700R4 Lockup Control
Thread Starter
Heel & Toe
Joined: Oct 2005
Posts: 22
Likes: 0
700R4 Lockup Control
I am ready to embark on putting a 700R4 in my 79 vette. I have read in the forum many different ways to contol the lockup. What is the best method? I am meeting with my tranny guy tommorrow -- he wired it for 1 wire operation. Bear with me cuz I'm not a tranny pro. He will have his directions for me but thought I would get some additional input (too much is never enough).
Thanx
Thanx
Safety Car
Joined: Oct 2004
Posts: 3,725
Likes: 5
From: Minnesota
The first thing you need is a brake switch cutout so the lockup is disabled anytime you use the brakes. The second thing I have is a vacuum switch that will disable the lockup under load. This gives you something of an intermediate gear between third and locked up fourth. The guy who built my tranny also got this switch for me so I'd have to look and see if I can find a part #. One thing I needed was a little black and white valve/restrictor that goes on the vacuum line going to this switch. It's a junkyard item. Without it the switch would go back and forth too much. Hope this helps. 
Safety Car
Joined: Aug 2001
Posts: 3,681
Likes: 200
From: Waterford Mi
My setup from BTO has the pressure switch and the bake switch. I added a switch to keep it from locking up unless I am driving on the highway. I can turn on the switch to let it lock up when it is in the OD gear. If the switch is off I can use the OD gear witrhout it locking. The biggest problem with the setup occurs when I am in OD with it locked and I have to slow down below 35mph. Once I try to take off again it hasn't downshifted and the motor lugs. If I turn off the lockup convertor it doesn't lug.
Pro
Joined: May 2002
Posts: 518
Likes: 17
This is what I've done as well (lock in fourth only)...
For the street I've found that the stock Vette 2000 stall TC a bit sloppy around town, so I prefer the stock truck converter that stalls at roughly 1500 RPM, though I have a 406ci in my 71 Coupe and can't leave at anything over 1500 RPM without killing the tires anyway (3.06 first gear) . I knew someone with a TPI 350 in his Shark and he also prefered the lower stall TC, though those with stock carb'd 350's might not?
A couple of things...
a) Unless the trans is modified accordingly you'll need to lock up the TCC in fourth at minimum, and failure to do so will overheat the trans.
b) You must properly adjust the TV Cable or again you can damage the trans. GM OD has a properly designed adaptor for the Q-Jet I believe?
c) Watch your Pinion Angle to avoid vibration at speed.
Otherwise, you'll love it! I have 3.08's in mine (3.08 - 3.36 is ideal for the street depending on tire height), and I cruise very comfortably at around 2K RPM at 70 MPH.
Doug
For the street I've found that the stock Vette 2000 stall TC a bit sloppy around town, so I prefer the stock truck converter that stalls at roughly 1500 RPM, though I have a 406ci in my 71 Coupe and can't leave at anything over 1500 RPM without killing the tires anyway (3.06 first gear) . I knew someone with a TPI 350 in his Shark and he also prefered the lower stall TC, though those with stock carb'd 350's might not?
A couple of things...
a) Unless the trans is modified accordingly you'll need to lock up the TCC in fourth at minimum, and failure to do so will overheat the trans.
b) You must properly adjust the TV Cable or again you can damage the trans. GM OD has a properly designed adaptor for the Q-Jet I believe?
c) Watch your Pinion Angle to avoid vibration at speed.
Otherwise, you'll love it! I have 3.08's in mine (3.08 - 3.36 is ideal for the street depending on tire height), and I cruise very comfortably at around 2K RPM at 70 MPH.
Doug
Originally Posted by Pete K
My favorite way to do it is to wire the lock up for 4th gear only. A pressure switch screws into the 4th gear port and a single 12volt ignition feed goes to the trans. Simple, cheap and nice drivability.
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
My Formula has an Accel computer which was very erratic on its lock up control, would be engaged all the time one drive and lock as soon as it shifted into 2nd bogging the eng and then next time out it would not lock up at all. I bypassed the computer and use a toggle switch now. Thinking of getting an aftermarket shifter with a button built in the handle to control it.
As far as stall speed, with a 700r4, 2600 stall, 3.73 and 350 my Formula does not need a line lock to sit and spin the tires from a dead stop, just push the loud pedal and start the smoke show.
As far as stall speed, with a 700r4, 2600 stall, 3.73 and 350 my Formula does not need a line lock to sit and spin the tires from a dead stop, just push the loud pedal and start the smoke show.
Pro
Joined: Jun 2005
Posts: 581
Likes: 60
From: USA
I bought the Painless Wiring kit. it comes with the 4th gear pressure switch, a brake-pedal switch, and a vacuum switch. I wired it all up, and it worked as advertised, but I got tired of the TCC unlocking every time I tapped the brake pedal on the freeway, and the following lag in re-lockup again. so I bypassed the brake pedal switch. i then noticed that the vacuum switch was also annoying the way it caused unlocking not always when I wanted to go into slush-box mode, so I bypassed that. so then I was left with just the 4th gear pressure switch, and it works great with just that!
as soon as the trans downshifts as you're coming to a stop, it unlocks. and as soon as you hit 4th gear, it locks up, providing that solid coupling between engine and road.
as soon as the trans downshifts as you're coming to a stop, it unlocks. and as soon as you hit 4th gear, it locks up, providing that solid coupling between engine and road.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Thread Starter
Heel & Toe
Joined: Oct 2005
Posts: 22
Likes: 0
Got the tranny...now what about the shifter?
OK, now I have the trans. The tranny shop hooked me up w/ 1 wire operation so I will just use switch operation (fine for me). They also set me up on the mounting so I don't need to mod the cross member. Now....what is the best shifter to use??? Any suggestions would be great!!!
