Rear end gear ratios

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Bnixon

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Going from 3.42's to 3.73's on a 29" tall tire really woke the truck up.
Assuming you have a 4L60e trans? what RPM are you at running 70 MPH? Looking at what to do with my 3.42 gears on my 94 Suburban. Thx
 

Nad_Yvalhosert

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Had the 245 tires, uh 30.5" height with 3.73's.
With 315/75/16 I found 4.88's spin the engine about 2400 at 60. And that's reasonable to me.
As for you, 4.10. Dont fear the gear.
 

Outlawborn

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What size tires are you running? I have 275/60/15s on the OE rims, with 373s and an Eaton trutrack. Love it. The bigger the tires, the lower gears you need. Also what trans do you have 373s do good with a 4L60E, it a 700R4. 1st gear, is low in those transmissions.
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I'm putting 33s on 18 inch tires and have a 4l60e trans
 

stutaeng

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How much are you towing? And what is your current gear ratio? Or did I miss that?

The 383 upgrade has pretty good torque. Depending on your existing ratio (if you have 3.42 or 3.73) and how much you are towing, it may be okay with what you have.

Generally, 3.73 and 4.10 are good towing/ hauling gears though.
 

sewlow

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Wow really! I am running more rpm than that with my 3.42 with 29" tires. I want to say I'm at 2100 or so.
Doh! My math was off.
Had me wondering. It's been 'a few' years too many since I drove it.
An actual speed/tire/rpm calculator is much more accurate than my mis-spent-youth brain.
70 mph w/29" tire/3.73 = 2174 rpm.
70 mph w/29" tire/3.42 = 1994 rpm


I tried a few other calculators & although there is some discrepancy between some, @ 70 mph, they are within 50 rpms either way. Both lower & higher equally depending on the site.
Could be that certain calculators are taking into account 5% for converter slippage.
 
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GMTMark

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Mine is a 4.10 up from a 3.42 with a Yukon posi, Moser axles and 255/60/15. It's a 4L60E and I plan to drag race it. With a Yank 3200 it will snap your neck. Most people do recommend the 3.73 for the street due to the low 1st gear in the 4L60E but I'm quite happy with mine. To me there's not a huge difference. I reprogrammed the shift points to stretch it out a little. Otherwise I'd be in overdrive just crossing an intersection.
 

Gmc3500HD

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Never Fear the Gear . I got 4.56 with 285 /70/16. 4l80 . If you have the 4l60 id go with 4.10 and never look back . Stock tires 3.73
 
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