Engine/Transmission (1994 - 1998) torque converter unlocking in 3rd under load

[LVJUNIOR]

I have a 98 12v with some mild modifications. It has a billet converter and a heavy duty trans (no Idea who built them) that are only 4000 or so miles old. When driving in 3rd gear with the converter in lockup if I lay into it a bit it will hold for about 200rpm and then let go and rev way up. If I back off it will lock up again. If I accelerate more gently it will not let go. this does not happen in 4th gear only 3rd



Do I have a line pressure problem. I know very little about autos and not sure where to start with this one.

 

[dieselshadow]

"Revs way up" "holds for about 200 rpm" Can you clarify with more details please?

 

[LVJUNIOR]

when I say it holds for about 200 rpm it will stay locked up as the power comes in and the boost starts to come up. But as the boost really starts coming in at about 15-20psi the converter unlocks and the rpm will go from wherever it is to about 2200-2400 rpm instantly.



I have always felt this converter was sloppy anyway. I had to replace the govenor solenoid and the fluid seemed slippery, nice and pink, and did not smell to bad, so I am assuming there has not been much wear on the converter

 

[Ridesamule]

Someone else can speak to it but Dave G. gave me a diode to clip feedback coming from the transmission to the ECM as transmission pressures build, to prevent an un-itended unlock/ downshift. Was one installed with your transmission upgrade?

 

[LVJUNIOR]

I do not know anything about what parts they put in the trans. I was just told it was heavy duty and had a billet converter. However, my trans will only unlock it does not down shift

 

[KLockliear]

Look under the dash for any "extra" modules. DTT used to make a box called the TC Saver that would force the TC out of lockup under WOT.

 

[LVJUNIOR]

There id a couple of things under there that I have not removed yet but I think they are all related to the alarm. I also don't believe it has the dtt box due to the fact it does not unlock under WOT in OD

 

[Larry Feenstral]

I'm interested in a solution since I have a similar problem with my 96. The TC unlocks at 2225 RPM in 3rd during acceleration. Isn't this controlled by the PCM?

 

[LVJUNIOR]

well it's been a year and 5 months since I started this post and I still have the same problem. I have since put a new billet converter from Goerend and set the TPS to the high side of the factory spec and installed a trans temp gage. The trans never gets hot or even close to it. I have left 5 messages with Dave to ask about the diode mentioned earlier in this thread but have yet to get a return phone call.



I have cycled my TPS with a meter hooked to it and the voltage apears smooth throughout the operation range.



Anyone have any insight as to why this thing is unlocking the converter in 3rd gear under full throttle?

 

[budnate]

have you checked the orange wire at the pcm to see what voltage is being sent to the trans???

 

[Bob4x4]

OEM software design to protect the lock up clutch... ... ... if you want to avoid it add a switch. Be aware that it will shorten the t/c life and most builders will not warranty the early failures