Sponsored

Gear Change from: 4.11 (Rear Gear) to: 4.56 in my GT350

eighty6gt

Well-Known Member
Joined
Feb 2, 2018
Threads
3
Messages
66
Reaction score
18
Location
Saskatoon
Vehicle(s)
2008 Bullitt
Bump @JohnVallo when are we going to get the 4.88's in there!!?

I am looking at beater GT350's for a daily in the next while, and am excited to see how these work. Seems really nice according to my gearing calc gsheet. Currently piloting a TVS blown S197, the extra torque from gears in a 350 will probably help me out.

Check out this example, just rub off those stupid tire decals, let the lot guys take it for one last donut and rev limiter session for their instagram, and there you go:


https://www.autotrader.com/cars-for-sale/vehicledetails.xhtml?listingId=508231026&zip=90078&referrer=/cars-for-sale/searchresults.xhtml?zip=90078&startYear=1981&sortBy=derivedpriceASC&incremental=all&firstRecord=0&marketExtension=on&endYear=2020&modelCodeList=MUST&makeCodeList=FORD&searchRadius=0&trimCodeList=MUST%7CShelby+GT350%2CMUST%7CShelby+GT350R&startYear=1981&numRecords=25&firstRecord=0&endYear=2020&modelCodeList=MUST&makeCodeList=FORD&searchRadius=0&makeCode1=FORD&modelCode1=MUST&clickType=listing




Sponsored

 

Lo Pony

Well-Known Member
Joined
Dec 17, 2015
Threads
5
Messages
308
Reaction score
119
Location
W. VA.
First Name
Take me home
Vehicle(s)
86 GT, red; 88 LX 5.0, black; 95 GT black; 99 Cobra with mods (still own); ‘16 GT, PP, manual, Ruby, drivetrain vibration!; Traded for ‘19 GT, A10, velocity blue, love it.
Great work and interesting technical read gentlemen. Have fun and keep the posts coming on these and other issues.
 

matthewr87

Well-Known Member
Joined
Oct 13, 2013
Threads
67
Messages
998
Reaction score
1,325
Location
Maryland
Vehicle(s)
2018 GT350
Damn. Very impressive. The amount of time and effort it takes to do this properly really cements how poor my decision was to bring my 2012 into the dealership to fix the 3.73 gear whine. That set off a 2 year saga of vibration, more whine, and other drivetrain issues that still have not been totally ironed out to this day. Will never be making that mistake again.
 

Goodiedutch

New Member
Joined
Jun 21, 2019
Threads
0
Messages
1
Reaction score
0
Location
United States
Vehicle(s)
2017 mustang
Damn. Very impressive. The amount of time and effort it takes to do this properly really cements how poor my decision was to bring my 2012 into the dealership to fix the 3.73 gear whine. That set off a 2 year saga of vibration, more whine, and other drivetrain issues that still have not been totally ironed out to this day. Will never be making that mistake again.
I personally use the dealership for one purpose only and that is to purchase the automobile , after that the dealership never touches it again ! The dealership in my opinion is not a repair shop and is there one purpose and the original purpose to sell a car not to fix them . That's My opinion .
 

Sponsored

stephenj37824

Member
Joined
Dec 9, 2019
Threads
0
Messages
5
Reaction score
1
Location
Tennessee
First Name
Steve
Vehicle(s)
2019 GT350
Awesome. So redline in first only moves from 55 down to 50... that's less than I would have thought.
Unfortunately I see a mistake. I was about to pull the trigger on the 4.56 when in this chart I realized you used 4.09 as final drive. These numbers are from 4.09. They look promising honestly. NA it would seem you will cross the 1/8 topping 3rd and the 1/4 topping 4th. 4.56 would add another gear change into the 1/8. I doubt the extra 60ft time savings would make up for the gear change. In the 1/4 4.56 or 4.30 may be better.
 

MAV

Well-Known Member
Joined
Aug 18, 2015
Threads
19
Messages
586
Reaction score
346
Location
Arkansas
First Name
Mark
Vehicle(s)
2016 Shelby GT350
Yep, you're right...never noticed that. Let me dig up that spreadsheet and check the calculations. I'll repost the results once corrected.
 

Spart

Well-Known Member
Joined
Jul 29, 2016
Threads
18
Messages
1,205
Reaction score
577
Location
Iowa
Vehicle(s)
17 GT350
Unfortunately I see a mistake. I was about to pull the trigger on the 4.56 when in this chart I realized you used 4.09 as final drive. These numbers are from 4.09. They look promising honestly. NA it would seem you will cross the 1/8 topping 3rd and the 1/4 topping 4th. 4.56 would add another gear change into the 1/8. I doubt the extra 60ft time savings would make up for the gear change. In the 1/4 4.56 or 4.30 may be better.
I came up with my own spreadsheet the other day to see what effect different tire sizes and rear end gears would have.

This is shared read-only, but feel free to copy it to your drive (File -> Make a copy) so you can play with the values.

https://docs.google.com/spreadsheets/d/1BYW5L86gdd_GN4Mzxqgrn3KZujhrSJbyzlWQVYLs0bo/edit?usp=sharing
 

MAV

Well-Known Member
Joined
Aug 18, 2015
Threads
19
Messages
586
Reaction score
346
Location
Arkansas
First Name
Mark
Vehicle(s)
2016 Shelby GT350
Corrected the original post.
 

Hack

Well-Known Member
Joined
Nov 26, 2014
Threads
83
Messages
12,283
Reaction score
7,445
Location
Minneapolis
Vehicle(s)
Mustang, Camaro
I adapted this spreadsheet from another one I found on the 'Net...
View attachment 322796

EDIT: Corrected for 4.56 gears.
gears.JPG
4.56 looks like a pretty good ratio for straight line acceleration and street driving. I bet they would make the GT350 a lot more violent and entertaining especially on the street.
 

Sponsored

Spart

Well-Known Member
Joined
Jul 29, 2016
Threads
18
Messages
1,205
Reaction score
577
Location
Iowa
Vehicle(s)
17 GT350
4.56 looks like a pretty good ratio for straight line acceleration and street driving. I bet they would make the GT350 a lot more violent and entertaining especially on the street.
Only thing I dislike about 4.56 is you go from doing 2193rpm in 6th gear at 74mph to 2681rpm.

4.11 is a bit more reasonable at 2417rpm.

(My spreadsheet I linked has a calculation for that if you want to check out other gear ratios.)
 

Hack

Well-Known Member
Joined
Nov 26, 2014
Threads
83
Messages
12,283
Reaction score
7,445
Location
Minneapolis
Vehicle(s)
Mustang, Camaro
Only thing I dislike about 4.56 is you go from doing 2193rpm in 6th gear at 74mph to 2681rpm.

4.11 is a bit more reasonable at 2417rpm.

(My spreadsheet I linked has a calculation for that if you want to check out other gear ratios.)
I think it's an advantage having a few more RPM in 6th gear. Rather than having to hold in 5th until 65 or greater, you can cruise in 6th a little more often. I always thought 6th was too tall. One of the things I was always conscious of was trying to avoid lugging the Voodoo. I don't think the Voodoo likes to be loaded up at 2,000 rpm or less - especially in 5th or 6th gears.
 

DCShelby

Well-Known Member
Joined
Jan 24, 2019
Threads
17
Messages
1,131
Reaction score
839
Location
DC
First Name
Robert
Vehicle(s)
2018 GT350 Lighting Blue and 2017 Ducati 1299S
I never use 6th gear unless I'm on the interstate all alone and doing 110 or so.....I'd like to see a kit to change the actual 6th gear in the Tremec itself.
 

Spart

Well-Known Member
Joined
Jul 29, 2016
Threads
18
Messages
1,205
Reaction score
577
Location
Iowa
Vehicle(s)
17 GT350
I think it's an advantage having a few more RPM in 6th gear. Rather than having to hold in 5th until 65 or greater, you can cruise in 6th a little more often. I always thought 6th was too tall. One of the things I was always conscious of was trying to avoid lugging the Voodoo. I don't think the Voodoo likes to be loaded up at 2,000 rpm or less - especially in 5th or 6th gears.
I never use 6th unless I'm on the interstate with cruise on.

That said, I don't want it to drone when I do.
 

Hack

Well-Known Member
Joined
Nov 26, 2014
Threads
83
Messages
12,283
Reaction score
7,445
Location
Minneapolis
Vehicle(s)
Mustang, Camaro
I never use 6th unless I'm on the interstate with cruise on.

That said, I don't want it to drone when I do.
I never had a problem with drone. I assume you changed the exhaust?
Sponsored

 
 




Top