Et difference with 3.91s - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

dadsz28 · 04-21-2020, 11:15 PM

Hey guys I am on the fence on doing 3.91 gears on my cammed and stalled Camaro car runs mid 11s. Can anyone give me what kind of improvement in ET they have gained. From what I gathered around .2 tenths?
Figured I would ask for anyone who has done it thanx.

Joe M 2012 2SS · 04-22-2020, 08:27 PM

.150 gain in the 1/8th mile. No 1/4 mile track near where I live. Car runs 7.1-7.3 in the 1/8th depending on prep/DA.

I ended up having to remove the first set I put in, Motive. Too much gear whine. Many others have experienced the same regardless of how well they are installed.

Went with AAM and they were originally quiet. Developed a slight gear whine over time, but much less than Motive.

I'd highly recommend swapping out the factory clutch pack differential with an Eaton True-Trac when you do the gear swap.

It will still depend on which cam/stall you have as to what rear end gear will work best. 391's do work for a wide variety.

Shift points will need adjustments, as well as speedo.

62nalide · 04-23-2020, 08:11 AM

I saw a solid .15 gain going to 3.91s on a H/C setup 2mph gain

StingrayblueSS · 06-06-2020, 01:53 AM

Quote:

Originally Posted by 62nalide

I saw a solid .15 gain going to 3.91s on a H/C setup 2mph gain

I thought mph would drop with 3.91s?

04-21-2020, 11:15 PM	#1
dadsz28 Drives: 5th gen pending Join Date: Jun 2018 Location: south jersey Posts: 27	Et difference with 3.91s Hey guys I am on the fence on doing 3.91 gears on my cammed and stalled Camaro car runs mid 11s. Can anyone give me what kind of improvement in ET they have gained. From what I gathered around .2 tenths? Figured I would ask for anyone who has done it thanx.

04-22-2020, 08:27 PM	#2
Joe M 2012 2SS Drives: 2012 2SS Join Date: Nov 2014 Location: Shelby NC Posts: 2,549 View My Garage	.150 gain in the 1/8th mile. No 1/4 mile track near where I live. Car runs 7.1-7.3 in the 1/8th depending on prep/DA. I ended up having to remove the first set I put in, Motive. Too much gear whine. Many others have experienced the same regardless of how well they are installed. Went with AAM and they were originally quiet. Developed a slight gear whine over time, but much less than Motive. I'd highly recommend swapping out the factory clutch pack differential with an Eaton True-Trac when you do the gear swap. It will still depend on which cam/stall you have as to what rear end gear will work best. 391's do work for a wide variety. Shift points will need adjustments, as well as speedo. __________________ Roto-Fab intake, SW 1 7/8" LT w/hi flow cats, Flowmaster outlaw exhaust, UDP, 160* stat, Circle D 3200, Moroso catch can, TCI line lock, Zex Nitrous 125 shot, 3.91 gear, Eaton True-trac, DSS 1000hp axles.

04-23-2020, 08:11 AM	#3
62nalide Drives: 2013 SS Join Date: May 2013 Location: DFW Posts: 4,102	I saw a solid .15 gain going to 3.91s on a H/C setup 2mph gain __________________ https://frankensteined.net/ Martin@Frankensteined.net