Will it hurt to run a L/U unlocked?

S

S10xGN

RETIRED!
Joined
May 26, 2001
Hi All,

I'm slowly getting miles put on my "Jakeshoe" built 200R4 ('72 Maverick w/LS-1 motor) and don't care too much for my L/U scheme. Right now, it's wired through my 4th gear switch and locks when the trans is in 4th. So, it's like a "double" shift from 3rd to 4th & locked. I've been driving in 3rd because of this (just around town). Any chance of damaging anything? I've seen some threads on Hotrodders.com concerning a vacuum switch with timer for a more "normal" L/U (not sure I want the complexity of that), but I may keep what I have and just use it on the highway...
 
I had a 4th gear lock up too. I hated it and just dropped the pan and pulled the wire off the sensor. Now I just have a micro switch on my shifter ball that I use to lock and unlock the converter at will. I much prefer this method. I believe it is detrimental to run the trans in 4th without locking the converter. I think when locked the fluid flow is redirected to the trans cooler. Something like that. I am too lazy to pull out my CK manual.
 
Ive posted about running a 200-4R/700R-4 with a LU converter unlocked for extended periods and its effects several times over the last few years. Its not a good thing to be doing if you do any extended driving.
 
bison said:
Ive posted about running a 200-4R/700R-4 with a LU converter unlocked for extended periods and its effects several times over the last few years. Its not a good thing to be doing if you do any extended driving.
Click to expand...


Brian,

Is that any gear or just 4th? I've been running (around town) unlocked in 3rd, but when the revs get uncomfortably high, I go to 4th & locked.
 
If you like the lockup feature and want to retain it, just add the B&M speed sensor kit. Easy as mud to install and you select the speed from a cockpit mounted dial. We have been running them for quite some time in our retrofit 200-4R project cars without issues.

You can select the speed up to @ 90 mph for the lockup to occur. Best part is when ever your car goes below that speed it automatically unlocks the converter as well. This has helped quite a bit with our choppy cam engines that tend to jerk like a manual trans when the converter is locked at a low speed.

I typically set it at @ 50-55 mph most of the time and leave it there. If I were to (hypothetically) get involved in a street race I roll the dial up to max. if I don't want the converter locking up on me. Beats the crap out of hokey toggle switches and tempermental vacuum switches. FWIW
 
Overkillphil I have a question about that kit. Let's say you are cruising at 60 and it is locked. You come to an incline does the kit unlock automatically or does it go to a 3RD gear downshift?
 
S10xGN said:
Brian,

Is that any gear or just 4th? I've been running (around town) unlocked in 3rd, but when the revs get uncomfortably high, I go to 4th & locked.
Click to expand...

You dont spend enough time cruising around town unlocked to cause a problen most of time. Id lock it in 3rd if i was doing an extended cruise at 25-40mph though.
 
Sal Lubrano said:
Overkillphil I have a question about that kit. Let's say you are cruising at 60 and it is locked. You come to an incline does the kit unlock automatically or does it go to a 3RD gear downshift?
Click to expand...

You could run a pressure switch in line with the wiring to open the circuit if the throttle angle was increasing and the road speed was staying the same
 
Sal, the speed sensor kit locks it up at the selected speed (that you select). So to answer your question, it would stay locked until you either went below the speed you dialed in or, if you were on the type of road that would require frequent lock/unlocks, I typically will just turn the dial up to max to avoid lockups.

Then, once on a steady crusing road again, simply dial back to desired speed. Also, important to note: This kit doesn't care whether the trans is in 2nd, 3rd or 4th. In other words, if you chose 25 mph for lockup it would lockup in that speed in any gear (except 1st) once you hit 25 mph. I don't see a need for lockup at anything below @ 45-50 mph. My personal preference is @ 55-up. You could also wire in a 4th gear pressure switch which would customize the kit even more if you were only interested in lockup in 'overdrive'. That way, lockup only occurs at a predetermined speed (your choice) and only in 4th gear.

You could install a vacuum switch in between as well which may give you even more "automatic" behavior with changing inclines, etc. I have heard of adjustable vacuum units but have never seen one. If I were to pursue a vacuum unit I would look for an adjustable one as I have not been pleased with the stock GM ones in the past on retrofit projects.
 
Thank you for the replies. I am going to look at getting one of those adjustable vac switches. I have a fixed one on now and the car acts horrible. Lets say I am cruising at 45mph. The trans is in 4th and locked. Push the gas enough to lower vacuum to trigger the release of the converter then the rpms go up and the vacuum goes back up locking the converter. It is a never ending cycle locked then unlocked. I was thinking about using a switch with a lower set point. Maybe that will help. Thanks again for the information.
 
Yep, that's exactly why I stopped using those ("fixed", as you say) vacuum switches back in the 80's.

I am interested however in the adjustable ones as well, thanks to the other member for posting the info.

Sal, if the adjustable one does the trick, great. If it doesn't, you can still add the speed sensor later on and retain the adjustable vacuum switch. In either case, please let us know how the adjustable switch works for you.
 
I'm using the fixed in my 385 sb & have no problems. It opens at about 4in. vac. Do you guys have the delay valve in the vac. line & if so do you have it install in the right direction?
I had mine messed up like that for awhile & wasn't too crazy about the way it worked, but when I got it hooked up right it works great.
 
Vacuum Delay Valve Info

Vacuum Delay Valve, GM #14020691
Delays vacuum switch engagement; helps ensure TCC lockup only under stable engine operation.
 
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