F-Superduty gear change: OD or re-gear?

What tire size, axle ratio and transmission do you have now?

----------------- TheSnoMan.com

265-75-16 tires. Not sure of the axle ratio, but the way I understand it the five speeds have an OD ratio of about .75... did they use more than one tansmission in these?

Lets see, 8k trailer and 5 k in the bed is 13k, the truck weighs what some where around

5,700 lbs? So you combned weight is 28,300 pounds. I'ld say your just about right. peak torque comes in at 2,800 rpm.

Whitelightning

8+5+5.7=28,300? I get 18,700. I presume that you left something out of your thought pattern there. So running that fast doesn't adversly effect the engine life? Anyway, I guess would still like to get the speed down for highway running when empty or light, ect. So I guess the question remains if there is an OD unit that is worth my while.

Thanks

You need to see where you are at now tranny, axle ratio and tires size to properly determine what you be the best path to take. Without knowing this info, anyone that recommands a possible solution for you is not doing the homework.

----------------- TheSnoMan.com

Your right on the math, my oops there should have proof read it better lol. I dont think there is an auxilery over drive unit I would trust with the loads you can carry. and if you regear the axle, then yes, you can get the rpm down for when your empty, but I think loaded you will find yourself sliding out of overdrive and into drive because you'll be lugging the engine. 3,000 rpm isnt going to hurt that rig assuming it wasnt abused in the past, and you maintain it the way ford says to maintain it.. Now then if you really wanted to do some modifying, you might try a 2 or 3 speed "brownie" box. These were used on medium duty trucks years ago and buses. They came in a different configurations, they frame mount, a "jack" shaft went between the tranny and it, and a shortend drive shaft from the brownie to the rear diff.. You would then end up with 8-12 foreward gears, and 2-3 reverse. They weigh as much as your tranny, maybe a tad more. Gear Venders says they can handle motorhomes, but most mothorhomes dont get driven that much, and most drivers well, they never ever really stress them that I ever see. Spicer also made aux gear boxes, they were quieter than the brownies (brownies had straight cut gears, and no syncs)

Whitelightning

Seriously, cost effective? no.

Check Trailer Life magazine. I recall a firm that advertises a over drive for diesels. W W

Get your info from the tag on your pumpkin. Reply to me with that info and it will tell me all I need to know about your axle and differential, and then we can see if there is another gear ratio you can slip into for your truck. I think that would be easiest, atleast then you can recal the speedo to be accurate, as long as its a standard gear ratio like 3.55, 3.73, or

4.10..

Ford Tech

If it was anything like my old 96 e-150 van, the vehicle speed sensor reads its signal from a tone ring in the rear differential and will not need recalibrating after a gear change.

Matt, Actually you are right. I was tired and not thinking straight last night.. LOL You wont have to recal anything cause the exciter ring wont change in size, only the number of teeth on the gears you are putting into the rear diff will change... Ford Tech