FuzzFace2 Posted April 2 Share Posted April 2 Thanks for the tip Gary. I’ll be doing that for sure. And Mat, I might be doing a ZF5 swap since the top loader that’s in there is bad. Got that info from the last owner as I was buying it but at 400 bucks, hey, what are you gonna do? I figure I’d be better off going ahead and changing it out with a better one. I’ve located one at a local pick and pull out of a brick nose that’s on a 4.9 2wd like mine. Plan on yanking the clutch master and slave cylinder, trans crossmember, trans, and flywheel. I have a bead on an 84 clutch and brake pedal assembly to switch over to the hydraulic clutch and I plan on buying the firewall reinforcement panel from bronco graveyard. After that, I’ll reevaluate the gearing in the rear end. Might do a posi diff too unless you guys on here have a better option? As Mat said drive the truck with the 2.47 rear gear to see how it goes even with the ZF5. My 81 F100 parts truck came with a SOD 3sp OD and a 2.47 rear gear. I never drove it, no motor and was rolled over, but my 81 F100 flare side has a NP435 granny 4sp, Advance over drive and a 2.75 rear gear and on the high way at 70 MPH is 1800 RPM. 1800 is the sweet spot for power on the 300 motors. Oh tire size is 235 / 75 / 15 and is a 4x2 truck. Dave ---- Link to comment Share on other sites More sharing options...
Waylon109 Posted April 2 Author Share Posted April 2 As Mat said drive the truck with the 2.47 rear gear to see how it goes even with the ZF5. My 81 F100 parts truck came with a SOD 3sp OD and a 2.47 rear gear. I never drove it, no motor and was rolled over, but my 81 F100 flare side has a NP435 granny 4sp, Advance over drive and a 2.75 rear gear and on the high way at 70 MPH is 1800 RPM. 1800 is the sweet spot for power on the 300 motors. Oh tire size is 235 / 75 / 15 and is a 4x2 truck. Dave ---- Oh yeah I might do that then. I just looked up the ratios for the ZF5 and with the tires I have, at 80 mph and 2.47 gears, I’d be sitting at 1800 RPM. I like that combo. See? That’s why I’m here. So much helpful information and people. Thank you. Link to comment Share on other sites More sharing options...
mat in tn Posted April 2 Share Posted April 2 As Mat said drive the truck with the 2.47 rear gear to see how it goes even with the ZF5. My 81 F100 parts truck came with a SOD 3sp OD and a 2.47 rear gear. I never drove it, no motor and was rolled over, but my 81 F100 flare side has a NP435 granny 4sp, Advance over drive and a 2.75 rear gear and on the high way at 70 MPH is 1800 RPM. 1800 is the sweet spot for power on the 300 motors. Oh tire size is 235 / 75 / 15 and is a 4x2 truck. Dave ---- I also have a 2.47 on the shelf from a conversion that I did. it is an 8.8 size. otherwise, I would put it in my f100. but it is a 9" and has a 2.75. my next best adjustment for it will possibly be 235/75 size tires. however the tires are nearly new, and I will probably put this one up for sale before too long. I'm wanting to build a 4wd and this one is almost completed as a driver. I'm driving it daily and almost have 3k miles on the new engine. Link to comment Share on other sites More sharing options...
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