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Shifting hard into overdrive.


LUMINATOR

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My 90 Lumina seems to shift hard into overdrive. I changed the trans fluid and filter and that didn't seem to help. If anyone has any idea on what the possible problem could be I would really appreciate it!

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wonder if the 3-4 accumulator spring broke... wouldn't be the first time i've heard of it.

 

i think that one is in the sidepan though, so not as easy to check as 1-2 and 2-3.

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is there any consistent factor at work?

 

hard shifts only when cold or hot? or going downhill? or ???

 

being a 90 4T60, during the 3-4 shift, can almost guarantee that the TCC is locked during the shift. at least, that's the way wifey's 90GP was, you had to be giving it significant throttle for it to go through the 3-4 shift before the TCC locks. or be under the minimum coolant temp threshold for TCC.

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It doesn't really mater if its cold or hot seems to do it ether way. Usually going up hills it will shift hard. Does the TCC wear-out overtime and is it difficult to replace?

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Where would be the connector for the TCC be located on a 1990 Chevy Lumina with the 3.1. How many wires will the plug have going into it?

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the plug for the TCC is the same plug as everything else going into the transmission. right above the vacuum modulator. i THINK about 5 wires?

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it should have went into 4th gear.... the ECM only controls the TCC while the trans itself bases the shift points on the TV cable.

 

is it possible you didn't feel the 3-4 shift?

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It did, my bad haha! It shifted a lot better with it unplugged. No hard shift into 4th and shifts a lot smoother! So would this mean the TCC is bad in the transmission?

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Well when I plug the connector back in, it shifts hard into 4th gear and when I unplug it shifts smooth. Changing the TCC looks pretty difficult already. But the accumulator is that harder yet? Or does the transmission have to be pulled from the vehicle?

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Not to hijack the thread, but two questions:

 

What is a TCC?

 

Also, I'm looking at a 94 'vert and was told it is starting to not always go into OD? Would this be a similar issue that the OP is having?

 

Thanks,

 

Greg

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Perhaps a faulty (or beginning to become faulty) Modulator valve?

From what I recall about my 90 Lumina, the bad modulator valve affected all gears.

When it first began to go out, it scared the hell outta me...the shift was so hard, I thought I had been rear-ended!

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Yeah I've noticed a reduction in my MPG's. I looked to see how difficult it would be to remove the TCC and it looks to be quite the job. Removing the engine mount that covers the whole side pan :mad: Doesn't look like fun! I'm positive it's the TCC because when I plugged it back in, it would go right back to shifting hard into overdrive. And at a cursing speed of about 55 mph the car would have a some what of a grabbing/jumpy feeling when the cruise is set. Like the TCC is trying to disengage and engage.

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And at a cursing speed of about 55 mph

I absolutely agree. I had my driver's license through the entire 21 years of the National Mandated Speed Limit (NMSL) of 55 mph, and the cursing about it was from coast-to-coast, north-to-south, and everywhere in-between. :smile:

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i'm reminded of a quote from i THINK the Gumball Rally.... something along the lines of "traveling 55MPH across the country? that's dangerous."

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