I am thinking about switching to either 4.10's or 4.56's. Or maybe something in between? I just want to get my heavy *** 3 ton SUV moving off the line quicker. It will sometimes churp the rear tires off the line but not always. Then its slow and steady for a few seconds till it gets over 3500rpms. I didnt figure I'd do much towing, but then I bought a boat. Between the boats shape and 28' trailer it gets to be a real pain towing at 70mph. Its like a dead spot or something. At 70 it keeps downshifting, but at 80 it tows like a dream.

Right now I'm sure I have 3.73's, turns 2krpms at 70mph and about 2300 at 80.

Can anyone help figure out what my rpms would be with 4.10's and 4.56's at 70 and 75mph? My tires are the stock 265/70R16.

Thanks.

 

4.10s are an excellant choice with a 4L60E with 30"tires you turn about 2520rpm in 4th at 75mph,with the 4.56s you'll turn close to 2800rpm.The shift points at 6300rpm with 4.10s are 43/81/132,with 4.56s the shifts would occur at 39/73/118.

 

With my 6,000 lb Avalanche I noticed a significant difference going from 3.73's to 4.10's, and I had 32" tires (305/50-20). With 4.56's and 30" tires you'd really be revving it out on the highway...like Whitt said, at 2800 RPM.

You can figure the 10% change in gearing (3.73 -> 4.10 = 10%) would push your 80 mph 'dream towing' vehicle behavior down 10% to 72 mph.

 

the calculator is saying with 456 and 30" tall tire at 70 mph youll be at 2500rpms
at 2350 rpms and a 32"tire youll be at 70mph

 

Personally I would go with the 4.10

 

I would go with the 4.10's. I have called around to see if there is anybody making 4.30's for the 8.5"/8.6" 10 bolt, and I didn't have any luck.

 

No body makes a 4.30 or a 4.33 for our rear ends.

I had 4.56's and a 32" tire with a 60E when I was NA and it was very livable IMO. I wouldn't have a NA 4.8 any other way due to the lack of torque.

 

I have 4.56's and I have 31" tires so my highway rpms are 2520 at 75 mph and that's not a problem for me but I'd not want anything higher. I guess I'd say get a bigger tire or choose the 4.10's.

 

where do I find the ring and pinion kit for the front axle? I think I may go with 4.56's. My highway MPG may drop to 21 or so, but thats livable. Also, when these tires wear out and I need new ones I will be getting something like the 285/75's. These tires just look too small.

 

Mine does about 2350 to 2400 rpms at 70mph with 4.10s and 28" tire (275/50/17's Nitos).