lsutigers93

Advantages and disadvantages to each one? Swap will be a 6.0 (bored/stroked to 394 ci) into a '64 Olds Jetstar I (B-body) with 394 2V/Slim Jim auto...planning stages for now.

John

poorhousenext

6l80/90E are transmissions you need to do your home work on.
Need to look close at them and take a good look at application, daily driver, daily driver/weekend racer, race only and HP & TQ you plan on putting in front of it.

Check with Century and RPM Transmission shop about what it costs to rebuild one and/or build one to hold HP/TQ if you plan on doing any racing.

Look close at it gearing. Gearing is designed more for gas mileage than racing. You have no 1:1 gear and it has two Overdriven gears, 5th and 6th and depending on weight of vehicle and terrain you will understand why it has that 0.85 5th gear.

Rear end gear choice needs to match up with weight of car. Depending on it you might want to think twice about running tallest rear gearing you can buy. Good example to look at is G8 Pontiac to see how it's geared manual Vs 6L80E. Remember no 1:1 gear.

6L80/90
4.03
2.36 -- 58.56% (high) RPM Retention 41.44% RPM DROP (Note you could say it has two 1st gears if you compare it's 2nd gear to T10/M21/M22 close ratio 4 speed manuals 2.20 1st gear)
1.53 -- 64.83% (high) RPM Retention 35.17% RPM DROP
1.15 -- 75.16% (high) RPM Retention 24.84% RPM DROP
0.852 -- 74.09% (high) RPM Retention 25.91% RPM DROP
0.67/.70

4l80/85
2.48
1.48 -- 59.68% (high) RPM Retention 40.32% RPM DROP
1.00 -- 67.57% (high) RPM Retention 32.43% RPM DROP
0.75

You need to understand 6L's will not work with LS1 based engine. If your going to put LS2 in front of it check with Mast Motorsports and make sure their ECM will work with it. They are the only one I know of that claims to have LS 2 ECM that will work with it. Only GM's LS3/7 or 9 ECM work with it.

I do have a 6L80E in the driver below. 3.07 rear gear and car weighs 2879 Lbs without fuel. Multiply 4.03 1st gear X 3.07 rear gear. A C6 Corvette with manual trans would need a 4.60 rear gear instead of 3.42 to match up with it's 1st gear ratio...LOL My 4th gear with 3.07 matches up with the C6 1:1 4th and 3.42 rear gear with it's 3.49 ratio with it's 1.14 4th gear. It's also 400 lbs lighter with lot less rear tire width to try and get traction with.