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Discussion Starter #1
Ok I am going to ask on here before I end up regretting my decision. I sent a few guys on here PM's asking there opinions on gears but still got mixed opinions. I have a 98 Silverado lifted 6" on 295/75/16(which is equal to almost a 34" tire) I will be running it like this for a while because the tires are only a few months old. When its time for tires, I will probably go with a 35" which really isn't all that different. I was pretty convinced that I wanted 4.10s. I have 3.42s right now..BUT I have been getting a lot of people saying that I should definitely get 4.56s. What do you guys suggest? The truck is my daily driver and basically do a majority of city driving but still am on the highway quite a bit too. I want to pick the gears that are going to be best for gas mileage. I really don't care about power because the motor is all stock and it is going to stay that way. Also, I don't do any offroading either. So what do you think 4.10s or 4.56 and why?
 

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oakleyguy
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hell if u want mpg stay with 3.42s or go with 3.73s. even a 4.10 is gonna make mpg get alot worse. just help with gettin power back to where it should be
 

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If you go 4.10. I have the front ring and pinion for IFS. IDK if that pertains to you but just 1 less thing to buy. $90 shipped
 

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Multiple GMFS owner
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hell if u want mpg stay with 3.42s or go with 3.73s. even a 4.10 is gonna make mpg get alot worse. just help with gettin power back to where it should be
my cousin doubled his mileage(about 3-4 up to 8 after gears) when regeared his 76 RCSB 3/4 ton from 4.10s to 4.56s or 4.88s cant remeber now
 

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flight medic
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if you daily it and dont tow much the 4.10s with 35s will be like running stock gears and tires. 4.56 will do you better if you plan on towing a good bit.
 

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go with 4.56...will help with the added weight of the rubber

if you're trying to get MPGs, the LAST thing you want to do is stay with 3.42...you're only lugging the engine and making it work outside of its powerband...
 

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GMFS Enforcer
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hell if u want mpg stay with 3.42s or go with 3.73s. even a 4.10 is gonna make mpg get alot worse. just help with gettin power back to where it should be
His mileage will be worse with 3.42 gears or 3.73s. Higher RPM does not always equate to worse MPG. Engine load plays a factor.

OP, find out at what RPM your engine makes peak torque. You want to be at or roughly 250 rpm below this particular engine speed when you are cruising down the highway. That said, pick a gear that allows you to do this with the tire size you have.
 

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shucks i'm not sure if it'll fit a 98'. as long as it's a 8.25 then it'll work. it is OEM ring and pinion with 85k on it. used for stock tires except the last 2k or so. worked well with my setup.
 

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flight medic
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his over drive ratio for that tranny is .70 the truck came stock with a 31in tire. run that through the gear ratio computer to get the 35s and close to stock gearing is what he will want to make better mpg and it comes out to using a 4.10 gear. he can meet in the middle and run a 4.30 and it would have good power but better highway mpg then 4.56 for driving highway all the time and wanting better milage a 4.56 is a bit to low but in the city the 4.56 will do better.
 

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flight medic
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that chart is assuming a 1-1 ratio in the tranny and based on a standard best to use http://www.ringpinion.com/Calc_RPM.aspx

put your numbers into the one for specific tranny radio and the speed of 65mph it will give you the rpms. to get your comparison put your stock gear ratio with stock tire height and then write down that rpm number. after that put in the setup your wanting to run and get the rpm number close to what the stock one was or above it.

i think 4.30 would do him the best of both worlds though.
 

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Ha, I see you're still on the fence and I can see why. One reply completely contradicts the other. I was thinking you were doing mostly highway driving??

I would say if it's mostly highway, 4.10's
Mostly city 4.56

Also, when it comes time to buy tires I'd stick with a bfg or similar because they run a bit small and don't weigh shit. This helps tremendously with suspension wear and getting good mpg's! Just something to think about.
 

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I have the 4.56 with a set of 315/75/16 (basically a 35) and I love it! It has awesome get up and go in town and on the freeway. I didn't notice any difference in mileage from 4.11 to 4.56. (yes i had both!) Both if I were to be driving it everyday on the freeway I would have stayed with 4.10, I just got the 4.56's and Detroit for free so i figured might as well through them in the 10 bolt. I also live 30 mins from Pismo so that was also a decision maker for me to go 4.56
 

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I have the 4.56 with a set of 315/75/16 (basically a 35) and I love it! It has awesome get up and go in town and on the freeway. I didn't notice any difference in mileage from 4.11 to 4.56. (yes i had both!) Both if I were to be driving it everyday on the freeway I would have stayed with 4.10, I just got the 4.56's and Detroit for free so i figured might as well through them in the 10 bolt. I also live 30 mins from Pismo so that was also a decision maker for me to go 4.56
OP, this is why I was telling you 4.10 because you said you were mostly highway driving. I've got 4.56 but I rarely get on the highway so they are perfect for around town, 0-60 city driving.
 

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Discussion Starter #18
Thanks for the help. I think I am pretty much decided on 4.56's. Sounthern Pride I guess I sort of mislead you. I don't do a majority of my driving highway but I definitely do some highway driving. Mostly on weekends going to places and a little through the week sometimes but a majority is in the city. I was using the calculator provided above and using it with a 34" tire 4.56 gears and at different mph the 4.56 seem pretty good. I usually never go past 70 around here oh highway and the RPMs are around 2200 which doesn't sound bad at all. The setup I have now the RPMs are around 1656. Also, around town anywhere from 45-55 RPMs are between 1400-1700 with the 4.56s.
 

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Yep. I actually just bumped up to true 37" toyos with my 4.56's and I like it alot better than when I had 35's...Cons of the combo with 35's was that 70 or above it was screaming @ 22-2500 rpms so I was wasting a ton of gas and now with 37's it's mellowed out alot and 70 and above I'm a bit below 2 grand so I'm saving a bit of gas, it's nice, and it's funny how it works but, it does.
 

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I usually never go past 70 around here oh highway and the RPMs are around 2200 which doesn't sound bad at all.
I run about 2100 at 65 in my 04, 265/70R17 with 4.10s, and getting to hills and stuff the engine doesnt have to work at all to pull it up. My 88 runs about 1300-1400 at 65, 3.42s with 285/75R16, and its a fucking DOG at any speed. I'd say 4.56
 
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