How to Manufacture a Rear Axle Housing for a Dwarf Car / Modlite Race Car

By Anthony Leary aka 44Dwarf

In this article I will assume you have use of a well equipped machine shop and hand tools.

The pictures here are from a job that was just completed. The old housing was an early Datsun rear and the owner of the car could not find axles or gears in the ratios needed for the modern motors. He elected to go with the 10 bolt “T” code Toyota rear. I was to copy the existing rear housing. The only change that was made to the housing was the addition of a slider for the panhard /track bar were the old unit had a fixed height bolt on unit.

Start off with a stock Toyota rear housing, strip the axles, backing plates and remove the gears. Like seen here.

Now cut the axle bearing ends off. Cut as close to the stock trailing links as possible so you have a long stub remaining in the bearing block. Like so.

Now cut the housing near the end of the taper. You’ll see the factory weld cut just on the side of it if possible. So you end up with a center section like this.

Now cut the other side. For cutting I have used in the past Sawz-alls but now use a port-a-band saw.

Now using a lathe trim the axle tube stub at the weld try to leave as much of the bearing block as possible so you will have maximum depth for the new tube.

You’ll know when you’ve cut the weld. Now push out the old tube like so.

You can see hear how deep the factory pushes the tube in to the bearing block.

Next you’ll need to decide how long the new axle tube needs to be in this case all I had to do was copy the old housing, HOWEVER the pinion locations between Toyota and Datsun were different so I used a carpenters square up from the bearing block face to the pinion center line.

For 10 bolt rears I use D.O.M. tubing with a OD of 2.5 inches and a 0.188 wall this is slightly thicker then stock Toyota, but is in stock at most real tubing suppliers like Marmon Keystone. I like DOM as it is precision OD and no variations in the wall thickness to worry about. It also machines very nice as it is normalized. ERW would work but it machines like crap

Use inside micrometers or dial calipers to measure the bore of the bearing block. They do vary so measure both blocks! You will have to machine the end of the new tube slightly to fit in to the bearing block. Most of the time it’s easier to machine the tube instead of the bearing block as it has an odd shape and take to much time to set up in a four jaw chuck. I like my new tubes to be 0.0 or – 0.0003 so cut slowly. If you end up on the + side you’ll have to warm up the block before inserting the tube. Sorry no pictures of this as of yet.

Now the inside of the center section you will note is not round nor flat you’ll see the factory weld line on the outside and normally see a parting line on the inside use a Dyna-file or carbide bit and smooth the inside of the center section. Use dial calipers and try to find out how much if any you need to trim off the OD of the tube so it can fit in side the center section. You may find you need to grind the OD of the tube along the length to make it fit with out having to machine the tube down, this is fine to do. I run my new tube in as far as I can. This extended tube helps in two ways. 1) It helps stabilize the tubes as it gets welded inside the center section. 2) Keeps the oil from going up the tubes in the corners. Oil control will help your gear life.

Next you need an empty chuck /center section / hog head what ever you wish to call it. I call it a chuck.

You will need to fit some machined bushings in place of the carrier bearings like so.

While your making the bushings make two more to fit in the axle bearing blocks as seen above.

I used 1 and 7/8 bore in my bushings as it was the largest that will fit in an 8 bolt Toyota bearing block. My bushings are a tight slip fit honed to size.

You will need a section of TGP (Turn, Ground and Polished) bar stock the same size as the bushing bores. Thomson way rod is excellent as it is hardened as well. Yes it is expensive!!

Now that you have both axle tubes machined stuff them in to the center section and push on the axle bearing blocks. Now bolt on the chuck with the bushings clamped in the bearing spots.

SIDE NOTE: I would prefer racers used a gasket between the chuck and the housing as that’s the way the factory designed it but racers never do, as such I now MFG my housing not to be used with a gasket. Gasket thickness will change your toe on the assembly so if you don’t use a gasket of the same thickness every time you toe will change. This is why I no longer use one when making my housings.

Bolt the chuck in to the center section with all the bolts / nuts. Now double check the measurements of the axle tubes. Now slide one axle bearing bushing down the TGP bar a light oil will help here. DO NOT use grease! Grease will carbon up under heat latter and make removal a pain. Now slide the bar from the long axle side in to the bushings in the chuck and out the other axle tube. Support the bar end and push in axle bearing bushing in to the axle bearing block like so. NOTE: This is a finished picture you’ve not welded yet!

Now do the short side the same way.

Now spot weld the tubes and the bearing blocks in only two spots per connection places. Remove the bar and bushings and test fit in the car. Now’s the time to find any overall width problems!

Next refit the bar and bushings. Now fit all shock mounts, third link attachment point, trailing arm attachment points and brake flex line stud. Do all this BEFORE you weld the tubes if possible. Any welding on the tubes after they are welded to the center section will bend the tubes big time. As you can see above on this housing the short side shock mount is half on the tube and half on the center section. I had no choice but to weld the tube to the center section first. Then added the shock mount then welded the bearing block. Weld the tubes in ¼ radius swapping 180 degs to keep any warpage to a minimum. Spin the bar as you weld and try to spin the axle bearing bushings as well. After all welding is finished leave it to cool over night in the jig.

The next day wiggle out one axle bearing block, you’ll feel the bar push the bushing off to the side a little. Now side the bushing back next to the bearing block if it sides right in great, if not you will see space turn the housing so the space is up a way from you. Next get a terry towel rag or a dipper (you want to hold lots of water) and get a bucket / pail of ice water or as cold as you can water. Near the middle of the tube use a torch to heat a spot to a cherry red dull orange about the size of a quarter (US 25cent piece) 180 deg from the space in the bushing, now act fast hand over the torch and grab the soaked rag and force it in to the hot spot swap rags and continue soaking the hot spot until the sizzle it gone. Now look at the bushing the space should be less now. Move over an inch or so and heat a new spot and repeat until you can slide the bushing in to the bearing block. When finished leave the bushing in and wrap a cold rag around the tube and go to the other end. Repeat the heat shrink on this end.

Allow the housing to cool to room temp and remove the bushings and slide out the bar. For storage purposes only! Grease the bar! No rust on this expensive bar. Put it back in the cardboard tube and stand in on end in the dry corner.

Remove the chuck.

Now I use a quick check tool I made to check for toe and camber. This tool was made back when Dwarfs had 2 doors that opened. It was made to check the housing in the car.

2X2 angle iron ~ 50 inches long drilled with the bolt pattern of the bearing blocks bolt each section to the block and run tape measurements if you did everything right both should read the same, like so.

Next remove one bolt per side and twist the angle 90 deg to check for camber. The measurements should be the same.

This tool is handy to use any time your car has taken a hit and the handling is off you can vise-grip the angle to the axle flanges to quick check.

If all is good it’s time for paint, install and square to the front end.

Oh if you’re wondering how to clean up the rusty old housing parts I’ve used the method on this site with great results.

http://antique-engines.com/electrol.asp

Best of luck.

- 44Dwarf