| [GMCnet] Interesting mileage comparison. A no tech post. [message #367023] |
Sun, 03 October 2021 02:16  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma:
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Senior Member |
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Both GMCs are very well maintained. Didn't really want to post this. But I find this too fascinating. Sorry.
Got this 76 GMC for our daughter last May. Our 78 GMC Royale Heavy
76 -455 10,500 LBS X 78 -403 12,000LBS
Towing a Tracker 2,900LBS. 4 down. X Towing a Chavy Uplander Van 5,350 LBS. On a Dolly. Total GVW 13,400 LBS X Total GVW 17,350 LBS.
Engine milage 18,000 Engine mileage 38,000
Howell EFI EBL Howell EFI EBL
No cold air induction in grill X Cold air induction in grill
Synthetic Engine oil X Standard mineral oil
E-85 gas E-85 gas
Headers X Stock exhaust manifolds
3-inch exhaust system X 2.5- inch stock exhaust system
3:42 Final Drive. X 3:70 Final Drive
One A/C unit on roof ( Wind Drag. ) X Two A/C units on roof. ( Wind Drag. )
Trip speed. Mostly 65 to 70 Trip speed. Mostly 65 to 70
Larger outside rear-view mirrors Same larger rear-view mirrors
Lt 225/75 R 16s LT 225/75 R 16s
Tire pressures at 60 PSI Tire pressures at 60 PSI
Aluminum 16 rims Aluminum 16 rim
Cruise control used Cruise control used
Center axle disc brakes Linz Center axle disc brakes Harris
8.9 MPG X 9.3 MPG.
No real point to be made. Just interesting. the X makes note. That of those differences. To me. Seeing that the 403- 3:70 FD. Got better MPG. And pulling just under 4,000 LBS more. Then the 455- 3:42.
It's been noted many times. That the 403s love RPMs. I pull my 24 ft enclosed race trailer a lot. With a GVW of around 24,000 LBS. That's like pulling another complete GMC along as a trailer. People on this site. Have seen that trailer at some GMCMI events. With that trailer. I generally keep the RPMs above 3,000. Plus. Those higher RPMs help keep trans temps lower. I rebuilt that trans myself in 2004. Has over 100,000 miles on it. All is still well.
Bob Dunahugh
78 Royale since 2003
4 real COPO Yenkos
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