Ok first the lockup clutch in a converter is simply that a clutch. Just like any clutch in the trans it is applied by a piston with seals. Fluid is directed thru the input shaft that applies the piston which in turn applies the clutch.

1-Possible reasons for failure within the converter
There are only two. One is the rubber seals are not sealing however if the converter is relativley new and the clutch has appled since it was installed this is the least likley possibility and very unlikley.
The other is the Lockup clutch friction material either was burned off or just separated from the surface. If this occured there would be several tell tail signs. Rubbing or grinding noise at lockup,metal and or what appears to be friction material in pan and or a distinct burned smell to accompany this. Neither of these will result in occasional lockup and should result in a code PO1870 if the PCM comands lockup and it does not ocur this code will always set So you can be sure that if you dont have lockup and are not seting this code or any other TCC related code your issue is tuning or sensor related.

2- Possible reasons within the trans in order of likley hood
A- PWM solenoid. filter becoming clogged or converter regulator valve bore worn out. This should not be and issue if PWM is eleiminated which it should be with any performance trans and all with a small diameter converter 9.5 or other smaller converters. These cannot handle the slip of the PWM regulated properly. There is just not enough friction area .
B-Damaged or worn seal on the input shaft this will result in No LOCKUP.SLIPPING LOCKUP not to be confused with the PWM which is intentional slipping lockup. Will set code PO1870 if no lockup and may set this if slipping lockup.
C- Excessive bushing clearance or wear in the input shaft or pump stator ,
This will result in partial lockup. no lockup , slipping lockup eventual converter clutch burn up but again will not be intermitant.Will set code PO1870 if no lockup and may for slipping lockup.
D- STUCK TCC VALVE this will result in no lockup ussually hot or cold or not at all is generally predictable. Will set code PO1870

3-Engine running issues, These are the most irratic.
A-ENGINE MISSFIRE Will result in intermitant lockup or none is the most comon cause of lockup issues particulary with a cam. This may or may not set a code. Cure is repair cause of missfire and or raise missfire tables threshold.
B-TPS also very comon but will ussually result in poor trans and engine performance.Improper shift times and poor engine idle. This may or may not set a code cdes only set if TPS is outside its operation range, These can give incorrect readings yet still be within that range.
C-VSS No lockup will occur without a speedo signal. Again this will result in poor shift quality or timing.
D-MAF a dirty or failing MAF will cause the PCM to missinterperate engine load and disable lockup this same condition can also result in trans failure.This again may or may not set a code since though it may be sending the wrong readings it may still be in range.
E-Coolant temp sensor , The PCM will not comand lockup if it does not know the engine is warm Aprox 130 degrees. This may or may not set a code.

4-Trans electrical -
Bad TCC enable solenoid , This will cause no lockup period.
Bad PWM solenoid again this will not be a factor if PWM eliminated mechanically. Will result in slipping lockup ,No lockup and intermitant lockup ussually temperature sensitive. This will allmost allways set a TCC related code.

All the lockup issues I have seen over the years that did not set a code have been tuning or other sensor related.

Hope this helps someone I see so many no lockup post though this would be good info.

 

So what do you think would cause a slipping lockup, it doesn't happen all the time. Sometimes going over 50mph while in complete lockup I can push the gas moderatly(sp) heavy and hear the rpms go up but the car speed doesnt change in relation to rpms. Stock transmission with a TCI 3500, cooler,shift kit and deep trans pan. No codes have been set...I am thinking the converter is a piece o sh-t, its 3 years old. Any thoughts would be appreciated.

 

Great informative post. Thanks.

 

Well the lockup clutch could of course be worn or burned , But also bear in mind depending on the tune set up the PCM will generally disable lockup with a slight tilt in on the throttle you have to bear in mind lockup was not designed to stay on during accelleration.The purpose was to improve efficency at cruising speeds at very light throttle.

 

Moderator should add this thread to the sticky threads.

 

Thanks I was hoping it would help some people. I see so much confusion about lockup isues and also so many times the converter or trans is imediatley blamed I though this info would help people to think through there issue a little first and hopefully be better able to diagnois there problem.

 

I am really going to have to get this tranny figured out, I had intermittent lock-up problems when I got the converter,it wouldn't lock-up while cruising. I am going to see the shop that put it in so they can diagnose it, which I should have done in the first place. But I am wondering if they can increase the pressure to get it to hold lock-up harder because I know if it is slipping then it's burning it up. Thanks performabuilt for the informative post.

 

Your welcome that was the idea to help people solve problems and missunderstandings about lockup. I hate to se people chasing there tails lol

 

I am also having a lockup problem, the car will not go in to lockup at all, no SES light, did have a p1870 code when it was plugged into a transmission scanner. Built transmission and precision 3.6k stall.

 

If its a history code do not count , Bt typically and 1870 code means the PCM comanded it but it did not happen. May be a trans or converter issue, Clear codes and rescan.

 

I got the converter from another member here, he says its only got 3k, trans is only got a few hundred miles, my transmission guy said something about changing the TCC lockup solenoid in the transmission? When he scanned it, it was showing 14% tps voltage at idle? Possibly Linked? also, every once and a while it shifts between 2 and 3 early, like 4800 rpm under WOT

 

Well it certainly sounds like you may have some tuning or sensor issues also , But 1870 is only set if the PCM comands lockup there is no TCC related electrical code already present. And though comanded lockup does not occur or slips excessivly . I would say the other conditions probably are not related.
As for the LOCKUP solenoid replace. That sounds like a good idea and I would also replace the PWM solenoid with it unless you know that PWM has been mechanically disabled in the valve body.

 

Thank you for your help.

 

Your welcome

 

bump since i noticed a couple people with lockup issues posting

 

i just installed a 3600 with my freshly rebuilt tranny. Mine will lockup when i get on the interstate, will last about 5 minutes and then will unlock everytime. any ideas?? the car hasnt saw a tune since i bought it. I made it a full bolt on car. Does it just need a tune?? Is it bad for the TC when its unlocking a locking a lot??? Thanks!

 

You need to get ittuned this will likley solve your issue, Anytime a converter is locked and unlocked rapidly wear increases of course but this would be long term wear not in the short term

 

Did you solve your lockup issue ?

 

Very informative. Should be a sticky. As I'm also having lockup issues, I can at least ask some educated questions of my tuner, now.

 

no, not yet. i'm a little short on funds right now. I noticed it didnt unlock driving to and from work today. The weather has sucked, so havnt had much time to play with it. i did some more research, does it sound like this missfire im hearing about??