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I am having a slight slip in my transmission. It only really happens when it's cold and in top gear. I have never flushed the trans fluid and the car has 184k miles. Would that be a fluid problem or would that be something more serious?

Also, I have an auto LT. I know that it's supposed to have 4 gears but it has 4 gear changes and acts like it has 5. Is the trans a 4-speed overdrive?

Thanks.
 

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The lockup torque converter feels like a gear shift. I don’t recommend a flush, I’ve personally seen it cause issues in some vehicles. A pan drop, filter and fluid change is all that’s needed. Be aware that a slipping tranny can go at any time, and a fluid change on a tranny with unknown service history can be its kiss of death. If you decide to change the fluid, stick with a licensed DexVI ATF.
 

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The lockup torque converter feels like a gear shift. I don’t recommend a flush, I’ve personally seen it cause issues in some vehicles. A pan drop, filter and fluid change is all that’s needed. Be aware that a slipping tranny can go at any time, and a fluid change on a tranny with unknown service history can be its kiss of death. If you decide to change the fluid, stick with a licensed DexVI ATF.
Really? Because in 1st position on the trans is limited to 1st and 2nd. Low is limited to 3rd and 4th. But when I put it in Drive in a pull it drops the rpm massively and it feels like an overdrive.
I have heard that a fluid flush can be the last push to kill the trans.

On another note, I am wanting to add some power someday but with the trans, I was trying to find a six-speed conversion. Would I be better off buying a manual car and build that one or could I put a six-speed in the one that I have?
 

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I would say your best option with an automatic would be to build the 4T45E - I don't think you'll have any luck fitting any of the 6AT options available, and especially not being able to get them and the car/engine to communicate. The 4T45E holds quite a bit more power than any of the 6-speed options anyway.

There is the 6-speed manual conversion, but that's pretty pricey.
 

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Really? Because in 1st position on the trans is limited to 1st and 2nd. Low is limited to 3rd and 4th. But when I put it in Drive in a pull it drops the rpm massively and it feels like an overdrive.
I have heard that a fluid flush can be the last push to kill the trans.

On another note, I am wanting to add some power someday but with the trans, I was trying to find a six-speed conversion. Would I be better off buying a manual car and build that one or could I put a six-speed in the one that I have?
Yes, the 4T45E is a 4 speed automatic, with an electronically controlled torque converter clutch. The 4th speed isn’t a gear like gears 1,2, and 3, but it’s an overdrive band that engages.
The shift sequence of a 4T45E (and most over GM electronically controlled 4 speed autos) is as follows:
1st gear - 2nd gear
2nd gear - 3rd gear
3rd gear - torque converter clutch lockup
3rd TCC locked - 4th gear (aka overdrive).
These will all feel like shifts.

TCC won’t lock if the transmission isn’t at the appropriate operating temp.

When the TCC is locked in 3rd gear, it will momentarily unlock as the tranny shifts to 4th gear, and then TCC will lock simultaneously as 4th gear OD is engaged.
 

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I am having a slight slip in my transmission. It only really happens when it's cold and in top gear. I have never flushed the trans fluid and the car has 184k miles. Would that be a fluid problem or would that be something more serious?

Also, I have an auto LT. I know that it's supposed to have 4 gears but it has 4 gear changes and acts like it has 5. Is the trans a 4-speed overdrive?

Thanks.
Sounds like I would start with pulling any service records and seeing what previous repairs and service were performed.
I would be willing to bet that you need a fluid and filter changes for the transmission.
 

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Have you done any engine modifications? An aftermarket air intake without reprograming will cause what you describe. Engine in need of a tune up will also make transmissions act strange. However since it's doing it when cold the above statement is very likely.

TCC won’t lock if the transmission isn’t at the appropriate operating temp.

When the TCC is locked in 3rd gear, it will momentarily unlock as the tranny shifts to 4th gear, and then TCC will lock simultaneously as 4th gear OD is engaged.

Watch your temp gauge and see if car is taking too long to warm up indicating a possible bad thermostat.
 
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