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Discussion Starter · #1 ·
OK. I know everyone seems to have a question about what gear they should run and I do to, but mine is a little different. I have a 2009 GMC 1500 that I am running 40x14.50s on with a 22x12 rim (lift and tires will be on late next week). The issue that is different with mine is that my truck has the new allison 6 speed transmission with the 6.2L gas motor in it. I need to know what the proper gear is for someone that will do no more then 5k miles a year driving mostly in town or on the highway. I was told by one "expert" that a 4:56 with my combo will be 200 rpm's more at 60 mph then what stock is. Does this sound about right? I know a few people on this forum have mentioned 5.11 and 4.88 but I am not really sure if they were throwing out random numbers that wd work on older GMC's with the 5.3 and the other tranny. If anyone has seen or knows of anyone with the same motor/tranny combo as me that has changed their gears then I would love to know what they done. Any help is appreciated.
 

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i would do 4.88s or 5.13s. yes its alot of gear but thats alot of rolling mass. the six speed overdrive is like .67 to 1 where the 4l60e is .77 to 1. but first is lower geared in 6l80e thats is why people are liking higher gear ratios with those trannys. for a street queen mall crawlin truck i would do 4.88s for a truck that is huntin, fishin, towin on a regular basis or might accidently see 4wd i would use 5.13s
 

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OK. I know everyone seems to have a question about what gear they should run and I do to, but mine is a little different. I have a 2009 GMC 1500 that I am running 40x14.50s on with a 22x12 rim (lift and tires will be on late next week). The issue that is different with mine is that my truck has the new allison 6 speed transmission with the 6.2L gas motor in it. I need to know what the proper gear is for someone that will do no more then 5k miles a year driving mostly in town or on the highway. I was told by one "expert" that a 4:56 with my combo will be 200 rpm's more at 60 mph then what stock is. Does this sound about right? I know a few people on this forum have mentioned 5.11 and 4.88 but I am not really sure if they were throwing out random numbers that wd work on older GMC's with the 5.3 and the other tranny. If anyone has seen or knows of anyone with the same motor/tranny combo as me that has changed their gears then I would love to know what they done. Any help is appreciated.
big tires+big rims*only 9000 miles per year = 5.13's
 

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Discussion Starter · #4 ·
i would do 4.88s or 5.13s. yes its alot of gear but thats alot of rolling mass. the six speed overdrive is like .67 to 1 where the 4l60e is .77 to 1. but first is lower geared in 6l80e thats is why people are liking higher gear ratios with those trannys. for a street queen mall crawlin truck i would do 4.88s for a truck that is huntin, fishin, towin on a regular basis or might accidently see 4wd i would use 5.13s
Thanks alot. This helps me alot and could not have been phrased better. I may crawl around the FSU games and not the mall, but I get your point. Thanks for the help.
 

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i would do 4.88s or 5.13s. yes its alot of gear but thats alot of rolling mass. the six speed overdrive is like .67 to 1 where the 4l60e is .77 to 1. but first is lower geared in 6l80e thats is why people are liking higher gear ratios with those trannys. for a street queen mall crawlin truck i would do 4.88s for a truck that is huntin, fishin, towin on a regular basis or might accidently see 4wd i would use 5.13s


4L60e OD ratio is 0.70:1

Allison 1000 OD ratio is 0.61:1 (6th) and 0.75:1 (5th)


jsygk
 

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Swamper Brotherhood
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5.13s... might want to consider a 14bolt semi float... thats a lot of rolling mass for the bearings in a 10bolt.

edit... i just thought about this... your truck should already have a 14sf IIRC.
 

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SierraDime
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^^ its not the allison trans. its the 6L80e.. just for the right info. but personaly with a 40 inch tire i would run minimum 4.88s
 

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LULZ at the "allison" ..Anyways Id still run 5.13z with that 6L80E at 40z :imo
 

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Discussion Starter · #11 ·
40's on a 1500 is just a bad plan to begin with :imo
Luckily this post was not about the 40's and whether its a good plan or not. I plan on doing it the very best way possible and plan on upgrading all the necessary parts (which I mostly already have). Sounds like a good plan to me :dancingpoop:
 

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Discussion Starter · #12 ·
^^ its not the allison trans. its the 6L80e.. just for the right info. but personaly with a 40 inch tire i would run minimum 4.88s
Thanks. I am not the most technical. Allison was the only company I thought made a 6 speed for GM. Either way, I think the 4.88's sound like they would be a good choice for me and how I plan on driving. I think I am going to go with that. Thanks to all for the help.
 

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NCOR
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The 6l80e 6th gear is .67:1, even higher (but numerically lower) than the 4l60e 4th gear (.70:1).

Run more gear than you would comparatively with the 4L60e in the 6L80e. With that much rolling mass, you really do need more than just a stock final drive ratio to most economically push those down the road.

It won't feel as bad from a launch with the low 4.xx:1 1st, but you will feel the lack of power up in 6th if you pick a 4.56 or 4.88 gear. Don't make the mistake of simply equating low rpm to high mpg.

Stock on grades my rig felt adequate even with the low hp output in comparison to yours, when I went to 33's with stock 3.73's I could feel it dropping in and out of OD more often. 4.88's with 38's should fix that right? Wrong, it was just as bad, if not worse than 33 and 3.73 combo on grades. What finally fixed it was going to the 4l80e with it's deeper (numerically higher) .75:1 OD, it was finally deep enough to feel adequate in OD.
 

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The 6l80e 6th gear is .67:1, even higher (but numerically lower) than the 4l60e 4th gear (.70:1).

Run more gear than you would comparatively with the 4L60e in the 6L80e. With that much rolling mass, you really do need more than just a stock final drive ratio to most economically push those down the road.

It won't feel as bad from a launch with the low 4.xx:1 1st, but you will feel the lack of power up in 6th if you pick a 4.56 or 4.88 gear. Don't make the mistake of simply equating low rpm to high mpg.

Stock on grades my rig felt adequate even with the low hp output in comparison to yours, when I went to 33's with stock 3.73's I could feel it dropping in and out of OD more often. 4.88's with 38's should fix that right? Wrong, it was just as bad, if not worse than 33 and 3.73 combo on grades. What finally fixed it was going to the 4l80e with it's deeper (numerically higher) .75:1 OD, it was finally deep enough to feel adequate in OD.
:worship:

and run 5.13s and a Tru Trac
 

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Bayou Surface Drive, LLC
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If that rig has a 6.2L id hope it has the 9.5 SF rear axle.
 

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SierraDime
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Thanks. I am not the most technical. Allison was the only company I thought made a 6 speed for GM. Either way, I think the 4.88's sound like they would be a good choice for me and how I plan on driving. I think I am going to go with that. Thanks to all for the help.
They make that trans. for the duramax only... but with these 6 spd trans. they have 2 O/D gears, which i know are work trucks rarely use the 6th gear while having any load on them... so higher gearing maybe be the answer.?
 
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