700R4 TCC Lock-up

I've got an 88 Caprice (305 4bbl) with the 700R4 transmission, and a 90 (307 4bbl) 200R4, both with E4ME carbs and EST.

At freeway speed in 4th locked up, with my 200R4, when I lightly press the accelerator, I can feel the RPM kickup when the TCC disengages, and if I press further, it will drop from 4th to 3rd. I find the 200R4 very responsive.

My 88 caprice with the 700R4 however, if you step on the gas, it tends to bog down and the TCC won't disengage. You have to almost mat it, and it drops down into 3rd, but if you release the medal it wants to immediatley go back to 4th and locked up, bogging it down again. If you drive in 3rd gear, as you step on the gas you can feel the TCC engaging and disengaging, while remaining in 3rd. Its very frustrating on freeway on-ramps, so you have to manually shift it into 3rd a lot.

Not sure if this is a problem with the 700R4 or if its per design. No error codes and the new Throttle Position sensor (TPS) didn't change anything.

Just curious has experienced bogging down because of the TCC not disengaging with the 700R4.

Thanks

I've got an 88 Caprice (305 4bbl) with the 700R4 transmission, and a 90 (307 4bbl) 200R4, both with E4ME carbs and EST.

At freeway speed in 4th locked up, with my 200R4, when I lightly press the accelerator, I can feel the RPM kickup when the TCC disengages, and if I press further, it will drop from 4th to 3rd. I find the 200R4 very responsive.

My 88 caprice with the 700R4 however, if you step on the gas, it tends to bog down and the TCC won't disengage. You have to almost mat it, and it drops down into 3rd, but if you release the medal it wants to immediatley go back to 4th and locked up, bogging it down again. If you drive in 3rd gear, as you step on the gas you can feel the TCC engaging and disengaging, while remaining in 3rd. Its very frustrating on freeway on-ramps, so you have to manually shift it into 3rd a lot.

Not sure if this is a problem with the 700R4 or if its per design. No error codes and the new Throttle Position sensor (TPS) didn't change anything.

Just curious has experienced bogging down because of the TCC not disengaging with the 700R4.

Thanks

You might be having a problem with the TCC solenoid. Does it seem to stay in lockup at lower speeds (such as when slowing for a light)?

Thanks for the reply.

The TCC disengages with the brake pedal and seems to work fine. On the freeway in the morning, I can feel the TCC engage after about 5 min driving when the coolant temp hits 170. And when warmed up, I can feel the TCC engage as soon as I hit 35 mph.

So everything seem to be working. The problem is that when I'm accelerating up a freeway on -ramp, as soon as I hit 35mph it engages, bogging it down, even though I'm stepping on it. And once cruising at fwy speed, it won't disengage unless I mat it, dropping it into 3rd.

I do occasionally get a throttle position sensor (TPS) Code 21, for high voltage. But I only get this error when the car is cold, after 5 min run time it shuts off. On a hot day I don't get it, and it doens't seem to have any relationship wtih the TCC issue.

Thanks

Thanks for the reply.

The TCC disengages with the brake pedal and seems to work fine. On the freeway in the morning, I can feel the TCC engage after about 5 min driving when the coolant temp hits 170. And when warmed up, I can feel the TCC engage as soon as I hit 35 mph.

So everything seem to be working. The problem is that when I'm accelerating up a freeway on -ramp, as soon as I hit 35mph it engages, bogging it down, even though I'm stepping on it. And once cruising at fwy speed, it won't disengage unless I mat it, dropping it into 3rd.

I do occasionally get a throttle position sensor (TPS) Code 21, for high voltage. But I only get this error when the car is cold, after 5 min run time it shuts off. On a hot day I don't get it, and it doens't seem to have any relationship wtih the TCC issue.

Thanks

In that case, it seems to be working fine. Mine does the same thing - the only time the TCC disengages is when I stomp on it or hit the brakes. With the power of my 350 though, it doesn't affect anything.

If the TCC "dumps" when the brake is depressed,the solenoid is not sticking. The rest is in the ECM programming, and it will operate the TCC solenoid based on RPM (distributor reference pulses), vehicle speed (based on VSS input), and throttle position (TPS). Is your throttle position sensor adjusted to provide 0.48VDC at the hot closed-throttle position?

Thanks for that. If yours acts the same, than its probably working the way it was designed.

I suspect maybe GM made the TCC lock-up more sensitive to changes in throttle in later years, or maybe on the 200R4, cause my 90 wagon (olds 307) is very responsive to changes in throttle position. Maybe the Olds engineers actually beat chevy at something!

Thanks for that. If yours acts the same, than its probably working the way it was designed.

I suspect maybe GM made the TCC lock-up more sensitive to changes in throttle in later years, or maybe on the 200R4, cause my 90 wagon (olds 307) is very responsive to changes in throttle position. Maybe the Olds engineers actually beat chevy at something!

I would look into Blue Bowtie's suggestion above about the TPS - especially if you've been having TPS related DTCs.

Edit - wow, too many TLAs!

My '84 did the same thing and it has the 700-R4. No matter what the condition, if the tranny hit 4th gear, the TCC would lockup, and only disengage if I hit the brake or it dropped out of 4th. I had so much trouble climbing hills that it'd stay locked up even down to 35mph, and the engine would bog and sometimes even ping unless i mashed it to get it to downshift. Most of the time I downshifted myself to get it to unlock, but now that my ECM is gone it doesnt lockup anymore. I'm soon to be running a switch to it so I can control when it gets locked up and when it isn't. Someone before said something about ruing the tranny by not having it lock up, and drive it like that.... how did all the other trannies do it before the TCC such as the Turbo 350 and the Turbo 400.

PS: My '88 GMC Vandura has the TH700-R4 and it works properly.... it goeth through all the gears, holds it in fourth for a little bit, then locks up. Then without mashing it, just normal acceleration, the TCC will disengage but the tranny will stay in 4th allowing the van to accelerate norally, then when you reach a decent speed, it locks up again. The second you hit the brake, it "dumps" just like it should.

Pete, the reason the TH350s and 400s could do it and not the 700 or 2004R is because the first two didn't have OD, as well as the fact that a lockup converter has more slip to it (when it's not locked) than a non-lockup design. The 3-4 clutch on the 700 can easily be damaged by the heat created by converter slippage, especially in OD when the speed exiting the transmission is above the speed entering it.

Hmm, makes sense. Thanks for clearing that up. Any explination for the difference in personalities of the two same trannies in different vehicles?