4.56 Gears

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stutaeng

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'00 K3500 CCLB 5.7 L31 with 4L80 . I'm running LT265/75/R16 over stock LT245/75/R16. I bought the truck for a home addition project. I haven't towed with it, but have carried heavy loads of up to 3,400 lbs. When I bought the truck it had a gooseneck hitch, and the previous owner lived in the country, so I figured it hauled hay most of it's life. I've hauled 1 yard loads of sand or flexbase, 1 pallet of bagged concrete, building materials, construction waste to the landfill, etc. Honestly, it's not bad for a such a heavy loads and heavy truck, especially for a SBC.
 

L31MaxExpress

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'00 K3500 CCLB 5.7 L31 with 4L80 . I'm running LT265/75/R16 over stock LT245/75/R16. I bought the truck for a home addition project. I haven't towed with it, but have carried heavy loads of up to 3,400 lbs. When I bought the truck it had a gooseneck hitch, and the previous owner lived in the country, so I figured it hauled hay most of it's life. I've hauled 1 yard loads of sand or flexbase, 1 pallet of bagged concrete, building materials, construction waste to the landfill, etc. Honestly, it's not bad for a such a heavy loads and heavy truck, especially for a SBC.

With the Vortec 5.7 and that much load with that tire size I would go for 4.88 or 5.13. I run the same size tire and the 85E in my Express van. When I still had the 5.7, I went from a 3.73 to a 5.13 gear in the 10.5 rear. BIG difference in the way it pulled empty or loaded down with the travel trailer.

IIRC your truck should have the 9.25 IFS front diff and a 10.5" 14-bolt rear. You can get 4.56, 4.88 or 5.13 gears for both.

4.10s have you at 2,300 rpm @ 70.
4.56s would put you at 2,550 @ 70.
4.88 would put you at 2,700 @ 70.
5.13 would be 2,850 rpm @ 70.

If I did not spend much time at 70+ MPH on the highway I would consider 5.13s. 4.88s might net a slight increase in highway mileage compared to a 5.13 but not much. I think 4.56s would be a waste of time and effort. Not enough of a difference from the 4.10s to spend the money.
 

stutaeng

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Cool, thanks! I bought the truck thinking of only owning for only the time being, but have thought about keeping it as a project truck. I was previously wrecked and has a bit of frame damage that I want to fix, but have also thought about doing a SAS. I also have a LQ9 junk engine with a spun bearing that might rebuild and swap into it.

Thanks for the suggestion. I will certainly consider it down the road.
 

Wheeler

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Stopped by the shop today...

All has been going well. They have the front all done. NO issues there. They said everything looked good up front. They had the back apart when I stopped in. Looks good so far, but the rear brakes are shot. So I'll have them replaced while its in the shop!

Yes that's my K1500 in the Avatar.

I'm really looking forward to this. For those of you who were happy with your gear changes, that just re-enforces my decision going to the 4.56!

Truck doesn't see the winter roads, so when I get it back, she's gonna sit in the driveway until it finally warms up in a couple months! Well I'll surely go for a good rip on the way home though! lol
 

Wheeler

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Gears are installed now. Rear brakes replaced, & the one e-brake cable seized, so that's all new as well. This Monday they will be going over the Holley Sniper & all the settings & tuning.

Can't wait!
 

Wheeler

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Well picked er up today. I put 60 miles on before I came home. It's not near as bad as I was expecting from what people say it will be like on the internet....

75mph (120km/hr) was 2500rpm in 4th locked up

68mph (110km/hr) was 3100rpm in 3rd (can't remember if I locked it or not!)

I have the Torque Convertor Lock up on a toggle... can lock it anytime other than 1st...

That was with 285/75/16s

I'm considering going up to a 295/75/17...


Over all the initial impressions are good. However for what I paid to have the rear brakes & gears installed was too much! Made me sick... but it's done now...


oh rite, I'll have to change the speedo gear as now it reads 20km/hr faster than what I'm really going...
 

Wheeler

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UPDATE....


So I've towed my 7K/LB trailer/quad set up now twice... It's a lot better than before. 3200rpm on the highway around 60-65mph locked up in 3rd. Last trip made NO sense.... 5.6mpg towing on fairly flat road to the bush, coming home I got 9mpg & was driving faster.... I did have less weight from having no water & was driving east... I dunno...

Overall I like the gears, however still crave more power... I'm contemplating 2 things... Just call it a day & upgrade to a Diesel Truck, OR... toss some larger heads, & long tube headers one in liu of the stock vortex heads & shorty JBA Headers....

Thoughts??

OH rite... I've upgraded my wheels. Stockers are now gone, & 295/70/17 Fuel Shok with Firestone MT-2s now...
 

b454rat

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Get a vortec 454. I towed with mine a lil bit, got better mpg than what you did, being all stock. Prolly more weight as well. And I don't think it dropped out of OD....
 

b454rat

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Also I think 95 was the last year to get 4.10s in a 1/2 ton, even the 2500 6 lug. Im looking for a set for my Yukon, can't find em.
 
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