700 R4 lock up issue
Thread Starter
Burning Brakes
Joined: Feb 2009
Posts: 780
Likes: 1
From: Shelby NC
700 R4 lock up issue
I have a 700R4 that does not have a lock up switch but uses a valve kit that was put in the valve body assy which controls the lock up converter. My issue seems to be that when it is good and warmed up and pressure is applied to the throttle assy the converter engages and the rpm drops about 200 or so. When I let off the throttle or try to hold it steady it will suddenly seem as if it is upshifting and the rpm goes up. All this is at road speed and the trans is in OD. Shift pattern is good and the down shifts are working good--only problem is this erractic pattern that occurs when throttle pressure is applied. If the valve is working right then it would seem that when pressure is applied the converter would up shift and the rpm would go up then not drop and then only hold for a very short peroid of time and then the rpms would increase.
Any ideas? Thanks for any advice or insight into this. Anyone else ever use this mod to the valve body assy for lock up converters?
Any ideas? Thanks for any advice or insight into this. Anyone else ever use this mod to the valve body assy for lock up converters?
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Do you have injection on the engine?? if so what computer/controller??
Look at the ATSG for overhaul of those trannies, and you will see wiring and locations for the 4th gear lockup IF internal to the tranny, you need to know to jumper out the temperature switch GM puts in there, just cut and splice the wires together....
I have a remarkably similar problem with a L98 speed density computer the computer insists on unlocking the computer when lifting the accelerator in ~45 mph traffic....but not on computer cruise control....
In MY case I have it narrowed down to a bad VSS signal, and it was a aftermarket unit from 18 years ago, and so a L O N G story....
Look at the ATSG for overhaul of those trannies, and you will see wiring and locations for the 4th gear lockup IF internal to the tranny, you need to know to jumper out the temperature switch GM puts in there, just cut and splice the wires together....
I have a remarkably similar problem with a L98 speed density computer the computer insists on unlocking the computer when lifting the accelerator in ~45 mph traffic....but not on computer cruise control....
In MY case I have it narrowed down to a bad VSS signal, and it was a aftermarket unit from 18 years ago, and so a L O N G story....
Advanced
Joined: Aug 2007
Posts: 66
Likes: 4
From: Perth, Western Austraila
By any chance do you have a single wire going to the trans 4 pin plug? If its like mine I have it wired just to lock up in 4th, with no overide switch. I had a similar problem with the pressure switch on the 4th gear port on the valve body . It should of gone into lockup when it goes into overdrive, but it would only lockup when accelerated in because the increased pressure , changed the switch all good ! not even a local trans guys or bto (bto stage2 trans ) could work it out
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
It sounds like someone installed a hydraulic lock up kit and there is no electrical input? The hydraulic kit works, but IMHO leaves some on the table as far as adjustability. IT may be that the spring in it needs to be a little softer or stiffer. Problem is that to change the spring, it's drop the pan and possibly the valve body.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Sounds like it is working as intended. You should be aware that the lockup clutch in a 700R4 (well, all of them really) won't handle much torque. So, when you let off the throttle...or hit the brake...or punch the accelerator to get up that big hill...the lockup clutch is supposed to drop out. If it did not, eventually, it would become "toast". It is not just another gear; it's intent is to eliminate torque converter losses when the car is running in high gear at a steady rate (give or take a little on small hills, etc.). If that is not how you intend to use the lockup clutch, you should just not have it operational.
Thread Starter
Burning Brakes
Joined: Feb 2009
Posts: 780
Likes: 1
From: Shelby NC
I can honestly say I have no idea whats going on. Its a pain in the butt for sure. Slightest up hill pull and it is going in and out--in and out --so I don't know. When it is not good and hot it doesn't seem to do it. There is no computer or wiring connected to it--just the TV cable and that was bad enough to set. Got the adj kit from BTO for that and then worked with it for a long time to get it like it is now, which seems to be OK as shift patterns go. Drops into OD at about 45 no problem. Out of first real fast but the others work fine but I have a 3.73 rear gear so from what I've heard the first shift is going to be real quick.
