Home » Public Forums » GMCnet » [GMCnet] Final Drive. 4:10
| [GMCnet] Final Drive. 4:10 [message #222227] |
Fri, 13 September 2013 00:44  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
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Have a 78 Royale, 403, and the 3:70. Sometimes my GVW is in the 20,000 lbs range. Depending on the trailer I'm pulling. You've herd about how the short stroke, big bore 403 comes into it's own above 3,100 rpm's. So, so true, When I got the 3:70 in 2004. Best change that I ever made to that GMC. The 4:10 wasn't out yet. Engine, and trans run cooler, and my mileage went up. ( Not a lot ) Thinking of selling the 3:70. And going to the 4:10. Most 1 ton trucks run 3:70 tops, to 4:88. You could keep it above 3,100 RPM,s more of the time.When I'm in the mountains. I shift it down. And run it up to 4,500 RPM's. And just leave it there. The trans at that point is running a lot of fluid to that cooler. And the load on pistons, rings, and bearings is reduced. There is 145,000. miles on the clock. Runs great.
Bob Dunahugh GMCMI Member
78 Royale4 Yenko Chevrolet's
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| Re: [GMCnet] Final Drive. 4:10 [message #222245 is a reply to message #222227] |
Fri, 13 September 2013 07:51  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Bob,
The 403 has a shorter stroke than the 455. I can't remember what the stroke of both engines is off the top of my head and I'm too
lazy to look it up at the moment. The shorter stroke of the 403 means you can rev it higher with no negative effect.
However, IMO if you run a 455 at the same RPM ranges as the 403 you will be operating the engine at piston speeds that are not
conducive to long term wear / reliability.
Regards,
Rob M.
-----Original Message-----
From: Bob Dunahugh
Have a 78 Royale, 403, and the 3:70. Sometimes my GVW is in the 20,000 lbs range. Depending on the trailer I'm pulling. You've herd
about how the short stroke, big bore 403 comes into it's own above 3,100 rpm's. So, so true, When I got the 3:70 in 2004. Best
change that I ever made to that GMC. The 4:10 wasn't out yet. Engine, and trans run cooler, and my mileage went up. ( Not a lot )
Thinking of selling the 3:70. And going to the 4:10. Most 1 ton trucks run 3:70 tops, to 4:88. You could keep it above 3,100 RPM,s
more of the time.When I'm in the mountains. I shift it down. And run it up to 4,500 RPM's. And just leave it there. The trans at
that point is running a lot of fluid to that cooler. And the load on pistons, rings, and bearings is reduced. There is 145,000.
miles on the clock. Runs great.
Bob
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Final Drive. 4:10 [message #222307 is a reply to message #222227] |
Fri, 13 September 2013 16:22 |
Ray Erspamer
Messages: 1707
Registered: May 2007
Location: Milwaukee Wisconsin
Karma: -3
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Senior Member |
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Hi everyone. I'm running the 403 with the 3:70. I had posted a short time ago that my mileage goes way up when I travel 70-75 vs 60-65 mph. I finally got my tach and vac gauge hooked up and we're heading out this weekend. I'll record some data at various speeds and let you know how it goes. Who ever said that the 403 comes into it's own above 3100 rpm I feel is dead on, it just seems to smooth out and purr right along.
Ray Erspamer
78 Royale
SeHI e b eryonent from my Galaxy S®III
-------- Original message --------
From: Rob Mueller <robmueller@iinet.net.au>
Date: 09/13/2013 7:51 AM (GMT-06:00)
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Final Drive. 4:10
Bob,
The 403 has a shorter stroke than the 455. I can't remember what the stroke of both engines is off the top of my head and I'm too
lazy to look it up at the moment. The shorter stroke of the 403 means you can rev it higher with no negative effect.
However, IMO if you run a 455 at the same RPM ranges as the 403 you will be operating the engine at piston speeds that are not
conducive to long term wear / reliability.
Regards,
Rob M.
-----Original Message-----
From: Bob Dunahugh
Have a 78 Royale, 403, and the 3:70. Sometimes my GVW is in the 20,000 lbs range. Depending on the trailer I'm pulling. You've herd
about how the short stroke, big bore 403 comes into it's own above 3,100 rpm's. So, so true, When I got the 3:70 in 2004. Best
change that I ever made to that GMC. The 4:10 wasn't out yet. Engine, and trans run cooler, and my mileage went up. ( Not a lot )
Thinking of selling the 3:70. And going to the 4:10. Most 1 ton trucks run 3:70 tops, to 4:88. You could keep it above 3,100 RPM,s
more of the time.When I'm in the mountains. I shift it down. And run it up to 4,500 RPM's. And just leave it there. The trans at
that point is running a lot of fluid to that cooler. And the load on pistons, rings, and bearings is reduced. There is 145,000.
miles on the clock. Runs great.
Bob
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Ray Erspamer
78 GMC Royale Center Kitchen
403, 3.70 Final Drive
Holley Sniper Quadrajet EFI System,
Holley Hyperspark Ignition System
414-484-9431
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