I was looking at the horrible gearing of the 4l60e as compared to the m6. Has anyone put a 6 speed automatic in their 4th gen f body? It would seem to me with the added 6 gears that the rpm drop between gear changes would not be as great and would allow for lower gears to be used in the rear. I am not interested in swapping to an m6.

 

OD isn't as long as T56 top gear. 6L80 has same final OD as one of the 4L trans.

Lower gears do help keep in the powerband (other than 1st really only good for towing lol)

AFAIK we don't have an aftermarket 6L80E controller, so it requires a full Gen4 PCM and harness swap.

 

Might want to do a search on "6L80E in a 4th gen" in this forum section.

Might want to ask yourself if you are going to put the 6L80E behind an LS1-LS2 or a LS3, because of reluctor differences between the engine designs, has and effect on choice. Don't do the research on that and you could find yourself spending money you didn't plan for.

Gearing and RPM retention wise of the two transmission. The 6L should beat the 4L all things being equal. All things being the same, the 6L want need as much stall due to 1st gear ratio, and also if you want to Paddle or TU/TD shift it. Paddle or TU/TD shifting is slow enough with 6L, so the more stall you try to run, the slower the execution of the shifts will be an they are slow enough stock stall wise.

6L80/90
4.03
2.36 -- 58.56% (high) RPM Retention 41.44% RPM DROP
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

4l65/70
3.06
1.62 -- 52.94% (high) RPM Retention 47.06% RPM DROP
1.00 -- 61.73% (high) RPM Retention 38.27% RPM DROP

You can make most anything fit. The 6L80e has a pan depth problem you need to know about too, so ground clearance can be a problem too. You want be slamming your ride.

I have a 6L80E in one of my cars, and it's not all that great driving wise or performance wise. It's more for the " WOW", Look at My Car, I have a 6 sp tranny you can brag about when parked.

Trans has 2 OD gears and no 1:1 gear. This is for Fuel Mileage only, and on level ground, so if you live in area of South East I do or for that matter a lot of other areas of country, you will find the 6L hunting back and forth between 6th and 5th gear due to there not being that much level ground. I have that problem, my car with the 6L80, that only weighs 2868 LB, and has a 3.07 rear gear.

If you look a Pontiac GTO, you can run a, as you call it, a lower gear than if car was a manual and get around the same performance level. The Manual GTO has a 3.70 gear, while the 6L use a 3.27 gear to match up with the manual performance wise.

 

You can tighten up the 4L60E ratios to 2.84, 1.55, 1.00 with a special input carrier from Sonnax:
http://www.sonnax.com/parts/3734-2-8...ut-carrier-kit

Installing a 6L80E in a Gen-4 would be very challenging electronically. The 6L80E has a built-in trans controller which expects to talk to the engine and other computers over the CAN bus. The Gen-4 does not have a CAN bus and the Gen-4 PCM is not a CAN device. If you upgraded to e.g. an LS3 engine with a E38 or newer ECM which is a CAN device, you might have a fighting chance.

 

I did not realize this was an option. I like the idea you present. I imagine I may have to up the final drive ratio from 323 to maybe 342 to have a similar off the line launch which in turn will affect my highway rpm negligibly in OD. Combined with a stall of around 3000 rpm I think this would really wake the car up and make better use of the available power the engine produces in stock form.

I am am really trying to have my cake and eat it too without going to an all out 1/4 mile beast. In essence maximizing the efficiency of what the car already has available.

 

That Sonnax input carrier just made the 4L60 a lot more appealing!

 

The Sonnax carrier change is pretty expensive, why not just go with a 4l80e instead? Gear ratio is pretty close to the input carrier mod for the 4l60e.