Drilling the 8.8 axles for your S10
, redneck style
I've searched the 8.8 threads and not found any information to re-drill the axles for Chevy wheels other than to have a machine shop do it.
Being the resourceful (cheap) person that I am I gave some thought as to how I could best do this myself with limited machine shop tools. I currently have 2 Ford 8.8 swaps to do and if I can save some money, or at least learn something I'm ahead of the game. Now if you are doing just one pair of axles I would suggest calling around the machine shops or the custom rear end shops for a price.
I would think that most of us if we had the choice would opt for using Chevy wheels on our trucks. Of course, if it's a track only and not a DD then you can save you money on modifying the axles for Chevy wheels.
To fit Chevy wheels to the 8.8 axles, 2 modifications need to be done. First the 8.8 wheel pilot is too big for the Chevy wheel to fit. I haven't got a cheap DIY for this, I had a local machine shop do this.
The 8.8 hub pilot is stepped; next to the wheel bolt flange is the pilot for the drum/rotor. This you need to leave as is, do not touch it!
The outer step must be machined to 70mm or2.755"
, the Chevy wheel pilot size.
Once this is done, the Chevy wheel bolt pattern must be drilled in between the Ford stud holes.
To do this I used an old alloy Blazer wheel and cut the center out of it. I began with a cut-off wheel but quickly changed over to a Sawzall.
I dropped off the wheel center at the machine shop with instructions to mill out the wheel bolts holes, preserving the indexing, and machine up an insert that I can move to each hole to drill it. These holes MUST be square to the wheel center!
This is what I got.
I drilled 3 mounting holes between the Chevy holes to secure it to the 8.8 flange while I drilled the new Chevy wheel bolt holes. The milled out Chevy bolt hole size isn't important, just had them make the insert a snug fit. I put a handle on it so I can remove it without resorting to Vise-grips. The hole in the center of the insert is 31/64 or .484"
. This is the size of hole needed in the flange to fit the Chevy wheel studs.
With that all done I mounted the jig to the 8.8 flange. It's not critical that the Chevy holes you drill are EXACTLY between the Ford holes.
I began with a DeWalt Pilot Point drill thinking I could do the drilling in one pass. It worked real slick for the first 3 holes, the 4th hole was a struggle as the pilot point was done! I had to drill a pilot hole free hand to get the drill through.
I finished that axle by marking the flange with the DeWalt bit first to locate a pilot hole location.
For the second axle I picked up a Jet "Gold" brand drill bit. I've not had or heard good stuff about Jet brand tools but I needed to get this done. I just marked the flange with the Jet bit and drilled the pilot holes free hand, followed by the 31/64 Jet bit. The job went fine with this bit.
A tip here; I would suggest new high quality bits for this. These flanges are tough stuff, and use lots off cutting oil and drill in steps cleaning & flushing the chips out as you go.
So now the axles are done, but we need to re-drill the rotors/drums.
The drums have a lip that centers the drum on the hub pilot, the one you DIDN'T machine down. You must place 3 large same size washers to space it above the lip or you will distort the drum when you tighten the axle down. This is not necessary for a brake rotor, so just mount the axle directly to the rotor. Again, it's not critical that the holes are located exactly between the original wheel bolt holes.
Now use the 31/64 drill to mark the location on the drum/rotor. I chose not to run the drill all the way through because I didn't want any excess wear on the insert, and it's not a critical operation anyways.
Almost done now.
Remove the axle form the drum/rotor and drill a pilot hole, about 3/16" will do.
Follow this with a 17/32 or 5/8 drill. It's OK that the holes are a bit big, the drum/rotors are sandwiched between the axle flange and the wheel, it won't move when the wheels are tightened.
Now, place the axle face down on a hard supporting surface, like these heavy press plates, or you can use a big vise. Drive those studs in just like nails!
Make sure they are down all the way. Re-check your wheel nuts after driving a few miles to make sure they haven't loosened up.
On with the drum,
The critical measurements you need to know, whether you do this yourself or send it out for machining is;
the OUTER hub pilot must be reduced to 2.755" or 70mm
The Chevy wheel bolt pattern for our trucks is 5 by 4.75" circle.
And the hole to drill for the wheel studs is 31/64" or .484
I used Raybestos wheel studs P/N 2093B. These will protrude 31.78mm or 1.250 inches. These should be long enough for the thicker disc rotor and an alloy wheel.
EDIT: I might add, my FIRST choice was a nice thick Chevy wheel spacer, but I'd had no cheap source so I went with what I had. The nice thing is that the insert is easily made by a shop when it wheres from use.
I paid the machine shop $140 to turn down the pilot hubs on 2 axles and mill the holes in the wheel center and make the insert for me. I didn't inquire as to how much they would charge for doing the index drilling and turning the pilot hubs. I also haven't inquired at the local custom rear end shop. Maybe it would have cost me less, and certainly less work, just drop the axles off and pick them up when ready, but where's the fun in that!