Differential Ratio Suggestions
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Joined: Dec 2002
Posts: 53
Likes: 0
From: Port Charlotte FL
Differential Ratio Suggestions
Need suggestions for the rear end of my 383/TH350 '76. What would it take to munch on a C5 Z06 and still be very streetable? Will the 3.08 perform with the following...
383
Heads - Wedge/Fully ported, Large Valves, 1.94 intake, 1.6 Exh
6way comp valve job
11:1
Holley 750 DP Mech.
Weiand Stealth Intake, match port
Running 2:1 Cam2 110
Hooker headers, 4" sidepipes
Crane Roller cam, Scorpion 1.5 roller lifters
0.050 lift, Int lift 0.561, Exh lift 0.561, lobe center 116.0, Overlap 22.0, Int Dur. 250.0, Exh Dur. 258.0
Minimum RPM 3700, Max. RPM 7200, Valve float 7800
Specs say 465 HP
TH350
HD rebuild...Kevlar...shift kit...had to replace the 3500 stall...too much for the street. Going with 2500...resetting shift points.
NOS 250 Cheater system
Zip Performance suspension...360 lb. rear spring, etc.
Will be running on 255/45/17 Firehawks most of the time...
[Modified by MGSFJET, 3:04 AM 6/27/2003]
[Modified by MGSFJET, 3:08 AM 6/27/2003]
[Modified by MGSFJET, 3:29 AM 6/27/2003]
383
Heads - Wedge/Fully ported, Large Valves, 1.94 intake, 1.6 Exh
6way comp valve job
11:1
Holley 750 DP Mech.
Weiand Stealth Intake, match port
Running 2:1 Cam2 110
Hooker headers, 4" sidepipes
Crane Roller cam, Scorpion 1.5 roller lifters
0.050 lift, Int lift 0.561, Exh lift 0.561, lobe center 116.0, Overlap 22.0, Int Dur. 250.0, Exh Dur. 258.0
Minimum RPM 3700, Max. RPM 7200, Valve float 7800
Specs say 465 HP
TH350
HD rebuild...Kevlar...shift kit...had to replace the 3500 stall...too much for the street. Going with 2500...resetting shift points.
NOS 250 Cheater system
Zip Performance suspension...360 lb. rear spring, etc.
Will be running on 255/45/17 Firehawks most of the time...
[Modified by MGSFJET, 3:04 AM 6/27/2003]
[Modified by MGSFJET, 3:08 AM 6/27/2003]
[Modified by MGSFJET, 3:29 AM 6/27/2003]
Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
Re: Differential Ratio Suggestions (MGSFJET)
Street and strip? Consider 3.70s.
Lots of freeway driving? Stay with 3.08s.
Some people say 3.55s are about the best "all-around" gear with a TH350 if you do a real mix of all of the above. Just depends on what you want.
Your call.
[Modified by The Dude, 9:31 AM 6/27/2003]
Lots of freeway driving? Stay with 3.08s.
Some people say 3.55s are about the best "all-around" gear with a TH350 if you do a real mix of all of the above. Just depends on what you want.
Your call.
[Modified by The Dude, 9:31 AM 6/27/2003]
Le Mans Master
Joined: Apr 2000
Posts: 7,562
Likes: 9
From: B'Ville NY
Cruise-In III Veteran
St. Jude Donor '05
Re: Differential Ratio Suggestions (MGSFJET)
Im my opinion, 3.55 mmis a nice all around ratio that allows both improved performance off the line & still allows some freeway driving. I've driven my car on the freeway with my 3.90's and it can get to be a bit rough without an O/D gear ;) .
Advanced
Joined: Jun 2003
Posts: 74
Likes: 0
From: Santo Domingo DR
Re: Differential Ratio Suggestions (wayne_69_427)
The 3.55:1 is the intermediate between a long and a short ratio.
I changed from 4.11 to 3.55 on my 396 Z11 Camaro. One of the first things I noticed was that the fuel consumption decreased. Then, less shifting and higher speeds on less rpm. I'm really happy with this combination, and that's the one I just installed on my 68 vette now. Again as everybody says for cruising keep the long ratio (under 3.55's) :thumbs:
I changed from 4.11 to 3.55 on my 396 Z11 Camaro. One of the first things I noticed was that the fuel consumption decreased. Then, less shifting and higher speeds on less rpm. I'm really happy with this combination, and that's the one I just installed on my 68 vette now. Again as everybody says for cruising keep the long ratio (under 3.55's) :thumbs:
Le Mans Master
Joined: Nov 1999
Posts: 5,768
Likes: 3
From: San Diego CA
Re: Differential Ratio Suggestions (The Dude)
Street and strip? Consider 3.70s.
Lots of freeway driving? Stay with 3.08s.
Some people say 3.55s are about the best "all-around" gear with a TH350 if you do a real mix of all of the above. Just depends on what you want.
Your call.
[Modified by The Dude, 9:31 AM 6/27/2003]
Lots of freeway driving? Stay with 3.08s.
Some people say 3.55s are about the best "all-around" gear with a TH350 if you do a real mix of all of the above. Just depends on what you want.
Your call.
[Modified by The Dude, 9:31 AM 6/27/2003]
3.55:1 is a great all-around gear - consider a overdrive tranny and 3.70 - 4.11 rear for best results.
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Re: Differential Ratio Suggestions (MGSFJET)
For decent rear gears to be streetable, especially if you like to cruise on the highway, you might wanna look into an O/D trans/gear swap. The 3.90/2004r setup I got is pretty sweet. 2250rpm@65mph in 4th. Tons of TQ from the hole. Only challange is to get the tires to stick.
:smash: :cheers:
:smash: :cheers:
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Melting Slicks
Joined: May 2000
Posts: 2,305
Likes: 5
From: Orlando,Fl,USA
Re: Differential Ratio Suggestions (Jvette73)
I'm so sorry I didn't swap out to a 200r or 700r o/d tranny. The first gear ratio on these units combined with a higher than 3:08 rear would give you the best of all worlds. Traction would be an issue. Next time..
Race Director
Joined: Jan 2003
Posts: 15,176
Likes: 88
From: State of Confusion
Re: Differential Ratio Suggestions (MGSFJET)
If it's not TOO late, get a set of TCI extra-low gear-sets for a THM350. I run 'em in my THM400 in my Z28. 1st is 2.75 (stock is 2.48), 2nd is 1.57 (stock is 1.48). It'll give you 11% more gear in first; my 4.11s launch like 4.56s; the 4.56s launch like 5.13s, yet High (3rd) remains 1-to-1. 3.08s would 'feel' like 3.40s; 3.36s would be 3.73s; 3.55s would be 3.90s; 3.70s would be 4.10; 3.90s would be 4.30s. Don't worry about the wider RPM drop-off; I'd think your 'long arm', and the N2O, would make PLENTY of torque to 'pull' the drop-off. I'm guessing 3.36s with 2.75:1 1st gear ratio is :thumbs: :thumbs: :thumbs:
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Differential Ratio Suggestions (Glensgages)
Your running a mismatch of parts.
tiny valves make for low rpm motors
Very radical cam for high rpm
Low stall and low 3.08 ratio will never have you in the power range.
I'm not saying that it can't be done, but i never had TH350's last very long shifting at high rpm at WOT. 4-5 speeds would work very nice with a 3.08
tiny valves make for low rpm motors
Very radical cam for high rpm
Low stall and low 3.08 ratio will never have you in the power range.
I'm not saying that it can't be done, but i never had TH350's last very long shifting at high rpm at WOT. 4-5 speeds would work very nice with a 3.08
