I've been through the entire torque converter lockup posts and I'm more confused now than ever. I've got a few q's that you fella's might be able to help me with. First the basics.

Bone stock '87 IROC L98 700R4. As far as I know the engine & transmission are original w/290,000 kilometers on them.

Q1/ Does this setup come from the factory with TCC lockup?

Q2/ If it does what would be the most likely problem with the TCC not locking up? I went through this with my '99 Jimmy 460LE (burning it up twice).

Q3/ If it didn't come equipped with TCC lockup from the factory I understand I'll need a kit (TCI, B&M etc.) but will I need to change the torque converter itself?

I wasn't totally sure on that one. It seems most of the info in the posts here are about TPI to carb swaps and loosing the TCC lockup function.

When I burned up the first transmission in the Jimmy I had no idea what the TCC lockup function was and that it wasn't workin in the Jimmy. No one else could tell me either. I found out after the fact and I got robbed in a rebuild. The second time it burned up was related to the first guy not cleaning out the tranny cooler and the junk that got left there destroyed it a second time. Now it's got an oversized external cooler.

So back to the IROC, anybody know which would be my best approach? I'd like to have the TCC lockup function for highway use. Currently I'm at about 2600 RPM at 120 Km/h (75 mph). With TCC lockup I should be around 2000 - 2100 RPM correct?

Thnx for your help. Standing by.....

 

Anybody know?

 

Q1/ Yes, comes from factory with a TC lockup

Q2/ ECM (computer) controls this function.

Computer recognizes engine speed, vehicle speed, current gear, and uses this info to lock the TC. There is a solenoid inside the tranny, gets 12v to it. ECM makes aground connection for this (under the right circumstances) and the solenoid switches, pushing tranny fluid forward into the converter. Converter is like 2 pieces put together, two ends with fan blades (like turbine engine fins). If there's minimal fluid, the blades on each side have less resistance, and thus can turn at different rates, the rear one turns with the wheels, the front one turns with the engine. The fluid "connects" the two, but allows slippage to occur, thus the engine can turn a different speed than the trans. Forcing the extra fluid into the TC causes more pressure, thus it's harder for the fins to turn at different rates since the space between is literally full of fluid, so the engine and trans turn at the same rate, with the fluid now acting as 'connection' between the two, rather than a 'puddle of resistance'. This is the poor, old moron explaination (me being the poor old moron).

The TC could lock and you just aren't feeling it - it only reduces RPM's by a few hundred when it locks, and is barely noticeable. Count shifts, and after it switches into 4th watch the tach and see if there's another very slight RPM drop - it will only do it under light acceleration.

Fluid level could make a huge difference, so check that first - remember it gets checked when car is hot and in park.

You can also jump two connectors on the ALDL diagnostic plug under the driver dash to lock the TC - so maybe make a simple switch to turn on and off while at highway speeds and see if that makes a difference. There is a diagram in the tech articles about the ALDL and shows which two pins to jump to lock the TC.

Hope any of that helps, and good luck!

 

Thanks Mate. I couldn't remember what the lockup was like on a Camaro. It's pretty pronounced on the Jimmy dropping the RPM's over 500. I've watched the tach every time on the highway and I can't see any drop or feel any lockup. I'm suspecting my ECM might be toast with the other problems I'm having with it. The wiring might be suspect as well.

I'll try that jumper thingy when the weather straightens out. It snowed here today!

 

Ok, tried it. Nothing. Any other ideas?