View Poll Results: Rear End ratio
3.73
16
84.21%
4.11
3
15.79%
Voters: 19. You may not vote on this poll
Rear End Ratio ?
Thread Starter
Race Director
Joined: Jun 2000
Posts: 10,023
Likes: 657
From: FL
Rear End Ratio ?
All,
Looking for some advice regarding rear end gear ratios.
My '75 was delivered with 3.36 gears and Super T-10 with 2.64 first. This gave me an 8.87 first gear multiplication and 3.36 final drive in 4th.
Back in 2001, I swapped in a Tremec 3550 with 3.27 1st and .68 OD. Ended up with 10.99 first gear multiplication and 2.28 in OD.
Right now, I am about to get a 12 bolt conversion rear with 3.73 gears built. Plan right now is to swap to a T-56 Magnum with 2.66 first and 0.63 OD. This will give me 9.92/2.35 overall ratios. I am concerned that I would be happier with a 4.11 rear which would mean 10.93/2.59 overall ratios.
Other option is to get a TKO-600 with the 3.73 (2.87/0.64) which with a 3.73 rear results in a 10.71/2.39 overall ratios.
Current engine is a warmed over 350 but plans are for a big block swap (debating 454 or 496 right now).
Just looking for some thoughts/options.
Looking for some advice regarding rear end gear ratios.
My '75 was delivered with 3.36 gears and Super T-10 with 2.64 first. This gave me an 8.87 first gear multiplication and 3.36 final drive in 4th.
Back in 2001, I swapped in a Tremec 3550 with 3.27 1st and .68 OD. Ended up with 10.99 first gear multiplication and 2.28 in OD.
Right now, I am about to get a 12 bolt conversion rear with 3.73 gears built. Plan right now is to swap to a T-56 Magnum with 2.66 first and 0.63 OD. This will give me 9.92/2.35 overall ratios. I am concerned that I would be happier with a 4.11 rear which would mean 10.93/2.59 overall ratios.
Other option is to get a TKO-600 with the 3.73 (2.87/0.64) which with a 3.73 rear results in a 10.71/2.39 overall ratios.
Current engine is a warmed over 350 but plans are for a big block swap (debating 454 or 496 right now).
Just looking for some thoughts/options.
Le Mans Master
Joined: Jan 2006
Posts: 6,497
Likes: 136
From: Butler Pa
Without knowing how the car will be driven, nobody can say what is best, let alone what you'll be happy with.
I have a 502 with an M-21 and 3.08 gears. That gives me a 7.75 first gear multiplication and I'm perfectly happy with that. I had 3.55's and 1st gear was useless.
I have a 502 with an M-21 and 3.08 gears. That gives me a 7.75 first gear multiplication and I'm perfectly happy with that. I had 3.55's and 1st gear was useless.
Thread Starter
Race Director
Joined: Jun 2000
Posts: 10,023
Likes: 657
From: FL
Without knowing how the car will be driven, nobody can say what is best, let alone what you'll be happy with.
I have a 502 with an M-21 and 3.08 gears. That gives me a 7.75 first gear multiplication and I'm perfectly happy with that. I had 3.55's and 1st gear was useless.
I have a 502 with an M-21 and 3.08 gears. That gives me a 7.75 first gear multiplication and I'm perfectly happy with that. I had 3.55's and 1st gear was useless.
Thanks for the info. Never owned a big block so used to RPM's vice torque (other toy is a '77 308, 3 liter V-8 that comes alive at 4000 rpm).
Starting to feel that the project is getting away from me. Gary Ramadei is building the rear and we already have the 3.73's on order. Just second guessing my decisions.
Car is a semi-daily driver with enough power to back up the looks. Not looking to go drag racing.
Pro
Joined: Feb 2002
Posts: 730
Likes: 51
From: ATLANTIC HIGHLANDS NJ
So many variables to consider or not yet determined. But, you're talking about probably 500 + Lbs. Torque from a big Big Block. Just in general I would say 3.70 would be overkill.
If your build includes a cam that comes on in the 2000 to 2500 RPM range, low end torque, even a 3.36 rear would be like launching a Saturn rocket.
If your build includes a cam that comes on in the 2000 to 2500 RPM range, low end torque, even a 3.36 rear would be like launching a Saturn rocket.
Pro
Joined: Feb 2002
Posts: 730
Likes: 51
From: ATLANTIC HIGHLANDS NJ
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
7 Bolt-On Upgrades From Extreme Online Store to Level Up Your C6 Corvette
Pouria Savadkouei
Pro
Joined: Feb 2002
Posts: 730
Likes: 51
From: ATLANTIC HIGHLANDS NJ
Le Mans Master
Joined: Jan 2006
Posts: 6,497
Likes: 136
From: Butler Pa
Pro
Joined: Feb 2002
Posts: 730
Likes: 51
From: ATLANTIC HIGHLANDS NJ
Your 10 bolt is fine, but would not hold up too well I think if you had drag radials and were able to hook up and hammered it.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 121
From: Millington Illinois
St. Jude Donor '08-'09
3.73 with TKO600. That said I have the 4.11 with T56. With 2 OD's it is fine but the T56 is more of a pain to install and more $ but Im running N20, total hp 700. Needed stronger trans
Thread Starter
Race Director
Joined: Jun 2000
Posts: 10,023
Likes: 657
From: FL
One reason that I am doing the 12 bolt is that I want this car to rock solid for any future upgrades. I have owned the car for 20 years and plan on owning it another 20+.
The other reason for the upgrade is that the supply of 30 spline spiders has basically dried up. No one is making any more and everything is turned into powdered metal crap made offshore. Richmond Gear has also shut its doors. So, do the upgrade now or maybe never be able to do it. So, I am spring for the full Tom's 12 bolt setup with 30 spline inner and outers and 1350 halfshafts.
Plus, the last used setup that was for sale went for $6k so really just investing the $$$. LOL.
Right now, I am leaning towards 3.73 (original plan). 4.11's would be better for small block that revs but I do so want a big block. LOL.
The other reason for the upgrade is that the supply of 30 spline spiders has basically dried up. No one is making any more and everything is turned into powdered metal crap made offshore. Richmond Gear has also shut its doors. So, do the upgrade now or maybe never be able to do it. So, I am spring for the full Tom's 12 bolt setup with 30 spline inner and outers and 1350 halfshafts.
Plus, the last used setup that was for sale went for $6k so really just investing the $$$. LOL.
Right now, I am leaning towards 3.73 (original plan). 4.11's would be better for small block that revs but I do so want a big block. LOL.
Last edited by SteveG75; Jan 19, 2012 at 11:36 AM.
Melting Slicks
Joined: Oct 2002
Posts: 2,314
Likes: 111
From: St Louis MO
Multiply your first gear ratio by the rear end ratio. A total ratio of 10:1 is ideal - any greater and you won't hook up; any less and you'll wear out clutches from slipping them to start.
Race Director
Joined: Apr 2000
Posts: 17,646
Likes: 189
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Rear is gears are bandaids for no torque. Anyone with 500ft/lbs or more a 3.08 is fine. The best setup would be for you currently is 3.36 and TKO 600 with 2.87 first gear and when you get the torque monster you don't have to change anything. We always worry about the dragstrip then never even go. Spend 5 grand and never go and still no guarantee it won't blow up 
How many post do we get where someone has blown their rear end. I have the Dana 3.08 in mine with tons of torque and HP and yet it works perfect.
Big difference comes when your toting around time and smashing gears at the drag strip becomes 50/50, if you go to strip a couple of times a year a sub 2 second granny launch and then get on it will still get you a good timeslip
How many post do we get where someone has blown their rear end. I have the Dana 3.08 in mine with tons of torque and HP and yet it works perfect.
Big difference comes when your toting around time and smashing gears at the drag strip becomes 50/50, if you go to strip a couple of times a year a sub 2 second granny launch and then get on it will still get you a good timeslip
Burning Brakes
Joined: Apr 2008
Posts: 825
Likes: 40
From: Glasgow, Scotland
All,
Looking for some advice regarding rear end gear ratios.
My '75 was delivered with 3.36 gears and Super T-10 with 2.64 first. This gave me an 8.87 first gear multiplication and 3.36 final drive in 4th.
Back in 2001, I swapped in a Tremec 3550 with 3.27 1st and .68 OD. Ended up with 10.99 first gear multiplication and 2.28 in OD.
Right now, I am about to get a 12 bolt conversion rear with 3.73 gears built. Plan right now is to swap to a T-56 Magnum with 2.66 first and 0.63 OD. This will give me 9.92/2.35 overall ratios. I am concerned that I would be happier with a 4.11 rear which would mean 10.93/2.59 overall ratios.
Other option is to get a TKO-600 with the 3.73 (2.87/0.64) which with a 3.73 rear results in a 10.71/2.39 overall ratios.
Current engine is a warmed over 350 but plans are for a big block swap (debating 454 or 496 right now).
Just looking for some thoughts/options.
Looking for some advice regarding rear end gear ratios.
My '75 was delivered with 3.36 gears and Super T-10 with 2.64 first. This gave me an 8.87 first gear multiplication and 3.36 final drive in 4th.
Back in 2001, I swapped in a Tremec 3550 with 3.27 1st and .68 OD. Ended up with 10.99 first gear multiplication and 2.28 in OD.
Right now, I am about to get a 12 bolt conversion rear with 3.73 gears built. Plan right now is to swap to a T-56 Magnum with 2.66 first and 0.63 OD. This will give me 9.92/2.35 overall ratios. I am concerned that I would be happier with a 4.11 rear which would mean 10.93/2.59 overall ratios.
Other option is to get a TKO-600 with the 3.73 (2.87/0.64) which with a 3.73 rear results in a 10.71/2.39 overall ratios.
Current engine is a warmed over 350 but plans are for a big block swap (debating 454 or 496 right now).
Just looking for some thoughts/options.
good luck
dave
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Since you're pretty well versed in the overall package gearing deal, here's what I've observed. If running a tranny with 1st in the 3's and say 0.70 od top gear, then a mid 3's axle is a hard combination to beat on the street. You pretty much get it all. Good digs on launch, and decent highway cruising.
Burning Brakes
Joined: Dec 2003
Posts: 1,004
Likes: 7
From: Adelaide South Australia
I have a TKO-600 (0.82 OD) fitted with a 383 sb. which lacks torque below 2000 rpm.
I had 3.36 diff initially, but motor didn't feel comfortable.
The overall gearing had me either lugging in 3rd gear, or screaming in 2nd gear in the hills twisties I enjoy driving.... speeds in range 40~70mph.
I changed diff gears to 3.73 and it transformed my entire driving experience.
The gearing now works perfectly for my driving style.
The 3.73 will be good for your 350ci sb.
But as many have already stated, a big block can pull much taller gearing....
You could fit taller tyres when you get the big block to offset the 3.73 gearing if you have issues.
Or better yet, when you build that big block, aim for a spec which pushes peak torque higher in the rpm, thereby keeping torque at lower rpm more manageable, whilst also providing a genuine adrenalin rush when you do get into it.
I had 3.36 diff initially, but motor didn't feel comfortable.
The overall gearing had me either lugging in 3rd gear, or screaming in 2nd gear in the hills twisties I enjoy driving.... speeds in range 40~70mph.
I changed diff gears to 3.73 and it transformed my entire driving experience.
The gearing now works perfectly for my driving style.
The 3.73 will be good for your 350ci sb.
But as many have already stated, a big block can pull much taller gearing....
You could fit taller tyres when you get the big block to offset the 3.73 gearing if you have issues.
Or better yet, when you build that big block, aim for a spec which pushes peak torque higher in the rpm, thereby keeping torque at lower rpm more manageable, whilst also providing a genuine adrenalin rush when you do get into it.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
A lot depends on the torque curve of the prospective engine (and where it falls RPM wise), but FWIW...
TKO 600 w/3.73:
1st - 2.87 = 10.71
2nd - 1.89 = 7.05 (34%)
3rd - 1.28 = 4.77 (32%)
4th - 1.00 = 3.73 (22%)
5th - 0.64 = 2.39 (36%)
TKO 600 RR w/3.73:
1st - 2.87 = 10.71
2nd - 1.89 = 7.05 (34%)
3rd - 1.28 = 4.77 (32%)
4th - 1.00 = 3.73 (22%)
5th - 0.82 = 3.06 (18%)
Richmond SS w/3.73:
1st - 2.89 = 10.78 (optional ratio)
2nd - 1.85 = 6.90 (36%)
3rd - 1.31 = 4.89 (29%)
4th - 1.00 = 3.73 (24%)
5th - 0.77 = 2.87 (23%)
From a strictly performance standpoint, I'd caution going too tall (in 5th) without huge top end HP, and I'd also note how the steps will work out for your intended uses. The 600's 5th gear is fairly tall and a big step, so it's pretty much just for highway cruising.
And, be careful not to build a dump truck motor that's done before the fun really begins.
Oh, and given enough torque and sufficient bite, IMOE one doesn't have to be on slicks or dumping the clutch at insane RPM's to break a 10-bolt. Thus, no regrets for having gone with a 12-bolt IRS conversion (3.55:1 w/Eaton) long ago.
My $.02
TKO 600 w/3.73:
1st - 2.87 = 10.71
2nd - 1.89 = 7.05 (34%)
3rd - 1.28 = 4.77 (32%)
4th - 1.00 = 3.73 (22%)
5th - 0.64 = 2.39 (36%)
TKO 600 RR w/3.73:
1st - 2.87 = 10.71
2nd - 1.89 = 7.05 (34%)
3rd - 1.28 = 4.77 (32%)
4th - 1.00 = 3.73 (22%)
5th - 0.82 = 3.06 (18%)
Richmond SS w/3.73:
1st - 2.89 = 10.78 (optional ratio)
2nd - 1.85 = 6.90 (36%)
3rd - 1.31 = 4.89 (29%)
4th - 1.00 = 3.73 (24%)
5th - 0.77 = 2.87 (23%)
From a strictly performance standpoint, I'd caution going too tall (in 5th) without huge top end HP, and I'd also note how the steps will work out for your intended uses. The 600's 5th gear is fairly tall and a big step, so it's pretty much just for highway cruising.
And, be careful not to build a dump truck motor that's done before the fun really begins.
Oh, and given enough torque and sufficient bite, IMOE one doesn't have to be on slicks or dumping the clutch at insane RPM's to break a 10-bolt. Thus, no regrets for having gone with a 12-bolt IRS conversion (3.55:1 w/Eaton) long ago.
My $.02