Gear ratios

I'm swapping out my 7.25" rear end for a 9" rear end I bought. I, like others, want to reduce my RPMs at highway speed with the new rear end. I'm unable to decipher the printed numbers and letters on the metal tag on my old rear end, so I don't know what gear ratio it has. See the attached picture for the tag on the differential housing on the 9" rear end.



It appears to be a 3:1 gear ratio. From what I've read, a 3.5: 1 is the "best" gear ratio for lowering highway RPM while not having to resort to 2nd gear on too many hills. I have 16" wheels on the back, but with my low profile tires the outside diameter of my tires is about the same as the diameter of a stock 14" wheel and tire I have (25 3/4"). So, I'm wondering if I can get away with the 3:1 gear ratio. Any thoughts?

There are a couple of shops locally that rebuild rear ends and differentials. One of them gave me an estimate of $800 to rebuild the 9" rear end. It's been sitting in a van in a field for 20 years, and I was thinking it'd be good to have it disassembled, inspected and at least have the seals replaced. The $800 price included swapping the ring and pinion gear to make it have a 3:5:1 gear ratio. He said if that wasn't needed it'd be $160 less. My neighbor, a car guy asked me, "Is it leaking?" and said if it isn't to just put it in without rebuilding it. If it did  need rebuilding, I'd rather leave that to a pro.

I would try the 3:1. 3.5:1 is to low imo for highway speeds w/o OD.  

With your wheels you'll be running around 2750rpm @ 60mph with a 3.5:1

w/ a 3:1 you'll be @ 2350rpm @ 60mph

w/ a 3.25:1 you'd be @ 2550

@ 65 your pushing around 3000 rpm w/ a 3.5:1 rear

This website has a good ratio calculator:
http://www.grimmjeeper.com/gears.html

After running the 3:1 you'll have a better idea of what you want and where you're at. If you do alot of highway driving, you may want to go higher, like to a 2.7:1

You truck likely has a 3.5:1 in it now, but it may have a 4:1. What does your vin tag state? It should state the ratio that came from the factory in your rig. The rear may have been swapped, but it's unlikely. Also you can check it manually by jacking up one tire, mark the pinion and snout and the tire and fender. Rotate the tire twice and count the number of turns @ the pinion. If the pinion turns 3 1/2 rotations with 2 complete tire rotations you have a 3.5:1 ratio

As far as the rebuild goes I wouldn't have them rebuild the chunk. Instead, pull the axles and have the bearings replaced, clean the inside of the housing thoroughly and have the housing and the brake backing plates blasted and powder coated. Unless water has gotten into the differential the 3rd member is probably ok, you could visually check it out or take it to someone to check out. They are generally indestructible behind a small six or even a 300. That's why they are the go to differential in racing. Then rebuild the brakes completely and slap it all back together with new axle seals and fill it with fresh 80/90 weight. If there is a problem with the 3rd member or you want a different ratio, it's actually cheaper to buy one than to have your ring and pinion swapped and the 3rd member rebuilt. And the beauty of buying another one with a different ratio is you can swap it back out if you don't like the results with the new ratio.

Thanks Seth. Good info. Forgot to mention, I have a 200 ci engine too, so I suspect it could drive the 3:1 OK.

Seth G wrote:I would try the 3:1. 3.5:1 is to low imo for highway speeds w/o OD.  

With your wheels you'll be running around 2750rpm @ 60mph with a 3.5:1

w/ a 3:1 you'll be @ 2350rpm @ 60mph

w/ a 3.25:1 you'd be @ 2550

@ 65 your pushing around 3000 rpm w/ a 3.5:1 rear

This website has a good ratio calculator:
http://www.grimmjeeper.com/gears.html

You truck likely has a 3.5:1 in it now, but it may have a 4:1. What does your vin tag state? It should state the ratio that came from the factory in your rig. The rear may have been swapped, but it's unlikely. Also you can check it manually by jacking up one tire, mark the pinion and snout and the tire and fender. Rotate the tire twice and count the number of turns @ the pinion. If the pinion turns 3 1/2 rotations with 2 complete tire rotations you have a 3.5:1 ratio

As far as the rebuild goes I wouldn't have them rebuild the chunk. Instead, pull the axles and have the bearings replaced, clean the inside of the housing thoroughly and have the housing and the brake backing plates blasted and powder coated. Unless water has gotten into the differential the 3rd member is probably ok, you could visually check it out or take it to someone to check out. They are generally indestructible behind a small six or even a 300. That's why they are the go to differential in racing. Then rebuild the brakes completely and slap it all back together with new axle seals and fill it with fresh 80/90 weight. If there is a problem with the 3rd member or you want a different ratio, it's actually cheaper to buy one than to have your ring and pinion swapped and the 3rd member rebuilt. And the beauty of buying another one with a different ratio is you can swap it back out if you don't like the results with the new ratio.

That tag says it is a 3:00 ratio.

See all of the vintage Econoline axles here:
http://econoline.org/axle.php?s=code

I watched this video:

https://www.youtube.com/watch?v=iPvCpb8HsUI

Seth, the seals you suggest replacing are at the ends of the housing right? Any way to point me to the specific ones I should buy?

So I guess I'll only need to bring the axles to a shop rather than the whole rear end, correct?

With the brake rebuild, think it's worth replacing the steel brake lines attached to the rear end?

Yeah, you may as well replace those lines and the axle vent hose. Yes, the seals go in the tubes, You'll see them in there when you pull the axles to have the bearings replaced. Rock auto lists them as Centric #41765011. I used National seals but I can't find the xref.

A guy at "Rears and Gears" near me quoted me a price of about $400 to put new seals and bearings on the axles, and to pull the 3rd member to inspect it and replace bearings if needed. Plus the cost of the 3rd member bearings if needed. I just schlepped the whole thing to him to have him do it. Told him to leave the axles out when he's done so I can rebuild the brakes more easily. I tried heating up my drums with my acetylene torch to remove them before taking it to him, but they wouldn't come off. He asked me how much I care about the drums in case they break when he tries taking them off. Which leads me to ask which specific parts I'd need to rebuild my brakes. Are these the applicable parts?

https://www.macsautoparts.com/store/rear-brake-shoes-relined-10-x-2-1-2-e100.html/?crosssell=Product_Viewed

https://www.macsautoparts.com/ford_econoline/drum-brake-hardware-kit-front-or-rear.html

https://www.macsautoparts.com/ford_econoline/rear-brake-wheel-cylinder-left-13-16-bore-e100.html

https://www.macsautoparts.com/ford_econoline/rear-brake-wheel-cylinder-right-13-16-bore-e100.html

https://www.macsautoparts.com/store/rear-brake-drum-11-e200-and-e250.html/?crosssell=Product_Viewed

https://www.macsautoparts.com/ford_econoline/brake-backing-plate-gasket-to-rear-axle-housing-379015.html

Anything else I would need?

I bought everything I needed to rebuild the brakes for $125 shipped from Rock Auto including the drums. I'll pull up the invoice later and post the part numbers. I used the "front" finned drums for better cooling and they were cheaper. They are the same size as the ones on a 9" rear.

Awesome, thanks!

Seth G wrote:I bought everything I needed to rebuild the brakes for $125 shipped from Rock Auto including the drums. I'll pull up the invoice later and post the part numbers. I used the "front" finned drums for better cooling and they were cheaper. They are the same size as the ones on a 9" rear.

Right Self Adjuster kit: WAGNER H2515 x1
Left Self Adjuster Kit: WAGNER H2514 x1
Right Wheel Cylinder: DORMAN W37783 x1
Left Wheel Cylinder: DORMAN W37782 x1
Brake Shoes: RAYBESTOS 169PG x1
Drums: CENTRIC 12365007 x2
Brake "Hardware Kit" i.e. springs pins ect.: CARLSON H7142 x1

The only other thing I needed other than some anti-seize were different brake pins. The pins that came with that kit didn't match the originals in length. I went to my local napa with one of my old pins and was able to find the pins I needed. But they did have to get out an old book to find them. So you may want to reuse the old pins if they are reusable. If not, they can be found. They're used on alot of vehicles.

When assembling the brakes it's very helpful to have a picture/diagram of the assy. A color diagram, for the springs. And remember they are mirror images. The diagram will have an arrow to the front of the vehicle. I've seen diagrams of both sides, so start with the side the diagram was made for. And if they aren't mirrored one of them is backwards. Also keep in mind the adjusters are not the same. One has left hand threads and they need to be on the correct side. They both turn the "same" way. Clicks tighten the brakes. Btw, yes it's great to be able to assemble the brakes on the backing plates on the bench before they are bolted on, just remember which one you are working on

Use anti-seize on the threads of the adjusters, all the threads. Also the braided wire for the auto adjusting mech, the guide, ect. Use anti-seize on all the contact points on the backing plates, for the pads and all the mechanisms. And file, grind or sand the brake pad contact points on the backing plates flat to eliminate any grooves that are worn into them. If they are really bad, weld may be needed to fill the grooves before you grind them flat and do that before you have them powder coated or paint them and the brake pad links.

Basically put some anti-seize anywhere anything contacts anything other than the brake shoe to drum contact

As far as the "old" 3:1 9" dif, think 400HP+ easy. It can handle your 100 horses from here to eternity

Thanks again Seth. I just ordered those parts. Looks like it's cheaper than Mac's. In what way did the pins not fit?

I read this guy's page:

http://67fastbackproject.blogspot.com/2015/06/rear-drum-brake-rebuild.html

I think I'm going to do what he did and rebuild one side at a time, and use the other side as a reference. Did you use a tool set with a spring puller, spring compressor, and a pry bar?

I just use vise grips and screw drivers. Watch your eyes! The pins were too short.

nwguy wrote:

I read this guy's page:

http://67fastbackproject.blogspot.com/2015/06/rear-drum-brake-rebuild.html

That's a good guide, but I have at least one problem with it. Why didn't he paint the brake links? They're painted from the factory. They're going to rust badly. The other thing is, if you don't have a sandblaster or know someone who does, it's really cheap to have done. If you were up here I'd do it for you. Nothing preps for paint like sand blasting. I'm sure you can easily find someone near you to sandblast the backing plates and the brake links for $20-40. Or a 6 pack of beer.

I did sandblast and paint my parts.

What color are you going to paint the truck?

Seth G wrote:What color are you going to paint the truck?

Initially I was thinking about dark blue with jumbo silver metal flake with lots of clear coat. Now I'm thinking 2-tone, mainly seafoam green with off-white around the windows. Runner ups are now hot rod orange, or periwinkle like I used when I painted my old Suzuki VX 800:

http://www.outsideconnection.com/gallant/vx/paint/

I've decided to use single stage paint with no clear coat to make it easier to fix chips or scratches.

Have been installing my newly rebuilt 9" rear end, and rebuilt my rear brakes. Aren't they pretty?

Very nice!!!

I love giant 70's flake to. But I'm also not sure I want to run a ride everyday with it I like that periwinkle color on your bike. I've been leaning towards a similar shade of metallic blue or a metallic green. I'd like to do a 2 tone with an off white. I wander back and forth on whether or not I want the 2 tone and how to do it but I definitely want to do the roof.