So I am looking at getting a 1975 F600 that has a 4x4 setup. The body and motor of the truck are completely shot so I would be swapping the 4x4 components over to my 1971 F600. The 4x4 truck has set gear ratio's at 7.80 and that would make it a pain to drive at higher speeds (55 mph). Is there a way I can change out the low gears in the two speed under the truck now to make the low range match the front axle. Currently my truck has 5.83/8.11's. Is it possible to change the 8.11's to 7.80's?

 

Perhaps Number Dummy would have the answer. But he will need the truck info: VIN, or the axle info, so he can find out if different gears were available.

 

When referring to gear ratios the lower number is easier to turn. In pickups a 3.00 will run faster at less rpms than a 4.11. From what I know most 4x4 6 wheelers are electric co line workers that 45-50 mph top speed is about all that they are asked to do moving from one job to the next.

No idea of chassis differences but I think it might be easier to move your sheet metal over to the 4x6 chassis.

What is your use goal for the truck when complete?


John

 

2X with John idea of moving the sheet metal over to the 4wd frame.
would be the least problems. Those type of vehicle are not for fast Hwy. traveling.

The front an rear gearing must match while in 4wd and trying to use a 2 spd rear end sounds like a money pit to setup.

Orich

 

Yeah the frame and motor on the 4x4 are junk. Swapping the axles over is really the only option. As for use, it's going to remain a dump truck, mainly used in the woods up north for hauling trees and gravel. And I know the gearing would have to match for the 4x4 to work, that's why I want to see if the low range gearing can be changed. To my understanding the low range on a two speed rear end is planetary reduction. So could swapping the carrier, sun, ring, and planet gears change the 8.11's to 7.80's? Even if I need a lower numerically high range, like 5.13/4.88 to do so that's not a problem. With the 5.83/8.11 setup the truck has currently the top speed is around 60/65, if I have use the 7.80 ratio the 4x4 has I'm assuming the top end speed is going to drop to 45/50 or be redlining the entire time it's driven above that.

 

Forgot I was going to add pictures, the first one is of my '71 dump truck and the second one is of the '75 4x4 (the orange one)

 

Just for giggles I checked the front end for 5.83. I found 7.80 not listed in 1975 "regular production" F600 front drive axles. 6.14,6.20,6.80,6.83,7.17, and 7.20. BTW, Full Time Four Wheel Drive front ends only. On the rear end I would have to find out your tag number or the code on the door warranty (Vin) plate. Different choices. Eaton 15201 or Eaton 16244.

 

I think it would be simpler to use an O/D transmission or an overdrive secondary transmission between the tranny and T-case.
Jeff, didn't know Ford offered the front axle. My 74 F600 was a Marmon-Herrington, as were the thousand or so other mechanic trucks on the Alaska pipeline back then. Some were F750s too.

 

Yepper. Listed as Rockford FDS-75. D1TD-** and D5TA-*** tag numbers. And yes, as you guessed they started listing them in 1971.

 

FordTruckGuy96, Will you share with us what your plans of use are for the truck?

Your red truck looks decent, frankly I would go slow on the orange one. A lot of work there.


John

 

Plans are just to make the red truck, which has an extremely rusty body 4x4, and the orange truck is to be scrapped minus the axles and transfer case. And currently use it as a trail rig and firewood hauler, though this summer it will help repair the road on my property. Just want the 4x4 for the off chance that I ever get stuck

 

So bottom line is having 4wd is the most important for you.

But you want to fine tune the gearing for a higher top end speed if possible right.

I'd first be working on the change over making the red truck into a 4wd.
and put up the a little slower hwy speeds.

Then if you happen to figure out a way to setup an over drive unit later then it all depends is it worth the extra cost of driving a little faster when you want and how often would you be doing that to make it all worth it cost affective.

Orich

 

Yea right now having 4x4 is the most important, but the truck does get driven for around 50 miles to the nearest "big" city, and as for an overdrive unit, are you referring to a gear vendors? Or did they make extra gears like you would find in a twin stick Pete?

 

Is the tag still on the front drive axle to see what ratio it really is? And the tag on the back axle to identify also.

 

FordTruckGuy96 I have lived in North Carolina all my life, and have no idea what is used in your area. Unlike pickups that are moving towards 4wd, we don't see 6wd trucks on the roads here at all. My house faces a 2 lane road with 24-7 truck traffic, all rear axle pull. We have some large military bases here and I do see current and retired all wheel pull trucks. The ones in use are in a line crew or logging.

Have you considered buying an older Farmall, John Deere, or Ferguson tractor to use for those times when all wheel pull is needed? You possibly could come out ahead going in that direction.

It's your party and your fun so be happy, spend your money the way you want.


John