109 Salisbury ATB and 4.1:1 Gears

Ashcroft ATB, Salisbury

Well, I bit the bullet last summer and ordered an Ashcroft Transmissions ATB for the Salisbury axle, a new product from them that has been on the cards for them for the last couple of years.  This is made to replace the Salisbury 8HA as used in Defender 110s and 130s rather than that used in 109s and 101s.  The principle difference is that 109s and 110s use 4.71 and 3.54 ratio diffs respectively, which have such different diameter pinion gear heads that the flange for mounting the ring gear needs to be in a different position, closer to centreline on the 109 and nearer one end on the 110.  101s use the same flange position as the 109, but they use a much thicker half shaft diameter, so their side gears differ from the 109 and Defender (which both have the same spec splines).

Dana 4.1:1 gears

So, that means the Ashcroft (and Eaton) ATBs for Salisbury axles fit directly to 109, 110 and 130 as long as you are using the higher ration final drive gears, but need a spacer ring (like I used on the front ATB I built up) for lower gear sets.  As far as I have found, with several sources saying the same thing, the cut off is at 4.3:1 and lower needing the spacer, 4.1 and above being fitted without.  So, if I can use the 4.1 Dana gears, it goes straight in, but should I need to retain the 109’s original 4,71 gears, it’ll need a spacer.

Finding the dimensions for the spacer has yielded varying results from a little over 2mm to approximately 4mm.  I think either extreme would work, the side shims being thick enough to compensate.

Dana pinion dimensions – please help with Salisbury dimensions

I have also had a response to requests on a forum for pinion measurements, so that I can determine what might need doing to fit the Dana 4.1 pinion to the 110 axle casing.  It appears that all the dimensions are the same except for the diameter where the outer (nearest the prop shaft) bearing sits.  That section appears to be significantly thinner than on a Salisbury pinion, but a collar should enable the use of standard LR bearing kits, simplifying future maintenance.  I have included my Dana measurements in a photo – if anyone can provide similar for a Salisbury, then that would be an enormous help in confirming what dimensions to have the collar made to fit that standard bearing.

Incidentally, the reason for measuring the diff (many measurements were taken) was that a contact is rebuilding a 101 and wants ATBs – this is when we learned about the difference in half shaft diameter (they won’t even fit through the ATB’s side bearing stubs, let alone into the side gears), and were trying to determine exact difference in ring gear flange offsets for deciding the correct ring gear spacer thickness.