53 Rear Diff project

[DanOlson]

Since there's too much snow and ice to tempt me to take the Dodge out, I may as well start the rear end project. Plan is to do a complete swap with a Ford 9" (I know I know). I'll remove the extra spring pack and take out a few of the shortest leafs. You can see the 9" sitting on the back of the frame.

Dan

[pflaming]

Others may know but I don't. Why take out the leafs'? Is the axle housing larger? One of the Jeep Cherokee dif's work and I hear the 69 Ferd Country Squire works bolt perfect, why the 9" choice? Rear end is a near future project for me so . . .

PF

[DanOlson]

Main reason for the 9" is availablility. I've had the housing and 3 3rd members around from my Jeep rock crawling days. A new pair of spring perches and I'm good to go.

As far as removing a few of the leafs go, it's for a little softer ride.

Dan

[Young Ed]

I thought the idea was to remove every other leaf for a few. Not to remove all the smallest ones.

[DanOlson]

It may be. I've not heard that before but that doesn't mean anything.

I'll search some old threads.

Dan

[tinlizzy]

does anyone know if this set will work in a 1948 1/2 ton? What would be nessecary to make anyone of them fit?

Lee

[pflaming]

Does one remove the same leafs from the front then also? Would that also lower the truck a bit?

[48Dodger]

Paul, you may not have the extra spring pack Dan has. if you do have them, you most likley will want to take them out. You'll need shorter U bolts. Dan has overload springs which are shorter springs laid on top of the the standard springs. They come with a perch mounted on the frame, one front one back. I imagine you wont be putting any heavy loads in the back of your truck, so the standard leaf springs should be just find.

48D

[pflaming]

Thank you for the clarification. I do NOT have the overloads. Are the springs in a 1/2 T truck about the same as in a sedan? Does a sedan weigh about the same as a 1/2 ton truck. Unless the frames are different, wouldn't the extra body on a sedan and the bed on a 1/2 T would be about the same weight?

Is the steering in the trucks similiar to that in the cars? Seems my '50 Plymouth was a nice steering / driving vehical. As stated in earlier threads, I drove that car from Nebr to CA and back in 1958. It was my college car.

[48Dodger]

Well.....weight distribution (or polar moment inertia), suspension, and tires are a big factor in what you just asked. Our trucks were designed to haul payloads and trailers. Suspension was designed more to go straight than corner. With a large percentage of weight in the front of the truck, the rear live axle (hotchkiss drive) offers very little in the way of ride comfort or suspension perfomance. A sedan has better wieght distribution and lower center of gravity which equals better handling. Suspension geometry is a big subject. Tires, in the opinion of many, are the most important part of the driving experience. Tire height, tread, and ratings, can determine how you tune your suspension. Granted, in a stock B-1-B, there are not a lot of tuning options, but understanding the characteristic of the design you might find a set-up you can live with. What I mean by that is, you're not planning on loading your truck down 99% of the time, keep that in mind when your choosing tires, shocks and leaf springs.

Here's a decent suspension 101 link. http://rqriley.com/suspensn.htm

http://www.popularhotrodding.com/tech/0604_rear_suspension_guide/index.html

My experience in suspension design/geometry comes from stock car racing, not building trucks. But, my 50' will get the best from what a guy going in circles has to offer. lol.

48D

[DanOlson]

Good progress yesterday. Dropped the old diff and slid the 9" housing in. Spring perch spacing is within 1/4" and minor surgery was performed to allow use of narrower u-bolts. I need to find some wedges to straighten the pinion angle. I believe the 9" donor was a Bronco and has a 10 degree PA compared to the 2 degrees on the Dodge.

Dan

[wayfarer]

Be cautious about removing all of the 'short' leaves at the perch. In addition to adding stiffness to the spring directly above, the short leaf keeps the amount of flex, in porportion to its length, to a minimum....when the axle tries to rotate it also tries to make the long unsupported leaf into an 'S'.

An extreme example is GM and their 'mono-leaf' spring, they just made the leaf very thick at centre and tapered to the eyes to control the rate, wrap, et al.

If you really need to soften the ride the best bet is a long discussion with a spring maker. The tapered shims you want will be available at the spring shop or at a decent truck alignment shop.

[DanOlson]

You're right. I spent some time at a spring shop this afternoon having them bend up u-bolts. After discussing my project I decided to take out 2 leaves and see what happens. I'm not too worried about torqueing the springs too out of shape with the flatty still in.

Dan

[grey beard]

please give us a little more info on your Bronco rear swap. Was the tread width similar? How did you fix the 1/4-inch difference in spring saddle width? Whaf ratio did you find and use? Lastly, what modifications were needed at the pinion yoke/prop shaft mating of the original drive shaft and the Bronco rear?

This idea appeals greatly to me. Sounds like one of the smoothest and least workaround swaps I've heard of to date. On the other hand, if you just wanted longer gear ratios, why not simply find an automobile lump and dump into the stock banjo/rear housing, keaving the stock suspension all original?

If one uses a Bronco rear in a Pilothouse, do you simply not use the Bronco emergency brake circuit?

Thanis for your time.

[carl b51]

Dan, I think you will find that the price of the wedge is about the same price as a new pair of perches . when I did my 51 B3b I used a 87 cherakee rearend and installed new perches and the drive shaft hooked right up it was a dana 40.

[DanOlson]

grey beard,

I like having options and not burning bridges behind me so to speak. Two factors lead me to consider a rear diff swap, gear ratio and brakes. I know that I could've put in a car pumpkin and solved the gear ratio issue but I'd still have the brake issue. I had one rear brake leaking for quite a while and as you know rebuilding the rears on the Dodge is not a cheap endeavor. So, I had saved a 9" housing from my rock crawling days and have pumpkins with 4.10, 3.50, and 2.73 ratios. For now, I'm going to put in the 3.50 which will save me about 400 rpm at 55 mph. If I find a T5, I'll put in the 4.10 pumpkin if the 3.50 proves too steep. The 9" uses a standard 3.250" u-joint just like the Dodge but I may have to lengthen the driveshaft if I don't find a T5 by spring. You can leave the e-brake cable off and cover the hole but I'd like to hook up cables and leave them tied up under the box just in case. The spring perch width difference is so close that by a little grinding on the head of the spring bolt, it fits just fine. I prefer to start with the spring wedges until the optimum pinion angle is determined. I actually have new spring perches but the originals are so close and I trust the factory welding more than I trust mine.

Dan

[grey beard]

Thnaks, Dan

Please let us know what you have to do on the prop shaft adaptation. Is the rear you are using from a Bronco? Jeep? What was it's original home?

This is good info. Again, thanks for sharing this with us.

[DanOlson]

I can't be sure what the donor was for the housing, but based on the pinion angle, I think a Bronco would be a good guess over a full size truck or car.

Dan

[DanOlson]

As the pictures show, the Ford 9 inch is now under the 53 Dodge. After narrowing up the existing spring perches and getting new u-bolts bent, it bolted right up. The pinion yoke sits back about an inch closer to the axle and the stock 53 drive shaft bolted in without any mods. I even used the stock u-joint u-bolts. New axle seals go in today and get brakes and axles bolted in. I'm waiting on the brake hose from the frame to the diff and once that's in and brakes bled, it's on the road. I know I will need to tweak the pinion angle but I'm going to wait until it's on the ground.

Dan

[pflaming]

I noticed the level on the drive shaft. Is that to be level to the floor in a correct installation or is the angle to the differential the key point. Seems the angle to the differential would be key, different size tires would change the level to the floor position. Please define "spring perch". To me that would be the 'mount' spot of the spring, is that correct?

[Frank Elder]

yes. also called spring pad.

[DanOlson]

Yes, the spring perch (pad) is the flat mounting surface on the differential housing. This is where the spring is attached via u-bolts. I can't set any angles until the truck is on the ground on the wheels. Right now the truck is being supported by the frame and the springs and rear end are 'hanging'. Once weight is put on the springs the angle of the drive shaft and rear end will change. The link is an article on the ideal geometry between transmission, drive shaft, and pinion.

http://www.carcraft.com/howto/91758/photo_08.html

Dan

[grey beard]

Dan,

Does your nine inch Ford housing have a drain plug in the bottom of the housing center section? If it does, I can help you identify it.

Do you know the centerbolt-to-centerbolt dimension? The axle flange to foange tead width?

Can you tell me the width of the pinion yoke where it bolts onto the universal joint?

I jhave a bropther who has 26-pllus years experience in a Junk Yard using Holander interchange numbers. He speaks thie stuff like another language. Let me know what you can about this rear, and I[ll do my best to identify it for the group. Suce many of us would like to have higher ratio gear numbers and later/cheaper brakes, this would be really good stuff to know.

Thanks,

[DanOlson]

There is not a drain plug in the housing. What do you mean by center bolt to center bolt? I'll get the axle flange to flange measurement tonight.

It's ready for a road test once I get the wheel spacers. As expected the 9" drums will not fit into the stock wheels.

Dan

[grey beard]

center bolt is the one that ties the spring leaves together. The distance between the two axle housing holes the center bolts sit into is critical. I understood you to say earlier that this measurement was just 1/4 inch off from the old to the new axle. If the drums don't fit inside the stock wheels, will spacers help? Is the bolt pattern for wheel lugs the same as stock Dodge?

Thanks