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| | | | Joined: Jan 2015 Posts: 4 New Guy | | New Guy Joined: Jan 2015 Posts: 4 | I am restoring a 64 Chevy C-10. I have a 350 motor and a 700R4 transmission. The rear I have is a 3.42. Is that a good combination? I'm looking for something with good highway speed and lower rpm's. Not looking to race it. | | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 |
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: May 2001 Posts: 7,438 Extreme Gabster | | Extreme Gabster Joined: May 2001 Posts: 7,438 | That would give an OD ratio of about 2.40. That sounds high geared to me. | | | | | Joined: Feb 2000 Posts: 5,198 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 5,198 | Here is a bunch of good information, http://www.jalopyjournal.com/forum/threads/[censored]-poor-mileage-from-a-700r4.972740/I would think a 3.73 or 3.90 would be a much better choice. You have a heavy truck that is going to push a bunch of air at highway speeds, so if the motor doesn't make all its torque at very low rpm, you are going to have trouble with downshifting and poor milage. joe | | | | | Joined: Jan 2008 Posts: 4,961 'Bolter | | 'Bolter Joined: Jan 2008 Posts: 4,961 | You must remember that carbureted engines are happier at about 500 to 1000 RPM more than today's EFI engines. A 3.42 with OD would only run good down hill or with a strong tail wind. | | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | I have 3:38 rear gears in my 56 & a t5 with .73 O-drive. 350 stock engine. It will run up hill on the freeway all day long with out bogging. I had a 70 stepside with 3:08 gears, 350 engine & 700R4 trans. I have a long hill on the freeway going home from the shop. It will pull it at 70 MPH in o-drive with A/C on. These 350 engines have a lot of low speed grunt unless a guy puts too much cam in it.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Jan 2015 Posts: 4 New Guy | | New Guy Joined: Jan 2015 Posts: 4 | Thanks for the info. Right now I will try the 3:42 rear. Once I get this baby running, I think I might move to the 3:73. Everyone I spoke with said that would be the better choice. | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | The 3.42 might be good swapping material, too, although not many mountains in MD.
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Feb 2014 Posts: 48 Wrench Fetcher | | Wrench Fetcher Joined: Feb 2014 Posts: 48 | I would think you would want to account for you tire size when you are doing this too. Without putting the tire size into the equation, you cannot get an accurate final reading of what your rpm's will be. There are all kinds of rpm calculators on the interwebs. They figure out your engine rpm based on tire size, transmission gear ratio, and rear-end gear ratio. I did a bunch of this when I changed out my 3 speed for a 5 speed on my car.
Matt
Blacktop Cannibals Car Club
1954 Chevy mild custom car
1955 Chevy second series 3200
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