You can program in each gear ratio with Tunercat.

pauly

 

so let me get this striaght . this will fix the lonnng gears the 4l80 has and make it like a 4l60 e , but way stronger . am i correct . and with this u can run a lower (number wise ) rear end gear and still have awesome acceleration and have fuel economy overdrive gear ? sounds like the best of the all worlds to me

 

The gear ratios in the PCM are all individually customizable. No problem, even on older PCMs.

 

so this could be a fairly inexpensive mod

 

I would think that the torque capacity of the transmission with the 2.75 first gear might be slightly lower but still way way above an L60, L65, L70.

Maybe someone will show up with some more detail.

 

Why would think the torque capacity would decrease? A set of 4:10 will handle a lot more torque than a set of 3.42, the lower the gearing the more torque it can handle. This would be true for the 60E, so they use a lower gearing to handle the more torque, but the weak link of the 60E is the sun shell.

 

Because lower gear ratios multiply torque more. Check the torque capacity of the various manual transmissions with different gearsets available.

And no the 4.1 will not handle more torque without breaking although it does multiply torque more for delivery to the axles.

When a gearset of any type multiplies torque, that multiplied torque load is handled by that gearset. Nothing is free, especially not mechanical advantage with gears, levers, or whatever.

 

What are your opinions on the altenate ratios?

 

In addition the tooth count usually goes down as the gear ratio gets numerically higher, thus making them weaker.

 

I realize many of my opions are unpopular with a lot of people, but I do try to view things across a very broad spectrum.

There are a few reasons that the TH400 was built with a narrow range of gear ratio. First, this transmission was built to handle the torque produced by GM's strongest engines of the day. The narrow the range of ratios is in the trans the closer the ratios can be to each other. The less engine RPM change between rotating component during a shift the more torque the same clutch pack can handle if it were shifting a wider ratio. Clutch packs are sized to handle the specified torque at the desired shift softness without overheating. Increasing shift firmness or narrowing the ratios between gear increases the amount of torque that clutch will handle. Second, the close ratios make the TH400 and 4L80-E ideal for the 6.2 and 6.5L Diesel and Turbo-Diesel since they have a much narrower RPM range than gas engines.

I personally love the ratios in the 4L80-E because they're close together and the engine never falls out of it's torque band even with a stock converter. My experience with them is a little bit biased because I have 4.56 gears for strong launches and a Gear Vendors Overdrive to give me a wider overall range. I only use the GV on the freeway over 60MPH, but without it I'd have to be running 3.73 or 3.42 gears in the back because highway engine RPM is too high at anything over 60mph.

Changing the ratios in the 80 will increase the amount of work the clutches have to do, that can be easily compensated for with additional line pressure in programming or by enlarging the feed holes in the valve body. The 4L80-E has the advantage of NOT being overworked in stock trim where as the 4L60-E is grotesquely inadequate for most of the stock vehicles it's installed into.

As for this discussion on torque handling and gear ratios, some of the things stated are the opposite of what is true. Given two shafts, one driven by the other through gearing (for example axle and pinion, or output shaft and input shaft) any time you increase the gear ratio you are increasing the amount of torque the driven shaft has to deal with. In the case of a rear end, the ring gear has to transfer power through the differential to the axles. The differential and its lock-up or limited slip mechanism will have to deal with increased torque from the increased gearing. For this reason and because tooth contact takes place over a wider collective surface area between the ring and pinion, 3.42 gears would survive MUCH higher torque loads than 4.10 gears would, always.

-James