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| | | | Joined: Mar 2009 Posts: 40 Apprentice | | Apprentice Joined: Mar 2009 Posts: 40 | I rebuilt a 235 from a 55 car and put it in my 62 half ton , I also went to a t-5 from a 92 s-10. the truck is running great but I still get bad gas milage 12 ish mpg. I took it on a long trip this week to go fishing (240 miles round trip) Thats about 60 in gas and it was a beating . I dont have a tach but at about 60-65 it was reving pretty high. My question is can I do the rear end gear swap my self and if so what do I look for? I am not concerned about power I want to cruise comfortably and get much better gas milag. Thanks fellow bolters ! | | | | | Joined: Jan 2001 Posts: 5,337 'Bolter | | 'Bolter Joined: Jan 2001 Posts: 5,337 | Do you know what ratio the OD is in your trans? There are some that are only 10%, those are not much help.
You really need 30%.
See the USA in your vintage Chevrolet! My Blog | | | | | Joined: Mar 2009 Posts: 40 Apprentice | | Apprentice Joined: Mar 2009 Posts: 40 | Yes I just looked it up, my 5th gear is .72 . I also did the axle ratio calculation on deve's web site. It looks like i can do about 67 mph at 2000 rpm if i switch to a 3.55. thats only about 300 rpm difference from 4.11 . would this make much diff in my milage? | | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | The replacement gears for that rear end are3.38. You probably have 3.90 in it now. I don't know what your tire dia. is but I don't think a 235 can pull any higher gears then what you have. If you gear it too high it is unpleasant to drive & will get worse mileage. You might look into the engine for better mileage. Advance the timing a little & make sure the advance mechanism's are working. Check the carb for running rich.
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: Dec 2004 Posts: 1,897 Shop Shark | | Shop Shark Joined: Dec 2004 Posts: 1,897 | It may not help your gas mileage at all. These trucks are as areodynamic as a brick. Slowing down to 55 mph should show you a modest jump in mileage. Tuning your engine, adjusting your valves, and properly jetting your carb will also help.
Does Texas have a winter gas formula? California does and it can affect mileage by up to 25% on older vehicles. | | | | | Joined: Jan 2001 Posts: 5,337 'Bolter | | 'Bolter Joined: Jan 2001 Posts: 5,337 | What carb are you using?
If it is a Rochester, make sure the power valve port on the base is not blocked by the wrong gasket, good for a few MPGs.
See the USA in your vintage Chevrolet! My Blog | | | | | Joined: Mar 2009 Posts: 40 Apprentice | | Apprentice Joined: Mar 2009 Posts: 40 | I am running a rochester , the jet is only one turn out I am finaly getting a nice cinnamon color on my spark plugs. my timing is between 12-14 deg advance. I do have a small air filter on it could that play a part ? Like I said it is running strong so I dont think I can get the engine running any better. The gears were my last hope. | | |
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