3.91 vs 4.11 on Cammed Manual SS

[Rhino79]

I concur, 4.10s for sure on a M6 car with a nice cam.

[bkevind]

So what is the equivalent of 4.10 on SS M6 for the 1LE M6?

[zz430camaro]

Originally Posted by bkevind

So what is the equivalent of 4.10 on SS M6 for the 1LE M6?

equivalent in what way?

[bkevind]

Originally Posted by zz430camaro

equivalent in what way?

1LE gear ratios are not the same as the SS, they are close ratio and longer, which is why GM used a 3.91 in the 1LE to start with. Net result is similar acceleration between them even though they have different transmission gear ratios, and a different final ratio in the diff.

So, going to 4.10 in the 1LE will not net the same as it does in the SS. I'm too lazy to figure it out

I'm finding that tire diameter makes even more of an impact. Going to 305/30-19 has more of an impact than going to 4.10 on my 1LE, using online calculators.

[Ajax2112]

Won’t changing the tire diameter affect ABS, stabilitrac and traction control

[InFiD3ViL]

Originally Posted by Ajax2112

Won’t changing the tire diameter affect ABS, stabilitrac and traction control

Not if the front and rear tires are kept within a certain percentage size difference from each other. The issue is if there is too big a difference between front/back.

[acammer]

Originally Posted by bkevind

1LE gear ratios are not the same as the SS, they are close ratio and longer, which is why GM used a 3.91 in the 1LE to start with. Net result is similar acceleration between them even though they have different transmission gear ratios, and a different final ratio in the diff.

So, going to 4.10 in the 1LE will not net the same as it does in the SS. I'm too lazy to figure it out

I'm finding that tire diameter makes even more of an impact. Going to 305/30-19 has more of an impact than going to 4.10 on my 1LE, using online calculators.

A regular SS and a 1LE, in factory configuration (including the differences in the trans gearing, final drive gearing, and tire size), have an essentially identical final drive ratio in first and second gear. In third the 1LE has a little more ratio, and then in fourth it has significantly more ratio, and then fifth and sixth are very close again.

I think the best setup for an all motor 5th gen would be a MM6 (1LE) trans with a 4.56 rear end (which we can't get, would have to be an aftermarket diff like an S60, Hammerhead, DSS 9", etc). That setup would give you about the same 1st and 2nd gear as an M10 (SS) with 4.10s, and then an even better 3rd and 4th gear, and still have a decent cruise RPM (the MM6 has the lowest 6th gear cruise RPM of any TR6060).

But to answer the original posters question about 3.91 vs. 4.10 - you've heard it - 4.10s all the way. The car should come like this from the factory.
70mph cruising speed is 1870rpm with a stock 28.8" tall tire so you're definitely not dealing with too much cruising rpm. I went from the stock gear to 4.10s when I was bolt-ons, and I lost about 1.5mpg (25mpg to 23.5mpg) with the gear swap at highway cruise speeds. Hardly enough to even think about for me.

These are heavy cars, and they love the change. Its easier to launch the car because they don't bog as easily, so don't need quite as much launch rpm (they still need TONS of launch rpm on sticky tires). It's much more RPM on the back half of a quarter mile in 4th, which helps the trap speed out. Once you've got a big cam in the car they are basically a requirement to keep the rpms in a suitable place for day to day cruising.

I will echo the comments about the noise - everything I've seen or heard associates some degree of gear noise with 4.10s. Any set of gears can be noisy, installation is crucial to getting any rear gear to stay quiet and happy. 4.10s are at the limit of what we can cram into this way too small stock rear diff, and as with most things that are at the design limits there are some compromises in fitting a ratio that aggressive into that housing. If you add in aggressive bushings and a diff support cover you're giving that noise a much easier path into the car - I don't think it's reasonable to expect a car with solid subframe bushings, aggressive poly diff bushings and a diff cover with load bolts right on the right gear caps not to transmit some noise into the car. But properly setup they shouldn't be outrageous. I had Richmonds, they made noise (with all stock bushings), I have Motive now, they make noise, I haven't tried Yukon but those might next (mine are hurt again - failed a crush collar last season and nuked the pinion bearings - and didn't do the gearset any favors in the process).

[steakmaker]

acammer,
Hey,Belated Merry Christmas,and Happy New Year! With all the gearsets you're buying,you are working your way toward getting a 9" set up.....maybe one of those solid axle set ups,one peice driveshaft too.I'm too chicken to drag mine,I'm afraid of breaking something.I hope you find the right combination that works for you.

[acammer]

Originally Posted by steakmaker

acammer,
Hey,Belated Merry Christmas,and Happy New Year! With all the gearsets you're buying,you are working your way toward getting a 9" set up.....maybe one of those solid axle set ups,one peice driveshaft too.I'm too chicken to drag mine,I'm afraid of breaking something.I hope you find the right combination that works for you.

Hey Steakmaker - you're coming to the strip with Jay and I in 2019. I'll trailer mine over, if we break a car we'll load it on the the trailer and somebody else can drive mine home. Or just come and watch - but you'll wanna do it then for sure!

[4WDlifeform]

I got a shop lined up for my gear install. They are recommending "US Gears", he said they are a 5 cut gear, which I am not real familiar with the term. Going 4.10 ratio.

I am planning to pull the diff and take it to the shop. Pricing seems very fair. I am hoping to get to it soon. Will keep posted!

[zlathim]

Originally Posted by 4WDlifeform

I got a shop lined up for my gear install. They are recommending "US Gears", he said they are a 5 cut gear, which I am not real familiar with the term. Going 4.10 ratio.

I am planning to pull the diff and take it to the shop. Pricing seems very fair. I am hoping to get to it soon. Will keep posted!

You're going to love it. Far and away the best mod I made to my car.

[Nb1081]

Originally Posted by acammer

Hey Steakmaker - you're coming to the strip with Jay and I in 2019. I'll trailer mine over, if we break a car we'll load it on the the trailer and somebody else can drive mine home. Or just come and watch - but you'll wanna do it then for sure!

Strickly street every other Friday at empire ill probably see you there if i stop being lazy and put car together

[go_go_gadget88]

My setup is in my signature. I went with 3.91s, mostly because I plan to give her some boost one of these days, and didn't want to go any further with them.

If I planned to stay NA and keep my setup like it is, I would have went with 4.10's. These heavy cars can use all the gear they can get!

[dino2012ls3]

After reading another post bout 4.10s, I ordered me a set of motives which were backordered from the place I order ed from. April 19th is expected ship date. I'm excited. My car is cammed with cam motion .236/.242 663 lift.