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Narrowing the 60 (+35 Spline Shafts)

October 17th, 2008 Posted in Rear Axle, Tech

I knew I wanted to narrow my rear 60 and I knew I wanted to run 35 spline shafts in it, so the first thing I did was plug the BOM into the BOM Look-up on the Dana Expert site.

That gave me the part numbers for both axle shafts that came in the axle (which I did not take with me). The driver side was Spicer #39260-7 and the passenger side was #39260-8.

The next step was to take those axle shaft part numbers and find them in Dana’s “Axle General Information Catalog” (XGI.pdf). The XGI catalog told me that my axle shafts are 37.71″ (driver side) and 34.99″ (passenger side) long, the flange diameter is 4.75″, and the bolt pattern for the shafts is 8 on 3.96″. It also tells you the spline count and shaft diameter, but I already knew what that was.

This axle was 66.5″ wide, WMS to WMS when I pulled it. I really wanted something between 61″ and 62″ to match my Waggy width front 44, so I needed to remove about 5″ from the total width. I added the lengths of the two stock shafts together to get my total shaft length (37.71″ + 34.99″ = 72.70″). If I took 5″ away from that I would be looking at a total shaft length of approximately 67.70″. I wanted to run equal length shafts so that meant I needed to find a shaft that was about 33.85″ long.

Back to the XGI catalog
Skip down to page 86 where the full float axle shaft info is. I used the search feature to find the 35 spline shafts and then checked the “bolt circle” column to see if I had a match. If I did get a match, I checked the length. I ended up finding a shaft that would be perfect… Spicer #36113-23. It had the right spline count and shaft diameter, it had the right flange diameter and bolt pattern, and it was 33.78″ long!

OK, now we have to go back to the Dana Expert site and plug our part number into the “Bill of Materials/Where Used” section. That will give us the BOM numbers of the axles that this shaft came in… we got two… Dana 70U’s with the BOM’s 605205 & 605247.

Head back over to the regular “Axle Bill of Materials” section of the site and plug in those BOM numbers (separately). That tells us that the axle we’re looking for was primarily found in ’83.5-’85 F-350s. At first, I was discouraged by the small list of possible vehicles to search for, but it only took two trips to Pick-N-Pull to get 3 shafts (one for a spare). In fact, the second trip was on half-off day and there was actually a third shaft there if I wanted it, but I probably won’t even need the spare I already got.

Interestingly, I ended up finding one of the shafts in an ’84 F-350, one in an ’84 F-250 with a diesel, and one in an ’85 F-250 with a gas engine… all with the 605205 BOM. I’m guessing that Dana made those two axles for specific trucks, but Ford used them where ever they were needed at the time.

Luckily, my 60 was already equipped with “big bore” spindles. With a 1.60″ inside diameter, they are large enough to accommodate the 1.5″ shafts without any modifications. I did need to get some 35 spline side gears for the differential though, so I bought some used from a fellow Jeeper for only $20 shipped!

The final step in this conversion is actually cutting the axle housing down to size. I seriously considered taking a chop saw to the long side and then pressing the remaining tube out along with the short side. All in the hopes that pressing the tubes back in would alleviate the need for an alignment bar. After a lot of research I have decided to have Dean over at Performance Cryogenics take care of the narrowing for me. It’s just the way it should be done, and although I like to do my own work, it’s hard to pass up such a reasonable price.

The final width of the axle is 61.36″ WMS to WMS (approximately 62.5″ WMS to WMS with the rotors installed).

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