasoning for this is because the 1997 TC's used a woven carbon TC clutch. Older is cellulose(paper, newer is kevlar. If you go to an after market TC, I wonder what the quality of the clutch material will be. A quality TC with larger clutch area than stock is expensive, but well worth it in your instance. Higher stall will decrease your city mileage, build more heat(unlocked). A swap to a better rear gear will increase your city mileage, decrease loading of the rear, driveshaft, trans and engine.

    Your TCC strategy can be accomplished via PCM tuning.

    You certainly must be a patient driver. I hope it all works out.

    peace
    PAuly
    97 GMC 2wd RCSB 5.7, s10 2700 footstall, Hooker 24621hkr LT's , 2.5" cats dual 4"pipes exit B4 pass. side tire, custom driveshaft 3.42 G80 FIPK MAF descreen GM/Mercruiser Marine intake manifold 29lb LS2(EV6) injectors Ed Wright PCM(best mod), LT4 KM 14.8@94mph 2.007 4000lbs 122mph

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    Re: 4L60E manual TCC lock

    Impressed.

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    Re: 4L60E manual TCC lock

    I know it has been awhile since you have been active but I am hoping for the best! This is the first thread that I have found that has exactly what I have been looking for. I have a SFA 1996 s10 and I have been unable to get it to shift into overdrive for 2 transmissions now (1 factory w/ 155k that ended life puking fluid out of the dipstick tube from excessive heat, and another one that is currently in it from a 97 that caught fire in the guys driveway. Only paid 100 for it.) But I still can't get this sucker to lockup the torque converter clutch. It shifts fine otherwise has a vette servo and on a wet road will roast the 33 in the back (its an open diff) through 2nd gear. Only other issue is a delay going from park to any gear or from reverse to drive. I have the valve to eliminate the PWM but haven't installed it. Is there any way I can get your plans you used to put a switch to lock it up manually. This rig has 33's and 4.10s and drives stock , but I would love to be able to leave the tcc unlocked in the city, and be able to control it manually on a highway drive. I don't drive it but would love to get some mileage back since the lift. Any info would be greatly appreciated!
    Last edited by 96superflow; 10-14-2013 at 09:41 AM.
    1996 S10 Blazer SAS in progress
    2001 Chevy Tahoe

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    Re: 4L60E manual TCC lock

    I had diagrams for wiring color codes, etc........ but seem to have lost them somewhere in my computer............ They aren't however difficult to find on the internet. What I did was very simple and works well. I obtained wiring harness parts from a transmission rebuilder and a salvage yard so that I had both male and female connectors. I then disconnected the harness at the transmission and plugged a short piece of harness in between the transmission and the cable to the ECM. I used this as a "breakout" so that I didn't have to snip any original wiring. I snipped the TCC wire and spliced wires to both ends of it which went back up under the hood where it enters a generic Radio Shack project box (plastic) which contains a couple of relays. In normal operating mode these two wires are connected so that the ECM operates the TCC normally. When I flip a switch on the dash which is connected to a 12V fused power source (15A in this case), power is supplied to the relays shifting them so that 12V is supplied to the TCC, and an old TCC relay coil is connected to the ECM so it sees the normal electrical load. If you don't do this, the ECM will generate "check engine" error codes. I have an indicator light which reminds me that the TCC is locked up manually................

    The ECM will generate error codes if you aren't judicious in how you shift anyway, and I occasionally find myself having to cancel an error code. I have a scangauge mounted in the vehicle, so this is no problem. I highly recommend the scangauge. It's a dash mount unit that reads out all kinds of parameters (you choose), as well as gas mileage. At $180.00, it has paid for itself in fuel savings many times over.......... You change your driving style when you see what it is costing you!! It will read out in dollars if you want! It also will tell you exactly what horsepower your vehicle is putting out at any moment, what your TPS and MAP and MAF are reading, and countless other things. Buy one!!

    Do not be afraid of leaving the TCC switch flipped on......... The TCC will not engage in 1st gear........... Manually shift when the TCC is locked to avoid error codes and to make the shift points work. Otherwise the RPM will be far too low before the ECM shifts. The ECM is programmed to operate with the TCC acting as a gear. If I could reprogram the ECM to shift the tranny the way I want, I would NEVER run without the TCC locked up!

    ********************DO NOT NEGLECT TO DISABLE YOUR PWM VALVE *************

    The PWM valve is the number one killer of transmissions............. KILL IT BEFORE IT KILLS YOUR TRANNY

    I have between 60k & 70k on this transmission since I made these changes...... I just did my first filter change / flush, and the fluid looked very good, exhibited no burned appearance or smell. Considering the extremely heavy workload it gets periodically...........I've hauled dozens of loads of scrap iron to the recycler, many weighing in close to 5 tons, and done a great many other jobs that involved heavy work........ the condition of the fluid was superb! I took the advice of people here and did my flush myself by simply disconnecting the top line at the radiator, and screwing in a piece of brake line which went to a clear plastic hose. I refilled the transmission with the requisite 5Q of fluid, ran it until I saw bubbles, added another 5Q and repeated....... at which time It was running very clear, then added another 5Q to refill it, and disconnected everything. I buy all my oil in 5 gallon cans, so I have 5 Q of ATF left over. Oil cost for the flush and fill added up to $53 (approx). I probably will repeat this in a few years without the filter change.

    Howard

    Quote Originally Posted by 96superflow View Post
    I know it has been awhile since you have been active but I am hoping for the best! This is the first thread that I have found that has exactly what I have been looking for. I have a SFA 1996 s10 and I have been unable to get it to shift into overdrive for 2 transmissions now (1 factory w/ 155k that ended life puking fluid out of the dipstick tube from excessive heat, and another one that is currently in it from a 97 that caught fire in the guys driveway. Only paid 100 for it.) But I still can't get this sucker to lockup the torque converter clutch. It shifts fine otherwise has a vette servo and on a wet road will roast the 33 in the back (its an open diff) through 2nd gear. Only other issue is a delay going from park to any gear or from reverse to drive. I have the valve to eliminate the PWM but haven't installed it. Is there any way I can get your plans you used to put a switch to lock it up manually. This rig has 33's and 4.10s and drives stock , but I would love to be able to leave the tcc unlocked in the city, and be able to control it manually on a highway drive. I don't drive it but would love to get some mileage back since the lift. Any info would be greatly appreciated!

 

 

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