The Stovebolt Site Forums The Shop Area Driveline Bolt pattern change advice 6 to 5

For the back story, my dad bought a 54 Chevrolet 3100 back in the mid 60s. I have owned it since the late 70s. I finally got to the point in life that I tore it down for some major refurbishment. He also at that time put a set of vintage E-T torquethrust wheels on it using 6 bolt to 5 bolt adapter plates. I know they are not correct to the truck but they are all I have ever known it to have so they are correct to me.

I always hated the adapter plates. They resulted in bad suspension geometry and I always thought they were unsafe as they had screw in studs that tended to work their way out over time.

Part of the upgrade was to do 5 bolt "the right way". The fronts were easy. Car front drums from the same year. The rears not as easy. Moser Engineering said they could weld and re-drill the flanges for the new bolt pattern. That is until I sent the axles to them. As it turns out, time is no friend as when they weld up the flanges, they are too hard to re-drill. They cannot make new axles as the bearing surface is too large for their equipment. They say someone with an end mill may be able to do it. I am no machinist so I don't fully understand the obstacles.

What their suggestion is is to cut the rear end housing ends off and weld on later ends to get a different size bearing and the bolt in style axles vs. the C clip retained design. At that point, they could make me a set of axles to fit. Essentially, the $90 drill job just turned into a $700+ ordeal. I foresee problems with backing plates, brake design change, e-brake cable issues, and more,

Has anyone gone through this or have advice/suggestions? I want to retain the torque tube design as it is a hydra-matic truck so a later rear end as a whole is out of the question I think. Is there a set of axles that would be the correct length and spline to work with the old rear end components with the new axle ends and the 5 bolt wheel pattern? That could save the custom axle part of the project. Looking for advice or past experience.

Thanks,
G.H.

You're getting some really bad advice from Moser! I would think that an outfit like that would know better, or at least be willing to correct their mistake. You're going to need to find a machine shop with a Bridgeport mill and a dividing head to lay out the hole spacing, and solid carbide drills and milling cutters to cut the holes. They will need to spot-anneal the flanges to make the initial cuts for the 5-stud spacing.

I'd make a guess that about $100.00 worth of carbide cutters and a real machinist should be able to get you back in business!
Jerry

Hell's fire - I've welded up axles and re-drilled them myself in shop at the house using nothing more fancy than a simple drill press. Sounds to me like they just don't want to mess with it.

One another note - you can just locate an 8.5" 10-bolt axle out of a 3rd gen Nova or 2nd gen F-body and slap it in there. You can pick those up for little of nothing if you look hard enough. It'll have the correct 5-lug pattern and the correct width. You just have to shave the spring perches off and weld new ones on in the right spot. I guess the other part to note though is that you will then have an open driveline. Not sure if your '54 has a torque tube or an open driveline. I think they changed that somewhere around the '54-'55 year model.

The axles are currently en route to my shop. The last time I did the 6 to 5 lug conversion, I seem to recall that only one hole actually needed to be welded up. There's enough room to space the 5-lug hole pattern between the other lug bolt holes without overlapping the bolt patterns. Old Chevy rear axle flanges are harder than woodpecker lips, so some annealing to get the pilot holes drilled is sometimes a necessity.
Jerry

Thanks again Jerry, I have new hurdle in this project that advice would be appreciated on. Apparently (based off of other posts on other sites) the axle center is a little larger. I don't think it will be a problem with the wheels I have but I will investigate when I can. Should I re-drill the truck brake drums that already have the larger center? Or should I have the center turned down to fit car drums? Still reading on car drums...They are not perfectly dimensionally the same. I think car drums might be 3-4 mm deeper. I am trying to reason out if that would be a problem with backing plate interference or exactly where the overall depth difference is. Advice?

Since the drum center is relatively thin, and not hardened, just drill it to fit the new 5 lug pattern. Even if there's a slight overlap with one of the holes, it shouldn't compromise the braking effect. I'd suggest making a template out of thin sheet metal that will fit inside the center of the drum, and rotate it around to find the area that will have the best stud engagement, then drill there. Cutting the final hole diameter with a 4-flute end mill will give a much more accurate hole than trying to use a drill bit. Drill the holes a little undersize with a bit, then switch to an end mill for the final cuts.
Jerry

Works for me...That shall be the plan.