Yes. It's best to do all of the welding/fabrication on the rear housing before narrowing. Some people will tack the ends on so they can see their tire/wheel/width/fitment, then weld on all of the brackets, then cut the tacks and weld the ends on using a narrowing fixture (ie: bar and donuts).
If you use the correct donut properly clamped in the housing ends, you can be ***ured that the ends are parallel to each other and, just as important, they are concentric with the centerline of the differential.
Still gotta establish a centerline! I built a fixture years ago and used 1&1/2" TG&P for alignment shaft, that means turned, ground, and polished, a little overkill but got it for s**** priçe at work. Machined sleeves for carrier bearing bores in a dummy center section to establish centerline, made end pucks for light slip fit on both the shaft to puck bore and puck to housing end bores. Yes, I'm sure many people have gotten away with less, in my opinion, to get to the same end result you had a lot of luck on your side but I'm betting there is a fair amount of extra screwing around that people don't admit to.
This is one more thread where people ask for opinions. The very knowlegeable tell how they do it to make it good enough for resale. Others state how they have done it to get by. In life, people tend to ask questions looking for the answer they want to hear. Everyone has their own standards. What is good enough for some isn't good enough for others.
I'm gonna 'fess up and admit that many years ago I narrowed at least three housings with no tooling what so ever. Two '55-64 Chevy housings and an Olds. Being young and dumb I cut the housings with a hack saw and "squared it up" with a body grinder and a square. I cleaned up the ends by grinding off the factory weld and chiseling off the little piece of housing. The axles were built up with stick weld and resplined by Drag Machine. The two Chevy rear ends went into Chevy powered sports cars, my friends MGA and my MGB. The Olds went into a friends roadster. None of them had any trouble with bearings or spider gears and my MGB was driven daily and ran brackets at Lions regularly. Knowing what I do now, and having the proper tooling, I can't help but wonder how we got away with it, but I also wonder if we aren't obsessing a little too much over a fairly simple modification. When I do a housing, the acid test is whether my mandrel shaft will move fairly easily through all four bushings when I'm done welding and everything's cooled off. If it's crooked, it will bind up the shaft. Oh yeah, for the OP, no one has mentioned it but you need to check and record the rotation of the housing ends relative to the 3rd member surface and note the backing plate bolt pattern orientation if it's not symmetrical. You don't want to weld the ends on upside down or rotated one way or the other.
I built a setup just like DDD with the exception of my shaft is only 1-3/8 stainless augment 22 propeller shaft. Worked in a boat yard so,it was available. Center drilled and checked for straightness. Having the center section in with bushings really gives you a good feel with what’s going on. And when I was racing and just needed to get things done I’ve done some real sketchy stuff and got away with it. I’ve seen the fixture that sets up centerline and has the math on it and will most likely purchase it for my next job. Sent from my iPad using The H.A.M.B. mobile app
Had these in my watched threads- https://www.jalopyjournal.com/forum/threads/straighten-a-bent-9-ford-rear-end-housing.393748/ https://www.jalopyjournal.com/forum/threads/how-to-narrow-a-9-inch-ford-rear-end-housing.392570/
Talking longevity here. A quarter mile at a time for the life of a drag car is one thing, building a rearend to last THOUSANDS of miles for interstate driving is another. As to professional shops, the special fixtures aren't a luxury, they are an integral part of day to day business, a rework job even one or two is disruptive to business. The average Joe trying to save $$$ can mess around all weekend to TRY and fix a badly narrowed rearend, and another thing, a professional shop might not want to even touch one of these home garage rework jobs.
That isn't correct. To do it right, you need a center section with bushings AND you still need to check the ends for square and perpendicular. The law of averages says that if people only use the donuts, some of em will end up "good enuff" and some won't.......and many of them will work. The problem is that they may wear bearings faster and it won't be apparent for a while, so they are happy with it. Not all of them are going to be immediately apparent, and some are gonna luck out and not have a problem, but simply sliding the ends on a bar will not guarantee that they are square and perpendicular. Here are pictures of my rear end narrowing jig. I have posted these before. My point is that very few builders will go to this extreme, and most that do got some free material from work. I know I did. The saving grace in all of this is that the length of the axles will help a lot in ***uaging some misalignment from end to end cir***ferentially, but nothing helps out of parallel.
Yes, it is correct. 1. The donut faces are perpendicular to the shaft. 2. The donut is clamped to the housing end. 3. Donuts are clamped in the differential bearing registers. ( I believe this point had already been established) 4. The shaft is fitted through the donuts that are in the housing end and the differential registers. Please describe how the two housing ends would not be parallel to each other when ***embled in this manner.
First time I heard of a maple bar, was in a breakfast place near Mt Hood, OR. We were camping around western Canada and US, and stopped to ski for a few days, beginning of July. Sorry for the side--bar.
When I'm narrowing a housing, the dummy third member goes into the housing being narrowed and is simply a guide/support for the bar that will run all the way through. I place "doughnuts" in the bearing pocket of the end piece so it is concentric. Then I slide the end upright up to the Housing end flange and bolt the upright to the flange. Since the uprights are perpendicular to the table its on, the ends of the housing are automatically correct vertically. If the upright (front & back) measurements are the same distance apart, the ends are parallel. Since everything is also in concentric alignment because of the bar p***ing thru all related parts, everything is in correct alignment. What you are doing is a pretty decent way and probably works OK. The problem is that you are ***uming that everyone will have a bar thats perfectly straight, and that there isn't sufficient tolerance in the donut to allow the end to move about. Also if the donut you are using is inside the bearing pocket, its probably not a snug fit. Does the donut actually have a step with a shoulder ? How do you measure to insure its square? Are you sure both are perpendicular? You pretty much have to allow some tolerance in these parts to get them to ***emble and that tolerance can allow things to be off some. I don't know how you support the housing when ***embling the bar and doughnuts, but if its just sitting on a table, how do you hold the ends against the housing while you weld it? Can you post a picture of how you do it ?
Then they should welcome the opportunity to show everyone the quality of their work and how they go about it. They may indeed have something set up that works well. I showed how I go about doing it, and it's based on years of experience as both a machinist and a machined parts inspector. Just because something works initially doesn't mean it's ***embled correctly or that problems won't show up later on. If they have a simple way of doing it right, I'm willing to learn.
I'm not going to engage in an internet battle with you. I did not comment on your fixture. You stated that using a bar and donuts was not correct and the ends would not be parallel. I asked why. You now state it's because there are fitment tolerances that cause it to not be perfect. By the same token, your system has fitment tolerances. Beginning with using a tape measure to ***ure two plates are parallel. The world we live in is built using tolerances.
Absolutely right, the question is where and how much. All I asked you to do was to show us your set up instead of just telling us. The purpose of the forum is to provide an exchange of ideas and information, not to get upset when someone simply has a different viewpoint. Sorry that you take that as an internet battle rather than just exchanging different opinions on what/how something can be done.
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