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That would depend on the power level and trap speed. With a estimated trap speed of 117 to 119 mph , I would like to be at the top of 3rd or 4th going thru the traps.

 

Anyone here run 2.73 with a 26" tire and a 3600 converter? at what mph do you shift into 4th?

 

Just ran this scenario thru a RPM calculator system. With a 26.5 tall tire, 2.56 rear, 1.53 3rd gear ratio @ 119 mph = 5910 rpm, with 2.73 gear the RPM jumps to 6302 rpm with all the data being the same. My plan is to tweak a stock c6 auto trans C6 corvette to run 11.9's. I think I am close on the estimated trap speed that comes along with a 11.9 pass with at least a 60 ft in the high 1.8's. The calculation does not account for a 300 to 500 RPM torque converter slippage @ wot thru the traps. And yes, I would like to go thru the traps in 3rd gear. What do you think...

 

What is the typical cost for someone to install a converter in a C6?

 

I will guess the converter is about $900 to $1000, labor my guess is about 6 hrs at $80 per hour. So $1500 to $2000 should be a good ball park.

 

I have never taken my car to a 1/4 mile with my short tires. juts wondering as I have never used the 3-4 shift before.

 

it cost me $1000.

 

With stock tires and a stock C6 corvette automatic transmission car, you have no choice which gear your car will be in when you cross the finish line. It will be in 3rd gear as long as you do not let off on the gas or in other words wide open throttle the entire 1/4 mile and you will cross the line in 3rd gear. You will not have anywhere near enough speed to up shift to 4th.

 

I have 2.73 gears and a 3600 converter unlocked and a 26" tire. So it will go into 4th. Just wondering at what speed it would go into 4th. but I guess I will find out this weekend.

 

What miler per hour are you expecting and what RPM are you shifting at? if you are winding the engine to 6500 and your expecting 117 to 119 MPH, you will need to up shift to 4th. You say unlocked converter, I know what you saying but at WOT the converter would not lock up any way, but don't they tighten up at high rpm and only slip a few hundred RPM? What size tire are you running, 26 inches is short. A 285 35 19 factory size is 26.7 inches tall

 

Could you explain “unlocked” vs “locked”, the tuning involved, and how that translates to rear wheel HP and/or driveability.

 

I run a Yank converter, it is not recommended to be locked under WOT. So the car is tuned not to lock the converter under WOT. Some people will buy a Triple disk, and lock it under WOT. Normally yields a higher MPH in the 1/4. but from what I have seen. ET doesn't really change. I also have heard from people that a triple disc will lock up harsher under normal use.

 

Great info! What does it mean when the converter is locked?

 

Means the converter is not slipping.

 

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Hope you dont mind me giving my explanation, all late model automatic transmission cars have converters that lock and unlock depending on throttle position. A performance aftermarket converter can be built with out the lock up feature. Rear wheel horsepower is determined at wide open throttle or in the non lock up mode. Driveability doesnt really change, but gas mileage is reduced if you have a non lockup converter. A typical lock up will lower cruising rpm by a few hundred RPM.

 

Awesome! So it sounds like most folks would go with a single disc if the converter isn’t locking at WOT anyway?

 

Here's some quick facts. LS3 with A6 trans. Personal experience.
You can run 1.90 short times with decent grip street tires and a stock 1800 converter. A CAI and a dyno tune by someone who races is all you need with stock OEM runflats. 12.14 @ 119.16 in 1464' DA.
Add Z06 full exhaust, a CoW tune, MT DR's, and go 11.98 @ 119.59 in 1216' DA with a 1.91 60'.
Back to previous dyno tune and Hoosier DR's,11.89 @ 122.12 in 1363' DA with a 1.85 60'.
1st pass with a 3200 stall Yank - 11.60 @ 120.20 in 273' DA with a 1.71 60'.
Can't find the slip right now, but best with the 3200 was 11.49 @ 121.65.
Swapped to a 3600 Yank, ported TB, ported IM, and ran 10.82 @ 125.82 in about -700' DA
Had a 1.74 60' and 11.44 ET during a quick pass while on vacation in FL on Invos and a no prep track. Lots of spinning.
Swapped to a 4000 Yank, LG Street headers, and ran 10.80 @ 126.84 in -500 DA with a 1.54 60' on a poor prepped track and 7 plugs that had the iridium tips missing. (080 gap vs .040), I've had several 1.48 to 1.50 short times in 1200' DA with good prep.
All the tuning tweaks after swapping back from the CoW tune to the dyno tune were done by me, referencing timeslips, weather data, and computer scans.

2.56 gear with 25.7" DR's at 6500 rpm = 126.78 mph in 3rd gear
2.73 gear with 25.7" DR's at 6500 rpm = 118.89 mph in 3rd gear
3.42 gear with 25.7" DR's at 6500 rpm = 126.45 mph in 4th gear
Just because the redline is 6500 rpm, doesn't mean you have to shift there. A stock unmolested long block can go to 6900. My shift points are between 6690 and 6725)

 

Now that’s some great info! Is the trap speed correct on the 2.73 pass? About 7.5mph less? How did the ETs compare?

 

That last group of info was just to show what the speed is at 6500 rpm with a 25.7" tire, such as a Hoosier 275/40 x 17 DR. It was also sorta answering dieselracer who asked at what speed the trans would shift into 4th, although it depends on how well he hooks off the line, how high rpm he will stay in each gear, and if he has enough power to reach that speed before the stripe.

 

Funny how everyone has different opinions on converter feel, I for one have a Yank ss3600, and complain each time I drive the car as it feels very loose around town. Called Yank and asked about re-stalling to a 3200, and Dave stated he thought that would certainly solve my complaint.

This is an LS2 car with TFS Heads, Fast 102, 223/231 cam, and all other supporting bolt's but yet running 2:56 stock base gearing. The car made 460/420 on two seperate dyno's and the car has been 6.90's @ 103 and a 1.52 60ft. This was on a 315/35/17 MT ET Street. The car is a convertible, so it does not have a cage, my days of racing this car is over.

I'm fixing to swap the cam in the car due to being an old XER lobe design and its time for something new after 10 years. After the cam swap is complete I plan to either pull the converter and have Dave cut it open for 3200 or maybe just order a new Circle D just to try one out. Thought about swapping to 2:73's as well.

IMHO unless you are steady racing anything >3200 stall will be too much after a short period of time.