Mike6568
11-17-2014, 03:13 PM
Had a blast this summer driving #422, this was the first "finished" season with the car. I still have one bug to work out and wanted to get a second opinion here on the forum. The set up is a SBC crate motor with a new 700R4 transmission. The TV cable is adjusted properly and everything is great on that end. My problem is with the lock up converter.
When the car shifts into overdrive, the torque converter properly locks up and rpm drops. At highway speeds (55+) If I touch the brake it will momentarily unlock and then lock back up when I release the brake. Everything up to this point is good.
My problem is getting the converter to automatically unlock when I slow down AND ALSO when I kick it in the butt to accelerate while in 4th gear. If the car is cruising along at 65mph and I simply let off the gas and slow down to 25mph for example, the converter will not unlock on its own and it will be stuck in 4th gear and bog down, I HAVE to touch the brake and that immediately corrects the problem. Also if I'm cruising along at 65 and accelerate the converter will not unlock on its own unless I touch the brake pedal to activate the switch. Functionally it works perfectly once it goes into 4th gear, the problem is getting it to unlock when I need it to (speeding up or slowing down).
I explained this to a local transmission shop who drove it and installed 1. A vacuum switch under the dash (and connected to manifold) and 2. wired the lock up switch to the brake pedal. This was the first step, everything worked perfectly until you tried to accelerate and the car would for lack of a better word, pulsate (quickly the engine would rev up and down). He said we needed to add a check valve that would work with the vacuum switch. He installed a small check valve, which fixed the pulsating but still leaves me with a converter that will not automatically unlock by coming out of 4th gear or accelerating while in fourth gear.
It isn't too troublesome as long as you know the car and remember to touch the brake while slowing down. Any ideas? Seems like this is just a mechanical/electrical thing and someone much smarter than I will know the answer. The transmission seems to work properly when you tell it what to do, it just won't do it on its own.
I'd be happy to answer any questions or further clarify if that would help. Thanks in advance for your help!
When the car shifts into overdrive, the torque converter properly locks up and rpm drops. At highway speeds (55+) If I touch the brake it will momentarily unlock and then lock back up when I release the brake. Everything up to this point is good.
My problem is getting the converter to automatically unlock when I slow down AND ALSO when I kick it in the butt to accelerate while in 4th gear. If the car is cruising along at 65mph and I simply let off the gas and slow down to 25mph for example, the converter will not unlock on its own and it will be stuck in 4th gear and bog down, I HAVE to touch the brake and that immediately corrects the problem. Also if I'm cruising along at 65 and accelerate the converter will not unlock on its own unless I touch the brake pedal to activate the switch. Functionally it works perfectly once it goes into 4th gear, the problem is getting it to unlock when I need it to (speeding up or slowing down).
I explained this to a local transmission shop who drove it and installed 1. A vacuum switch under the dash (and connected to manifold) and 2. wired the lock up switch to the brake pedal. This was the first step, everything worked perfectly until you tried to accelerate and the car would for lack of a better word, pulsate (quickly the engine would rev up and down). He said we needed to add a check valve that would work with the vacuum switch. He installed a small check valve, which fixed the pulsating but still leaves me with a converter that will not automatically unlock by coming out of 4th gear or accelerating while in fourth gear.
It isn't too troublesome as long as you know the car and remember to touch the brake while slowing down. Any ideas? Seems like this is just a mechanical/electrical thing and someone much smarter than I will know the answer. The transmission seems to work properly when you tell it what to do, it just won't do it on its own.
I'd be happy to answer any questions or further clarify if that would help. Thanks in advance for your help!