Stall / Lock up
 

Historically, there was always a compromise between driveability and strip performance when choosing a stall.

Can the stall now lean more towards strip performance with a lockup convertor?

Discuss.

Yes, but unless you have a well designed expensive lock up converter they can only handle so much power.

Just ask the Buick guys who have run Buick factory lock up converters into the low 11s , that is into the low 11s for a while until it went south.

In some aspects, yes. A lockup converter is going to help at higher speed cruise that occurs below the converter stall. You enjoy better manners and lower temps here.

However the lockup converter strategy is always available to you and you may find the lower speed cruising in town still suffers from the same issues related to a loose converter.

My setup as an example uses a triple disc lockup converter. I can lock it up in 2nd through 4th gear at almost any rpm and throttle input. However the car drives better in the lower operating gears without being locked up. I use it instead in its performance application by locking it up at wide open throttle at about 4500 rpm in 3rd.

For cruise operation the converter locks only in 3rd and 4th at low throttle inputs and I have a fairly wide hysteresis set to keep the converter from cycling on and off. As a result a lot of in town driving does see lockup unless it’s a pretty steady state cruise.

For me this isn’t too terrible of a situation because even though the converter stalls around 3200 rpm, it is not incredibly loose and couples positively under that rpm when torque application is lower.

Mixed with a converter that is always very loose with a higher stall, the lockup is going to tend to be jerky as it engages.

I'm the wrong guy to ask but I just helped pick out a converter for my nephews 2000 TA. After researching what I could (not much useful information out there) I read many threads saying stall doesn't matter with a lock up. After pondering it for a while I ordered the tightest converter Hayes offers. My thinking was a higher stall will drive loose until the converter locks up in high gear. So he'd have three gears of slop and then a tight converter. Hopefully I made the right choice.

It all depends on what transmission you have too. The 200s aren't nearly as forgiving as a 4L80E, nor known for longevity when locking up under a lot of power.

There are some transmissions that are in race cars such as pro mods that use lockup convertors to gain some top speed at the end of the run. Companies such as Rossler, Hughes, etc. have lockup convertor transmissions for strictly race applications.

Link to YouTube video about the innards of a racing lockup convertor:

https://www.youtube.com/watch?v=0MJFceb9NHU&t=584s

The more slippage you have in the convertor, the bigger the shock when you lock the clutch. Race cars seem to have a lot more ring and pinion failures when they swap to a lockup convertor from a conventional convertor.

I plan to use a 4l80e, Less than 650 hp.

If I had it to do over again, I would not spend the extra money on a triple disc lockup. For a street car, I rarely use the WOT lockup capability. At that point I’ve just added cost and reciprocal weight.

The triple discs also have very little slip to them at the power levels being discussed here ~600 hp. So they have a somewhat harsh engagement.

Unless you are going racing a lot where the WOT lockup is beneficial, spec a good efficient converter that stalls where you need it to for your engine and still drives positively. It should have a conventional single disc lockup clutch that is used only for cruise operation.

Just my opinion based on my observations and actual usage.

My set-up is a 389 Tri-Power, 700R4, and a 2200 stall locking torque converter.
The converter will not lock-up until I am in 4th gear and the manifold vacuum is 13 pounds or greater. I do have a kill switch in the lock-up circuit for the long uphill pulls. Without the kill switch when the engine is loaded, I get the unlock because the vacuum drops below 13, then as soon as unlocks the vacuum goes back up. The kill switch stops the dance. With a 27 inch tire that gives me a 2000 RPM at 70 MPH. Street the car drives fine, and I never get the electronic converter lock-up on the strip.
Oh yea, normal driving I do not get to 4th gear until 40 MPH or better.

I have a multi disc lock up converter and I think it makes a world of difference . I lock it manually and don't use it below 45 mph.

INCREDIBLY important, and why I was so furious at TCI for selling a converter lock-up kit using a vacuum switch with zero hysteresis.

My '69 Falcon wagon had a 4R70W, and I tried a variety of converters in it. I had a controller that allowed me to fine tune the shift points, and the lock-up point.

At the track, the lock up would happen around the 1000' point, and it sounded like I had shifted gears. You can hear it at about the 1:03 point of this video
https://youtu.be/tHpXgrPAKmE?si=lKDv08RFywQ5jueR&t=50

With the OD and lock-up, the car was great on the highway. I think I had set to lock up around 50-55mph. I did 4,400 miles with it on the 2011 Power Tour, and the car averaged nearly 14mpg with 4.10 gears.

Sorry to hijack this thread. Is there a way of knowing exactly what torque convertor slip you have? My 600 HP stroker has a TCI saturday night special torque convertor in its manual valve bodied TH400. I have been told that I get a lot of slip as my shift light comes on at about 1000ft but have no more gears to shift into. My shift light is set at 5800 , 3.50 gears 27" tyre. Thanks in advance.

Do the math. Calculate what the MPH should be at the RPM when you cross the finish line, and compare that to the actual MPH.

If you are hitting 5800 @ 1000', with those gears and tire size, then I'd expect you to be close to 120mph at the finish line.