Regearing for 35s with 8 speed

[Justin88]

I have 2018 Silverado LTZ Z71 with the 8 speed transmission and running a 3 inch level kit on 35s. Stock gearing is 3.42 and looking to regear the front and rear diffs. Since I went 35s I can feel the difference in how it drives and MPG. I’ve  talked to many people and some say 4.56 and others say 4.10 since it’s an 8 speed transmission.  I’ve read many forum threads but never one specifying gearing and how it’s different with an 8speed. Most are talking about 6 speed. Does anyone here have this set up and what gearing are you running or do you recommend ? Thanks in advance. 

[lucas287]

4.56 all the way with 35s. The problem is I don't think they are made for the 9.5/9.76" AAM axle. Largest is 3.90/4.10 I believe. Maybe even 3.73.  

[lucas287]

I might have to eat crow on that statement!

 

https://www.nitro-gear.com/GM-Truck-with-5-3L-V8-Nitro-Gear-Package-p/gpsilverado-1-select.htm

[CamGTP]

With an 8 speed auto I would do 3.73's or 4.10's.

[pokismoki]

why do you need to go 35"?   not to be too logical  i'm guessing you where at 33" stock,  are you driving in lots of snow or sand trails? or do you need the extra ground clearance of the 35" to clear rocks?

 

the 8 speed has lower gearing built into it, for more torque vs the 6 speed. so 3.73 WorkTruck gear set will probably be all you need

 to buy from GM dealer

if you dont need the extra ground clearance I would go 33" on a 12-12.5" wide tire for the extra surface area , then air down to 20psi, this should handle everything a 35" can at 35-37 psi... but you benefit from less rotating inertia of the 33" tire.  and not have to spend $$$ to re-gear it either.

Edited June 30, 2021 by pokismoki

[M1ck3y]

The largest gear you can get from gm for the 8l90 (9.76) is 3.73. But I think aftermarket has a way of retrofitting 4.10's maybe 4.56's.

[lucas287]

@Justin88 or you could save the money on the re-gear and put it towards a blower. That torque would 'almost' solve your problem. 8th gear would still be useless under 75 MPH IMO. I have 32" tires, 6.2/8 speed and 3.23s - and I'm not too fond of 8th gear. It puts it in a load range that's sensitive to KR at such low RPM.