Hey guys,

I am told by the PO that the differential is missing a tooth on the main ring. He says I need to change the whole rear end and that it will involve welding. Is he right or can I find a bolt-on replacement? Do I need to have the spring pads welded at the top of the springs, or what? And should I replace the rear brakes as while I have it all apart?

Thanks!

tyler

 

I know there are some threads on what rear ends will pretty much bolt right on....Of course you have to have 25 posts to search I think. Let me look.

Maybe someone smart will show up before I find anything.

By the way congrats on the new purchase. It's going to be a great experience for you and your son.

 

Hello, Welcome to the forum. That coil spring is not stock or required. It might uncover the fact that your springs may be shot and that is why they installed the coil. Check out the other threads on substitution rear axles and differentials that will work. It will also likely give you a more highway gear, particularly if that rear is not the 3.92, but is the higher ratio. I hope that this helps and you will really love the journey. I am! Ciao, Steve

 

You have a lot more problems with that setup than just the "missing tooth"...what are your plans for this truck? The reason I ask is because if you are going to build it into a reliable driver then you may want to pull out the whole assembly...shocks, springs, brakes, rearend, etc and replace them with new parts. That muffler clamp setup for the shocks is kinda scary in itself. Good luck...

 

I can't imagine how the po knows there is a tooth missing on the ring gear. That rear access panel hasn't been off in ages.....

The only rear that is totally bolt in, no welding is an original 48-52 F1 axle.

Ford 9" rear end from 57-66 F100 is almost bolt in, requires a driveshaft adaption to add approx 1.25" Also need to do something with spring plates and larger U bolts due to the larger axle tubes
Ford 9" rear from 67-72 has wider brakes, but takes more fabrication on the shock mounts in addition to the above mods.

Others will work, but mods are similar to the last one.

Yes, replace everything on the brake system. ... stopping is more important than going.

 

Yeah Charlie, I think that is the realistic plan. Pull out all of it and put in new stuff.

t

 

I did a rear end swap on my '48 F1 as well..
Hang on there a second on dissing the coil springs guys - I have a question... I am only a lil bit familiar with the "Heavy Half" (overbuilt half ton), but my rear end looked dang similar to his and I believe mine is a heavy half. Instead of 8 leaves there are 9, plus secondary coil. If a guru of the heavy half can comment I would like to hear. I have this hunch we may be looking at a heavy half in this picture.

All of these old F1 (the half ton) in this forum's years, use 5 on 5 1/2 bolt spacing with a 61 1/4" wide rear end.

That said, a ford 9" rear end from 57-72 is "a direct bolt on" (for me) no fabing clamps, no fabing shock mounts, etc. I went to the junkyard and found 6 choices on my first day out, picked the 72 (which has auto adjusting brakes), and then went for the gear ratio which would give me the desired highway speeds (driving it home was 43mph redlined the whole way on the tall gears in a dana/spicer 41). I picked a 3.00 ratio.

The 9" rear end has a 3" tube (you need 3 inch U bolts) and my '48 dana/spicer was 2 1/2", so be sure to take the U bolts and top plates with you if you get a junk yard salvage. (take penetrating oil, a very large long breaker bar, some bandaids for the knuckles, and if you got (and the junk yard will let you in with it) a little propane bottle to heat up the nuts and bust em loose, they are a BEAST.

The one thing that did not work perfectly, my shock mounts were wider, so the bolt ran through the mount, shock, mount. Now they use a long bolt and go mount, (dead air), mount, shocks.

Before you pick a rear end and haul it out, figure out what your gear ratios are for every gear in the tranny, figure out your tire size (I am currently looking for 225/70/16 as that is 28.4" the same as my original 6.00x16 tube. And then plug those numbers into a ratio calculator: Gear Ratio Speed Calculator<table style="width: 132px; height: 20px;" border="0" cellpadding="0" cellspacing="0"><col width="132"><tr height="17"> <td style="height: 12.75pt; width: 99pt;" height="17" width="132">
</td></tr></table>Be sure you want that gear ratio before you haul it out and decide you really wanted a shorter or taller set of gears.

Feel free to PM me or post here (I prefer to share with all) if you have more questions on this, I have more calculators and such helped me with the decisions. The Locker or limited slip differential are preferred both by racers and because you have better traction in wet/snow don't get stuck as easy. So look for an L in the tag - 3L00 instead of 3.00 Very little chance of finding in trucks as all the lockers were in cars (wrong width) and bigger trucks (dana 60 rear ends etc - no Ford 9").

 

mtflat, the PO owned the car since about '58. He says the differential rumbles/growls and you can feel it when the broken tooth spins through. But I am sure you are right that the diff hasn't been opened in years--1985 at the most recent I would guess. He may have looked at it back then and that's why he parked it.

So it sounds like the rear end will require welding after all.

 

Hey Tyler,
I went with an 8.8 Explorer Axle - You get nice disc brakes with that one - Plenty of them out there - I don't think I paid more than $125 for it & I got the Ebrakes as well. It does require some welding to adjust where the shock mounts are mounted - not a huge job - you can get somebody to come by & take care of it for you if you aren't equipped to weld.

If you are going to put in a Mustang II front suspension at some point you might want to look at the 8.8 rear ends so the wheels match up in front & back. Just more things to think about - Welcome aboard...

Changing out the rear end is good first step - it's much more straight forward than replacing the front suspension/axle. If you are going to take the bed off to do the job you might consider doing the gas tank relocation while you are back there...

Ben in Austin

 

Oh, a thought for you on time/ difficulty, it took me a full saturday at the junk yard to find and pull the old (no heat, and short breaker bar), a half of sunday to pull the dana 41, and a half of sunday to put in the 9". So as far as difficulty, this was 10 nuts, 2 bolts, a brake hose, couple e-brake clips, a couple dozen shots of PB blaster - this is not a 100 little fiddly pieces hard project.

If you go to a junkyard that has lots of choices, then buy it as a "complete rear beam" (agreed $125 is right on price), and take the best brakes shoes / hubs you can get... The 72 I picked had both the best set of brakes and the best ratio, so I got basically brand new brakes as a bennie.

This is a one weekend project - as long as you push to get up early, don't spend 2 hours drinking coffee first, and work hard you can certainly get it done in one.

 

If you look at the shop manual and operator's manual, there was no such truck as a Heavy Half. Here are the designations for 1948 US trucks.

F1 half ton
F2 3/4 ton
F3 heavy 3/4 ton
F4 one ton
F5 1 1/2 ton
F6 two ton
F7 two and a half ton
F8 3 ton

All F1's had 8 leaves up front and 10 in the rear. The coil spring "helpers" were probably added in the 70's and purchased from JC Whitney. I bought a set for my 77 F100 back then that looked just like those... and just as worthless. Instead of adding usable payload, the spring pack bottoms out creating a solid pack between the axle and spring. Talk about a rough ride!

Ford's helper springs were flat leaf packs located above the regular springs.

Very nice 51 tyler - looks like a great solid project - even 5 star deluxe trim. Has a few mods - I wonder what that radio and panel came from?

 

F150 so called 'heavy half ton' introduced in 1975. Only the springs/shocks are different, but these same parts were available on F100's as an option.

 

Nice truck Tyler. For what it's worth, I have 2 original DANA 41 rear ends laying in my shop. You're a long way away. But thought I'd mention it. I can't tell if you still have your original spring hangers or not in those pictures. The stocks were 3.73.

I agree with Mtflat, never heard of a "heavy half" in our period trucks. Sounds like NumberDummy cleared that up.

 

What rear end do you think you want? Here is a great guy that I bought a pair of mirrror from. Who is selling a Dana 40 rear end... 1948 1949 1950 Ford F1 Parts

 

Just some additional info on the u-bolt shock mounts, Ford used that same style of set up on the the super dutys, my '02 F-250 shocks are mounted the same way.

Depending on your plans for the truck, if the gear is missing a tooth, and the truck is mainly going to be a stocker for cruising just replace the ring and pinion. It is not hard to do and you learn more along the way.

Good Luck.