Recommended gearing for 33's

[84_Chevy_K10]

Re: Recommended gearing for 33\'s

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whats all this about not towing in overdrive? is that an old O/D trans thing? because gm says its ok to tow in OD with the new trucks...

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Not with the 4L60E, only with the 4L80E.

 

[MousePowrd]

Re: Recommended gearing for 33\'s

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The new trucks have a "tow/haul" mode - a button you push somewhere on the dash or column (can't remember which). It probably turns off OD regardless of the shifter position... or it only enagages OD when its completely safe.

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No, it raises the rpms of all the shifts. Normally O/D would engage at about 40mph, but with the T/H button it raises the engagement of O/D to about 62mph.

I had a 99 Silverado and the manual did say it was ok to tow in overdrive (4L60E tranny). However the new trucks have much better tranny coolers, and they have sensors in the tranny to trigger the dash readout to alert the driver if the tranny is getting hot. Older trucks do not

 

[MousePowrd]

Re: Recommended gearing for 33\'s

To answer the orginal question, do not go over 4.10 gears if you plan on towing more than 3000#'s. Your rpms will be too high in Drive, and you will not be happy. If you are only going to be towing very small trailers go with 4.56's, since you will be in overdrive and not drive

 

[wrathORC]

Re: Recommended gearing for 33\'s

I'd go with 4.10s.

Why? At 70mph you'll be holding ~2100rpm in overdrive with a 32.4" tall tire. That's about right for the amount of ponies it takes to make these barn doors go down the road at 70mph. You'll be turning around 2800rpm in third gear though which is a bit much. However, it won't be very often you'll find yourself in third gear.

You get into a pretty itsy bitsy pinion gear on a 10 bolt once you get to 4.56s. You have just over a tooth of contact area which promotes spitting teeth off the ring gear. For someone like me who has blown up spider gears and fractured another set I don't need any other problems.


What do I want? I want 3.73s because I do run little tires (235s) in the wintertime instead of my 33s.

Right now, with my 2.73 gears, overdrive is useless. Trust me, I feel your pain. I turn 2000rpm at 70mph in third gear. When I do let her slide into fourth gear it feels like someone threw out a parachute because she falls flat on her face. I'm not kidding when I say I drive the truck in second gear a good chunk of the time in the city (45mph or less) because of all the hills around here. When I go to pass someone on the highway I manually put it in second gear because otherwise at about 65mph it shifts into third and chokes on it. She's good for right around 110mph in second gear anyway. Not that I'd do anything weird like race a 4400lb truck against a 2700lb ricer.