97 Camaro no 3rd gear TC Lock in D4

I've got a '97 Camaro PCM in my truck that is handling the engine and transmission control. I've been banging my head over a little issue that I can't tell if it is intentional or a fault. When the shifter is in the D4 position, I can get the truck to engage the torque converter lock-up in 2nd (for testing purposes) and 4th gear. 3rd gear lockup never occurs despite the vehicle speed set points being OK. If I drop the shifter into D3, the transmission then begins to lock-up and 2nd and 3rd as you would expect.

Checking in the datalogger shows that the PCM is indeed not commanding a 3rd gear TCC lock when the shifter is in D4. All other inputs (brake, shift position, transmission temp, current gear, etc) look OK. I talked to the tech support at Jet (as I am using the Dynamic Spectrum Tuner) and they confirmed they couldn't see anything wrong in my tune, but otherwise provided no help.

Anyone work with one of these PCMs before and know if this is normal behavior or not? In my case it kind of sucks as I'd like to treat the performance shift option as a tow/haul feature to change shift points and disable 4th gear, but as of right now I'll have to drop the shifter to D3 to keep it out of overdrive while retaining a torque converter lock. This doesn't stop the truck from working, but I'm at the stage where I'm starting to nit-pick functions. ;)

Some of the early LT1 autos had no provision for a manual 1st gear selection, it was either 2nd, 3rd or OD for manual gear selection. The trucks (at least the 93-99 GMT 400 trucks have always been 1, 2 ,3,OD selectable088-92 were 700r4). No idea what truck you are using though.

Not sure, just a theory.

Good luck with Jet tech support, esp. with their DST.

peace
Hog

It's been a while, but IIRC the Caprice was like this. The 9C1 cars (police option) were dealer modified if they received the wrong shifter.

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Originally Posted by 1project2many

It's been a while, but IIRC the Caprice was like this. The 9C1 cars (police option) were dealer modified if they received the wrong shifter.

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Pulled the console on my buddies 97 LT1 Camaro SS and fixed the issue here as well. A grinder with a carbide cutter made it easy.

I don't think you guys are following the problem. I've got detents for 1st, 2nd, 3rd and 4th. The problem is that while the shifter is in 4th gear, the torque converter doesn't lock when the transmission is in third. It's only if I drop to 3rd on the shifter that the PCM will lock the torque converter in that gear. To some degree I'd pass this off as normal, but then that doesn't explain why the torque converter will lock 2nd in either selection.

Bringing this one back from the dead for a second look. Thanks for your time!

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Originally Posted by Maxzillian

Bringing this one back from the dead for a second look. Thanks for your time!

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Are the 3-4 shift tables set at a lower speed than 3rd lock??

The truck has rather tall gearing at 2.73:1 so I don't make the shift into fourth until about 55-60 mph. The shift to third is around 35 with the TCC Lock set to happen around 40-45. TCC lock for fourth is only about 5 mph after the shift for that gear. Ultimately I'm going to re-gear the truck which will quench any need for 3rd gear TCC lock, but I had set the performance shift button to work more as a tow-haul mode; forcing the truck to stay out of fourth gear while it's active. It'd be nice to get 3rd to lock without needing to drop the shifter down a gear.

At one point I had sent my tune to Jet for their review and they only came back with suggestions to check on the truck itself; all of those being dead ends.