Gear clash sound while engine braking

[n9viw]

I recently finished a LuK single-mass flywheel and clutch conversion on my '95 F250, and other than a brief issue with some air in the clutch line, it's been fine.

I have noticed, however, a SIGNIFICANT increase in what I can only describe as 'gear clash' while engine braking. I never had this sound before with the DMF, and it's loud enough to cause me some concern. This occurs in all forward gears, but I have not tried reverse, nor have I tried it in either of the 4WD positions.

I asked a coworker who has a '97 with the ZF and a SMF, and he said he does not hear any sound like I describe when engine braking (which he does a considerable amount, to save the brakes, as I do). I have yet to ride in his truck (or he in mine) to hear the difference, but just the fact that mine DIDN'T before, and does now, makes me wonder.

I have changed the fluid, and used three quarts of Mercon V synthetic and one quart of Lucas Stop Slip to try to quiet the noise (and aid the aging synchro rings), but it hasn't had any effect. I was very careful to not 'hang' the trans on the input shaft while removing and installing it for the SMF conversion, and did not note any excessive or large particles of metal in the fluid I drained out; it was dark, but not 'gritty' or shiny with metal at all.

Would adding extra fluid help, or is there another product that can quiet the sound?

TIA,

[n9viw]

BTT... no input on this?