cjsdad

I am putting a TH200-4r behind my SBO 427 in my 67 Cutlass and wanting some input about whether to lock-up or not. The difference is only a couple hundred RPM at freeway speeds and I'm not building this thing for mileage but for fun. I will probably end up with a mid 3's diff gear and have been advised that a 26~2800 RPM stall converter will work best. I already have the trans so will I need to make any internal mods one way or the other? Is the hassle of getting the lock-up working right worth it? What say you all?

Tuffnut

I put a lock up on my 200-4R last year, had the internals beefed up. I use the electronic lock up from TCI. Works great... gears are 3:42 with 2600 stall convertor. Makes a big difference when cruising. Only running a 75 350 juiced a bit in my 75 cutlass.

Jeff

jensenracing77

If it is there then I figure why not? If you are never ever going to be on the highway for a good stretch then maybe there would not be a reason. I just wonder why you chose the 200 4R if you are not building it for mileage?

joe_padavano

Well, the lower first gear improves off-the-line acceleration, and the OD reduces engine wear and tear at speed. Neither of those is really mileage related. Having said that, I agree, why not hook it up? Not using it won't hurt anything, however.

cjsdad

That's the easy part, I want it to have low enough gears to accelerate quickly but I don't want excessive RPMs while cruising on the hwy. I don't care if it gets 12 mpg or 15 while doing that. OD gives both.

cdrod

Using a lock-up convertor eliminates the convertor slip and will lower the operating temps on the highway. Low temps equals longer transmission life!

oddball

I like the lockup, but I think it really depends on how you want to do the control. And I have a great deal on a high stall lockup converter right now!!

My control system:
constant power feeds to a cruise control brake switch (closed when brakes are all the way off)
"no brake" power feeds to a vacuum switch connected to ported vacuum that closes @ 8" vacuum (disconnects when foot all the way off the gas and when accelerating)
"no brake moderate power" power feeds to a 10 second delay timer from the 3rdbrakeflasher.com folks that uses the 4th gear switch in the trans as a trigger
4th gear switch in the trans closes when in 4th, giving a ground path to the trigger arm of the timer.

So, when in 4th, not on the brake and at moderate pedal, it waits 10 seconds then engages the clutch.

It hunts due to vacuum drops when driving slower than 50, but overall I like it.

ach1992880

Had my 2004r set up exactly this way when i had it in prior to going LS swap. Really worked well and was predictable. Locks only in 4th gear steady cruise and the delay box keeps it from hunting all the time. No switches to flip and unlocks upon downshifting or with a tap pf the brakes. Sold my wiring setup to someone here after going a different route.

JohnTN

I have a setup like Oddball on my Olds streetrod. But I also put an rpm switch in the circuit so circuit is not completed until rpm reach 1800 in 4th gear. Then lockup engages and rpms drop to about 1500 rpm (at 50 mph). If rpm drop below 1100 (about 35 mph) the lockup disengages, even if vacuum is still high. Also, put an off/on switch under the dash so lockup could be disabled entirely if desired.

The rpm switch is available with a timed delay feature also for $50-60 if I remember correctly.

ELY442

Ever think about using Gear Vendor?

JohnnyBs68S

I use the lockup in my CK-built 200-4R. Mine has an internal switch that disables the lock-up until you are in 4th gear. A simple external relay that provides IGN power to the transmission is triggered (energized) by the brake lights. When I tap the brakes, the relay opens the circuit and disengages the lockup. It won't lock-up until it gets into 4th gear. By the time 3rd gear winds out at WOT, you are way over any posted speed limit. If you want to temporarily disable it for towing, drag racing or such, add another switch in the circuit. Simple logic that works great, no need for vacuum switches and delay timers that don't do much except add complexity and failure modes.