any boosted guys have 3.91s and want to swap back 3.45? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

Bad70supreme · 01-04-2016, 07:42 PM

Wonder if anyone here with 3.91s are looking to go back to 3.45s? Looking to swap if any interest, I have a perfect working 3.45 diff

Js2fst · 01-05-2016, 09:40 AM

We went to 3.23

fif_gen_powa · 01-05-2016, 04:59 PM

Quote:

Originally Posted by Bad70supreme

Wonder if anyone here with 3.91s are looking to go back to 3.45s? Looking to swap if any interest, I have a perfect working 3.45 diff

1le diffs go for 1200, SS diffs go for 600

good luck finding a sucker to go for that one

BradySS · 01-05-2016, 07:06 PM

I thought you wanted to stay with that gear ratio with the TH400 for the highway. What's making you want to change?

Bo White · 01-06-2016, 11:20 AM

Because 3.91s are fine on the highway

BradySS · 01-06-2016, 11:58 AM

Quote:

Originally Posted by Bo White

Because 3.91s are fine on the highway

I'd prefer 3.91 gears overall for the TH400 considering its tall first gear it helps it get out of the hole but I'd hardly call 3.91s "fine on the highway" for your normal person.

Bo White · 01-07-2016, 01:50 PM

Its equivelent to 3.55s on a old school 1st or second gen Camaro. I know plenty of guys that have DD cars like that with 3.73s including myself.

BradySS · 01-07-2016, 03:26 PM

Quote:

Originally Posted by Bo White

Its equivelent to 3.55s on a old school 1st or second gen Camaro. I know plenty of guys that have DD cars like that with 3.73s including myself.

I knew it would be high as far as rpm because I had a Mustang with a C4 Trans which is like the TH400 with being a 3 speed and 3rd gear being 1.0. I had a 3.73 rear with a 26" tire and freeway wasn't that great. So I'm just going off that but putting it into this calculator found at http://www.csgnetwork.com/multirpmcalc.html

You'll be 3284 RPM at 70mph with a 3.91 and a 1.0 3rd gear and that's if you're running a 28" tall tire. Take into consideration this is calculated without converter slip so the RPM will actually be even higher then that 3284 number.

Is it doable? Yes but not for your average car guy. If you're putting a TH400 into a newer gen Camaro you are not your average car guy. I'd do 3.91s or 4.10s personally.

Bo White · 01-07-2016, 03:52 PM

Correct, th400 swap isnt for the average guy.
Your mustang was the same as my older camaro. I was 3500rpm at 70 with 3.73s and 3000 stall.
My first camaro was a 78 Z28 and it had factory 3.42 and thats just a touch taller than the 3.55 comparison I used.

01-04-2016, 07:42 PM	#1
Bad70supreme Drives: 2010 aqua blue SS/RS M6 Join Date: Feb 2010 Location: plainfield, IL Posts: 2,706	any boosted guys have 3.91s and want to swap back 3.45? Wonder if anyone here with 3.91s are looking to go back to 3.45s? Looking to swap if any interest, I have a perfect working 3.45 diff __________________ 10.91 at 122 H/C stock block N/A

01-05-2016, 09:40 AM	#2
Js2fst 2010 transformer Drives: 2010 ss camaro Join Date: Nov 2014 Location: Lee's summit mo Posts: 591	We went to 3.23 __________________ 2010 transformer, vertical doors, 315nt05 rears, pedders supercar coilovers, hotchkis sway bars, links, adjustable, toe bars, bmr poly cradle bushings, 1le control arms, bmr tunnel brace, bmr subframe connectors. Cam 227/239-623-620@114 Mast medium bore heads, sw 1 7/8 headers, cat delete, x pipe, 3" dynomax true duals, fuel rails, fast 102 intake and NW 102 throttle body, catch can, rotofab cai, shifter, raptor custom shift light. Dss drive shaft, 3.91 gears. 492 rwhp

01-05-2016, 07:06 PM	#4
BradySS Drives: 2010 Camaro 2SS Join Date: Jun 2015 Location: Roy, Utah Posts: 155	I thought you wanted to stay with that gear ratio with the TH400 for the highway. What's making you want to change?

01-06-2016, 11:20 AM	#5
Bo White Drives: 2015 Summit White 2SS 1LE Join Date: Feb 2012 Location: Vance Alabama Posts: 8,018	Because 3.91s are fine on the highway

01-07-2016, 01:50 PM	#7
Bo White Drives: 2015 Summit White 2SS 1LE Join Date: Feb 2012 Location: Vance Alabama Posts: 8,018	Its equivelent to 3.55s on a old school 1st or second gen Camaro. I know plenty of guys that have DD cars like that with 3.73s including myself.

01-07-2016, 03:52 PM	#9
Bo White Drives: 2015 Summit White 2SS 1LE Join Date: Feb 2012 Location: Vance Alabama Posts: 8,018	Correct, th400 swap isnt for the average guy. Your mustang was the same as my older camaro. I was 3500rpm at 70 with 3.73s and 3000 stall. My first camaro was a 78 Z28 and it had factory 3.42 and thats just a touch taller than the 3.55 comparison I used.