john 67

I have installed a 6l80 in my 67 chevelle , previously a 4l80. final ratio is more or less the same . 80 mph =3000 rpm and I am in 6th gear by 40 mph . rear is a 3.73 and tire are 26" I was thinking of a 3.08 or 2.90 .street car mostly . pro touring and an occasional run at the track.What are your thoughts ? Thanks . JOHN

ctd450

iTrader: (1)

Eighty is fast, 3k sounds about right for that speed. Why would you want lower?

Also, did you have your TCM tuned for TUTD? You're local to me and I'm looking for a tuner that can do it, preferably on a non-street legal vehicle.

john 67

better gas mileage , just drove 3700 miles , most of it at 80.

PowerAdder

You can't expect to get your best millage at 80mph. Its still going to require a good amount of power to keep the mass of a car at that speed. Your final gear is .667 4l80 final gear is .75 quite a difference. 26 inch tire 3.73s .667 is 2500 rpm... I think your fine...

Blackpanther99

iTrader: (8)

You are more than good. I have a 6l80e on my 2010 crew cab.

PowerAdder

Acctually i would look into if your getting into sixth gear the math shows a OD of .852 will set you at 3200 at 80 mph. You may not be shifting into sixth. Thats the rpm and speed for your 5th gear.

hicksport

iTrader: (1)

I feel your pain. The newer vehicles that the powertrains that we are using have huge tires compared to what looks right and fits the older cars. Ive done several swaps one has 3.42 and the other is 3.08. im not useing the auto 6 speed but I would think as long as you can keep your first gear final ratio around 9.5 to 1 it will drive good and get better mileage. What is the first gear ratio in the 6speed auto?

65impalass

How is your 1st gear with your 3.73s? Is it to low?I have 4.11s and I would be afraid it would shift out way to soon.

PowerAdder

1 2 3 4 5 6 r
4.027 2.364 1.532 1.152 0.852 0.667 3.064

john 67

To compare the 4l80 to the 6l80 it just feels like i have two extra gears on the front end and not much difference at final od .I am pretty sure it is getting into 6th but will confirm this weekend.

1989GTA

I have the exact same tire diameter as you have at 26". I chose a 3.23 rear gear ratio with my L92/6L80 setup. I am looking to be just under 2000 rpm at 70mph. With the 4.05 first gear you do not need a numerically tall rear gear to get you off the line. I don't have my car on the highway yet but should be shortly.

PowerAdder

Its just like 500 rpm differance, if you have that tire height and gears in the rear something is up, you should be around 2500 rpm at 80.

rockytopper

First off it was great meeting you on the Power Tour we had a blast. Your car looks great. Your tribute pin stripe to the max water level of Sandy was killer. Glad to see you made it the entire long haul and back home safely.



6L80E GEAR RATIOS
1st: 4.03:1 2nd: 2.36:1 3rd: 1.53:1 4th: 1.15:1 5th: 0.85:1 6th: 0.67:1

4L60E GEAR RATIOS
1st: 3.06, 2nd: 1.63, 3rd: 1.00, 4th: .70

According to this gear rpm calculator http://www.powerblocktv.com/resources/
You should be running about 2585 rpm @ 80 mph in 6th gear.

As a comparison I have a 3.08 ratio with 26 inch tire behind a 4l60E I run about 2230 rpm @ 80 mph. In my case my car likes to run 80 to 90 mph much better than 70.

You may not be getting 6th as stated above if the numbers you stated are correct. I would not go as tall as 3.08 in your case.

Rocky

hicksport

iTrader: (1)

With a first gear that low you could go with 3.08 or even 2.73 rear gear and still get out of the hole pretty good. Just depends on what rpm your setup likes to cruise at. my LY6 with the cam thats in it doesnt like to be below 1500 which works out great for 80mph cruising speed. Like was posted above make sure its goin into 6th and that the converter is locking up that alone is worth a few hundred rpm on a stock converter.

bczee

iTrader: (12)

How about a close up pic of the line !?

Question, what ratio did the car that supplied the Trans come from ?.. would think that using that ration would a a best all round gear to use.

BC

john 67

Best part of the tour is meeting people and the randomness of events throughout the week.Had fun hanging with you Rocky.and thanks for the pic. do you have a closeup for Brian? I still dont have a working camera .I did add to the pinstripe to go down the whole side of the car. the sticker says "water line hurricane sandy".I think the vette with the 6l80 has a 290 or a 273 ratio .

rockytopper