| [GMCnet] MPG with 3.7 gear ratio (403 engine, hilly conditions) [message #172599] |
Fri, 08 June 2012 14:44  |
Ek_Lektro
Messages: 167
Registered: March 2011
Karma: 2
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Senior Member |
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Maybe i should've used a different subject title for my post,
since it seems to have sparked the 'ole MPG thread... and making sure we're all grounded in reality :)
Even though a particularly trusted GMC mechanic had made the claim that one could get
12 to 14MPG with a 403 / 3.7 combo... I surely wasn't banking on this... though it DID spark my curiosity.
But this was only one part of the inquiry...
I was also checking into the much more serious financial concern
of keeping the transmission alive! ('cause if you do the math,
an extra 1 or 2 MPG would take a LOT of miles to pay for a tranny rebuild...
And... being able to climb hills more like my 455...
well, that'd be a hell of a bonus....
So i'm considering going from a 3.07 to a 3.55 as a bit of a happy medium,
and since 3.55's seem to be more readily available at OK prices.
Any words of advice against the 3.55??
Thanks Ray and Roy, and everybody for your replies...!
Greg
PS: we might not have much to brag about in terms of MPG,
but our solar array is recharging last night's usual battery drain
at 35amps right now... in the clouds!
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> I lived in the LA area for 35 years.I generally tow a boat or a car. In the early days it was always a boat. When I went from the 3:08 gears to 3:21 I picked up better fuel mileage and more pulling power. When I changed to 3:70 gears the mileage stayed about the same but the pulling power was even better. Now that I live in an even bigger Mountain state I'm sure the 3:70 gears would give an increase in fuel mileage over the 3:21 gears. It is no fun to be in low gear going 10 miles an hour an knowing if the pass gets any steeper you ain't going to be able to get over the top.
> --
> Roy Keen
> Minden,NV
> 76 X Glenbrook
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| Re: [GMCnet] MPG with 3.7 gear ratio (403 engine, hilly conditions) [message #172600 is a reply to message #172599] |
Fri, 08 June 2012 15:19  |
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WD0AFQ
Messages: 7111
Registered: November 2004
Location: Dexter, Mo.
Karma: 207
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Senior Member |
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Greg,
With the 403 I believe either 355 or 370 will make you happy. I have one with my 455 but I had to slow way down to keep the rpms under 3 grand. No big deal. Everyone I have known that has one with the 403 loves it. I don't see it being harder but easier on the trans.
Dan
with only 300 watts on the roof and could do with 250
3 In Stainless Exhaust Headers
One Ton All Discs/Reaction Arm
355 FD/Quad Bag/Alum Radiator Manny Tran/New eng.
Holley EFI/10 Tire Air Monitoring System
Solarized Coach/Upgraded Windows
Satelite TV/On Demand Hot Water/3Way Refer
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