Howdy, People.
I'm in the process of replacing the bed slats on my 82 F100, Leroy. I decided that once the bed is done, he's never gonna have to "work" again.


Powertrain: l6/300 in front of a C6. I know he's got a 9" rear end but I need help ciphering the tag.


I'm running P265/70/R15's. He's always been a slow mover and maxes out at around 75mph. (Always auto-dropping back into 2nd at the slightest of freeway incline) I'm pretty sure that I'll be putting on a Clifford 6=8 2x2bbl kit this summer and want some kind of change in the differential for highway as well as backroad and mountain cruising. I seriously doubt that he's ever going to tow anything more than a motorcycle. In addition, I'm wondering about a disc brake conversion but would like to keep the 5x4.5 bolt pattern so I don't have to buy a new set of wheels. Reckon I'm looking at a full axle swap?
I'm asking for input on my axle tag, best all-around change in gear ratio, and a possible recommendation on a direct swap to include gearing/disc brakes.
I'll save the 4X4 conversion for another post.
Thanks in advance.

 

If you are going to do a 4x4 conversion, you might as well do it now and do it once. And with the 4x4 conversion you will not be able to use your rims, so you are going to have to get used to that idea.

Your 4x4 conversion requires the back axle ratio matches the front axle ratio. It will be hard to predict what axle you might end up with, a common ratio is 3.50 or 3.55, but I would wait till you found a donor 4x4. You could install the rearend and the frontend, and drive it around like that as long as you wanted to, and it would work fine till you got the time to swap in the 4x4 transmission and transfer case.

The 4x4 frontend will come with disc brakes already. I would hunt very carefully for a rear disc conversion kit if you wanted to go that route, Some of the kits are not that great and do not have parking brake provisions. The front discs on the stock 4x4 frontend should be all you need.

I am not sure of your time frame and priorities, but I see no use messing with what you have now if you are going to a 4x4 conversion.

 

Need a better pic of the tag can not tell if it is 2.75 or 3.75. ratio I suspect it is 2.75

 

I couldn't find a picture of my tag. His looks about like mine. '82 F100 Flareside. When I looked up my axle code it came back as a 2.75 ratio. Got the same setup, 300 6 in front of a C6. I want to say the high gear ratios were in larger trucks/different applications that year. But been too long since I was looking all that up.

 

Thanks, guys. I'm gonna have to go back one more time and clean up that axle tag. In the meantime, say the 4X4 conversion is just a dream that will probably never come to fruition,
Is the another Ford anything with discs that will direct swap to my truck? I'm thinking 2.75 ratio is what I was told at some time in the past, so any input on a ratio that would me move along a bit
faster would be appreciated. Maybe the Clifford upgrade alone will solve my slow and steady issue?
I'll try and update the tag info tomorrow, truck is offsite at the ex gf's place.

 

Ok will also say it is a 2.75 gear as that's what my 81 w/T18 has. The other I have is a 2.47 w/SROD, both in 81 F100 trucks.

Now running a 300 six is not a speed demon or a power house motor.
From the sounds of it you are almost to the floor with the throttle being you are doing 75 MPH and any little hill it down shifts.
My gut feeling is you are at the max for top end speed. What RPM is the motor turning at 75 MPH speed?

The 2.75 and 2.47 gears are high way gears and will keep the motor RPM lower at higher speeds.
If you where to go for say 3.55 gears the motor would be turning a higher RPM at the same speed as the 2.75 / 2.47 gears are.
The 3.55 gears will pull the truck better from a stop than the other ratios but again with higher RPM at any given speed.

From what I have seen posted the 300 sweet spot is about 1800 to 2000 RPM so you try and gear the truck to run in that sweet spot for the most driving you would be doing. You can run above that RPM and when you hit a hill and the speed/RPM drops down you would be at that sweet spot. If pulling heavy loads you may want to run above the sweet spot as the speed will drop on hills to the point you may need to run a lower gear in the trany.
The 300 will never pull hills like a 460 will at the same speeds and same weights just will never happen. Then again I bet the 300 gets better MPG than the 460 when not pulling loads.
Enjoy the 300 for what it is. May not be fast but it gets the job done!
Dave ----

 

Oh I forgot your truck has disc brakes so why did you ask about them?
I bet your truck has power disc brakes right?
Not long after your year they went to 5 x 5.5 wheel, Non-power drakes are also 5 x 5.5 wheel before that switch.

If it was because you where thinking of a gear swap you don't need to swap the whole thing just the center section of the 9".
Pop the axles out, drive shaft down, undo all the center section nuts and pop it out.
Pop in the new one with sealer, install all the nuts, drive shaft, axles and fill with oil.
Dave ----

 

I'm currently running discs up front and the stock drums in the rear. The brake hardware mounting plate, (backplate) has worn down to nil where the shoes rest/ride.
What I was asking about was a direct swap axle that would include alternate gearing (though your reply sounds as if there's none suggested) and a disc brake setup.
I'll probably just wait until I do the Clifford upgrade and see how it feels on the road. Thanks.

 

That would be the best bet once you do the Clifford upgrade the truck will be less likely to drop down a gear when pulling a grade. Do that upgrade then assess how it is.
A 2.75 is high I would look at a 3.00 or 3.25 personally. In my experience this gives the best balance with cruise RPM's/torque and off line get up and go. Once you step down to a 3.55 it gets bit a buzzy on the hyway.

There are lots options for finding a center member in the 3.00/3.25 range look to cars from the 70's/60's

 

He needs to be careful about some of the 9 inch axles. Some are 28 spline and some are 31 spline. I am going to guess his axle is 31 spline though I am not sure. If it is, the 31 spline axle won't fit through the earlier 28 spline gear set. You can take it to the machine shop and pay them to open up the holes in the 28 spline carrier to accept the 31 spline axle. I did one long ago and I just swapped the carrier plate over and crossed my fingers, it all went together with no howling or gear mesh problems.

 

Being F100 on the 4.5" bolt pattern it will be 28 spline.

 

Are you sure about that bolt pattern?

 

He said in his first post he had the small car pattern wheels.

 

Yep he did say small wheel pattern.
I also hear something about small & large bearing axles too.
If it was me and I was going to change the ratio I would get a complete center section with LS or what ever Ford calls it in the right axle count.

As for the backing plate an easy cheap fix is to pull all the brake parts out, clean off the plate and build up the parts with weld.
Clean up as needed and put the brakes back together. It would not be the first time that has been done.
Dave ----

 

WDM-CL = Ford 9" Rear Axle / 2.75-1 / No Limited Slip / Rear axle parts list #88 = EOTZ-4234-K (replaced EOTZ-4234-H) .. 31 Spline Axle Shafts.

2F29 = Assembled June (F) 29, 1982 (2).

No F100 4WD's after 1976.