# Converting a rear end



## eugene13 (Mar 8, 2019)

for use in a WISSOTA Mod 4.  this is a Ford 6 3/4" inch rear end, commonly found in the Ford Pinto and Mercury Bobcat.  These are leaf spring cars with drum brakes.  I will be converting this one to a three link coil spring suspension with a panhard bar, and disc brakes, for use in this Mod 4 Chassis that is getting a new front clip and other repairs.  One of the first operations is to turn down the axle flanges to fit in the Ford Escort brake rotors, Here's a picture of the axle in the work stand with the rotors installed.  The next step is to build some spacers to fit between the bearing housing and the retainer.  We usually cut the center out of the brake backing plate for this purpose, but the client bought the rear end without brakes.  The problem with making big holes in small thin parts is holding them, I cut out two similar size parts from this plastic covered aluminum, drilled four corner holes, screwed them to a 2 X 6 and stuck them in the lathe.  Not having a 72 mm hole saw, I finished them with the boring bar, and cleaned them up on the belt sander.


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## eugene13 (Mar 12, 2019)

With the spacers done I can concentrate on mounting the Ford Escort front calipers.  I didn't design the brackets, I bought a pair from a fellow racer in Wyoming, and he said copy them if I desired.  I made a couple of improvements, then had a contractor cut out a 4' X 10' sheet of them on his pantagraph, which I sold on the internet for a number of years.  We bolt the caliper to the bracket and use compressed air to clamp it to the rotor, the hollow opposite the caliper indexes on the axle bearing, setting the position of the caliper on the rotor.  Scribe the outline of the axle flange and cut, fit, and weld.  Now that I'm waiting on the welder I'll build the top link.  these are some templates I built 20 odd years ago when we were racing these cars, some times it pays to be a hoarder.


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## samstu (Mar 13, 2019)

Hey that's really cool.  I like the "air clamp" and the creative use of wood for workholding in the four jaw chuck.  Maybe few others here are building race cars but those kinds of solutions can work for many other problems.  Thank you for sharing.  Looking forward to seeing more techniques and updates.


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## eugene13 (Mar 18, 2019)

The welder cometh, I don't know where my son got his welder genes, certainly not from me, perhaps his grandfather, the man was one heck of a bricklayer.  We use 7018  to weld the top links to the to the center section, and the wire feed for everything else.  Here's a detail shot of the installed brake bracket.  We pre-heat everything before welding, but it still distorts the bearing fit, a little time with the die grinder and the bearing will slide right in.


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## royesses (Mar 18, 2019)

Very nice work.

Roy


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## FOMOGO (Mar 19, 2019)

Nice job on the brackets. Is it a class rule thing on rear end choice? Mike


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## eugene13 (Mar 19, 2019)

WISSOTA rules prohibit any rear end ratio lower than 4:11.  That forces the Mod 4s to run in second gear in order to get a low enough ratio to keep the motor wound up, most run about 8000 RPM. These little rear ends are lightweight, tough, and very efficient.  We ran a transmission with a 2.14 second gear and a 3.18 rear end on a 3/8 mile track, for a 6.80 final, and on a 1/4 mile track we used the same tranny with a 3.55, for a 7.59 final.  I bought a Speedway Engineering Mini Stock Quick Change with change gears that gave similar ratios, and did some dyno work with the intention of getting WISSOTA to approve it, but they blew me off. The quick change is about 50 lbs heavier, and delivered 3 less horsepower and 4 fewer lbft of torque.  The quick change is now in my rat rod and very happy there.  thanks for the compliments.


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## eugene13 (Mar 25, 2019)

All done and sitting in the chassis.  We use swaged tubes for the lower links and I built the upper  link out of two threaded bungs and I" X .090 tubing, this sets the pinion angle.  We finished up yesterday, and the owner picked it up today, this has been a very busy winter, thanks for watching, Gene.


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