It depends on where Allison has the shift points programmed on the HD4060 transmission, specifically on downshift with the jake brake engaged. I had mine changed from pre-selecting fourth to pre-selecting fifth. When DD/Allison did it for me they downloaded all the shift parameters for my transmission. One of the parameters is the rpm allowed when downshifting to fourth with the jake engaged. Allison's rpm parameter for this particular shift was 2300 rpm on my bus; Allison decided it was "safe to do so" at 2300 rpm... There's a little bit of a disconnect between what Allison wants and what the DD S60 is happy with. I'm not saying that all HD4060's have identical shift points. I am suggesting keeping an eye on it till you know for sure. Steve, sounds like you know that yours never exceeds 2100 on the jake. That's good.
David Brady
'02 Blue Bird Wanderlodge LXi
Series 60, Allison HD4060
NC
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