Regearing Truck after lift kit and 35's tire

[Josh121]

Was looking into getting the 7-9" inch lift kit from Mcgaughys and putting some 35" tires on. I want to regear the truck and was wondering what recommendations people would have. Keep in mind I'm still gonna want to tow a trailer with the truck.

 

Currently the truck is a 2015 1500 Silverado Midnight Edition.
Crew cab, Short Box, 4WD, 3.42 rear axle ratio

Thanks
Josh.

[TXTruk15]

I think you're going to need Yukons 4.10s at the very least, possibly 4.56s if you can get them for the 2015....

[Vic15]

I haven't felt the need to re-gear. There's plenty of power even with the 6.2, 3.23 & 8 speed. My brother is plenty happy with his as well, 5.3, 3.42 & 6 speed. We both have a 6 inch lift on 35s. Try it before you spend the money to re-gear.

[Josh121]

I think you're going to need Yukons 4.10s at the very least, possibly 4.56s if you can get them for the 2015....

 

 

from what i understand, a basic method to find out what your new gear ratio should be is:

 

new tire size x old gear ratio divided by old tire size = new gear ratio

 

and i believe the midnight editions come with a 32 inch tire if I'm not mistaking.

 

i was also told, that instead of using your existing gear ratio, use the best available option that you could have got from chevrolet. so that would be the max towing package gear ratio of 3.73 . So i would be substituting my 3.42 for the max towing package of 3.73 in the equation.

 

So my equation would look like this :

 

35 x 3.73

------------ = 4.0796875

32

so it looks like my optimal gear ratio should be 4.07... but if I'm wrong let me know.

Edited July 12, 2016 by Josh121

[LongrangeLauber]

Gotta compensate for heavier tires too so I would say go up to 4.56 at that point for some more seat of the pants performance

[Josh121]

Yeah it looks like I'm gonna get the 4.56 gears. Anybody have a reccomendation on where to purchase?

[LongrangeLauber]

Well last I checked, almost two years ago, they don't even manufacture aftermarket gears for these new 9.5" and 9.76" 12 bolt rears. The 9.5" you can use a 14 bolt gearset (9.5" of course) but you have to swap a bunch of stuff like the yoke, carrier, different bearings, seals, etc.

 

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[arcasey]

I calculated just over a 3.73 ratio so that would mean that the closest option to stock would be the 4.10 and in reality it will probably be just fine for you. I think 4.56 may be overkill unless you are towing near the capacity of the truck for extended periods of time. How heavy is the trailer your towing and how much time is spent towing?

[Josh121]

I calculated just over a 3.73 ratio so that would mean that the closest option to stock would be the 4.10 and in reality it will probably be just fine for you. I think 4.56 may be overkill unless you are towing near the capacity of the truck for extended periods of time. How heavy is the trailer your towing and how much time is spent towing?

The trailer weighs around 7500 pounds loaded. Usually tow it on the weekends when camping.

[Silvern Sentry]

The trailer weighs around 7500 pounds loaded. Usually tow it on the weekends when camping.

 

I have been told/read that a lift will increase your towing capabilities ... to a certain lift height after which you should not really tow a big load at all. Is 7-9 inches above this threshold, I do not know but I am curious. I would check into this for sure OP before proceeding.

 

35s should be ok with 5-6 inch lift (stock tires are ~32 so no need to regear I am told but why not if have the cash I would love a 3.73 rear end), why 7-9 anyway?

Edited July 13, 2016 by Silvern Sentry

[Josh121]

 

 

I have been told/read that a lift will increase your towing capabilities ... to a certain lift height after which you should not really tow a big load at all. Is 7-9 inches above this threshold, I do not know but I am curious. I would check into this for sure OP before proceeding.

 

i would also be interested in hearing what other people have to say about this.

[Josh121]

Well last I checked, almost two years ago, they don't even manufacture aftermarket gears for these new 9.5" and 9.76" 12 bolt rears. The 9.5" you can use a 14 bolt gearset (9.5" of course) but you have to swap a bunch of stuff like the yoke, carrier, different bearings, seals, etc.

 

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I just got off the phone with one of the shops in my area and they said its no problem to change the gears, except for the fact that they want $3800 to do it. Seems ridiculously high to me.

[Silvern Sentry]

I just got off the phone with one of the shops in my area and they said its no problem to change the gears, except for the fact that they want $3800 to do it. Seems ridiculously high to me.

 

 

Did they give a parts / labor break down? I would bet it is a lot of work to regear, not a mechanic but as I understand you would have to dismantle the entire rear end (possibly off the truck) and basically rebuild it. If you are interested how one functions I found this kind of fascinating it is ancient but got to love those old documentaries and the principals are unchanged to this day. OF course now we have limited slip and stuff but gives you an idea how much of a pain it would be to rebuild one.

 

 

Edited July 13, 2016 by Silvern Sentry

[LongrangeLauber]

The rebuild can be done on the truck for the rear, the front diff has to be taken out and order to get torn down and rebuilt. As I stated above, these new 12 bolt axles have to utilize the 14 bolt 9.5 inch rear end parts. So that means they should include a new carrier, gearset, bearings, yoke, and a difference seal I believe. I got all the info from Yukon gear & Axle when I inquired about it about 2 years ago

 

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[Silvern Sentry]

The rebuild can be done on the truck for the rear, the front diff has to be taken out and order to get torn down and rebuilt. As I stated above, these new 12 bolt axles have to utilize the 14 bolt 9.5 inch rear end parts. So that means they should include a new carrier, gearset, bearings, yoke, and a difference seal I believe. I got all the info from Yukon gear & Axle when I inquired about it about 2 years ago

 

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With all that would it not just be easier to like replace the axels / diffs? That sounds like a crazy amount of work.