Topic: Lockup Converter
in Forum: C3 Driveline Components
Already a Member?
Click Here to Login
Not yet a Member?
Click Here to Register for Free!
I had my automatic trany rebuilt and have a 2000 or so stall converter and have 3:07 rear gears. I noticed if I have my lockup switch connected the lockup comes in around 35mph and the engine seems to want to lag or labor. When I disconnect the electrical switch everything is fine and smooth. Should I have it changed to have a different setpoint for the lockup at the trany side? come in at higher speed? or is there something else I should have the transmission shop look at?


1980 L82 (5069 made), Dark Green Metalic (844 made)
Gymkhana Suspension, AM/FM/CB, Sporting a ZZ383.........
SPONSOR AD:: (Our Sponsors help support C3VR)

Moderator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20219
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
The 350 lockup is controlled by a pressure switch inside the trans, on the valve body. If you look at the switch, there will be a number on it. Get a switch with a higher number.
The number on the switch equates to the speed(mph) the the switch closes, and therefore creates a ground for the lu solenoid. The switches are available in many different calibrations. I prefer to use the 45-55 range switches. This will put the lock up applying at 45mph, or whatever number switch you have.
The switch is pressurized by governor oil, and governor pressure is always within 2-5psi of road speed. If you are traveling at 50mph, there will be around 48-52psi of governor pressure.
Your trans will have a #35(or close) switch in it now if it is going into lu at 35mph. Change the switch, and your lu will come in at a higher road speed.
The switch is on the valve body, and is very easy to change. Drain & drop the pan, unscrew the old, screw in the new.
Adams' Apple 38955.8066898148
The number on the switch equates to the speed(mph) the the switch closes, and therefore creates a ground for the lu solenoid. The switches are available in many different calibrations. I prefer to use the 45-55 range switches. This will put the lock up applying at 45mph, or whatever number switch you have.
The switch is pressurized by governor oil, and governor pressure is always within 2-5psi of road speed. If you are traveling at 50mph, there will be around 48-52psi of governor pressure.
Your trans will have a #35(or close) switch in it now if it is going into lu at 35mph. Change the switch, and your lu will come in at a higher road speed.

The switch is on the valve body, and is very easy to change. Drain & drop the pan, unscrew the old, screw in the new.

Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Thanks Adam, I will bring her in to the shop that did the rebuild and have them change it. Is the goal to have the speed selected to be above your stall speed so that when it locks up it will be less noticeable?


1980 L82 (5069 made), Dark Green Metalic (844 made)
Gymkhana Suspension, AM/FM/CB, Sporting a ZZ383.........

Moderator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20219
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
The "stall speed" of the convertor is irrelevant when driving at speed. Once the car is moving, and in high gear, the convertor is practically passed it's rated stall.
Our goal is to raise the lu speed, so it doesn't lug the engine at lower, "in town" speeds. When the car was new, GM was trying to get the best possible fuel mileage, and getting the convertor into lu mode was important, as it lowered the operating RPMs, thus using less fuel. They wanted lu to occur as soon as, or shortly after, the trans shifted into high gear. That's not important to us!!!
You don't really want to have lu until you are cruizin, and in high gear. That's when the marginal fuel mileage increase does the most good.
Lu on a 350 will help fuel mileage to some extent, mostly on a longer drive. Around town, it is usless.
The real advantange is the decrease in heat created by the torque convertor as it constantly tries to keep the car moving. Once the convertor is in lu mode, the heat is dramatically reduced, and the life of the trans is increased.
One final note on "stall' convertors....they create a LOT more heat than stock convertors. An auxillary trans cooler is a must. The cooler in the radiator is not designed for, nor is it capable of cooling a trans equipped with a high stall convertor.

Our goal is to raise the lu speed, so it doesn't lug the engine at lower, "in town" speeds. When the car was new, GM was trying to get the best possible fuel mileage, and getting the convertor into lu mode was important, as it lowered the operating RPMs, thus using less fuel. They wanted lu to occur as soon as, or shortly after, the trans shifted into high gear. That's not important to us!!!

You don't really want to have lu until you are cruizin, and in high gear. That's when the marginal fuel mileage increase does the most good.
Lu on a 350 will help fuel mileage to some extent, mostly on a longer drive. Around town, it is usless.

One final note on "stall' convertors....they create a LOT more heat than stock convertors. An auxillary trans cooler is a must. The cooler in the radiator is not designed for, nor is it capable of cooling a trans equipped with a high stall convertor.

Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Thanks Adam, got it.


1980 L82 (5069 made), Dark Green Metalic (844 made)
Gymkhana Suspension, AM/FM/CB, Sporting a ZZ383.........
in Forum: C3 Driveline Components
SPONSOR AD: (Our Sponsors help support C3VR)